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64db4cff PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
87de1cfd PM |
15 | * along with this program; if not, you can access it online at |
16 | * http://www.gnu.org/licenses/gpl-2.0.html. | |
64db4cff PM |
17 | * |
18 | * Copyright IBM Corporation, 2008 | |
19 | * | |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version | |
23 | * | |
24 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> | |
25 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
26 | * | |
27 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 28 | * Documentation/RCU |
64db4cff PM |
29 | */ |
30 | #include <linux/types.h> | |
31 | #include <linux/kernel.h> | |
32 | #include <linux/init.h> | |
33 | #include <linux/spinlock.h> | |
34 | #include <linux/smp.h> | |
f9411ebe | 35 | #include <linux/rcupdate_wait.h> |
64db4cff PM |
36 | #include <linux/interrupt.h> |
37 | #include <linux/sched.h> | |
b17b0153 | 38 | #include <linux/sched/debug.h> |
c1dc0b9c | 39 | #include <linux/nmi.h> |
8826f3b0 | 40 | #include <linux/atomic.h> |
64db4cff | 41 | #include <linux/bitops.h> |
9984de1a | 42 | #include <linux/export.h> |
64db4cff PM |
43 | #include <linux/completion.h> |
44 | #include <linux/moduleparam.h> | |
45 | #include <linux/percpu.h> | |
46 | #include <linux/notifier.h> | |
47 | #include <linux/cpu.h> | |
48 | #include <linux/mutex.h> | |
49 | #include <linux/time.h> | |
bbad9379 | 50 | #include <linux/kernel_stat.h> |
a26ac245 PM |
51 | #include <linux/wait.h> |
52 | #include <linux/kthread.h> | |
ae7e81c0 | 53 | #include <uapi/linux/sched/types.h> |
268bb0ce | 54 | #include <linux/prefetch.h> |
3d3b7db0 PM |
55 | #include <linux/delay.h> |
56 | #include <linux/stop_machine.h> | |
661a85dc | 57 | #include <linux/random.h> |
af658dca | 58 | #include <linux/trace_events.h> |
d1d74d14 | 59 | #include <linux/suspend.h> |
a278d471 | 60 | #include <linux/ftrace.h> |
64db4cff | 61 | |
4102adab | 62 | #include "tree.h" |
29c00b4a | 63 | #include "rcu.h" |
9f77da9f | 64 | |
4102adab PM |
65 | #ifdef MODULE_PARAM_PREFIX |
66 | #undef MODULE_PARAM_PREFIX | |
67 | #endif | |
68 | #define MODULE_PARAM_PREFIX "rcutree." | |
69 | ||
64db4cff PM |
70 | /* Data structures. */ |
71 | ||
f7f7bac9 SRRH |
72 | /* |
73 | * In order to export the rcu_state name to the tracing tools, it | |
74 | * needs to be added in the __tracepoint_string section. | |
75 | * This requires defining a separate variable tp_<sname>_varname | |
76 | * that points to the string being used, and this will allow | |
77 | * the tracing userspace tools to be able to decipher the string | |
78 | * address to the matching string. | |
79 | */ | |
a8a29b3b AB |
80 | #ifdef CONFIG_TRACING |
81 | # define DEFINE_RCU_TPS(sname) \ | |
f7f7bac9 | 82 | static char sname##_varname[] = #sname; \ |
a8a29b3b AB |
83 | static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; |
84 | # define RCU_STATE_NAME(sname) sname##_varname | |
85 | #else | |
86 | # define DEFINE_RCU_TPS(sname) | |
87 | # define RCU_STATE_NAME(sname) __stringify(sname) | |
88 | #endif | |
89 | ||
90 | #define RCU_STATE_INITIALIZER(sname, sabbr, cr) \ | |
91 | DEFINE_RCU_TPS(sname) \ | |
c92fb057 | 92 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data); \ |
a41bfeb2 | 93 | struct rcu_state sname##_state = { \ |
6c90cc7b | 94 | .level = { &sname##_state.node[0] }, \ |
2723249a | 95 | .rda = &sname##_data, \ |
037b64ed | 96 | .call = cr, \ |
77f81fe0 | 97 | .gp_state = RCU_GP_IDLE, \ |
42c3533e PM |
98 | .gpnum = 0UL - 300UL, \ |
99 | .completed = 0UL - 300UL, \ | |
7be7f0be | 100 | .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ |
a8a29b3b | 101 | .name = RCU_STATE_NAME(sname), \ |
a4889858 | 102 | .abbr = sabbr, \ |
f6a12f34 | 103 | .exp_mutex = __MUTEX_INITIALIZER(sname##_state.exp_mutex), \ |
3b5f668e | 104 | .exp_wake_mutex = __MUTEX_INITIALIZER(sname##_state.exp_wake_mutex), \ |
2723249a | 105 | } |
64db4cff | 106 | |
a41bfeb2 SRRH |
107 | RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); |
108 | RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); | |
b1f77b05 | 109 | |
b28a7c01 | 110 | static struct rcu_state *const rcu_state_p; |
6ce75a23 | 111 | LIST_HEAD(rcu_struct_flavors); |
27f4d280 | 112 | |
a3dc2948 PM |
113 | /* Dump rcu_node combining tree at boot to verify correct setup. */ |
114 | static bool dump_tree; | |
115 | module_param(dump_tree, bool, 0444); | |
7fa27001 PM |
116 | /* Control rcu_node-tree auto-balancing at boot time. */ |
117 | static bool rcu_fanout_exact; | |
118 | module_param(rcu_fanout_exact, bool, 0444); | |
47d631af PM |
119 | /* Increase (but not decrease) the RCU_FANOUT_LEAF at boot time. */ |
120 | static int rcu_fanout_leaf = RCU_FANOUT_LEAF; | |
7e5c2dfb | 121 | module_param(rcu_fanout_leaf, int, 0444); |
f885b7f2 | 122 | int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; |
cb007102 | 123 | /* Number of rcu_nodes at specified level. */ |
e95d68d2 | 124 | int num_rcu_lvl[] = NUM_RCU_LVL_INIT; |
f885b7f2 | 125 | int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ |
088e9d25 DBO |
126 | /* panic() on RCU Stall sysctl. */ |
127 | int sysctl_panic_on_rcu_stall __read_mostly; | |
f885b7f2 | 128 | |
b0d30417 | 129 | /* |
52d7e48b PM |
130 | * The rcu_scheduler_active variable is initialized to the value |
131 | * RCU_SCHEDULER_INACTIVE and transitions RCU_SCHEDULER_INIT just before the | |
132 | * first task is spawned. So when this variable is RCU_SCHEDULER_INACTIVE, | |
133 | * RCU can assume that there is but one task, allowing RCU to (for example) | |
0d95092c | 134 | * optimize synchronize_rcu() to a simple barrier(). When this variable |
52d7e48b PM |
135 | * is RCU_SCHEDULER_INIT, RCU must actually do all the hard work required |
136 | * to detect real grace periods. This variable is also used to suppress | |
137 | * boot-time false positives from lockdep-RCU error checking. Finally, it | |
138 | * transitions from RCU_SCHEDULER_INIT to RCU_SCHEDULER_RUNNING after RCU | |
139 | * is fully initialized, including all of its kthreads having been spawned. | |
b0d30417 | 140 | */ |
bbad9379 PM |
141 | int rcu_scheduler_active __read_mostly; |
142 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
143 | ||
b0d30417 PM |
144 | /* |
145 | * The rcu_scheduler_fully_active variable transitions from zero to one | |
146 | * during the early_initcall() processing, which is after the scheduler | |
147 | * is capable of creating new tasks. So RCU processing (for example, | |
148 | * creating tasks for RCU priority boosting) must be delayed until after | |
149 | * rcu_scheduler_fully_active transitions from zero to one. We also | |
150 | * currently delay invocation of any RCU callbacks until after this point. | |
151 | * | |
152 | * It might later prove better for people registering RCU callbacks during | |
153 | * early boot to take responsibility for these callbacks, but one step at | |
154 | * a time. | |
155 | */ | |
156 | static int rcu_scheduler_fully_active __read_mostly; | |
157 | ||
0aa04b05 PM |
158 | static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); |
159 | static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); | |
5d01bbd1 | 160 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
a46e0899 PM |
161 | static void invoke_rcu_core(void); |
162 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); | |
6587a23b PM |
163 | static void rcu_report_exp_rdp(struct rcu_state *rsp, |
164 | struct rcu_data *rdp, bool wake); | |
3549c2bc | 165 | static void sync_sched_exp_online_cleanup(int cpu); |
a26ac245 | 166 | |
a94844b2 | 167 | /* rcuc/rcub kthread realtime priority */ |
26730f55 | 168 | static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; |
a94844b2 PM |
169 | module_param(kthread_prio, int, 0644); |
170 | ||
8d7dc928 | 171 | /* Delay in jiffies for grace-period initialization delays, debug only. */ |
0f41c0dd | 172 | |
90040c9e PM |
173 | static int gp_preinit_delay; |
174 | module_param(gp_preinit_delay, int, 0444); | |
175 | static int gp_init_delay; | |
176 | module_param(gp_init_delay, int, 0444); | |
177 | static int gp_cleanup_delay; | |
178 | module_param(gp_cleanup_delay, int, 0444); | |
0f41c0dd | 179 | |
eab128e8 PM |
180 | /* |
181 | * Number of grace periods between delays, normalized by the duration of | |
bfd090be | 182 | * the delay. The longer the delay, the more the grace periods between |
eab128e8 PM |
183 | * each delay. The reason for this normalization is that it means that, |
184 | * for non-zero delays, the overall slowdown of grace periods is constant | |
185 | * regardless of the duration of the delay. This arrangement balances | |
186 | * the need for long delays to increase some race probabilities with the | |
187 | * need for fast grace periods to increase other race probabilities. | |
188 | */ | |
189 | #define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */ | |
37745d28 | 190 | |
4a298656 PM |
191 | /* |
192 | * Track the rcutorture test sequence number and the update version | |
193 | * number within a given test. The rcutorture_testseq is incremented | |
194 | * on every rcutorture module load and unload, so has an odd value | |
195 | * when a test is running. The rcutorture_vernum is set to zero | |
196 | * when rcutorture starts and is incremented on each rcutorture update. | |
197 | * These variables enable correlating rcutorture output with the | |
198 | * RCU tracing information. | |
199 | */ | |
200 | unsigned long rcutorture_testseq; | |
201 | unsigned long rcutorture_vernum; | |
202 | ||
0aa04b05 PM |
203 | /* |
204 | * Compute the mask of online CPUs for the specified rcu_node structure. | |
205 | * This will not be stable unless the rcu_node structure's ->lock is | |
206 | * held, but the bit corresponding to the current CPU will be stable | |
207 | * in most contexts. | |
208 | */ | |
209 | unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp) | |
210 | { | |
7d0ae808 | 211 | return READ_ONCE(rnp->qsmaskinitnext); |
0aa04b05 PM |
212 | } |
213 | ||
fc2219d4 | 214 | /* |
7d0ae808 | 215 | * Return true if an RCU grace period is in progress. The READ_ONCE()s |
fc2219d4 PM |
216 | * permit this function to be invoked without holding the root rcu_node |
217 | * structure's ->lock, but of course results can be subject to change. | |
218 | */ | |
219 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
220 | { | |
7d0ae808 | 221 | return READ_ONCE(rsp->completed) != READ_ONCE(rsp->gpnum); |
fc2219d4 PM |
222 | } |
223 | ||
b1f77b05 | 224 | /* |
d6714c22 | 225 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 226 | * how many quiescent states passed, just if there was at least |
d6714c22 | 227 | * one since the start of the grace period, this just sets a flag. |
e4cc1f22 | 228 | * The caller must have disabled preemption. |
b1f77b05 | 229 | */ |
284a8c93 | 230 | void rcu_sched_qs(void) |
b1f77b05 | 231 | { |
f4687d26 | 232 | RCU_LOCKDEP_WARN(preemptible(), "rcu_sched_qs() invoked with preemption enabled!!!"); |
fecbf6f0 PM |
233 | if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.s)) |
234 | return; | |
235 | trace_rcu_grace_period(TPS("rcu_sched"), | |
236 | __this_cpu_read(rcu_sched_data.gpnum), | |
237 | TPS("cpuqs")); | |
238 | __this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false); | |
239 | if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp)) | |
240 | return; | |
46a5d164 PM |
241 | __this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, false); |
242 | rcu_report_exp_rdp(&rcu_sched_state, | |
243 | this_cpu_ptr(&rcu_sched_data), true); | |
b1f77b05 IM |
244 | } |
245 | ||
284a8c93 | 246 | void rcu_bh_qs(void) |
b1f77b05 | 247 | { |
f4687d26 | 248 | RCU_LOCKDEP_WARN(preemptible(), "rcu_bh_qs() invoked with preemption enabled!!!"); |
5b74c458 | 249 | if (__this_cpu_read(rcu_bh_data.cpu_no_qs.s)) { |
284a8c93 PM |
250 | trace_rcu_grace_period(TPS("rcu_bh"), |
251 | __this_cpu_read(rcu_bh_data.gpnum), | |
252 | TPS("cpuqs")); | |
5b74c458 | 253 | __this_cpu_write(rcu_bh_data.cpu_no_qs.b.norm, false); |
284a8c93 | 254 | } |
b1f77b05 | 255 | } |
64db4cff | 256 | |
b8c17e66 PM |
257 | /* |
258 | * Steal a bit from the bottom of ->dynticks for idle entry/exit | |
259 | * control. Initially this is for TLB flushing. | |
260 | */ | |
261 | #define RCU_DYNTICK_CTRL_MASK 0x1 | |
262 | #define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1) | |
263 | #ifndef rcu_eqs_special_exit | |
264 | #define rcu_eqs_special_exit() do { } while (0) | |
265 | #endif | |
4a81e832 PM |
266 | |
267 | static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { | |
268 | .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, | |
b8c17e66 | 269 | .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR), |
4a81e832 PM |
270 | }; |
271 | ||
03ecd3f4 SRV |
272 | /* |
273 | * There's a few places, currently just in the tracing infrastructure, | |
274 | * that uses rcu_irq_enter() to make sure RCU is watching. But there's | |
275 | * a small location where that will not even work. In those cases | |
276 | * rcu_irq_enter_disabled() needs to be checked to make sure rcu_irq_enter() | |
277 | * can be called. | |
278 | */ | |
279 | static DEFINE_PER_CPU(bool, disable_rcu_irq_enter); | |
280 | ||
281 | bool rcu_irq_enter_disabled(void) | |
282 | { | |
283 | return this_cpu_read(disable_rcu_irq_enter); | |
284 | } | |
285 | ||
2625d469 PM |
286 | /* |
287 | * Record entry into an extended quiescent state. This is only to be | |
288 | * called when not already in an extended quiescent state. | |
289 | */ | |
290 | static void rcu_dynticks_eqs_enter(void) | |
291 | { | |
292 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); | |
b8c17e66 | 293 | int seq; |
2625d469 PM |
294 | |
295 | /* | |
b8c17e66 | 296 | * CPUs seeing atomic_add_return() must see prior RCU read-side |
2625d469 PM |
297 | * critical sections, and we also must force ordering with the |
298 | * next idle sojourn. | |
299 | */ | |
b8c17e66 PM |
300 | seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks); |
301 | /* Better be in an extended quiescent state! */ | |
302 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && | |
303 | (seq & RCU_DYNTICK_CTRL_CTR)); | |
304 | /* Better not have special action (TLB flush) pending! */ | |
305 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && | |
306 | (seq & RCU_DYNTICK_CTRL_MASK)); | |
2625d469 PM |
307 | } |
308 | ||
309 | /* | |
310 | * Record exit from an extended quiescent state. This is only to be | |
311 | * called from an extended quiescent state. | |
312 | */ | |
313 | static void rcu_dynticks_eqs_exit(void) | |
314 | { | |
315 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); | |
b8c17e66 | 316 | int seq; |
2625d469 PM |
317 | |
318 | /* | |
b8c17e66 | 319 | * CPUs seeing atomic_add_return() must see prior idle sojourns, |
2625d469 PM |
320 | * and we also must force ordering with the next RCU read-side |
321 | * critical section. | |
322 | */ | |
b8c17e66 PM |
323 | seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks); |
324 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && | |
325 | !(seq & RCU_DYNTICK_CTRL_CTR)); | |
326 | if (seq & RCU_DYNTICK_CTRL_MASK) { | |
327 | atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdtp->dynticks); | |
328 | smp_mb__after_atomic(); /* _exit after clearing mask. */ | |
329 | /* Prefer duplicate flushes to losing a flush. */ | |
330 | rcu_eqs_special_exit(); | |
331 | } | |
2625d469 PM |
332 | } |
333 | ||
334 | /* | |
335 | * Reset the current CPU's ->dynticks counter to indicate that the | |
336 | * newly onlined CPU is no longer in an extended quiescent state. | |
337 | * This will either leave the counter unchanged, or increment it | |
338 | * to the next non-quiescent value. | |
339 | * | |
340 | * The non-atomic test/increment sequence works because the upper bits | |
341 | * of the ->dynticks counter are manipulated only by the corresponding CPU, | |
342 | * or when the corresponding CPU is offline. | |
343 | */ | |
344 | static void rcu_dynticks_eqs_online(void) | |
345 | { | |
346 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); | |
347 | ||
b8c17e66 | 348 | if (atomic_read(&rdtp->dynticks) & RCU_DYNTICK_CTRL_CTR) |
2625d469 | 349 | return; |
b8c17e66 | 350 | atomic_add(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks); |
2625d469 PM |
351 | } |
352 | ||
02a5c550 PM |
353 | /* |
354 | * Is the current CPU in an extended quiescent state? | |
355 | * | |
356 | * No ordering, as we are sampling CPU-local information. | |
357 | */ | |
358 | bool rcu_dynticks_curr_cpu_in_eqs(void) | |
359 | { | |
360 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); | |
361 | ||
b8c17e66 | 362 | return !(atomic_read(&rdtp->dynticks) & RCU_DYNTICK_CTRL_CTR); |
02a5c550 PM |
363 | } |
364 | ||
8b2f63ab PM |
365 | /* |
366 | * Snapshot the ->dynticks counter with full ordering so as to allow | |
367 | * stable comparison of this counter with past and future snapshots. | |
368 | */ | |
02a5c550 | 369 | int rcu_dynticks_snap(struct rcu_dynticks *rdtp) |
8b2f63ab PM |
370 | { |
371 | int snap = atomic_add_return(0, &rdtp->dynticks); | |
372 | ||
b8c17e66 | 373 | return snap & ~RCU_DYNTICK_CTRL_MASK; |
8b2f63ab PM |
374 | } |
375 | ||
02a5c550 PM |
376 | /* |
377 | * Return true if the snapshot returned from rcu_dynticks_snap() | |
378 | * indicates that RCU is in an extended quiescent state. | |
379 | */ | |
380 | static bool rcu_dynticks_in_eqs(int snap) | |
381 | { | |
b8c17e66 | 382 | return !(snap & RCU_DYNTICK_CTRL_CTR); |
02a5c550 PM |
383 | } |
384 | ||
385 | /* | |
386 | * Return true if the CPU corresponding to the specified rcu_dynticks | |
387 | * structure has spent some time in an extended quiescent state since | |
388 | * rcu_dynticks_snap() returned the specified snapshot. | |
389 | */ | |
390 | static bool rcu_dynticks_in_eqs_since(struct rcu_dynticks *rdtp, int snap) | |
391 | { | |
392 | return snap != rcu_dynticks_snap(rdtp); | |
393 | } | |
394 | ||
6563de9d PM |
395 | /* |
396 | * Do a double-increment of the ->dynticks counter to emulate a | |
397 | * momentary idle-CPU quiescent state. | |
398 | */ | |
399 | static void rcu_dynticks_momentary_idle(void) | |
400 | { | |
401 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); | |
b8c17e66 PM |
402 | int special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR, |
403 | &rdtp->dynticks); | |
6563de9d PM |
404 | |
405 | /* It is illegal to call this from idle state. */ | |
b8c17e66 | 406 | WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR)); |
6563de9d PM |
407 | } |
408 | ||
b8c17e66 PM |
409 | /* |
410 | * Set the special (bottom) bit of the specified CPU so that it | |
411 | * will take special action (such as flushing its TLB) on the | |
412 | * next exit from an extended quiescent state. Returns true if | |
413 | * the bit was successfully set, or false if the CPU was not in | |
414 | * an extended quiescent state. | |
415 | */ | |
416 | bool rcu_eqs_special_set(int cpu) | |
417 | { | |
418 | int old; | |
419 | int new; | |
420 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); | |
421 | ||
422 | do { | |
423 | old = atomic_read(&rdtp->dynticks); | |
424 | if (old & RCU_DYNTICK_CTRL_CTR) | |
425 | return false; | |
426 | new = old | RCU_DYNTICK_CTRL_MASK; | |
427 | } while (atomic_cmpxchg(&rdtp->dynticks, old, new) != old); | |
428 | return true; | |
6563de9d | 429 | } |
5cd37193 | 430 | |
4a81e832 PM |
431 | /* |
432 | * Let the RCU core know that this CPU has gone through the scheduler, | |
433 | * which is a quiescent state. This is called when the need for a | |
434 | * quiescent state is urgent, so we burn an atomic operation and full | |
435 | * memory barriers to let the RCU core know about it, regardless of what | |
436 | * this CPU might (or might not) do in the near future. | |
437 | * | |
0f9be8ca | 438 | * We inform the RCU core by emulating a zero-duration dyntick-idle period. |
46a5d164 PM |
439 | * |
440 | * The caller must have disabled interrupts. | |
4a81e832 PM |
441 | */ |
442 | static void rcu_momentary_dyntick_idle(void) | |
443 | { | |
0f9be8ca PM |
444 | raw_cpu_write(rcu_dynticks.rcu_need_heavy_qs, false); |
445 | rcu_dynticks_momentary_idle(); | |
4a81e832 PM |
446 | } |
447 | ||
25502a6c PM |
448 | /* |
449 | * Note a context switch. This is a quiescent state for RCU-sched, | |
450 | * and requires special handling for preemptible RCU. | |
46a5d164 | 451 | * The caller must have disabled interrupts. |
25502a6c | 452 | */ |
bcbfdd01 | 453 | void rcu_note_context_switch(bool preempt) |
25502a6c | 454 | { |
bb73c52b | 455 | barrier(); /* Avoid RCU read-side critical sections leaking down. */ |
f7f7bac9 | 456 | trace_rcu_utilization(TPS("Start context switch")); |
284a8c93 | 457 | rcu_sched_qs(); |
5b72f964 | 458 | rcu_preempt_note_context_switch(preempt); |
9226b10d PM |
459 | /* Load rcu_urgent_qs before other flags. */ |
460 | if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) | |
461 | goto out; | |
462 | this_cpu_write(rcu_dynticks.rcu_urgent_qs, false); | |
0f9be8ca | 463 | if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) |
4a81e832 | 464 | rcu_momentary_dyntick_idle(); |
9226b10d | 465 | this_cpu_inc(rcu_dynticks.rcu_qs_ctr); |
bcbfdd01 PM |
466 | if (!preempt) |
467 | rcu_note_voluntary_context_switch_lite(current); | |
9226b10d | 468 | out: |
f7f7bac9 | 469 | trace_rcu_utilization(TPS("End context switch")); |
bb73c52b | 470 | barrier(); /* Avoid RCU read-side critical sections leaking up. */ |
25502a6c | 471 | } |
29ce8310 | 472 | EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
25502a6c | 473 | |
5cd37193 | 474 | /* |
1925d196 | 475 | * Register a quiescent state for all RCU flavors. If there is an |
5cd37193 PM |
476 | * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight |
477 | * dyntick-idle quiescent state visible to other CPUs (but only for those | |
1925d196 | 478 | * RCU flavors in desperate need of a quiescent state, which will normally |
5cd37193 PM |
479 | * be none of them). Either way, do a lightweight quiescent state for |
480 | * all RCU flavors. | |
bb73c52b BF |
481 | * |
482 | * The barrier() calls are redundant in the common case when this is | |
483 | * called externally, but just in case this is called from within this | |
484 | * file. | |
485 | * | |
5cd37193 PM |
486 | */ |
487 | void rcu_all_qs(void) | |
488 | { | |
46a5d164 PM |
489 | unsigned long flags; |
490 | ||
9226b10d PM |
491 | if (!raw_cpu_read(rcu_dynticks.rcu_urgent_qs)) |
492 | return; | |
493 | preempt_disable(); | |
494 | /* Load rcu_urgent_qs before other flags. */ | |
495 | if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) { | |
496 | preempt_enable(); | |
497 | return; | |
498 | } | |
499 | this_cpu_write(rcu_dynticks.rcu_urgent_qs, false); | |
bb73c52b | 500 | barrier(); /* Avoid RCU read-side critical sections leaking down. */ |
0f9be8ca | 501 | if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) { |
46a5d164 | 502 | local_irq_save(flags); |
5cd37193 | 503 | rcu_momentary_dyntick_idle(); |
46a5d164 PM |
504 | local_irq_restore(flags); |
505 | } | |
9226b10d | 506 | if (unlikely(raw_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))) |
a1e12248 | 507 | rcu_sched_qs(); |
9577df9a | 508 | this_cpu_inc(rcu_dynticks.rcu_qs_ctr); |
bb73c52b | 509 | barrier(); /* Avoid RCU read-side critical sections leaking up. */ |
9226b10d | 510 | preempt_enable(); |
5cd37193 PM |
511 | } |
512 | EXPORT_SYMBOL_GPL(rcu_all_qs); | |
513 | ||
17c7798b PM |
514 | #define DEFAULT_RCU_BLIMIT 10 /* Maximum callbacks per rcu_do_batch. */ |
515 | static long blimit = DEFAULT_RCU_BLIMIT; | |
516 | #define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */ | |
517 | static long qhimark = DEFAULT_RCU_QHIMARK; | |
518 | #define DEFAULT_RCU_QLOMARK 100 /* Once only this many pending, use blimit. */ | |
519 | static long qlowmark = DEFAULT_RCU_QLOMARK; | |
64db4cff | 520 | |
878d7439 ED |
521 | module_param(blimit, long, 0444); |
522 | module_param(qhimark, long, 0444); | |
523 | module_param(qlowmark, long, 0444); | |
3d76c082 | 524 | |
026ad283 PM |
525 | static ulong jiffies_till_first_fqs = ULONG_MAX; |
526 | static ulong jiffies_till_next_fqs = ULONG_MAX; | |
8c7c4829 | 527 | static bool rcu_kick_kthreads; |
d40011f6 PM |
528 | |
529 | module_param(jiffies_till_first_fqs, ulong, 0644); | |
530 | module_param(jiffies_till_next_fqs, ulong, 0644); | |
8c7c4829 | 531 | module_param(rcu_kick_kthreads, bool, 0644); |
d40011f6 | 532 | |
4a81e832 PM |
533 | /* |
534 | * How long the grace period must be before we start recruiting | |
535 | * quiescent-state help from rcu_note_context_switch(). | |
536 | */ | |
f79c3ad6 PM |
537 | static ulong jiffies_till_sched_qs = HZ / 10; |
538 | module_param(jiffies_till_sched_qs, ulong, 0444); | |
4a81e832 | 539 | |
48a7639c | 540 | static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
910ee45d | 541 | struct rcu_data *rdp); |
fe5ac724 | 542 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)); |
4cdfc175 | 543 | static void force_quiescent_state(struct rcu_state *rsp); |
e3950ecd | 544 | static int rcu_pending(void); |
64db4cff PM |
545 | |
546 | /* | |
917963d0 | 547 | * Return the number of RCU batches started thus far for debug & stats. |
64db4cff | 548 | */ |
917963d0 PM |
549 | unsigned long rcu_batches_started(void) |
550 | { | |
551 | return rcu_state_p->gpnum; | |
552 | } | |
553 | EXPORT_SYMBOL_GPL(rcu_batches_started); | |
554 | ||
555 | /* | |
556 | * Return the number of RCU-sched batches started thus far for debug & stats. | |
64db4cff | 557 | */ |
917963d0 PM |
558 | unsigned long rcu_batches_started_sched(void) |
559 | { | |
560 | return rcu_sched_state.gpnum; | |
561 | } | |
562 | EXPORT_SYMBOL_GPL(rcu_batches_started_sched); | |
563 | ||
564 | /* | |
565 | * Return the number of RCU BH batches started thus far for debug & stats. | |
566 | */ | |
567 | unsigned long rcu_batches_started_bh(void) | |
568 | { | |
569 | return rcu_bh_state.gpnum; | |
570 | } | |
571 | EXPORT_SYMBOL_GPL(rcu_batches_started_bh); | |
572 | ||
573 | /* | |
574 | * Return the number of RCU batches completed thus far for debug & stats. | |
575 | */ | |
576 | unsigned long rcu_batches_completed(void) | |
577 | { | |
578 | return rcu_state_p->completed; | |
579 | } | |
580 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
581 | ||
582 | /* | |
583 | * Return the number of RCU-sched batches completed thus far for debug & stats. | |
64db4cff | 584 | */ |
9733e4f0 | 585 | unsigned long rcu_batches_completed_sched(void) |
64db4cff | 586 | { |
d6714c22 | 587 | return rcu_sched_state.completed; |
64db4cff | 588 | } |
d6714c22 | 589 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
590 | |
591 | /* | |
917963d0 | 592 | * Return the number of RCU BH batches completed thus far for debug & stats. |
64db4cff | 593 | */ |
9733e4f0 | 594 | unsigned long rcu_batches_completed_bh(void) |
64db4cff PM |
595 | { |
596 | return rcu_bh_state.completed; | |
597 | } | |
598 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
599 | ||
291783b8 PM |
600 | /* |
601 | * Return the number of RCU expedited batches completed thus far for | |
602 | * debug & stats. Odd numbers mean that a batch is in progress, even | |
603 | * numbers mean idle. The value returned will thus be roughly double | |
604 | * the cumulative batches since boot. | |
605 | */ | |
606 | unsigned long rcu_exp_batches_completed(void) | |
607 | { | |
608 | return rcu_state_p->expedited_sequence; | |
609 | } | |
610 | EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); | |
611 | ||
612 | /* | |
613 | * Return the number of RCU-sched expedited batches completed thus far | |
614 | * for debug & stats. Similar to rcu_exp_batches_completed(). | |
615 | */ | |
616 | unsigned long rcu_exp_batches_completed_sched(void) | |
617 | { | |
618 | return rcu_sched_state.expedited_sequence; | |
619 | } | |
620 | EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched); | |
621 | ||
a381d757 ACB |
622 | /* |
623 | * Force a quiescent state. | |
624 | */ | |
625 | void rcu_force_quiescent_state(void) | |
626 | { | |
e534165b | 627 | force_quiescent_state(rcu_state_p); |
a381d757 ACB |
628 | } |
629 | EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); | |
630 | ||
bf66f18e PM |
631 | /* |
632 | * Force a quiescent state for RCU BH. | |
633 | */ | |
634 | void rcu_bh_force_quiescent_state(void) | |
635 | { | |
4cdfc175 | 636 | force_quiescent_state(&rcu_bh_state); |
bf66f18e PM |
637 | } |
638 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
639 | ||
e7580f33 PM |
640 | /* |
641 | * Force a quiescent state for RCU-sched. | |
642 | */ | |
643 | void rcu_sched_force_quiescent_state(void) | |
644 | { | |
645 | force_quiescent_state(&rcu_sched_state); | |
646 | } | |
647 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
648 | ||
afea227f PM |
649 | /* |
650 | * Show the state of the grace-period kthreads. | |
651 | */ | |
652 | void show_rcu_gp_kthreads(void) | |
653 | { | |
654 | struct rcu_state *rsp; | |
655 | ||
656 | for_each_rcu_flavor(rsp) { | |
657 | pr_info("%s: wait state: %d ->state: %#lx\n", | |
658 | rsp->name, rsp->gp_state, rsp->gp_kthread->state); | |
659 | /* sched_show_task(rsp->gp_kthread); */ | |
660 | } | |
661 | } | |
662 | EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); | |
663 | ||
4a298656 PM |
664 | /* |
665 | * Record the number of times rcutorture tests have been initiated and | |
666 | * terminated. This information allows the debugfs tracing stats to be | |
667 | * correlated to the rcutorture messages, even when the rcutorture module | |
668 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
669 | * store this state in rcutorture itself. | |
670 | */ | |
671 | void rcutorture_record_test_transition(void) | |
672 | { | |
673 | rcutorture_testseq++; | |
674 | rcutorture_vernum = 0; | |
675 | } | |
676 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
677 | ||
ad0dc7f9 PM |
678 | /* |
679 | * Send along grace-period-related data for rcutorture diagnostics. | |
680 | */ | |
681 | void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, | |
682 | unsigned long *gpnum, unsigned long *completed) | |
683 | { | |
684 | struct rcu_state *rsp = NULL; | |
685 | ||
686 | switch (test_type) { | |
687 | case RCU_FLAVOR: | |
e534165b | 688 | rsp = rcu_state_p; |
ad0dc7f9 PM |
689 | break; |
690 | case RCU_BH_FLAVOR: | |
691 | rsp = &rcu_bh_state; | |
692 | break; | |
693 | case RCU_SCHED_FLAVOR: | |
694 | rsp = &rcu_sched_state; | |
695 | break; | |
696 | default: | |
697 | break; | |
698 | } | |
7f6733c3 | 699 | if (rsp == NULL) |
ad0dc7f9 | 700 | return; |
7f6733c3 PM |
701 | *flags = READ_ONCE(rsp->gp_flags); |
702 | *gpnum = READ_ONCE(rsp->gpnum); | |
703 | *completed = READ_ONCE(rsp->completed); | |
ad0dc7f9 PM |
704 | } |
705 | EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); | |
706 | ||
4a298656 PM |
707 | /* |
708 | * Record the number of writer passes through the current rcutorture test. | |
709 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
710 | * messages. | |
711 | */ | |
712 | void rcutorture_record_progress(unsigned long vernum) | |
713 | { | |
714 | rcutorture_vernum++; | |
715 | } | |
716 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
717 | ||
365187fb PM |
718 | /* |
719 | * Return the root node of the specified rcu_state structure. | |
720 | */ | |
721 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
722 | { | |
723 | return &rsp->node[0]; | |
724 | } | |
725 | ||
726 | /* | |
727 | * Is there any need for future grace periods? | |
728 | * Interrupts must be disabled. If the caller does not hold the root | |
729 | * rnp_node structure's ->lock, the results are advisory only. | |
730 | */ | |
731 | static int rcu_future_needs_gp(struct rcu_state *rsp) | |
732 | { | |
733 | struct rcu_node *rnp = rcu_get_root(rsp); | |
7d0ae808 | 734 | int idx = (READ_ONCE(rnp->completed) + 1) & 0x1; |
365187fb PM |
735 | int *fp = &rnp->need_future_gp[idx]; |
736 | ||
b04db8e1 | 737 | lockdep_assert_irqs_disabled(); |
7d0ae808 | 738 | return READ_ONCE(*fp); |
365187fb PM |
739 | } |
740 | ||
64db4cff | 741 | /* |
dc35c893 PM |
742 | * Does the current CPU require a not-yet-started grace period? |
743 | * The caller must have disabled interrupts to prevent races with | |
744 | * normal callback registry. | |
64db4cff | 745 | */ |
d117c8aa | 746 | static bool |
64db4cff PM |
747 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) |
748 | { | |
b04db8e1 | 749 | lockdep_assert_irqs_disabled(); |
dc35c893 | 750 | if (rcu_gp_in_progress(rsp)) |
d117c8aa | 751 | return false; /* No, a grace period is already in progress. */ |
365187fb | 752 | if (rcu_future_needs_gp(rsp)) |
d117c8aa | 753 | return true; /* Yes, a no-CBs CPU needs one. */ |
15fecf89 | 754 | if (!rcu_segcblist_is_enabled(&rdp->cblist)) |
d117c8aa | 755 | return false; /* No, this is a no-CBs (or offline) CPU. */ |
15fecf89 | 756 | if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) |
d117c8aa | 757 | return true; /* Yes, CPU has newly registered callbacks. */ |
15fecf89 PM |
758 | if (rcu_segcblist_future_gp_needed(&rdp->cblist, |
759 | READ_ONCE(rsp->completed))) | |
760 | return true; /* Yes, CBs for future grace period. */ | |
d117c8aa | 761 | return false; /* No grace period needed. */ |
64db4cff PM |
762 | } |
763 | ||
9b2e4f18 | 764 | /* |
a278d471 | 765 | * rcu_eqs_enter_common - current CPU is entering an extended quiescent state |
9b2e4f18 | 766 | * |
a278d471 PM |
767 | * Enter idle, doing appropriate accounting. The caller must have |
768 | * disabled interrupts. | |
9b2e4f18 | 769 | */ |
a278d471 | 770 | static void rcu_eqs_enter_common(bool user) |
9b2e4f18 | 771 | { |
96d3fd0d PM |
772 | struct rcu_state *rsp; |
773 | struct rcu_data *rdp; | |
a278d471 | 774 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
96d3fd0d | 775 | |
b04db8e1 | 776 | lockdep_assert_irqs_disabled(); |
a278d471 | 777 | trace_rcu_dyntick(TPS("Start"), rdtp->dynticks_nesting, 0); |
1ce46ee5 PM |
778 | if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
779 | !user && !is_idle_task(current)) { | |
289828e6 PM |
780 | struct task_struct *idle __maybe_unused = |
781 | idle_task(smp_processor_id()); | |
0989cb46 | 782 | |
a278d471 | 783 | trace_rcu_dyntick(TPS("Error on entry: not idle task"), rdtp->dynticks_nesting, 0); |
274529ba | 784 | rcu_ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
785 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
786 | current->pid, current->comm, | |
787 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 | 788 | } |
96d3fd0d PM |
789 | for_each_rcu_flavor(rsp) { |
790 | rdp = this_cpu_ptr(rsp->rda); | |
791 | do_nocb_deferred_wakeup(rdp); | |
792 | } | |
198bbf81 | 793 | rcu_prepare_for_idle(); |
03ecd3f4 | 794 | __this_cpu_inc(disable_rcu_irq_enter); |
a278d471 PM |
795 | rdtp->dynticks_nesting = 0; /* Breaks tracing momentarily. */ |
796 | rcu_dynticks_eqs_enter(); /* After this, tracing works again. */ | |
03ecd3f4 | 797 | __this_cpu_dec(disable_rcu_irq_enter); |
176f8f7a | 798 | rcu_dynticks_task_enter(); |
c44e2cdd PM |
799 | |
800 | /* | |
adf5091e | 801 | * It is illegal to enter an extended quiescent state while |
c44e2cdd PM |
802 | * in an RCU read-side critical section. |
803 | */ | |
f78f5b90 PM |
804 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_lock_map), |
805 | "Illegal idle entry in RCU read-side critical section."); | |
806 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map), | |
807 | "Illegal idle entry in RCU-bh read-side critical section."); | |
808 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map), | |
809 | "Illegal idle entry in RCU-sched read-side critical section."); | |
9b2e4f18 | 810 | } |
64db4cff | 811 | |
adf5091e FW |
812 | /* |
813 | * Enter an RCU extended quiescent state, which can be either the | |
814 | * idle loop or adaptive-tickless usermode execution. | |
64db4cff | 815 | */ |
adf5091e | 816 | static void rcu_eqs_enter(bool user) |
64db4cff | 817 | { |
64db4cff PM |
818 | struct rcu_dynticks *rdtp; |
819 | ||
c9d4b0af | 820 | rdtp = this_cpu_ptr(&rcu_dynticks); |
1ce46ee5 | 821 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
a278d471 PM |
822 | (rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0); |
823 | if ((rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) | |
824 | rcu_eqs_enter_common(user); | |
825 | else | |
29e37d81 | 826 | rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; |
64db4cff | 827 | } |
adf5091e FW |
828 | |
829 | /** | |
830 | * rcu_idle_enter - inform RCU that current CPU is entering idle | |
831 | * | |
832 | * Enter idle mode, in other words, -leave- the mode in which RCU | |
833 | * read-side critical sections can occur. (Though RCU read-side | |
834 | * critical sections can occur in irq handlers in idle, a possibility | |
835 | * handled by irq_enter() and irq_exit().) | |
836 | * | |
837 | * We crowbar the ->dynticks_nesting field to zero to allow for | |
838 | * the possibility of usermode upcalls having messed up our count | |
839 | * of interrupt nesting level during the prior busy period. | |
c0da313e PM |
840 | * |
841 | * If you add or remove a call to rcu_idle_enter(), be sure to test with | |
842 | * CONFIG_RCU_EQS_DEBUG=y. | |
adf5091e FW |
843 | */ |
844 | void rcu_idle_enter(void) | |
845 | { | |
b04db8e1 | 846 | lockdep_assert_irqs_disabled(); |
cb349ca9 | 847 | rcu_eqs_enter(false); |
adf5091e | 848 | } |
64db4cff | 849 | |
d1ec4c34 | 850 | #ifdef CONFIG_NO_HZ_FULL |
adf5091e FW |
851 | /** |
852 | * rcu_user_enter - inform RCU that we are resuming userspace. | |
853 | * | |
854 | * Enter RCU idle mode right before resuming userspace. No use of RCU | |
855 | * is permitted between this call and rcu_user_exit(). This way the | |
856 | * CPU doesn't need to maintain the tick for RCU maintenance purposes | |
857 | * when the CPU runs in userspace. | |
c0da313e PM |
858 | * |
859 | * If you add or remove a call to rcu_user_enter(), be sure to test with | |
860 | * CONFIG_RCU_EQS_DEBUG=y. | |
adf5091e FW |
861 | */ |
862 | void rcu_user_enter(void) | |
863 | { | |
b04db8e1 | 864 | lockdep_assert_irqs_disabled(); |
d4db30af | 865 | rcu_eqs_enter(true); |
adf5091e | 866 | } |
d1ec4c34 | 867 | #endif /* CONFIG_NO_HZ_FULL */ |
19dd1591 | 868 | |
9b2e4f18 PM |
869 | /** |
870 | * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle | |
871 | * | |
872 | * Exit from an interrupt handler, which might possibly result in entering | |
873 | * idle mode, in other words, leaving the mode in which read-side critical | |
7c9906ca | 874 | * sections can occur. The caller must have disabled interrupts. |
64db4cff | 875 | * |
9b2e4f18 PM |
876 | * This code assumes that the idle loop never does anything that might |
877 | * result in unbalanced calls to irq_enter() and irq_exit(). If your | |
878 | * architecture violates this assumption, RCU will give you what you | |
879 | * deserve, good and hard. But very infrequently and irreproducibly. | |
880 | * | |
881 | * Use things like work queues to work around this limitation. | |
882 | * | |
883 | * You have been warned. | |
c0da313e PM |
884 | * |
885 | * If you add or remove a call to rcu_irq_exit(), be sure to test with | |
886 | * CONFIG_RCU_EQS_DEBUG=y. | |
64db4cff | 887 | */ |
9b2e4f18 | 888 | void rcu_irq_exit(void) |
64db4cff | 889 | { |
64db4cff PM |
890 | struct rcu_dynticks *rdtp; |
891 | ||
b04db8e1 | 892 | lockdep_assert_irqs_disabled(); |
c9d4b0af | 893 | rdtp = this_cpu_ptr(&rcu_dynticks); |
28585a83 PM |
894 | |
895 | /* Page faults can happen in NMI handlers, so check... */ | |
f39b536c | 896 | if (rdtp->dynticks_nmi_nesting) |
28585a83 PM |
897 | return; |
898 | ||
1ce46ee5 | 899 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
a278d471 PM |
900 | rdtp->dynticks_nesting < 1); |
901 | if (rdtp->dynticks_nesting <= 1) { | |
902 | rcu_eqs_enter_common(true); | |
903 | } else { | |
904 | trace_rcu_dyntick(TPS("--="), rdtp->dynticks_nesting, rdtp->dynticks_nesting - 1); | |
905 | rdtp->dynticks_nesting--; | |
906 | } | |
7c9906ca PM |
907 | } |
908 | ||
909 | /* | |
910 | * Wrapper for rcu_irq_exit() where interrupts are enabled. | |
c0da313e PM |
911 | * |
912 | * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test | |
913 | * with CONFIG_RCU_EQS_DEBUG=y. | |
7c9906ca PM |
914 | */ |
915 | void rcu_irq_exit_irqson(void) | |
916 | { | |
917 | unsigned long flags; | |
918 | ||
919 | local_irq_save(flags); | |
920 | rcu_irq_exit(); | |
9b2e4f18 PM |
921 | local_irq_restore(flags); |
922 | } | |
923 | ||
924 | /* | |
adf5091e | 925 | * rcu_eqs_exit_common - current CPU moving away from extended quiescent state |
9b2e4f18 PM |
926 | * |
927 | * If the new value of the ->dynticks_nesting counter was previously zero, | |
928 | * we really have exited idle, and must do the appropriate accounting. | |
929 | * The caller must have disabled interrupts. | |
930 | */ | |
28ced795 | 931 | static void rcu_eqs_exit_common(long long oldval, int user) |
9b2e4f18 | 932 | { |
2625d469 | 933 | RCU_TRACE(struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);) |
28ced795 | 934 | |
176f8f7a | 935 | rcu_dynticks_task_exit(); |
2625d469 | 936 | rcu_dynticks_eqs_exit(); |
8fa7845d | 937 | rcu_cleanup_after_idle(); |
f7f7bac9 | 938 | trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting); |
1ce46ee5 PM |
939 | if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
940 | !user && !is_idle_task(current)) { | |
289828e6 PM |
941 | struct task_struct *idle __maybe_unused = |
942 | idle_task(smp_processor_id()); | |
0989cb46 | 943 | |
f7f7bac9 | 944 | trace_rcu_dyntick(TPS("Error on exit: not idle task"), |
4145fa7f | 945 | oldval, rdtp->dynticks_nesting); |
274529ba | 946 | rcu_ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
947 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
948 | current->pid, current->comm, | |
949 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 PM |
950 | } |
951 | } | |
952 | ||
adf5091e FW |
953 | /* |
954 | * Exit an RCU extended quiescent state, which can be either the | |
955 | * idle loop or adaptive-tickless usermode execution. | |
9b2e4f18 | 956 | */ |
adf5091e | 957 | static void rcu_eqs_exit(bool user) |
9b2e4f18 | 958 | { |
9b2e4f18 PM |
959 | struct rcu_dynticks *rdtp; |
960 | long long oldval; | |
961 | ||
b04db8e1 | 962 | lockdep_assert_irqs_disabled(); |
c9d4b0af | 963 | rdtp = this_cpu_ptr(&rcu_dynticks); |
9b2e4f18 | 964 | oldval = rdtp->dynticks_nesting; |
1ce46ee5 | 965 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0); |
3a592405 | 966 | if (oldval & DYNTICK_TASK_NEST_MASK) { |
29e37d81 | 967 | rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; |
3a592405 | 968 | } else { |
35fe723b | 969 | __this_cpu_inc(disable_rcu_irq_enter); |
29e37d81 | 970 | rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
28ced795 | 971 | rcu_eqs_exit_common(oldval, user); |
35fe723b | 972 | __this_cpu_dec(disable_rcu_irq_enter); |
3a592405 | 973 | } |
9b2e4f18 | 974 | } |
adf5091e FW |
975 | |
976 | /** | |
977 | * rcu_idle_exit - inform RCU that current CPU is leaving idle | |
978 | * | |
979 | * Exit idle mode, in other words, -enter- the mode in which RCU | |
980 | * read-side critical sections can occur. | |
981 | * | |
982 | * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to | |
983 | * allow for the possibility of usermode upcalls messing up our count | |
984 | * of interrupt nesting level during the busy period that is just | |
985 | * now starting. | |
c0da313e PM |
986 | * |
987 | * If you add or remove a call to rcu_idle_exit(), be sure to test with | |
988 | * CONFIG_RCU_EQS_DEBUG=y. | |
adf5091e FW |
989 | */ |
990 | void rcu_idle_exit(void) | |
991 | { | |
c5d900bf FW |
992 | unsigned long flags; |
993 | ||
994 | local_irq_save(flags); | |
cb349ca9 | 995 | rcu_eqs_exit(false); |
c5d900bf | 996 | local_irq_restore(flags); |
adf5091e | 997 | } |
9b2e4f18 | 998 | |
d1ec4c34 | 999 | #ifdef CONFIG_NO_HZ_FULL |
adf5091e FW |
1000 | /** |
1001 | * rcu_user_exit - inform RCU that we are exiting userspace. | |
1002 | * | |
1003 | * Exit RCU idle mode while entering the kernel because it can | |
1004 | * run a RCU read side critical section anytime. | |
c0da313e PM |
1005 | * |
1006 | * If you add or remove a call to rcu_user_exit(), be sure to test with | |
1007 | * CONFIG_RCU_EQS_DEBUG=y. | |
adf5091e FW |
1008 | */ |
1009 | void rcu_user_exit(void) | |
1010 | { | |
91d1aa43 | 1011 | rcu_eqs_exit(1); |
adf5091e | 1012 | } |
d1ec4c34 | 1013 | #endif /* CONFIG_NO_HZ_FULL */ |
19dd1591 | 1014 | |
9b2e4f18 PM |
1015 | /** |
1016 | * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle | |
1017 | * | |
1018 | * Enter an interrupt handler, which might possibly result in exiting | |
1019 | * idle mode, in other words, entering the mode in which read-side critical | |
7c9906ca | 1020 | * sections can occur. The caller must have disabled interrupts. |
9b2e4f18 PM |
1021 | * |
1022 | * Note that the Linux kernel is fully capable of entering an interrupt | |
1023 | * handler that it never exits, for example when doing upcalls to | |
1024 | * user mode! This code assumes that the idle loop never does upcalls to | |
1025 | * user mode. If your architecture does do upcalls from the idle loop (or | |
1026 | * does anything else that results in unbalanced calls to the irq_enter() | |
1027 | * and irq_exit() functions), RCU will give you what you deserve, good | |
1028 | * and hard. But very infrequently and irreproducibly. | |
1029 | * | |
1030 | * Use things like work queues to work around this limitation. | |
1031 | * | |
1032 | * You have been warned. | |
c0da313e PM |
1033 | * |
1034 | * If you add or remove a call to rcu_irq_enter(), be sure to test with | |
1035 | * CONFIG_RCU_EQS_DEBUG=y. | |
9b2e4f18 PM |
1036 | */ |
1037 | void rcu_irq_enter(void) | |
1038 | { | |
9b2e4f18 PM |
1039 | struct rcu_dynticks *rdtp; |
1040 | long long oldval; | |
1041 | ||
b04db8e1 | 1042 | lockdep_assert_irqs_disabled(); |
c9d4b0af | 1043 | rdtp = this_cpu_ptr(&rcu_dynticks); |
28585a83 PM |
1044 | |
1045 | /* Page faults can happen in NMI handlers, so check... */ | |
f39b536c | 1046 | if (rdtp->dynticks_nmi_nesting) |
28585a83 PM |
1047 | return; |
1048 | ||
9b2e4f18 PM |
1049 | oldval = rdtp->dynticks_nesting; |
1050 | rdtp->dynticks_nesting++; | |
1ce46ee5 PM |
1051 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
1052 | rdtp->dynticks_nesting == 0); | |
b6fc6020 | 1053 | if (oldval) |
f7f7bac9 | 1054 | trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting); |
b6fc6020 | 1055 | else |
28ced795 | 1056 | rcu_eqs_exit_common(oldval, true); |
7c9906ca PM |
1057 | } |
1058 | ||
1059 | /* | |
1060 | * Wrapper for rcu_irq_enter() where interrupts are enabled. | |
c0da313e PM |
1061 | * |
1062 | * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test | |
1063 | * with CONFIG_RCU_EQS_DEBUG=y. | |
7c9906ca PM |
1064 | */ |
1065 | void rcu_irq_enter_irqson(void) | |
1066 | { | |
1067 | unsigned long flags; | |
1068 | ||
1069 | local_irq_save(flags); | |
1070 | rcu_irq_enter(); | |
64db4cff | 1071 | local_irq_restore(flags); |
64db4cff PM |
1072 | } |
1073 | ||
1074 | /** | |
1075 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
1076 | * | |
734d1680 PM |
1077 | * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and |
1078 | * rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know | |
1079 | * that the CPU is active. This implementation permits nested NMIs, as | |
1080 | * long as the nesting level does not overflow an int. (You will probably | |
1081 | * run out of stack space first.) | |
c0da313e PM |
1082 | * |
1083 | * If you add or remove a call to rcu_nmi_enter(), be sure to test | |
1084 | * with CONFIG_RCU_EQS_DEBUG=y. | |
64db4cff PM |
1085 | */ |
1086 | void rcu_nmi_enter(void) | |
1087 | { | |
c9d4b0af | 1088 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
734d1680 | 1089 | int incby = 2; |
64db4cff | 1090 | |
734d1680 PM |
1091 | /* Complain about underflow. */ |
1092 | WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0); | |
1093 | ||
1094 | /* | |
1095 | * If idle from RCU viewpoint, atomically increment ->dynticks | |
1096 | * to mark non-idle and increment ->dynticks_nmi_nesting by one. | |
1097 | * Otherwise, increment ->dynticks_nmi_nesting by two. This means | |
1098 | * if ->dynticks_nmi_nesting is equal to one, we are guaranteed | |
1099 | * to be in the outermost NMI handler that interrupted an RCU-idle | |
1100 | * period (observation due to Andy Lutomirski). | |
1101 | */ | |
02a5c550 | 1102 | if (rcu_dynticks_curr_cpu_in_eqs()) { |
2625d469 | 1103 | rcu_dynticks_eqs_exit(); |
734d1680 PM |
1104 | incby = 1; |
1105 | } | |
1106 | rdtp->dynticks_nmi_nesting += incby; | |
1107 | barrier(); | |
64db4cff PM |
1108 | } |
1109 | ||
1110 | /** | |
1111 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
1112 | * | |
734d1680 PM |
1113 | * If we are returning from the outermost NMI handler that interrupted an |
1114 | * RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting | |
1115 | * to let the RCU grace-period handling know that the CPU is back to | |
1116 | * being RCU-idle. | |
c0da313e PM |
1117 | * |
1118 | * If you add or remove a call to rcu_nmi_exit(), be sure to test | |
1119 | * with CONFIG_RCU_EQS_DEBUG=y. | |
64db4cff PM |
1120 | */ |
1121 | void rcu_nmi_exit(void) | |
1122 | { | |
c9d4b0af | 1123 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
64db4cff | 1124 | |
734d1680 PM |
1125 | /* |
1126 | * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks. | |
1127 | * (We are exiting an NMI handler, so RCU better be paying attention | |
1128 | * to us!) | |
1129 | */ | |
1130 | WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0); | |
02a5c550 | 1131 | WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs()); |
734d1680 PM |
1132 | |
1133 | /* | |
1134 | * If the nesting level is not 1, the CPU wasn't RCU-idle, so | |
1135 | * leave it in non-RCU-idle state. | |
1136 | */ | |
1137 | if (rdtp->dynticks_nmi_nesting != 1) { | |
1138 | rdtp->dynticks_nmi_nesting -= 2; | |
64db4cff | 1139 | return; |
734d1680 PM |
1140 | } |
1141 | ||
1142 | /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ | |
1143 | rdtp->dynticks_nmi_nesting = 0; | |
2625d469 | 1144 | rcu_dynticks_eqs_enter(); |
64db4cff PM |
1145 | } |
1146 | ||
5c173eb8 PM |
1147 | /** |
1148 | * rcu_is_watching - see if RCU thinks that the current CPU is idle | |
64db4cff | 1149 | * |
791875d1 PM |
1150 | * Return true if RCU is watching the running CPU, which means that this |
1151 | * CPU can safely enter RCU read-side critical sections. In other words, | |
1152 | * if the current CPU is in its idle loop and is neither in an interrupt | |
34240697 | 1153 | * or NMI handler, return true. |
64db4cff | 1154 | */ |
9418fb20 | 1155 | bool notrace rcu_is_watching(void) |
64db4cff | 1156 | { |
f534ed1f | 1157 | bool ret; |
34240697 | 1158 | |
46f00d18 | 1159 | preempt_disable_notrace(); |
791875d1 | 1160 | ret = !rcu_dynticks_curr_cpu_in_eqs(); |
46f00d18 | 1161 | preempt_enable_notrace(); |
34240697 | 1162 | return ret; |
64db4cff | 1163 | } |
5c173eb8 | 1164 | EXPORT_SYMBOL_GPL(rcu_is_watching); |
64db4cff | 1165 | |
bcbfdd01 PM |
1166 | /* |
1167 | * If a holdout task is actually running, request an urgent quiescent | |
1168 | * state from its CPU. This is unsynchronized, so migrations can cause | |
1169 | * the request to go to the wrong CPU. Which is OK, all that will happen | |
1170 | * is that the CPU's next context switch will be a bit slower and next | |
1171 | * time around this task will generate another request. | |
1172 | */ | |
1173 | void rcu_request_urgent_qs_task(struct task_struct *t) | |
1174 | { | |
1175 | int cpu; | |
1176 | ||
1177 | barrier(); | |
1178 | cpu = task_cpu(t); | |
1179 | if (!task_curr(t)) | |
1180 | return; /* This task is not running on that CPU. */ | |
1181 | smp_store_release(per_cpu_ptr(&rcu_dynticks.rcu_urgent_qs, cpu), true); | |
1182 | } | |
1183 | ||
62fde6ed | 1184 | #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) |
c0d6d01b PM |
1185 | |
1186 | /* | |
1187 | * Is the current CPU online? Disable preemption to avoid false positives | |
1188 | * that could otherwise happen due to the current CPU number being sampled, | |
1189 | * this task being preempted, its old CPU being taken offline, resuming | |
1190 | * on some other CPU, then determining that its old CPU is now offline. | |
1191 | * It is OK to use RCU on an offline processor during initial boot, hence | |
2036d94a PM |
1192 | * the check for rcu_scheduler_fully_active. Note also that it is OK |
1193 | * for a CPU coming online to use RCU for one jiffy prior to marking itself | |
1194 | * online in the cpu_online_mask. Similarly, it is OK for a CPU going | |
1195 | * offline to continue to use RCU for one jiffy after marking itself | |
1196 | * offline in the cpu_online_mask. This leniency is necessary given the | |
1197 | * non-atomic nature of the online and offline processing, for example, | |
4df83742 TG |
1198 | * the fact that a CPU enters the scheduler after completing the teardown |
1199 | * of the CPU. | |
2036d94a | 1200 | * |
4df83742 TG |
1201 | * This is also why RCU internally marks CPUs online during in the |
1202 | * preparation phase and offline after the CPU has been taken down. | |
c0d6d01b PM |
1203 | * |
1204 | * Disable checking if in an NMI handler because we cannot safely report | |
1205 | * errors from NMI handlers anyway. | |
1206 | */ | |
1207 | bool rcu_lockdep_current_cpu_online(void) | |
1208 | { | |
2036d94a PM |
1209 | struct rcu_data *rdp; |
1210 | struct rcu_node *rnp; | |
c0d6d01b PM |
1211 | bool ret; |
1212 | ||
1213 | if (in_nmi()) | |
f6f7ee9a | 1214 | return true; |
c0d6d01b | 1215 | preempt_disable(); |
c9d4b0af | 1216 | rdp = this_cpu_ptr(&rcu_sched_data); |
2036d94a | 1217 | rnp = rdp->mynode; |
0aa04b05 | 1218 | ret = (rdp->grpmask & rcu_rnp_online_cpus(rnp)) || |
c0d6d01b PM |
1219 | !rcu_scheduler_fully_active; |
1220 | preempt_enable(); | |
1221 | return ret; | |
1222 | } | |
1223 | EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); | |
1224 | ||
62fde6ed | 1225 | #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ |
9b2e4f18 | 1226 | |
64db4cff | 1227 | /** |
9b2e4f18 | 1228 | * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle |
64db4cff | 1229 | * |
9b2e4f18 PM |
1230 | * If the current CPU is idle or running at a first-level (not nested) |
1231 | * interrupt from idle, return true. The caller must have at least | |
1232 | * disabled preemption. | |
64db4cff | 1233 | */ |
62e3cb14 | 1234 | static int rcu_is_cpu_rrupt_from_idle(void) |
64db4cff | 1235 | { |
c9d4b0af | 1236 | return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 1; |
64db4cff PM |
1237 | } |
1238 | ||
9b9500da PM |
1239 | /* |
1240 | * We are reporting a quiescent state on behalf of some other CPU, so | |
1241 | * it is our responsibility to check for and handle potential overflow | |
1242 | * of the rcu_node ->gpnum counter with respect to the rcu_data counters. | |
1243 | * After all, the CPU might be in deep idle state, and thus executing no | |
1244 | * code whatsoever. | |
1245 | */ | |
1246 | static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp) | |
1247 | { | |
1248 | lockdep_assert_held(&rnp->lock); | |
1249 | if (ULONG_CMP_LT(READ_ONCE(rdp->gpnum) + ULONG_MAX / 4, rnp->gpnum)) | |
1250 | WRITE_ONCE(rdp->gpwrap, true); | |
1251 | if (ULONG_CMP_LT(rdp->rcu_iw_gpnum + ULONG_MAX / 4, rnp->gpnum)) | |
1252 | rdp->rcu_iw_gpnum = rnp->gpnum + ULONG_MAX / 4; | |
1253 | } | |
1254 | ||
64db4cff PM |
1255 | /* |
1256 | * Snapshot the specified CPU's dynticks counter so that we can later | |
1257 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 1258 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff | 1259 | */ |
fe5ac724 | 1260 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
64db4cff | 1261 | { |
8b2f63ab | 1262 | rdp->dynticks_snap = rcu_dynticks_snap(rdp->dynticks); |
02a5c550 | 1263 | if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) { |
7941dbde | 1264 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); |
9b9500da | 1265 | rcu_gpnum_ovf(rdp->mynode, rdp); |
23a9bacd | 1266 | return 1; |
7941dbde | 1267 | } |
23a9bacd | 1268 | return 0; |
64db4cff PM |
1269 | } |
1270 | ||
9b9500da PM |
1271 | /* |
1272 | * Handler for the irq_work request posted when a grace period has | |
1273 | * gone on for too long, but not yet long enough for an RCU CPU | |
1274 | * stall warning. Set state appropriately, but just complain if | |
1275 | * there is unexpected state on entry. | |
1276 | */ | |
1277 | static void rcu_iw_handler(struct irq_work *iwp) | |
1278 | { | |
1279 | struct rcu_data *rdp; | |
1280 | struct rcu_node *rnp; | |
1281 | ||
1282 | rdp = container_of(iwp, struct rcu_data, rcu_iw); | |
1283 | rnp = rdp->mynode; | |
1284 | raw_spin_lock_rcu_node(rnp); | |
1285 | if (!WARN_ON_ONCE(!rdp->rcu_iw_pending)) { | |
1286 | rdp->rcu_iw_gpnum = rnp->gpnum; | |
1287 | rdp->rcu_iw_pending = false; | |
1288 | } | |
1289 | raw_spin_unlock_rcu_node(rnp); | |
1290 | } | |
1291 | ||
64db4cff PM |
1292 | /* |
1293 | * Return true if the specified CPU has passed through a quiescent | |
1294 | * state by virtue of being in or having passed through an dynticks | |
1295 | * idle state since the last call to dyntick_save_progress_counter() | |
a82dcc76 | 1296 | * for this same CPU, or by virtue of having been offline. |
64db4cff | 1297 | */ |
fe5ac724 | 1298 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
64db4cff | 1299 | { |
3a19b46a | 1300 | unsigned long jtsq; |
0f9be8ca | 1301 | bool *rnhqp; |
9226b10d | 1302 | bool *ruqp; |
9b9500da | 1303 | struct rcu_node *rnp = rdp->mynode; |
64db4cff PM |
1304 | |
1305 | /* | |
1306 | * If the CPU passed through or entered a dynticks idle phase with | |
1307 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
1308 | * already acknowledged the request to pass through a quiescent | |
1309 | * state. Either way, that CPU cannot possibly be in an RCU | |
1310 | * read-side critical section that started before the beginning | |
1311 | * of the current RCU grace period. | |
1312 | */ | |
02a5c550 | 1313 | if (rcu_dynticks_in_eqs_since(rdp->dynticks, rdp->dynticks_snap)) { |
f7f7bac9 | 1314 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); |
64db4cff | 1315 | rdp->dynticks_fqs++; |
9b9500da | 1316 | rcu_gpnum_ovf(rnp, rdp); |
64db4cff PM |
1317 | return 1; |
1318 | } | |
1319 | ||
a82dcc76 | 1320 | /* |
3a19b46a PM |
1321 | * Has this CPU encountered a cond_resched_rcu_qs() since the |
1322 | * beginning of the grace period? For this to be the case, | |
1323 | * the CPU has to have noticed the current grace period. This | |
1324 | * might not be the case for nohz_full CPUs looping in the kernel. | |
a82dcc76 | 1325 | */ |
f79c3ad6 | 1326 | jtsq = jiffies_till_sched_qs; |
9226b10d | 1327 | ruqp = per_cpu_ptr(&rcu_dynticks.rcu_urgent_qs, rdp->cpu); |
3a19b46a | 1328 | if (time_after(jiffies, rdp->rsp->gp_start + jtsq) && |
9577df9a | 1329 | READ_ONCE(rdp->rcu_qs_ctr_snap) != per_cpu(rcu_dynticks.rcu_qs_ctr, rdp->cpu) && |
3a19b46a PM |
1330 | READ_ONCE(rdp->gpnum) == rnp->gpnum && !rdp->gpwrap) { |
1331 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("rqc")); | |
9b9500da | 1332 | rcu_gpnum_ovf(rnp, rdp); |
3a19b46a | 1333 | return 1; |
f79c3ad6 | 1334 | } else if (time_after(jiffies, rdp->rsp->gp_start + jtsq)) { |
9226b10d PM |
1335 | /* Load rcu_qs_ctr before store to rcu_urgent_qs. */ |
1336 | smp_store_release(ruqp, true); | |
3a19b46a PM |
1337 | } |
1338 | ||
38d30b33 PM |
1339 | /* Check for the CPU being offline. */ |
1340 | if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp))) { | |
f7f7bac9 | 1341 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl")); |
a82dcc76 | 1342 | rdp->offline_fqs++; |
9b9500da | 1343 | rcu_gpnum_ovf(rnp, rdp); |
a82dcc76 PM |
1344 | return 1; |
1345 | } | |
65d798f0 PM |
1346 | |
1347 | /* | |
4a81e832 PM |
1348 | * A CPU running for an extended time within the kernel can |
1349 | * delay RCU grace periods. When the CPU is in NO_HZ_FULL mode, | |
1350 | * even context-switching back and forth between a pair of | |
1351 | * in-kernel CPU-bound tasks cannot advance grace periods. | |
1352 | * So if the grace period is old enough, make the CPU pay attention. | |
1353 | * Note that the unsynchronized assignments to the per-CPU | |
0f9be8ca | 1354 | * rcu_need_heavy_qs variable are safe. Yes, setting of |
4a81e832 PM |
1355 | * bits can be lost, but they will be set again on the next |
1356 | * force-quiescent-state pass. So lost bit sets do not result | |
1357 | * in incorrect behavior, merely in a grace period lasting | |
1358 | * a few jiffies longer than it might otherwise. Because | |
1359 | * there are at most four threads involved, and because the | |
1360 | * updates are only once every few jiffies, the probability of | |
1361 | * lossage (and thus of slight grace-period extension) is | |
1362 | * quite low. | |
6193c76a | 1363 | */ |
0f9be8ca PM |
1364 | rnhqp = &per_cpu(rcu_dynticks.rcu_need_heavy_qs, rdp->cpu); |
1365 | if (!READ_ONCE(*rnhqp) && | |
1366 | (time_after(jiffies, rdp->rsp->gp_start + jtsq) || | |
1367 | time_after(jiffies, rdp->rsp->jiffies_resched))) { | |
1368 | WRITE_ONCE(*rnhqp, true); | |
9226b10d PM |
1369 | /* Store rcu_need_heavy_qs before rcu_urgent_qs. */ |
1370 | smp_store_release(ruqp, true); | |
f79c3ad6 | 1371 | rdp->rsp->jiffies_resched += jtsq; /* Re-enable beating. */ |
6193c76a PM |
1372 | } |
1373 | ||
28053bc7 | 1374 | /* |
9b9500da PM |
1375 | * If more than halfway to RCU CPU stall-warning time, do a |
1376 | * resched_cpu() to try to loosen things up a bit. Also check to | |
1377 | * see if the CPU is getting hammered with interrupts, but only | |
1378 | * once per grace period, just to keep the IPIs down to a dull roar. | |
28053bc7 | 1379 | */ |
9b9500da | 1380 | if (jiffies - rdp->rsp->gp_start > rcu_jiffies_till_stall_check() / 2) { |
28053bc7 | 1381 | resched_cpu(rdp->cpu); |
9b9500da PM |
1382 | if (IS_ENABLED(CONFIG_IRQ_WORK) && |
1383 | !rdp->rcu_iw_pending && rdp->rcu_iw_gpnum != rnp->gpnum && | |
1384 | (rnp->ffmask & rdp->grpmask)) { | |
1385 | init_irq_work(&rdp->rcu_iw, rcu_iw_handler); | |
1386 | rdp->rcu_iw_pending = true; | |
1387 | rdp->rcu_iw_gpnum = rnp->gpnum; | |
1388 | irq_work_queue_on(&rdp->rcu_iw, rdp->cpu); | |
1389 | } | |
1390 | } | |
4914950a | 1391 | |
a82dcc76 | 1392 | return 0; |
64db4cff PM |
1393 | } |
1394 | ||
64db4cff PM |
1395 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
1396 | { | |
cb1e78cf | 1397 | unsigned long j = jiffies; |
6193c76a | 1398 | unsigned long j1; |
26cdfedf PM |
1399 | |
1400 | rsp->gp_start = j; | |
1401 | smp_wmb(); /* Record start time before stall time. */ | |
6193c76a | 1402 | j1 = rcu_jiffies_till_stall_check(); |
7d0ae808 | 1403 | WRITE_ONCE(rsp->jiffies_stall, j + j1); |
6193c76a | 1404 | rsp->jiffies_resched = j + j1 / 2; |
7d0ae808 | 1405 | rsp->n_force_qs_gpstart = READ_ONCE(rsp->n_force_qs); |
64db4cff PM |
1406 | } |
1407 | ||
6b50e119 PM |
1408 | /* |
1409 | * Convert a ->gp_state value to a character string. | |
1410 | */ | |
1411 | static const char *gp_state_getname(short gs) | |
1412 | { | |
1413 | if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names)) | |
1414 | return "???"; | |
1415 | return gp_state_names[gs]; | |
1416 | } | |
1417 | ||
fb81a44b PM |
1418 | /* |
1419 | * Complain about starvation of grace-period kthread. | |
1420 | */ | |
1421 | static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp) | |
1422 | { | |
1423 | unsigned long gpa; | |
1424 | unsigned long j; | |
1425 | ||
1426 | j = jiffies; | |
7d0ae808 | 1427 | gpa = READ_ONCE(rsp->gp_activity); |
b1adb3e2 | 1428 | if (j - gpa > 2 * HZ) { |
96036c43 | 1429 | pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx ->cpu=%d\n", |
81e701e4 | 1430 | rsp->name, j - gpa, |
319362c9 | 1431 | rsp->gpnum, rsp->completed, |
6b50e119 PM |
1432 | rsp->gp_flags, |
1433 | gp_state_getname(rsp->gp_state), rsp->gp_state, | |
96036c43 PM |
1434 | rsp->gp_kthread ? rsp->gp_kthread->state : ~0, |
1435 | rsp->gp_kthread ? task_cpu(rsp->gp_kthread) : -1); | |
86057b80 | 1436 | if (rsp->gp_kthread) { |
b1adb3e2 | 1437 | sched_show_task(rsp->gp_kthread); |
86057b80 PM |
1438 | wake_up_process(rsp->gp_kthread); |
1439 | } | |
b1adb3e2 | 1440 | } |
64db4cff PM |
1441 | } |
1442 | ||
b637a328 | 1443 | /* |
7aa92230 PM |
1444 | * Dump stacks of all tasks running on stalled CPUs. First try using |
1445 | * NMIs, but fall back to manual remote stack tracing on architectures | |
1446 | * that don't support NMI-based stack dumps. The NMI-triggered stack | |
1447 | * traces are more accurate because they are printed by the target CPU. | |
b637a328 PM |
1448 | */ |
1449 | static void rcu_dump_cpu_stacks(struct rcu_state *rsp) | |
1450 | { | |
1451 | int cpu; | |
1452 | unsigned long flags; | |
1453 | struct rcu_node *rnp; | |
1454 | ||
1455 | rcu_for_each_leaf_node(rsp, rnp) { | |
6cf10081 | 1456 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
7aa92230 PM |
1457 | for_each_leaf_node_possible_cpu(rnp, cpu) |
1458 | if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) | |
1459 | if (!trigger_single_cpu_backtrace(cpu)) | |
bc75e999 | 1460 | dump_cpu_task(cpu); |
67c583a7 | 1461 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
b637a328 PM |
1462 | } |
1463 | } | |
1464 | ||
8c7c4829 PM |
1465 | /* |
1466 | * If too much time has passed in the current grace period, and if | |
1467 | * so configured, go kick the relevant kthreads. | |
1468 | */ | |
1469 | static void rcu_stall_kick_kthreads(struct rcu_state *rsp) | |
1470 | { | |
1471 | unsigned long j; | |
1472 | ||
1473 | if (!rcu_kick_kthreads) | |
1474 | return; | |
1475 | j = READ_ONCE(rsp->jiffies_kick_kthreads); | |
aa3e0bf1 PM |
1476 | if (time_after(jiffies, j) && rsp->gp_kthread && |
1477 | (rcu_gp_in_progress(rsp) || READ_ONCE(rsp->gp_flags))) { | |
8c7c4829 | 1478 | WARN_ONCE(1, "Kicking %s grace-period kthread\n", rsp->name); |
5dffed1e | 1479 | rcu_ftrace_dump(DUMP_ALL); |
8c7c4829 PM |
1480 | wake_up_process(rsp->gp_kthread); |
1481 | WRITE_ONCE(rsp->jiffies_kick_kthreads, j + HZ); | |
1482 | } | |
1483 | } | |
1484 | ||
088e9d25 DBO |
1485 | static inline void panic_on_rcu_stall(void) |
1486 | { | |
1487 | if (sysctl_panic_on_rcu_stall) | |
1488 | panic("RCU Stall\n"); | |
1489 | } | |
1490 | ||
6ccd2ecd | 1491 | static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) |
64db4cff PM |
1492 | { |
1493 | int cpu; | |
1494 | long delta; | |
1495 | unsigned long flags; | |
6ccd2ecd PM |
1496 | unsigned long gpa; |
1497 | unsigned long j; | |
285fe294 | 1498 | int ndetected = 0; |
64db4cff | 1499 | struct rcu_node *rnp = rcu_get_root(rsp); |
53bb857c | 1500 | long totqlen = 0; |
64db4cff | 1501 | |
8c7c4829 PM |
1502 | /* Kick and suppress, if so configured. */ |
1503 | rcu_stall_kick_kthreads(rsp); | |
1504 | if (rcu_cpu_stall_suppress) | |
1505 | return; | |
1506 | ||
64db4cff PM |
1507 | /* Only let one CPU complain about others per time interval. */ |
1508 | ||
6cf10081 | 1509 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
7d0ae808 | 1510 | delta = jiffies - READ_ONCE(rsp->jiffies_stall); |
fc2219d4 | 1511 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
67c583a7 | 1512 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff PM |
1513 | return; |
1514 | } | |
7d0ae808 PM |
1515 | WRITE_ONCE(rsp->jiffies_stall, |
1516 | jiffies + 3 * rcu_jiffies_till_stall_check() + 3); | |
67c583a7 | 1517 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff | 1518 | |
8cdd32a9 PM |
1519 | /* |
1520 | * OK, time to rat on our buddy... | |
1521 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
1522 | * RCU CPU stall warnings. | |
1523 | */ | |
d7f3e207 | 1524 | pr_err("INFO: %s detected stalls on CPUs/tasks:", |
4300aa64 | 1525 | rsp->name); |
a858af28 | 1526 | print_cpu_stall_info_begin(); |
a0b6c9a7 | 1527 | rcu_for_each_leaf_node(rsp, rnp) { |
6cf10081 | 1528 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
9bc8b558 | 1529 | ndetected += rcu_print_task_stall(rnp); |
c8020a67 | 1530 | if (rnp->qsmask != 0) { |
bc75e999 MR |
1531 | for_each_leaf_node_possible_cpu(rnp, cpu) |
1532 | if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) { | |
1533 | print_cpu_stall_info(rsp, cpu); | |
c8020a67 PM |
1534 | ndetected++; |
1535 | } | |
1536 | } | |
67c583a7 | 1537 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff | 1538 | } |
a858af28 | 1539 | |
a858af28 | 1540 | print_cpu_stall_info_end(); |
53bb857c | 1541 | for_each_possible_cpu(cpu) |
15fecf89 PM |
1542 | totqlen += rcu_segcblist_n_cbs(&per_cpu_ptr(rsp->rda, |
1543 | cpu)->cblist); | |
83ebe63e | 1544 | pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n", |
eee05882 | 1545 | smp_processor_id(), (long)(jiffies - rsp->gp_start), |
83ebe63e | 1546 | (long)rsp->gpnum, (long)rsp->completed, totqlen); |
6ccd2ecd | 1547 | if (ndetected) { |
b637a328 | 1548 | rcu_dump_cpu_stacks(rsp); |
c4402b27 BP |
1549 | |
1550 | /* Complain about tasks blocking the grace period. */ | |
1551 | rcu_print_detail_task_stall(rsp); | |
6ccd2ecd | 1552 | } else { |
7d0ae808 PM |
1553 | if (READ_ONCE(rsp->gpnum) != gpnum || |
1554 | READ_ONCE(rsp->completed) == gpnum) { | |
6ccd2ecd PM |
1555 | pr_err("INFO: Stall ended before state dump start\n"); |
1556 | } else { | |
1557 | j = jiffies; | |
7d0ae808 | 1558 | gpa = READ_ONCE(rsp->gp_activity); |
237a0f21 | 1559 | pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", |
6ccd2ecd | 1560 | rsp->name, j - gpa, j, gpa, |
237a0f21 PM |
1561 | jiffies_till_next_fqs, |
1562 | rcu_get_root(rsp)->qsmask); | |
6ccd2ecd PM |
1563 | /* In this case, the current CPU might be at fault. */ |
1564 | sched_show_task(current); | |
1565 | } | |
1566 | } | |
c1dc0b9c | 1567 | |
fb81a44b PM |
1568 | rcu_check_gp_kthread_starvation(rsp); |
1569 | ||
088e9d25 DBO |
1570 | panic_on_rcu_stall(); |
1571 | ||
4cdfc175 | 1572 | force_quiescent_state(rsp); /* Kick them all. */ |
64db4cff PM |
1573 | } |
1574 | ||
1575 | static void print_cpu_stall(struct rcu_state *rsp) | |
1576 | { | |
53bb857c | 1577 | int cpu; |
64db4cff | 1578 | unsigned long flags; |
9b9500da | 1579 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
64db4cff | 1580 | struct rcu_node *rnp = rcu_get_root(rsp); |
53bb857c | 1581 | long totqlen = 0; |
64db4cff | 1582 | |
8c7c4829 PM |
1583 | /* Kick and suppress, if so configured. */ |
1584 | rcu_stall_kick_kthreads(rsp); | |
1585 | if (rcu_cpu_stall_suppress) | |
1586 | return; | |
1587 | ||
8cdd32a9 PM |
1588 | /* |
1589 | * OK, time to rat on ourselves... | |
1590 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
1591 | * RCU CPU stall warnings. | |
1592 | */ | |
d7f3e207 | 1593 | pr_err("INFO: %s self-detected stall on CPU", rsp->name); |
a858af28 | 1594 | print_cpu_stall_info_begin(); |
9b9500da | 1595 | raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags); |
a858af28 | 1596 | print_cpu_stall_info(rsp, smp_processor_id()); |
9b9500da | 1597 | raw_spin_unlock_irqrestore_rcu_node(rdp->mynode, flags); |
a858af28 | 1598 | print_cpu_stall_info_end(); |
53bb857c | 1599 | for_each_possible_cpu(cpu) |
15fecf89 PM |
1600 | totqlen += rcu_segcblist_n_cbs(&per_cpu_ptr(rsp->rda, |
1601 | cpu)->cblist); | |
83ebe63e PM |
1602 | pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n", |
1603 | jiffies - rsp->gp_start, | |
1604 | (long)rsp->gpnum, (long)rsp->completed, totqlen); | |
fb81a44b PM |
1605 | |
1606 | rcu_check_gp_kthread_starvation(rsp); | |
1607 | ||
bc1dce51 | 1608 | rcu_dump_cpu_stacks(rsp); |
c1dc0b9c | 1609 | |
6cf10081 | 1610 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
7d0ae808 PM |
1611 | if (ULONG_CMP_GE(jiffies, READ_ONCE(rsp->jiffies_stall))) |
1612 | WRITE_ONCE(rsp->jiffies_stall, | |
1613 | jiffies + 3 * rcu_jiffies_till_stall_check() + 3); | |
67c583a7 | 1614 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
c1dc0b9c | 1615 | |
088e9d25 DBO |
1616 | panic_on_rcu_stall(); |
1617 | ||
b021fe3e PZ |
1618 | /* |
1619 | * Attempt to revive the RCU machinery by forcing a context switch. | |
1620 | * | |
1621 | * A context switch would normally allow the RCU state machine to make | |
1622 | * progress and it could be we're stuck in kernel space without context | |
1623 | * switches for an entirely unreasonable amount of time. | |
1624 | */ | |
1625 | resched_cpu(smp_processor_id()); | |
64db4cff PM |
1626 | } |
1627 | ||
1628 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
1629 | { | |
26cdfedf PM |
1630 | unsigned long completed; |
1631 | unsigned long gpnum; | |
1632 | unsigned long gps; | |
bad6e139 PM |
1633 | unsigned long j; |
1634 | unsigned long js; | |
64db4cff PM |
1635 | struct rcu_node *rnp; |
1636 | ||
8c7c4829 PM |
1637 | if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) || |
1638 | !rcu_gp_in_progress(rsp)) | |
c68de209 | 1639 | return; |
8c7c4829 | 1640 | rcu_stall_kick_kthreads(rsp); |
cb1e78cf | 1641 | j = jiffies; |
26cdfedf PM |
1642 | |
1643 | /* | |
1644 | * Lots of memory barriers to reject false positives. | |
1645 | * | |
1646 | * The idea is to pick up rsp->gpnum, then rsp->jiffies_stall, | |
1647 | * then rsp->gp_start, and finally rsp->completed. These values | |
1648 | * are updated in the opposite order with memory barriers (or | |
1649 | * equivalent) during grace-period initialization and cleanup. | |
1650 | * Now, a false positive can occur if we get an new value of | |
1651 | * rsp->gp_start and a old value of rsp->jiffies_stall. But given | |
1652 | * the memory barriers, the only way that this can happen is if one | |
1653 | * grace period ends and another starts between these two fetches. | |
1654 | * Detect this by comparing rsp->completed with the previous fetch | |
1655 | * from rsp->gpnum. | |
1656 | * | |
1657 | * Given this check, comparisons of jiffies, rsp->jiffies_stall, | |
1658 | * and rsp->gp_start suffice to forestall false positives. | |
1659 | */ | |
7d0ae808 | 1660 | gpnum = READ_ONCE(rsp->gpnum); |
26cdfedf | 1661 | smp_rmb(); /* Pick up ->gpnum first... */ |
7d0ae808 | 1662 | js = READ_ONCE(rsp->jiffies_stall); |
26cdfedf | 1663 | smp_rmb(); /* ...then ->jiffies_stall before the rest... */ |
7d0ae808 | 1664 | gps = READ_ONCE(rsp->gp_start); |
26cdfedf | 1665 | smp_rmb(); /* ...and finally ->gp_start before ->completed. */ |
7d0ae808 | 1666 | completed = READ_ONCE(rsp->completed); |
26cdfedf PM |
1667 | if (ULONG_CMP_GE(completed, gpnum) || |
1668 | ULONG_CMP_LT(j, js) || | |
1669 | ULONG_CMP_GE(gps, js)) | |
1670 | return; /* No stall or GP completed since entering function. */ | |
64db4cff | 1671 | rnp = rdp->mynode; |
c96ea7cf | 1672 | if (rcu_gp_in_progress(rsp) && |
7d0ae808 | 1673 | (READ_ONCE(rnp->qsmask) & rdp->grpmask)) { |
64db4cff PM |
1674 | |
1675 | /* We haven't checked in, so go dump stack. */ | |
1676 | print_cpu_stall(rsp); | |
1677 | ||
bad6e139 PM |
1678 | } else if (rcu_gp_in_progress(rsp) && |
1679 | ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { | |
64db4cff | 1680 | |
bad6e139 | 1681 | /* They had a few time units to dump stack, so complain. */ |
6ccd2ecd | 1682 | print_other_cpu_stall(rsp, gpnum); |
64db4cff PM |
1683 | } |
1684 | } | |
1685 | ||
53d84e00 PM |
1686 | /** |
1687 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
1688 | * | |
1689 | * Set the stall-warning timeout way off into the future, thus preventing | |
1690 | * any RCU CPU stall-warning messages from appearing in the current set of | |
1691 | * RCU grace periods. | |
1692 | * | |
1693 | * The caller must disable hard irqs. | |
1694 | */ | |
1695 | void rcu_cpu_stall_reset(void) | |
1696 | { | |
6ce75a23 PM |
1697 | struct rcu_state *rsp; |
1698 | ||
1699 | for_each_rcu_flavor(rsp) | |
7d0ae808 | 1700 | WRITE_ONCE(rsp->jiffies_stall, jiffies + ULONG_MAX / 2); |
53d84e00 PM |
1701 | } |
1702 | ||
dc35c893 PM |
1703 | /* |
1704 | * Determine the value that ->completed will have at the end of the | |
1705 | * next subsequent grace period. This is used to tag callbacks so that | |
1706 | * a CPU can invoke callbacks in a timely fashion even if that CPU has | |
1707 | * been dyntick-idle for an extended period with callbacks under the | |
1708 | * influence of RCU_FAST_NO_HZ. | |
1709 | * | |
1710 | * The caller must hold rnp->lock with interrupts disabled. | |
1711 | */ | |
1712 | static unsigned long rcu_cbs_completed(struct rcu_state *rsp, | |
1713 | struct rcu_node *rnp) | |
1714 | { | |
c0b334c5 PM |
1715 | lockdep_assert_held(&rnp->lock); |
1716 | ||
dc35c893 PM |
1717 | /* |
1718 | * If RCU is idle, we just wait for the next grace period. | |
1719 | * But we can only be sure that RCU is idle if we are looking | |
1720 | * at the root rcu_node structure -- otherwise, a new grace | |
1721 | * period might have started, but just not yet gotten around | |
1722 | * to initializing the current non-root rcu_node structure. | |
1723 | */ | |
1724 | if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed) | |
1725 | return rnp->completed + 1; | |
1726 | ||
1727 | /* | |
1728 | * Otherwise, wait for a possible partial grace period and | |
1729 | * then the subsequent full grace period. | |
1730 | */ | |
1731 | return rnp->completed + 2; | |
1732 | } | |
1733 | ||
0446be48 PM |
1734 | /* |
1735 | * Trace-event helper function for rcu_start_future_gp() and | |
1736 | * rcu_nocb_wait_gp(). | |
1737 | */ | |
1738 | static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, | |
e66c33d5 | 1739 | unsigned long c, const char *s) |
0446be48 PM |
1740 | { |
1741 | trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, | |
1742 | rnp->completed, c, rnp->level, | |
1743 | rnp->grplo, rnp->grphi, s); | |
1744 | } | |
1745 | ||
1746 | /* | |
1747 | * Start some future grace period, as needed to handle newly arrived | |
1748 | * callbacks. The required future grace periods are recorded in each | |
48a7639c PM |
1749 | * rcu_node structure's ->need_future_gp field. Returns true if there |
1750 | * is reason to awaken the grace-period kthread. | |
0446be48 PM |
1751 | * |
1752 | * The caller must hold the specified rcu_node structure's ->lock. | |
1753 | */ | |
48a7639c PM |
1754 | static bool __maybe_unused |
1755 | rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, | |
1756 | unsigned long *c_out) | |
0446be48 PM |
1757 | { |
1758 | unsigned long c; | |
48a7639c | 1759 | bool ret = false; |
0446be48 PM |
1760 | struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); |
1761 | ||
c0b334c5 PM |
1762 | lockdep_assert_held(&rnp->lock); |
1763 | ||
0446be48 PM |
1764 | /* |
1765 | * Pick up grace-period number for new callbacks. If this | |
1766 | * grace period is already marked as needed, return to the caller. | |
1767 | */ | |
1768 | c = rcu_cbs_completed(rdp->rsp, rnp); | |
f7f7bac9 | 1769 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); |
0446be48 | 1770 | if (rnp->need_future_gp[c & 0x1]) { |
f7f7bac9 | 1771 | trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); |
48a7639c | 1772 | goto out; |
0446be48 PM |
1773 | } |
1774 | ||
1775 | /* | |
1776 | * If either this rcu_node structure or the root rcu_node structure | |
1777 | * believe that a grace period is in progress, then we must wait | |
1778 | * for the one following, which is in "c". Because our request | |
1779 | * will be noticed at the end of the current grace period, we don't | |
48bd8e9b PK |
1780 | * need to explicitly start one. We only do the lockless check |
1781 | * of rnp_root's fields if the current rcu_node structure thinks | |
1782 | * there is no grace period in flight, and because we hold rnp->lock, | |
1783 | * the only possible change is when rnp_root's two fields are | |
1784 | * equal, in which case rnp_root->gpnum might be concurrently | |
1785 | * incremented. But that is OK, as it will just result in our | |
1786 | * doing some extra useless work. | |
0446be48 PM |
1787 | */ |
1788 | if (rnp->gpnum != rnp->completed || | |
7d0ae808 | 1789 | READ_ONCE(rnp_root->gpnum) != READ_ONCE(rnp_root->completed)) { |
0446be48 | 1790 | rnp->need_future_gp[c & 0x1]++; |
f7f7bac9 | 1791 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); |
48a7639c | 1792 | goto out; |
0446be48 PM |
1793 | } |
1794 | ||
1795 | /* | |
1796 | * There might be no grace period in progress. If we don't already | |
1797 | * hold it, acquire the root rcu_node structure's lock in order to | |
1798 | * start one (if needed). | |
1799 | */ | |
2a67e741 PZ |
1800 | if (rnp != rnp_root) |
1801 | raw_spin_lock_rcu_node(rnp_root); | |
0446be48 PM |
1802 | |
1803 | /* | |
1804 | * Get a new grace-period number. If there really is no grace | |
1805 | * period in progress, it will be smaller than the one we obtained | |
15fecf89 | 1806 | * earlier. Adjust callbacks as needed. |
0446be48 PM |
1807 | */ |
1808 | c = rcu_cbs_completed(rdp->rsp, rnp_root); | |
15fecf89 PM |
1809 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
1810 | (void)rcu_segcblist_accelerate(&rdp->cblist, c); | |
0446be48 PM |
1811 | |
1812 | /* | |
1813 | * If the needed for the required grace period is already | |
1814 | * recorded, trace and leave. | |
1815 | */ | |
1816 | if (rnp_root->need_future_gp[c & 0x1]) { | |
f7f7bac9 | 1817 | trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); |
0446be48 PM |
1818 | goto unlock_out; |
1819 | } | |
1820 | ||
1821 | /* Record the need for the future grace period. */ | |
1822 | rnp_root->need_future_gp[c & 0x1]++; | |
1823 | ||
1824 | /* If a grace period is not already in progress, start one. */ | |
1825 | if (rnp_root->gpnum != rnp_root->completed) { | |
f7f7bac9 | 1826 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); |
0446be48 | 1827 | } else { |
f7f7bac9 | 1828 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); |
48a7639c | 1829 | ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); |
0446be48 PM |
1830 | } |
1831 | unlock_out: | |
1832 | if (rnp != rnp_root) | |
67c583a7 | 1833 | raw_spin_unlock_rcu_node(rnp_root); |
48a7639c PM |
1834 | out: |
1835 | if (c_out != NULL) | |
1836 | *c_out = c; | |
1837 | return ret; | |
0446be48 PM |
1838 | } |
1839 | ||
1840 | /* | |
1841 | * Clean up any old requests for the just-ended grace period. Also return | |
d1e4f01d | 1842 | * whether any additional grace periods have been requested. |
0446be48 PM |
1843 | */ |
1844 | static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) | |
1845 | { | |
1846 | int c = rnp->completed; | |
1847 | int needmore; | |
1848 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
1849 | ||
0446be48 PM |
1850 | rnp->need_future_gp[c & 0x1] = 0; |
1851 | needmore = rnp->need_future_gp[(c + 1) & 0x1]; | |
f7f7bac9 SRRH |
1852 | trace_rcu_future_gp(rnp, rdp, c, |
1853 | needmore ? TPS("CleanupMore") : TPS("Cleanup")); | |
0446be48 PM |
1854 | return needmore; |
1855 | } | |
1856 | ||
48a7639c PM |
1857 | /* |
1858 | * Awaken the grace-period kthread for the specified flavor of RCU. | |
1859 | * Don't do a self-awaken, and don't bother awakening when there is | |
1860 | * nothing for the grace-period kthread to do (as in several CPUs | |
1861 | * raced to awaken, and we lost), and finally don't try to awaken | |
1862 | * a kthread that has not yet been created. | |
1863 | */ | |
1864 | static void rcu_gp_kthread_wake(struct rcu_state *rsp) | |
1865 | { | |
1866 | if (current == rsp->gp_kthread || | |
7d0ae808 | 1867 | !READ_ONCE(rsp->gp_flags) || |
48a7639c PM |
1868 | !rsp->gp_kthread) |
1869 | return; | |
abedf8e2 | 1870 | swake_up(&rsp->gp_wq); |
48a7639c PM |
1871 | } |
1872 | ||
dc35c893 PM |
1873 | /* |
1874 | * If there is room, assign a ->completed number to any callbacks on | |
1875 | * this CPU that have not already been assigned. Also accelerate any | |
1876 | * callbacks that were previously assigned a ->completed number that has | |
1877 | * since proven to be too conservative, which can happen if callbacks get | |
1878 | * assigned a ->completed number while RCU is idle, but with reference to | |
1879 | * a non-root rcu_node structure. This function is idempotent, so it does | |
48a7639c PM |
1880 | * not hurt to call it repeatedly. Returns an flag saying that we should |
1881 | * awaken the RCU grace-period kthread. | |
dc35c893 PM |
1882 | * |
1883 | * The caller must hold rnp->lock with interrupts disabled. | |
1884 | */ | |
48a7639c | 1885 | static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, |
dc35c893 PM |
1886 | struct rcu_data *rdp) |
1887 | { | |
15fecf89 | 1888 | bool ret = false; |
dc35c893 | 1889 | |
c0b334c5 PM |
1890 | lockdep_assert_held(&rnp->lock); |
1891 | ||
15fecf89 PM |
1892 | /* If no pending (not yet ready to invoke) callbacks, nothing to do. */ |
1893 | if (!rcu_segcblist_pend_cbs(&rdp->cblist)) | |
48a7639c | 1894 | return false; |
dc35c893 PM |
1895 | |
1896 | /* | |
15fecf89 PM |
1897 | * Callbacks are often registered with incomplete grace-period |
1898 | * information. Something about the fact that getting exact | |
1899 | * information requires acquiring a global lock... RCU therefore | |
1900 | * makes a conservative estimate of the grace period number at which | |
1901 | * a given callback will become ready to invoke. The following | |
1902 | * code checks this estimate and improves it when possible, thus | |
1903 | * accelerating callback invocation to an earlier grace-period | |
1904 | * number. | |
dc35c893 | 1905 | */ |
15fecf89 PM |
1906 | if (rcu_segcblist_accelerate(&rdp->cblist, rcu_cbs_completed(rsp, rnp))) |
1907 | ret = rcu_start_future_gp(rnp, rdp, NULL); | |
6d4b418c PM |
1908 | |
1909 | /* Trace depending on how much we were able to accelerate. */ | |
15fecf89 | 1910 | if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL)) |
f7f7bac9 | 1911 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB")); |
6d4b418c | 1912 | else |
f7f7bac9 | 1913 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB")); |
48a7639c | 1914 | return ret; |
dc35c893 PM |
1915 | } |
1916 | ||
1917 | /* | |
1918 | * Move any callbacks whose grace period has completed to the | |
1919 | * RCU_DONE_TAIL sublist, then compact the remaining sublists and | |
1920 | * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL | |
1921 | * sublist. This function is idempotent, so it does not hurt to | |
1922 | * invoke it repeatedly. As long as it is not invoked -too- often... | |
48a7639c | 1923 | * Returns true if the RCU grace-period kthread needs to be awakened. |
dc35c893 PM |
1924 | * |
1925 | * The caller must hold rnp->lock with interrupts disabled. | |
1926 | */ | |
48a7639c | 1927 | static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, |
dc35c893 PM |
1928 | struct rcu_data *rdp) |
1929 | { | |
c0b334c5 PM |
1930 | lockdep_assert_held(&rnp->lock); |
1931 | ||
15fecf89 PM |
1932 | /* If no pending (not yet ready to invoke) callbacks, nothing to do. */ |
1933 | if (!rcu_segcblist_pend_cbs(&rdp->cblist)) | |
48a7639c | 1934 | return false; |
dc35c893 PM |
1935 | |
1936 | /* | |
1937 | * Find all callbacks whose ->completed numbers indicate that they | |
1938 | * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. | |
1939 | */ | |
15fecf89 | 1940 | rcu_segcblist_advance(&rdp->cblist, rnp->completed); |
dc35c893 PM |
1941 | |
1942 | /* Classify any remaining callbacks. */ | |
48a7639c | 1943 | return rcu_accelerate_cbs(rsp, rnp, rdp); |
dc35c893 PM |
1944 | } |
1945 | ||
d09b62df | 1946 | /* |
ba9fbe95 PM |
1947 | * Update CPU-local rcu_data state to record the beginnings and ends of |
1948 | * grace periods. The caller must hold the ->lock of the leaf rcu_node | |
1949 | * structure corresponding to the current CPU, and must have irqs disabled. | |
48a7639c | 1950 | * Returns true if the grace-period kthread needs to be awakened. |
d09b62df | 1951 | */ |
48a7639c PM |
1952 | static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, |
1953 | struct rcu_data *rdp) | |
d09b62df | 1954 | { |
48a7639c | 1955 | bool ret; |
3563a438 | 1956 | bool need_gp; |
48a7639c | 1957 | |
c0b334c5 PM |
1958 | lockdep_assert_held(&rnp->lock); |
1959 | ||
ba9fbe95 | 1960 | /* Handle the ends of any preceding grace periods first. */ |
e3663b10 | 1961 | if (rdp->completed == rnp->completed && |
7d0ae808 | 1962 | !unlikely(READ_ONCE(rdp->gpwrap))) { |
d09b62df | 1963 | |
ba9fbe95 | 1964 | /* No grace period end, so just accelerate recent callbacks. */ |
48a7639c | 1965 | ret = rcu_accelerate_cbs(rsp, rnp, rdp); |
d09b62df | 1966 | |
dc35c893 PM |
1967 | } else { |
1968 | ||
1969 | /* Advance callbacks. */ | |
48a7639c | 1970 | ret = rcu_advance_cbs(rsp, rnp, rdp); |
d09b62df PM |
1971 | |
1972 | /* Remember that we saw this grace-period completion. */ | |
1973 | rdp->completed = rnp->completed; | |
f7f7bac9 | 1974 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend")); |
d09b62df | 1975 | } |
398ebe60 | 1976 | |
7d0ae808 | 1977 | if (rdp->gpnum != rnp->gpnum || unlikely(READ_ONCE(rdp->gpwrap))) { |
6eaef633 PM |
1978 | /* |
1979 | * If the current grace period is waiting for this CPU, | |
1980 | * set up to detect a quiescent state, otherwise don't | |
1981 | * go looking for one. | |
1982 | */ | |
1983 | rdp->gpnum = rnp->gpnum; | |
f7f7bac9 | 1984 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart")); |
3563a438 PM |
1985 | need_gp = !!(rnp->qsmask & rdp->grpmask); |
1986 | rdp->cpu_no_qs.b.norm = need_gp; | |
9577df9a | 1987 | rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_dynticks.rcu_qs_ctr); |
3563a438 | 1988 | rdp->core_needs_qs = need_gp; |
6eaef633 | 1989 | zero_cpu_stall_ticks(rdp); |
7d0ae808 | 1990 | WRITE_ONCE(rdp->gpwrap, false); |
9b9500da | 1991 | rcu_gpnum_ovf(rnp, rdp); |
6eaef633 | 1992 | } |
48a7639c | 1993 | return ret; |
6eaef633 PM |
1994 | } |
1995 | ||
d34ea322 | 1996 | static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) |
6eaef633 PM |
1997 | { |
1998 | unsigned long flags; | |
48a7639c | 1999 | bool needwake; |
6eaef633 PM |
2000 | struct rcu_node *rnp; |
2001 | ||
2002 | local_irq_save(flags); | |
2003 | rnp = rdp->mynode; | |
7d0ae808 PM |
2004 | if ((rdp->gpnum == READ_ONCE(rnp->gpnum) && |
2005 | rdp->completed == READ_ONCE(rnp->completed) && | |
2006 | !unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */ | |
2a67e741 | 2007 | !raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */ |
6eaef633 PM |
2008 | local_irq_restore(flags); |
2009 | return; | |
2010 | } | |
48a7639c | 2011 | needwake = __note_gp_changes(rsp, rnp, rdp); |
67c583a7 | 2012 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
48a7639c PM |
2013 | if (needwake) |
2014 | rcu_gp_kthread_wake(rsp); | |
6eaef633 PM |
2015 | } |
2016 | ||
0f41c0dd PM |
2017 | static void rcu_gp_slow(struct rcu_state *rsp, int delay) |
2018 | { | |
2019 | if (delay > 0 && | |
2020 | !(rsp->gpnum % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay))) | |
2021 | schedule_timeout_uninterruptible(delay); | |
2022 | } | |
2023 | ||
b3dbec76 | 2024 | /* |
45fed3e7 | 2025 | * Initialize a new grace period. Return false if no grace period required. |
b3dbec76 | 2026 | */ |
45fed3e7 | 2027 | static bool rcu_gp_init(struct rcu_state *rsp) |
b3dbec76 | 2028 | { |
0aa04b05 | 2029 | unsigned long oldmask; |
b3dbec76 | 2030 | struct rcu_data *rdp; |
7fdefc10 | 2031 | struct rcu_node *rnp = rcu_get_root(rsp); |
b3dbec76 | 2032 | |
7d0ae808 | 2033 | WRITE_ONCE(rsp->gp_activity, jiffies); |
2a67e741 | 2034 | raw_spin_lock_irq_rcu_node(rnp); |
7d0ae808 | 2035 | if (!READ_ONCE(rsp->gp_flags)) { |
f7be8209 | 2036 | /* Spurious wakeup, tell caller to go back to sleep. */ |
67c583a7 | 2037 | raw_spin_unlock_irq_rcu_node(rnp); |
45fed3e7 | 2038 | return false; |
f7be8209 | 2039 | } |
7d0ae808 | 2040 | WRITE_ONCE(rsp->gp_flags, 0); /* Clear all flags: New grace period. */ |
b3dbec76 | 2041 | |
f7be8209 PM |
2042 | if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) { |
2043 | /* | |
2044 | * Grace period already in progress, don't start another. | |
2045 | * Not supposed to be able to happen. | |
2046 | */ | |
67c583a7 | 2047 | raw_spin_unlock_irq_rcu_node(rnp); |
45fed3e7 | 2048 | return false; |
7fdefc10 PM |
2049 | } |
2050 | ||
7fdefc10 | 2051 | /* Advance to a new grace period and initialize state. */ |
26cdfedf | 2052 | record_gp_stall_check_time(rsp); |
765a3f4f PM |
2053 | /* Record GP times before starting GP, hence smp_store_release(). */ |
2054 | smp_store_release(&rsp->gpnum, rsp->gpnum + 1); | |
f7f7bac9 | 2055 | trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start")); |
67c583a7 | 2056 | raw_spin_unlock_irq_rcu_node(rnp); |
7fdefc10 | 2057 | |
0aa04b05 PM |
2058 | /* |
2059 | * Apply per-leaf buffered online and offline operations to the | |
2060 | * rcu_node tree. Note that this new grace period need not wait | |
2061 | * for subsequent online CPUs, and that quiescent-state forcing | |
2062 | * will handle subsequent offline CPUs. | |
2063 | */ | |
2064 | rcu_for_each_leaf_node(rsp, rnp) { | |
0f41c0dd | 2065 | rcu_gp_slow(rsp, gp_preinit_delay); |
2a67e741 | 2066 | raw_spin_lock_irq_rcu_node(rnp); |
0aa04b05 PM |
2067 | if (rnp->qsmaskinit == rnp->qsmaskinitnext && |
2068 | !rnp->wait_blkd_tasks) { | |
2069 | /* Nothing to do on this leaf rcu_node structure. */ | |
67c583a7 | 2070 | raw_spin_unlock_irq_rcu_node(rnp); |
0aa04b05 PM |
2071 | continue; |
2072 | } | |
2073 | ||
2074 | /* Record old state, apply changes to ->qsmaskinit field. */ | |
2075 | oldmask = rnp->qsmaskinit; | |
2076 | rnp->qsmaskinit = rnp->qsmaskinitnext; | |
2077 | ||
2078 | /* If zero-ness of ->qsmaskinit changed, propagate up tree. */ | |
2079 | if (!oldmask != !rnp->qsmaskinit) { | |
2080 | if (!oldmask) /* First online CPU for this rcu_node. */ | |
2081 | rcu_init_new_rnp(rnp); | |
2082 | else if (rcu_preempt_has_tasks(rnp)) /* blocked tasks */ | |
2083 | rnp->wait_blkd_tasks = true; | |
2084 | else /* Last offline CPU and can propagate. */ | |
2085 | rcu_cleanup_dead_rnp(rnp); | |
2086 | } | |
2087 | ||
2088 | /* | |
2089 | * If all waited-on tasks from prior grace period are | |
2090 | * done, and if all this rcu_node structure's CPUs are | |
2091 | * still offline, propagate up the rcu_node tree and | |
2092 | * clear ->wait_blkd_tasks. Otherwise, if one of this | |
2093 | * rcu_node structure's CPUs has since come back online, | |
2094 | * simply clear ->wait_blkd_tasks (but rcu_cleanup_dead_rnp() | |
2095 | * checks for this, so just call it unconditionally). | |
2096 | */ | |
2097 | if (rnp->wait_blkd_tasks && | |
2098 | (!rcu_preempt_has_tasks(rnp) || | |
2099 | rnp->qsmaskinit)) { | |
2100 | rnp->wait_blkd_tasks = false; | |
2101 | rcu_cleanup_dead_rnp(rnp); | |
2102 | } | |
2103 | ||
67c583a7 | 2104 | raw_spin_unlock_irq_rcu_node(rnp); |
0aa04b05 | 2105 | } |
7fdefc10 PM |
2106 | |
2107 | /* | |
2108 | * Set the quiescent-state-needed bits in all the rcu_node | |
2109 | * structures for all currently online CPUs in breadth-first order, | |
2110 | * starting from the root rcu_node structure, relying on the layout | |
2111 | * of the tree within the rsp->node[] array. Note that other CPUs | |
2112 | * will access only the leaves of the hierarchy, thus seeing that no | |
2113 | * grace period is in progress, at least until the corresponding | |
590d1757 | 2114 | * leaf node has been initialized. |
7fdefc10 PM |
2115 | * |
2116 | * The grace period cannot complete until the initialization | |
2117 | * process finishes, because this kthread handles both. | |
2118 | */ | |
2119 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
0f41c0dd | 2120 | rcu_gp_slow(rsp, gp_init_delay); |
2a67e741 | 2121 | raw_spin_lock_irq_rcu_node(rnp); |
b3dbec76 | 2122 | rdp = this_cpu_ptr(rsp->rda); |
7fdefc10 PM |
2123 | rcu_preempt_check_blocked_tasks(rnp); |
2124 | rnp->qsmask = rnp->qsmaskinit; | |
7d0ae808 | 2125 | WRITE_ONCE(rnp->gpnum, rsp->gpnum); |
3f47da0f | 2126 | if (WARN_ON_ONCE(rnp->completed != rsp->completed)) |
7d0ae808 | 2127 | WRITE_ONCE(rnp->completed, rsp->completed); |
7fdefc10 | 2128 | if (rnp == rdp->mynode) |
48a7639c | 2129 | (void)__note_gp_changes(rsp, rnp, rdp); |
7fdefc10 PM |
2130 | rcu_preempt_boost_start_gp(rnp); |
2131 | trace_rcu_grace_period_init(rsp->name, rnp->gpnum, | |
2132 | rnp->level, rnp->grplo, | |
2133 | rnp->grphi, rnp->qsmask); | |
67c583a7 | 2134 | raw_spin_unlock_irq_rcu_node(rnp); |
bde6c3aa | 2135 | cond_resched_rcu_qs(); |
7d0ae808 | 2136 | WRITE_ONCE(rsp->gp_activity, jiffies); |
7fdefc10 | 2137 | } |
b3dbec76 | 2138 | |
45fed3e7 | 2139 | return true; |
7fdefc10 | 2140 | } |
b3dbec76 | 2141 | |
b9a425cf | 2142 | /* |
d5374226 LR |
2143 | * Helper function for swait_event_idle() wakeup at force-quiescent-state |
2144 | * time. | |
b9a425cf PM |
2145 | */ |
2146 | static bool rcu_gp_fqs_check_wake(struct rcu_state *rsp, int *gfp) | |
2147 | { | |
2148 | struct rcu_node *rnp = rcu_get_root(rsp); | |
2149 | ||
2150 | /* Someone like call_rcu() requested a force-quiescent-state scan. */ | |
2151 | *gfp = READ_ONCE(rsp->gp_flags); | |
2152 | if (*gfp & RCU_GP_FLAG_FQS) | |
2153 | return true; | |
2154 | ||
2155 | /* The current grace period has completed. */ | |
2156 | if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)) | |
2157 | return true; | |
2158 | ||
2159 | return false; | |
2160 | } | |
2161 | ||
4cdfc175 PM |
2162 | /* |
2163 | * Do one round of quiescent-state forcing. | |
2164 | */ | |
77f81fe0 | 2165 | static void rcu_gp_fqs(struct rcu_state *rsp, bool first_time) |
4cdfc175 | 2166 | { |
4cdfc175 PM |
2167 | struct rcu_node *rnp = rcu_get_root(rsp); |
2168 | ||
7d0ae808 | 2169 | WRITE_ONCE(rsp->gp_activity, jiffies); |
4cdfc175 | 2170 | rsp->n_force_qs++; |
77f81fe0 | 2171 | if (first_time) { |
4cdfc175 | 2172 | /* Collect dyntick-idle snapshots. */ |
fe5ac724 | 2173 | force_qs_rnp(rsp, dyntick_save_progress_counter); |
4cdfc175 PM |
2174 | } else { |
2175 | /* Handle dyntick-idle and offline CPUs. */ | |
fe5ac724 | 2176 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
4cdfc175 PM |
2177 | } |
2178 | /* Clear flag to prevent immediate re-entry. */ | |
7d0ae808 | 2179 | if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { |
2a67e741 | 2180 | raw_spin_lock_irq_rcu_node(rnp); |
7d0ae808 PM |
2181 | WRITE_ONCE(rsp->gp_flags, |
2182 | READ_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS); | |
67c583a7 | 2183 | raw_spin_unlock_irq_rcu_node(rnp); |
4cdfc175 | 2184 | } |
4cdfc175 PM |
2185 | } |
2186 | ||
7fdefc10 PM |
2187 | /* |
2188 | * Clean up after the old grace period. | |
2189 | */ | |
4cdfc175 | 2190 | static void rcu_gp_cleanup(struct rcu_state *rsp) |
7fdefc10 PM |
2191 | { |
2192 | unsigned long gp_duration; | |
48a7639c | 2193 | bool needgp = false; |
dae6e64d | 2194 | int nocb = 0; |
7fdefc10 PM |
2195 | struct rcu_data *rdp; |
2196 | struct rcu_node *rnp = rcu_get_root(rsp); | |
abedf8e2 | 2197 | struct swait_queue_head *sq; |
b3dbec76 | 2198 | |
7d0ae808 | 2199 | WRITE_ONCE(rsp->gp_activity, jiffies); |
2a67e741 | 2200 | raw_spin_lock_irq_rcu_node(rnp); |
7fdefc10 PM |
2201 | gp_duration = jiffies - rsp->gp_start; |
2202 | if (gp_duration > rsp->gp_max) | |
2203 | rsp->gp_max = gp_duration; | |
b3dbec76 | 2204 | |
7fdefc10 PM |
2205 | /* |
2206 | * We know the grace period is complete, but to everyone else | |
2207 | * it appears to still be ongoing. But it is also the case | |
2208 | * that to everyone else it looks like there is nothing that | |
2209 | * they can do to advance the grace period. It is therefore | |
2210 | * safe for us to drop the lock in order to mark the grace | |
2211 | * period as completed in all of the rcu_node structures. | |
7fdefc10 | 2212 | */ |
67c583a7 | 2213 | raw_spin_unlock_irq_rcu_node(rnp); |
b3dbec76 | 2214 | |
5d4b8659 PM |
2215 | /* |
2216 | * Propagate new ->completed value to rcu_node structures so | |
2217 | * that other CPUs don't have to wait until the start of the next | |
2218 | * grace period to process their callbacks. This also avoids | |
2219 | * some nasty RCU grace-period initialization races by forcing | |
2220 | * the end of the current grace period to be completely recorded in | |
2221 | * all of the rcu_node structures before the beginning of the next | |
2222 | * grace period is recorded in any of the rcu_node structures. | |
2223 | */ | |
2224 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
2a67e741 | 2225 | raw_spin_lock_irq_rcu_node(rnp); |
5c60d25f PM |
2226 | WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
2227 | WARN_ON_ONCE(rnp->qsmask); | |
7d0ae808 | 2228 | WRITE_ONCE(rnp->completed, rsp->gpnum); |
b11cc576 PM |
2229 | rdp = this_cpu_ptr(rsp->rda); |
2230 | if (rnp == rdp->mynode) | |
48a7639c | 2231 | needgp = __note_gp_changes(rsp, rnp, rdp) || needgp; |
78e4bc34 | 2232 | /* smp_mb() provided by prior unlock-lock pair. */ |
0446be48 | 2233 | nocb += rcu_future_gp_cleanup(rsp, rnp); |
065bb78c | 2234 | sq = rcu_nocb_gp_get(rnp); |
67c583a7 | 2235 | raw_spin_unlock_irq_rcu_node(rnp); |
065bb78c | 2236 | rcu_nocb_gp_cleanup(sq); |
bde6c3aa | 2237 | cond_resched_rcu_qs(); |
7d0ae808 | 2238 | WRITE_ONCE(rsp->gp_activity, jiffies); |
0f41c0dd | 2239 | rcu_gp_slow(rsp, gp_cleanup_delay); |
7fdefc10 | 2240 | } |
5d4b8659 | 2241 | rnp = rcu_get_root(rsp); |
2a67e741 | 2242 | raw_spin_lock_irq_rcu_node(rnp); /* Order GP before ->completed update. */ |
dae6e64d | 2243 | rcu_nocb_gp_set(rnp, nocb); |
7fdefc10 | 2244 | |
765a3f4f | 2245 | /* Declare grace period done. */ |
7d0ae808 | 2246 | WRITE_ONCE(rsp->completed, rsp->gpnum); |
f7f7bac9 | 2247 | trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end")); |
77f81fe0 | 2248 | rsp->gp_state = RCU_GP_IDLE; |
5d4b8659 | 2249 | rdp = this_cpu_ptr(rsp->rda); |
48a7639c PM |
2250 | /* Advance CBs to reduce false positives below. */ |
2251 | needgp = rcu_advance_cbs(rsp, rnp, rdp) || needgp; | |
2252 | if (needgp || cpu_needs_another_gp(rsp, rdp)) { | |
7d0ae808 | 2253 | WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT); |
bb311ecc | 2254 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2255 | READ_ONCE(rsp->gpnum), |
bb311ecc PM |
2256 | TPS("newreq")); |
2257 | } | |
67c583a7 | 2258 | raw_spin_unlock_irq_rcu_node(rnp); |
7fdefc10 PM |
2259 | } |
2260 | ||
2261 | /* | |
2262 | * Body of kthread that handles grace periods. | |
2263 | */ | |
2264 | static int __noreturn rcu_gp_kthread(void *arg) | |
2265 | { | |
77f81fe0 | 2266 | bool first_gp_fqs; |
88d6df61 | 2267 | int gf; |
d40011f6 | 2268 | unsigned long j; |
4cdfc175 | 2269 | int ret; |
7fdefc10 PM |
2270 | struct rcu_state *rsp = arg; |
2271 | struct rcu_node *rnp = rcu_get_root(rsp); | |
2272 | ||
5871968d | 2273 | rcu_bind_gp_kthread(); |
7fdefc10 PM |
2274 | for (;;) { |
2275 | ||
2276 | /* Handle grace-period start. */ | |
2277 | for (;;) { | |
63c4db78 | 2278 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2279 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2280 | TPS("reqwait")); |
afea227f | 2281 | rsp->gp_state = RCU_GP_WAIT_GPS; |
d5374226 LR |
2282 | swait_event_idle(rsp->gp_wq, READ_ONCE(rsp->gp_flags) & |
2283 | RCU_GP_FLAG_INIT); | |
319362c9 | 2284 | rsp->gp_state = RCU_GP_DONE_GPS; |
78e4bc34 | 2285 | /* Locking provides needed memory barrier. */ |
f7be8209 | 2286 | if (rcu_gp_init(rsp)) |
7fdefc10 | 2287 | break; |
bde6c3aa | 2288 | cond_resched_rcu_qs(); |
7d0ae808 | 2289 | WRITE_ONCE(rsp->gp_activity, jiffies); |
73a860cd | 2290 | WARN_ON(signal_pending(current)); |
63c4db78 | 2291 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2292 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2293 | TPS("reqwaitsig")); |
7fdefc10 | 2294 | } |
cabc49c1 | 2295 | |
4cdfc175 | 2296 | /* Handle quiescent-state forcing. */ |
77f81fe0 | 2297 | first_gp_fqs = true; |
d40011f6 PM |
2298 | j = jiffies_till_first_fqs; |
2299 | if (j > HZ) { | |
2300 | j = HZ; | |
2301 | jiffies_till_first_fqs = HZ; | |
2302 | } | |
88d6df61 | 2303 | ret = 0; |
cabc49c1 | 2304 | for (;;) { |
8c7c4829 | 2305 | if (!ret) { |
88d6df61 | 2306 | rsp->jiffies_force_qs = jiffies + j; |
8c7c4829 PM |
2307 | WRITE_ONCE(rsp->jiffies_kick_kthreads, |
2308 | jiffies + 3 * j); | |
2309 | } | |
63c4db78 | 2310 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2311 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2312 | TPS("fqswait")); |
afea227f | 2313 | rsp->gp_state = RCU_GP_WAIT_FQS; |
d5374226 | 2314 | ret = swait_event_idle_timeout(rsp->gp_wq, |
b9a425cf | 2315 | rcu_gp_fqs_check_wake(rsp, &gf), j); |
32bb1c79 | 2316 | rsp->gp_state = RCU_GP_DOING_FQS; |
78e4bc34 | 2317 | /* Locking provides needed memory barriers. */ |
4cdfc175 | 2318 | /* If grace period done, leave loop. */ |
7d0ae808 | 2319 | if (!READ_ONCE(rnp->qsmask) && |
4cdfc175 | 2320 | !rcu_preempt_blocked_readers_cgp(rnp)) |
cabc49c1 | 2321 | break; |
4cdfc175 | 2322 | /* If time for quiescent-state forcing, do it. */ |
88d6df61 PM |
2323 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) || |
2324 | (gf & RCU_GP_FLAG_FQS)) { | |
63c4db78 | 2325 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2326 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2327 | TPS("fqsstart")); |
77f81fe0 PM |
2328 | rcu_gp_fqs(rsp, first_gp_fqs); |
2329 | first_gp_fqs = false; | |
63c4db78 | 2330 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2331 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2332 | TPS("fqsend")); |
bde6c3aa | 2333 | cond_resched_rcu_qs(); |
7d0ae808 | 2334 | WRITE_ONCE(rsp->gp_activity, jiffies); |
fcfd0a23 PM |
2335 | ret = 0; /* Force full wait till next FQS. */ |
2336 | j = jiffies_till_next_fqs; | |
2337 | if (j > HZ) { | |
2338 | j = HZ; | |
2339 | jiffies_till_next_fqs = HZ; | |
2340 | } else if (j < 1) { | |
2341 | j = 1; | |
2342 | jiffies_till_next_fqs = 1; | |
2343 | } | |
4cdfc175 PM |
2344 | } else { |
2345 | /* Deal with stray signal. */ | |
bde6c3aa | 2346 | cond_resched_rcu_qs(); |
7d0ae808 | 2347 | WRITE_ONCE(rsp->gp_activity, jiffies); |
73a860cd | 2348 | WARN_ON(signal_pending(current)); |
63c4db78 | 2349 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2350 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2351 | TPS("fqswaitsig")); |
fcfd0a23 PM |
2352 | ret = 1; /* Keep old FQS timing. */ |
2353 | j = jiffies; | |
2354 | if (time_after(jiffies, rsp->jiffies_force_qs)) | |
2355 | j = 1; | |
2356 | else | |
2357 | j = rsp->jiffies_force_qs - j; | |
d40011f6 | 2358 | } |
cabc49c1 | 2359 | } |
4cdfc175 PM |
2360 | |
2361 | /* Handle grace-period end. */ | |
319362c9 | 2362 | rsp->gp_state = RCU_GP_CLEANUP; |
4cdfc175 | 2363 | rcu_gp_cleanup(rsp); |
319362c9 | 2364 | rsp->gp_state = RCU_GP_CLEANED; |
b3dbec76 | 2365 | } |
b3dbec76 PM |
2366 | } |
2367 | ||
64db4cff PM |
2368 | /* |
2369 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
2370 | * in preparation for detecting the next grace period. The caller must hold | |
b8462084 | 2371 | * the root node's ->lock and hard irqs must be disabled. |
e5601400 PM |
2372 | * |
2373 | * Note that it is legal for a dying CPU (which is marked as offline) to | |
2374 | * invoke this function. This can happen when the dying CPU reports its | |
2375 | * quiescent state. | |
48a7639c PM |
2376 | * |
2377 | * Returns true if the grace-period kthread must be awakened. | |
64db4cff | 2378 | */ |
48a7639c | 2379 | static bool |
910ee45d PM |
2380 | rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
2381 | struct rcu_data *rdp) | |
64db4cff | 2382 | { |
c0b334c5 | 2383 | lockdep_assert_held(&rnp->lock); |
b8462084 | 2384 | if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { |
afe24b12 | 2385 | /* |
b3dbec76 | 2386 | * Either we have not yet spawned the grace-period |
62da1921 PM |
2387 | * task, this CPU does not need another grace period, |
2388 | * or a grace period is already in progress. | |
b3dbec76 | 2389 | * Either way, don't start a new grace period. |
afe24b12 | 2390 | */ |
48a7639c | 2391 | return false; |
afe24b12 | 2392 | } |
7d0ae808 PM |
2393 | WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT); |
2394 | trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), | |
bb311ecc | 2395 | TPS("newreq")); |
62da1921 | 2396 | |
016a8d5b SR |
2397 | /* |
2398 | * We can't do wakeups while holding the rnp->lock, as that | |
1eafd31c | 2399 | * could cause possible deadlocks with the rq->lock. Defer |
48a7639c | 2400 | * the wakeup to our caller. |
016a8d5b | 2401 | */ |
48a7639c | 2402 | return true; |
64db4cff PM |
2403 | } |
2404 | ||
910ee45d PM |
2405 | /* |
2406 | * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's | |
2407 | * callbacks. Note that rcu_start_gp_advanced() cannot do this because it | |
2408 | * is invoked indirectly from rcu_advance_cbs(), which would result in | |
2409 | * endless recursion -- or would do so if it wasn't for the self-deadlock | |
2410 | * that is encountered beforehand. | |
48a7639c PM |
2411 | * |
2412 | * Returns true if the grace-period kthread needs to be awakened. | |
910ee45d | 2413 | */ |
48a7639c | 2414 | static bool rcu_start_gp(struct rcu_state *rsp) |
910ee45d PM |
2415 | { |
2416 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
2417 | struct rcu_node *rnp = rcu_get_root(rsp); | |
48a7639c | 2418 | bool ret = false; |
910ee45d PM |
2419 | |
2420 | /* | |
2421 | * If there is no grace period in progress right now, any | |
2422 | * callbacks we have up to this point will be satisfied by the | |
2423 | * next grace period. Also, advancing the callbacks reduces the | |
2424 | * probability of false positives from cpu_needs_another_gp() | |
2425 | * resulting in pointless grace periods. So, advance callbacks | |
2426 | * then start the grace period! | |
2427 | */ | |
48a7639c PM |
2428 | ret = rcu_advance_cbs(rsp, rnp, rdp) || ret; |
2429 | ret = rcu_start_gp_advanced(rsp, rnp, rdp) || ret; | |
2430 | return ret; | |
910ee45d PM |
2431 | } |
2432 | ||
f41d911f | 2433 | /* |
8994515c PM |
2434 | * Report a full set of quiescent states to the specified rcu_state data |
2435 | * structure. Invoke rcu_gp_kthread_wake() to awaken the grace-period | |
2436 | * kthread if another grace period is required. Whether we wake | |
2437 | * the grace-period kthread or it awakens itself for the next round | |
2438 | * of quiescent-state forcing, that kthread will clean up after the | |
2439 | * just-completed grace period. Note that the caller must hold rnp->lock, | |
2440 | * which is released before return. | |
f41d911f | 2441 | */ |
d3f6bad3 | 2442 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 2443 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 2444 | { |
c0b334c5 | 2445 | lockdep_assert_held(&rcu_get_root(rsp)->lock); |
fc2219d4 | 2446 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
cd73ca21 | 2447 | WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS); |
67c583a7 | 2448 | raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(rsp), flags); |
94d44776 | 2449 | rcu_gp_kthread_wake(rsp); |
f41d911f PM |
2450 | } |
2451 | ||
64db4cff | 2452 | /* |
d3f6bad3 PM |
2453 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
2454 | * Allows quiescent states for a group of CPUs to be reported at one go | |
2455 | * to the specified rcu_node structure, though all the CPUs in the group | |
654e9533 PM |
2456 | * must be represented by the same rcu_node structure (which need not be a |
2457 | * leaf rcu_node structure, though it often will be). The gps parameter | |
2458 | * is the grace-period snapshot, which means that the quiescent states | |
2459 | * are valid only if rnp->gpnum is equal to gps. That structure's lock | |
2460 | * must be held upon entry, and it is released before return. | |
64db4cff PM |
2461 | */ |
2462 | static void | |
d3f6bad3 | 2463 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
654e9533 | 2464 | struct rcu_node *rnp, unsigned long gps, unsigned long flags) |
64db4cff PM |
2465 | __releases(rnp->lock) |
2466 | { | |
654e9533 | 2467 | unsigned long oldmask = 0; |
28ecd580 PM |
2468 | struct rcu_node *rnp_c; |
2469 | ||
c0b334c5 PM |
2470 | lockdep_assert_held(&rnp->lock); |
2471 | ||
64db4cff PM |
2472 | /* Walk up the rcu_node hierarchy. */ |
2473 | for (;;) { | |
654e9533 | 2474 | if (!(rnp->qsmask & mask) || rnp->gpnum != gps) { |
64db4cff | 2475 | |
654e9533 PM |
2476 | /* |
2477 | * Our bit has already been cleared, or the | |
2478 | * relevant grace period is already over, so done. | |
2479 | */ | |
67c583a7 | 2480 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff PM |
2481 | return; |
2482 | } | |
654e9533 | 2483 | WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */ |
2dee9404 PM |
2484 | WARN_ON_ONCE(rnp->level != rcu_num_lvls - 1 && |
2485 | rcu_preempt_blocked_readers_cgp(rnp)); | |
64db4cff | 2486 | rnp->qsmask &= ~mask; |
d4c08f2a PM |
2487 | trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, |
2488 | mask, rnp->qsmask, rnp->level, | |
2489 | rnp->grplo, rnp->grphi, | |
2490 | !!rnp->gp_tasks); | |
27f4d280 | 2491 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
2492 | |
2493 | /* Other bits still set at this level, so done. */ | |
67c583a7 | 2494 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff PM |
2495 | return; |
2496 | } | |
2497 | mask = rnp->grpmask; | |
2498 | if (rnp->parent == NULL) { | |
2499 | ||
2500 | /* No more levels. Exit loop holding root lock. */ | |
2501 | ||
2502 | break; | |
2503 | } | |
67c583a7 | 2504 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
28ecd580 | 2505 | rnp_c = rnp; |
64db4cff | 2506 | rnp = rnp->parent; |
2a67e741 | 2507 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
654e9533 | 2508 | oldmask = rnp_c->qsmask; |
64db4cff PM |
2509 | } |
2510 | ||
2511 | /* | |
2512 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 2513 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 2514 | * to clean up and start the next grace period if one is needed. |
64db4cff | 2515 | */ |
d3f6bad3 | 2516 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
2517 | } |
2518 | ||
cc99a310 PM |
2519 | /* |
2520 | * Record a quiescent state for all tasks that were previously queued | |
2521 | * on the specified rcu_node structure and that were blocking the current | |
2522 | * RCU grace period. The caller must hold the specified rnp->lock with | |
2523 | * irqs disabled, and this lock is released upon return, but irqs remain | |
2524 | * disabled. | |
2525 | */ | |
0aa04b05 | 2526 | static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp, |
cc99a310 PM |
2527 | struct rcu_node *rnp, unsigned long flags) |
2528 | __releases(rnp->lock) | |
2529 | { | |
654e9533 | 2530 | unsigned long gps; |
cc99a310 PM |
2531 | unsigned long mask; |
2532 | struct rcu_node *rnp_p; | |
2533 | ||
c0b334c5 | 2534 | lockdep_assert_held(&rnp->lock); |
a77da14c PM |
2535 | if (rcu_state_p == &rcu_sched_state || rsp != rcu_state_p || |
2536 | rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { | |
67c583a7 | 2537 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
cc99a310 PM |
2538 | return; /* Still need more quiescent states! */ |
2539 | } | |
2540 | ||
2541 | rnp_p = rnp->parent; | |
2542 | if (rnp_p == NULL) { | |
2543 | /* | |
a77da14c PM |
2544 | * Only one rcu_node structure in the tree, so don't |
2545 | * try to report up to its nonexistent parent! | |
cc99a310 PM |
2546 | */ |
2547 | rcu_report_qs_rsp(rsp, flags); | |
2548 | return; | |
2549 | } | |
2550 | ||
654e9533 PM |
2551 | /* Report up the rest of the hierarchy, tracking current ->gpnum. */ |
2552 | gps = rnp->gpnum; | |
cc99a310 | 2553 | mask = rnp->grpmask; |
67c583a7 | 2554 | raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ |
2a67e741 | 2555 | raw_spin_lock_rcu_node(rnp_p); /* irqs already disabled. */ |
654e9533 | 2556 | rcu_report_qs_rnp(mask, rsp, rnp_p, gps, flags); |
cc99a310 PM |
2557 | } |
2558 | ||
64db4cff | 2559 | /* |
d3f6bad3 | 2560 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
4b455dc3 | 2561 | * structure. This must be called from the specified CPU. |
64db4cff PM |
2562 | */ |
2563 | static void | |
d7d6a11e | 2564 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
2565 | { |
2566 | unsigned long flags; | |
2567 | unsigned long mask; | |
48a7639c | 2568 | bool needwake; |
64db4cff PM |
2569 | struct rcu_node *rnp; |
2570 | ||
2571 | rnp = rdp->mynode; | |
2a67e741 | 2572 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
3a19b46a PM |
2573 | if (rdp->cpu_no_qs.b.norm || rdp->gpnum != rnp->gpnum || |
2574 | rnp->completed == rnp->gpnum || rdp->gpwrap) { | |
64db4cff PM |
2575 | |
2576 | /* | |
e4cc1f22 PM |
2577 | * The grace period in which this quiescent state was |
2578 | * recorded has ended, so don't report it upwards. | |
2579 | * We will instead need a new quiescent state that lies | |
2580 | * within the current grace period. | |
64db4cff | 2581 | */ |
5b74c458 | 2582 | rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */ |
9577df9a | 2583 | rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_dynticks.rcu_qs_ctr); |
67c583a7 | 2584 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff PM |
2585 | return; |
2586 | } | |
2587 | mask = rdp->grpmask; | |
2588 | if ((rnp->qsmask & mask) == 0) { | |
67c583a7 | 2589 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff | 2590 | } else { |
bb53e416 | 2591 | rdp->core_needs_qs = false; |
64db4cff PM |
2592 | |
2593 | /* | |
2594 | * This GP can't end until cpu checks in, so all of our | |
2595 | * callbacks can be processed during the next GP. | |
2596 | */ | |
48a7639c | 2597 | needwake = rcu_accelerate_cbs(rsp, rnp, rdp); |
64db4cff | 2598 | |
654e9533 PM |
2599 | rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); |
2600 | /* ^^^ Released rnp->lock */ | |
48a7639c PM |
2601 | if (needwake) |
2602 | rcu_gp_kthread_wake(rsp); | |
64db4cff PM |
2603 | } |
2604 | } | |
2605 | ||
2606 | /* | |
2607 | * Check to see if there is a new grace period of which this CPU | |
2608 | * is not yet aware, and if so, set up local rcu_data state for it. | |
2609 | * Otherwise, see if this CPU has just passed through its first | |
2610 | * quiescent state for this grace period, and record that fact if so. | |
2611 | */ | |
2612 | static void | |
2613 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
2614 | { | |
05eb552b PM |
2615 | /* Check for grace-period ends and beginnings. */ |
2616 | note_gp_changes(rsp, rdp); | |
64db4cff PM |
2617 | |
2618 | /* | |
2619 | * Does this CPU still need to do its part for current grace period? | |
2620 | * If no, return and let the other CPUs do their part as well. | |
2621 | */ | |
97c668b8 | 2622 | if (!rdp->core_needs_qs) |
64db4cff PM |
2623 | return; |
2624 | ||
2625 | /* | |
2626 | * Was there a quiescent state since the beginning of the grace | |
2627 | * period? If no, then exit and wait for the next call. | |
2628 | */ | |
3a19b46a | 2629 | if (rdp->cpu_no_qs.b.norm) |
64db4cff PM |
2630 | return; |
2631 | ||
d3f6bad3 PM |
2632 | /* |
2633 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
2634 | * judge of that). | |
2635 | */ | |
d7d6a11e | 2636 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp); |
64db4cff PM |
2637 | } |
2638 | ||
b1420f1c PM |
2639 | /* |
2640 | * Trace the fact that this CPU is going offline. | |
2641 | */ | |
2642 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) | |
2643 | { | |
88a4976d PM |
2644 | RCU_TRACE(unsigned long mask;) |
2645 | RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda);) | |
2646 | RCU_TRACE(struct rcu_node *rnp = rdp->mynode;) | |
b1420f1c | 2647 | |
ea46351c PM |
2648 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) |
2649 | return; | |
2650 | ||
88a4976d | 2651 | RCU_TRACE(mask = rdp->grpmask;) |
e5601400 PM |
2652 | trace_rcu_grace_period(rsp->name, |
2653 | rnp->gpnum + 1 - !!(rnp->qsmask & mask), | |
f7f7bac9 | 2654 | TPS("cpuofl")); |
64db4cff PM |
2655 | } |
2656 | ||
8af3a5e7 PM |
2657 | /* |
2658 | * All CPUs for the specified rcu_node structure have gone offline, | |
2659 | * and all tasks that were preempted within an RCU read-side critical | |
2660 | * section while running on one of those CPUs have since exited their RCU | |
2661 | * read-side critical section. Some other CPU is reporting this fact with | |
2662 | * the specified rcu_node structure's ->lock held and interrupts disabled. | |
2663 | * This function therefore goes up the tree of rcu_node structures, | |
2664 | * clearing the corresponding bits in the ->qsmaskinit fields. Note that | |
2665 | * the leaf rcu_node structure's ->qsmaskinit field has already been | |
2666 | * updated | |
2667 | * | |
2668 | * This function does check that the specified rcu_node structure has | |
2669 | * all CPUs offline and no blocked tasks, so it is OK to invoke it | |
2670 | * prematurely. That said, invoking it after the fact will cost you | |
2671 | * a needless lock acquisition. So once it has done its work, don't | |
2672 | * invoke it again. | |
2673 | */ | |
2674 | static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) | |
2675 | { | |
2676 | long mask; | |
2677 | struct rcu_node *rnp = rnp_leaf; | |
2678 | ||
c0b334c5 | 2679 | lockdep_assert_held(&rnp->lock); |
ea46351c PM |
2680 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || |
2681 | rnp->qsmaskinit || rcu_preempt_has_tasks(rnp)) | |
8af3a5e7 PM |
2682 | return; |
2683 | for (;;) { | |
2684 | mask = rnp->grpmask; | |
2685 | rnp = rnp->parent; | |
2686 | if (!rnp) | |
2687 | break; | |
2a67e741 | 2688 | raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ |
8af3a5e7 | 2689 | rnp->qsmaskinit &= ~mask; |
0aa04b05 | 2690 | rnp->qsmask &= ~mask; |
8af3a5e7 | 2691 | if (rnp->qsmaskinit) { |
67c583a7 BF |
2692 | raw_spin_unlock_rcu_node(rnp); |
2693 | /* irqs remain disabled. */ | |
8af3a5e7 PM |
2694 | return; |
2695 | } | |
67c583a7 | 2696 | raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ |
8af3a5e7 PM |
2697 | } |
2698 | } | |
2699 | ||
64db4cff | 2700 | /* |
e5601400 | 2701 | * The CPU has been completely removed, and some other CPU is reporting |
a58163d8 PM |
2702 | * this fact from process context. Do the remainder of the cleanup. |
2703 | * There can only be one CPU hotplug operation at a time, so no need for | |
2704 | * explicit locking. | |
64db4cff | 2705 | */ |
e5601400 | 2706 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff | 2707 | { |
e5601400 | 2708 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
b1420f1c | 2709 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
e5601400 | 2710 | |
ea46351c PM |
2711 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) |
2712 | return; | |
2713 | ||
2036d94a | 2714 | /* Adjust any no-longer-needed kthreads. */ |
5d01bbd1 | 2715 | rcu_boost_kthread_setaffinity(rnp, -1); |
64db4cff PM |
2716 | } |
2717 | ||
64db4cff PM |
2718 | /* |
2719 | * Invoke any RCU callbacks that have made it to the end of their grace | |
2720 | * period. Thottle as specified by rdp->blimit. | |
2721 | */ | |
37c72e56 | 2722 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
2723 | { |
2724 | unsigned long flags; | |
15fecf89 PM |
2725 | struct rcu_head *rhp; |
2726 | struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl); | |
2727 | long bl, count; | |
64db4cff | 2728 | |
dc35c893 | 2729 | /* If no callbacks are ready, just return. */ |
15fecf89 PM |
2730 | if (!rcu_segcblist_ready_cbs(&rdp->cblist)) { |
2731 | trace_rcu_batch_start(rsp->name, | |
2732 | rcu_segcblist_n_lazy_cbs(&rdp->cblist), | |
2733 | rcu_segcblist_n_cbs(&rdp->cblist), 0); | |
2734 | trace_rcu_batch_end(rsp->name, 0, | |
2735 | !rcu_segcblist_empty(&rdp->cblist), | |
4968c300 PM |
2736 | need_resched(), is_idle_task(current), |
2737 | rcu_is_callbacks_kthread()); | |
64db4cff | 2738 | return; |
29c00b4a | 2739 | } |
64db4cff PM |
2740 | |
2741 | /* | |
2742 | * Extract the list of ready callbacks, disabling to prevent | |
15fecf89 PM |
2743 | * races with call_rcu() from interrupt handlers. Leave the |
2744 | * callback counts, as rcu_barrier() needs to be conservative. | |
64db4cff PM |
2745 | */ |
2746 | local_irq_save(flags); | |
8146c4e2 | 2747 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
29c00b4a | 2748 | bl = rdp->blimit; |
15fecf89 PM |
2749 | trace_rcu_batch_start(rsp->name, rcu_segcblist_n_lazy_cbs(&rdp->cblist), |
2750 | rcu_segcblist_n_cbs(&rdp->cblist), bl); | |
2751 | rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl); | |
64db4cff PM |
2752 | local_irq_restore(flags); |
2753 | ||
2754 | /* Invoke callbacks. */ | |
15fecf89 PM |
2755 | rhp = rcu_cblist_dequeue(&rcl); |
2756 | for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) { | |
2757 | debug_rcu_head_unqueue(rhp); | |
2758 | if (__rcu_reclaim(rsp->name, rhp)) | |
2759 | rcu_cblist_dequeued_lazy(&rcl); | |
2760 | /* | |
2761 | * Stop only if limit reached and CPU has something to do. | |
2762 | * Note: The rcl structure counts down from zero. | |
2763 | */ | |
4b27f20b | 2764 | if (-rcl.len >= bl && |
dff1672d PM |
2765 | (need_resched() || |
2766 | (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) | |
64db4cff PM |
2767 | break; |
2768 | } | |
2769 | ||
2770 | local_irq_save(flags); | |
4b27f20b | 2771 | count = -rcl.len; |
8ef0f37e PM |
2772 | trace_rcu_batch_end(rsp->name, count, !!rcl.head, need_resched(), |
2773 | is_idle_task(current), rcu_is_callbacks_kthread()); | |
64db4cff | 2774 | |
15fecf89 PM |
2775 | /* Update counts and requeue any remaining callbacks. */ |
2776 | rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl); | |
b1420f1c | 2777 | smp_mb(); /* List handling before counting for rcu_barrier(). */ |
b1420f1c | 2778 | rdp->n_cbs_invoked += count; |
15fecf89 | 2779 | rcu_segcblist_insert_count(&rdp->cblist, &rcl); |
64db4cff PM |
2780 | |
2781 | /* Reinstate batch limit if we have worked down the excess. */ | |
15fecf89 PM |
2782 | count = rcu_segcblist_n_cbs(&rdp->cblist); |
2783 | if (rdp->blimit == LONG_MAX && count <= qlowmark) | |
64db4cff PM |
2784 | rdp->blimit = blimit; |
2785 | ||
37c72e56 | 2786 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
15fecf89 | 2787 | if (count == 0 && rdp->qlen_last_fqs_check != 0) { |
37c72e56 PM |
2788 | rdp->qlen_last_fqs_check = 0; |
2789 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
15fecf89 PM |
2790 | } else if (count < rdp->qlen_last_fqs_check - qhimark) |
2791 | rdp->qlen_last_fqs_check = count; | |
2792 | WARN_ON_ONCE(rcu_segcblist_empty(&rdp->cblist) != (count == 0)); | |
37c72e56 | 2793 | |
64db4cff PM |
2794 | local_irq_restore(flags); |
2795 | ||
e0f23060 | 2796 | /* Re-invoke RCU core processing if there are callbacks remaining. */ |
15fecf89 | 2797 | if (rcu_segcblist_ready_cbs(&rdp->cblist)) |
a46e0899 | 2798 | invoke_rcu_core(); |
64db4cff PM |
2799 | } |
2800 | ||
2801 | /* | |
2802 | * Check to see if this CPU is in a non-context-switch quiescent state | |
2803 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
e0f23060 | 2804 | * Also schedule RCU core processing. |
64db4cff | 2805 | * |
9b2e4f18 | 2806 | * This function must be called from hardirq context. It is normally |
5403d367 | 2807 | * invoked from the scheduling-clock interrupt. |
64db4cff | 2808 | */ |
c3377c2d | 2809 | void rcu_check_callbacks(int user) |
64db4cff | 2810 | { |
f7f7bac9 | 2811 | trace_rcu_utilization(TPS("Start scheduler-tick")); |
a858af28 | 2812 | increment_cpu_stall_ticks(); |
9b2e4f18 | 2813 | if (user || rcu_is_cpu_rrupt_from_idle()) { |
64db4cff PM |
2814 | |
2815 | /* | |
2816 | * Get here if this CPU took its interrupt from user | |
2817 | * mode or from the idle loop, and if this is not a | |
2818 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 2819 | * a quiescent state, so note it. |
64db4cff PM |
2820 | * |
2821 | * No memory barrier is required here because both | |
d6714c22 PM |
2822 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
2823 | * variables that other CPUs neither access nor modify, | |
2824 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
2825 | */ |
2826 | ||
284a8c93 PM |
2827 | rcu_sched_qs(); |
2828 | rcu_bh_qs(); | |
64db4cff PM |
2829 | |
2830 | } else if (!in_softirq()) { | |
2831 | ||
2832 | /* | |
2833 | * Get here if this CPU did not take its interrupt from | |
2834 | * softirq, in other words, if it is not interrupting | |
2835 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 2836 | * critical section, so note it. |
64db4cff PM |
2837 | */ |
2838 | ||
284a8c93 | 2839 | rcu_bh_qs(); |
64db4cff | 2840 | } |
86aea0e6 | 2841 | rcu_preempt_check_callbacks(); |
e3950ecd | 2842 | if (rcu_pending()) |
a46e0899 | 2843 | invoke_rcu_core(); |
8315f422 PM |
2844 | if (user) |
2845 | rcu_note_voluntary_context_switch(current); | |
f7f7bac9 | 2846 | trace_rcu_utilization(TPS("End scheduler-tick")); |
64db4cff PM |
2847 | } |
2848 | ||
64db4cff PM |
2849 | /* |
2850 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
2851 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
2852 | * Also initiate boosting for any threads blocked on the root rcu_node. |
2853 | * | |
ee47eb9f | 2854 | * The caller must have suppressed start of new grace periods. |
64db4cff | 2855 | */ |
fe5ac724 | 2856 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)) |
64db4cff | 2857 | { |
64db4cff PM |
2858 | int cpu; |
2859 | unsigned long flags; | |
2860 | unsigned long mask; | |
a0b6c9a7 | 2861 | struct rcu_node *rnp; |
64db4cff | 2862 | |
a0b6c9a7 | 2863 | rcu_for_each_leaf_node(rsp, rnp) { |
bde6c3aa | 2864 | cond_resched_rcu_qs(); |
64db4cff | 2865 | mask = 0; |
2a67e741 | 2866 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
a0b6c9a7 | 2867 | if (rnp->qsmask == 0) { |
a77da14c PM |
2868 | if (rcu_state_p == &rcu_sched_state || |
2869 | rsp != rcu_state_p || | |
2870 | rcu_preempt_blocked_readers_cgp(rnp)) { | |
2871 | /* | |
2872 | * No point in scanning bits because they | |
2873 | * are all zero. But we might need to | |
2874 | * priority-boost blocked readers. | |
2875 | */ | |
2876 | rcu_initiate_boost(rnp, flags); | |
2877 | /* rcu_initiate_boost() releases rnp->lock */ | |
2878 | continue; | |
2879 | } | |
2880 | if (rnp->parent && | |
2881 | (rnp->parent->qsmask & rnp->grpmask)) { | |
2882 | /* | |
2883 | * Race between grace-period | |
2884 | * initialization and task exiting RCU | |
2885 | * read-side critical section: Report. | |
2886 | */ | |
2887 | rcu_report_unblock_qs_rnp(rsp, rnp, flags); | |
2888 | /* rcu_report_unblock_qs_rnp() rlses ->lock */ | |
2889 | continue; | |
2890 | } | |
64db4cff | 2891 | } |
bc75e999 MR |
2892 | for_each_leaf_node_possible_cpu(rnp, cpu) { |
2893 | unsigned long bit = leaf_node_cpu_bit(rnp, cpu); | |
0edd1b17 | 2894 | if ((rnp->qsmask & bit) != 0) { |
fe5ac724 | 2895 | if (f(per_cpu_ptr(rsp->rda, cpu))) |
0edd1b17 PM |
2896 | mask |= bit; |
2897 | } | |
64db4cff | 2898 | } |
45f014c5 | 2899 | if (mask != 0) { |
654e9533 PM |
2900 | /* Idle/offline CPUs, report (releases rnp->lock. */ |
2901 | rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); | |
0aa04b05 PM |
2902 | } else { |
2903 | /* Nothing to do here, so just drop the lock. */ | |
67c583a7 | 2904 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff | 2905 | } |
64db4cff | 2906 | } |
64db4cff PM |
2907 | } |
2908 | ||
2909 | /* | |
2910 | * Force quiescent states on reluctant CPUs, and also detect which | |
2911 | * CPUs are in dyntick-idle mode. | |
2912 | */ | |
4cdfc175 | 2913 | static void force_quiescent_state(struct rcu_state *rsp) |
64db4cff PM |
2914 | { |
2915 | unsigned long flags; | |
394f2769 PM |
2916 | bool ret; |
2917 | struct rcu_node *rnp; | |
2918 | struct rcu_node *rnp_old = NULL; | |
2919 | ||
2920 | /* Funnel through hierarchy to reduce memory contention. */ | |
d860d403 | 2921 | rnp = __this_cpu_read(rsp->rda->mynode); |
394f2769 | 2922 | for (; rnp != NULL; rnp = rnp->parent) { |
7d0ae808 | 2923 | ret = (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || |
394f2769 PM |
2924 | !raw_spin_trylock(&rnp->fqslock); |
2925 | if (rnp_old != NULL) | |
2926 | raw_spin_unlock(&rnp_old->fqslock); | |
2927 | if (ret) { | |
a792563b | 2928 | rsp->n_force_qs_lh++; |
394f2769 PM |
2929 | return; |
2930 | } | |
2931 | rnp_old = rnp; | |
2932 | } | |
2933 | /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ | |
64db4cff | 2934 | |
394f2769 | 2935 | /* Reached the root of the rcu_node tree, acquire lock. */ |
2a67e741 | 2936 | raw_spin_lock_irqsave_rcu_node(rnp_old, flags); |
394f2769 | 2937 | raw_spin_unlock(&rnp_old->fqslock); |
7d0ae808 | 2938 | if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { |
a792563b | 2939 | rsp->n_force_qs_lh++; |
67c583a7 | 2940 | raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); |
4cdfc175 | 2941 | return; /* Someone beat us to it. */ |
46a1e34e | 2942 | } |
7d0ae808 | 2943 | WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS); |
67c583a7 | 2944 | raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); |
94d44776 | 2945 | rcu_gp_kthread_wake(rsp); |
64db4cff PM |
2946 | } |
2947 | ||
64db4cff | 2948 | /* |
e0f23060 PM |
2949 | * This does the RCU core processing work for the specified rcu_state |
2950 | * and rcu_data structures. This may be called only from the CPU to | |
2951 | * whom the rdp belongs. | |
64db4cff PM |
2952 | */ |
2953 | static void | |
1bca8cf1 | 2954 | __rcu_process_callbacks(struct rcu_state *rsp) |
64db4cff PM |
2955 | { |
2956 | unsigned long flags; | |
48a7639c | 2957 | bool needwake; |
fa07a58f | 2958 | struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); |
64db4cff | 2959 | |
50dc7def | 2960 | WARN_ON_ONCE(!rdp->beenonline); |
2e597558 | 2961 | |
64db4cff PM |
2962 | /* Update RCU state based on any recent quiescent states. */ |
2963 | rcu_check_quiescent_state(rsp, rdp); | |
2964 | ||
2965 | /* Does this CPU require a not-yet-started grace period? */ | |
dc35c893 | 2966 | local_irq_save(flags); |
64db4cff | 2967 | if (cpu_needs_another_gp(rsp, rdp)) { |
6cf10081 | 2968 | raw_spin_lock_rcu_node(rcu_get_root(rsp)); /* irqs disabled. */ |
48a7639c | 2969 | needwake = rcu_start_gp(rsp); |
67c583a7 | 2970 | raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(rsp), flags); |
48a7639c PM |
2971 | if (needwake) |
2972 | rcu_gp_kthread_wake(rsp); | |
dc35c893 PM |
2973 | } else { |
2974 | local_irq_restore(flags); | |
64db4cff PM |
2975 | } |
2976 | ||
2977 | /* If there are callbacks ready, invoke them. */ | |
15fecf89 | 2978 | if (rcu_segcblist_ready_cbs(&rdp->cblist)) |
a46e0899 | 2979 | invoke_rcu_callbacks(rsp, rdp); |
96d3fd0d PM |
2980 | |
2981 | /* Do any needed deferred wakeups of rcuo kthreads. */ | |
2982 | do_nocb_deferred_wakeup(rdp); | |
09223371 SL |
2983 | } |
2984 | ||
64db4cff | 2985 | /* |
e0f23060 | 2986 | * Do RCU core processing for the current CPU. |
64db4cff | 2987 | */ |
0766f788 | 2988 | static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) |
64db4cff | 2989 | { |
6ce75a23 PM |
2990 | struct rcu_state *rsp; |
2991 | ||
bfa00b4c PM |
2992 | if (cpu_is_offline(smp_processor_id())) |
2993 | return; | |
f7f7bac9 | 2994 | trace_rcu_utilization(TPS("Start RCU core")); |
6ce75a23 PM |
2995 | for_each_rcu_flavor(rsp) |
2996 | __rcu_process_callbacks(rsp); | |
f7f7bac9 | 2997 | trace_rcu_utilization(TPS("End RCU core")); |
64db4cff PM |
2998 | } |
2999 | ||
a26ac245 | 3000 | /* |
e0f23060 PM |
3001 | * Schedule RCU callback invocation. If the specified type of RCU |
3002 | * does not support RCU priority boosting, just do a direct call, | |
3003 | * otherwise wake up the per-CPU kernel kthread. Note that because we | |
924df8a0 | 3004 | * are running on the current CPU with softirqs disabled, the |
e0f23060 | 3005 | * rcu_cpu_kthread_task cannot disappear out from under us. |
a26ac245 | 3006 | */ |
a46e0899 | 3007 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
a26ac245 | 3008 | { |
7d0ae808 | 3009 | if (unlikely(!READ_ONCE(rcu_scheduler_fully_active))) |
b0d30417 | 3010 | return; |
a46e0899 PM |
3011 | if (likely(!rsp->boost)) { |
3012 | rcu_do_batch(rsp, rdp); | |
a26ac245 PM |
3013 | return; |
3014 | } | |
a46e0899 | 3015 | invoke_rcu_callbacks_kthread(); |
a26ac245 PM |
3016 | } |
3017 | ||
a46e0899 | 3018 | static void invoke_rcu_core(void) |
09223371 | 3019 | { |
b0f74036 PM |
3020 | if (cpu_online(smp_processor_id())) |
3021 | raise_softirq(RCU_SOFTIRQ); | |
09223371 SL |
3022 | } |
3023 | ||
29154c57 PM |
3024 | /* |
3025 | * Handle any core-RCU processing required by a call_rcu() invocation. | |
3026 | */ | |
3027 | static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, | |
3028 | struct rcu_head *head, unsigned long flags) | |
64db4cff | 3029 | { |
48a7639c PM |
3030 | bool needwake; |
3031 | ||
62fde6ed PM |
3032 | /* |
3033 | * If called from an extended quiescent state, invoke the RCU | |
3034 | * core in order to force a re-evaluation of RCU's idleness. | |
3035 | */ | |
9910affa | 3036 | if (!rcu_is_watching()) |
62fde6ed PM |
3037 | invoke_rcu_core(); |
3038 | ||
a16b7a69 | 3039 | /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ |
29154c57 | 3040 | if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) |
2655d57e | 3041 | return; |
64db4cff | 3042 | |
37c72e56 PM |
3043 | /* |
3044 | * Force the grace period if too many callbacks or too long waiting. | |
3045 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
3046 | * if some other CPU has recently done so. Also, don't bother | |
3047 | * invoking force_quiescent_state() if the newly enqueued callback | |
3048 | * is the only one waiting for a grace period to complete. | |
3049 | */ | |
15fecf89 PM |
3050 | if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > |
3051 | rdp->qlen_last_fqs_check + qhimark)) { | |
b52573d2 PM |
3052 | |
3053 | /* Are we ignoring a completed grace period? */ | |
470716fc | 3054 | note_gp_changes(rsp, rdp); |
b52573d2 PM |
3055 | |
3056 | /* Start a new grace period if one not already started. */ | |
3057 | if (!rcu_gp_in_progress(rsp)) { | |
b52573d2 PM |
3058 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
3059 | ||
2a67e741 | 3060 | raw_spin_lock_rcu_node(rnp_root); |
48a7639c | 3061 | needwake = rcu_start_gp(rsp); |
67c583a7 | 3062 | raw_spin_unlock_rcu_node(rnp_root); |
48a7639c PM |
3063 | if (needwake) |
3064 | rcu_gp_kthread_wake(rsp); | |
b52573d2 PM |
3065 | } else { |
3066 | /* Give the grace period a kick. */ | |
3067 | rdp->blimit = LONG_MAX; | |
3068 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
15fecf89 | 3069 | rcu_segcblist_first_pend_cb(&rdp->cblist) != head) |
4cdfc175 | 3070 | force_quiescent_state(rsp); |
b52573d2 | 3071 | rdp->n_force_qs_snap = rsp->n_force_qs; |
15fecf89 | 3072 | rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); |
b52573d2 | 3073 | } |
4cdfc175 | 3074 | } |
29154c57 PM |
3075 | } |
3076 | ||
ae150184 PM |
3077 | /* |
3078 | * RCU callback function to leak a callback. | |
3079 | */ | |
3080 | static void rcu_leak_callback(struct rcu_head *rhp) | |
3081 | { | |
3082 | } | |
3083 | ||
3fbfbf7a PM |
3084 | /* |
3085 | * Helper function for call_rcu() and friends. The cpu argument will | |
3086 | * normally be -1, indicating "currently running CPU". It may specify | |
3087 | * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier() | |
3088 | * is expected to specify a CPU. | |
3089 | */ | |
64db4cff | 3090 | static void |
b6a4ae76 | 3091 | __call_rcu(struct rcu_head *head, rcu_callback_t func, |
3fbfbf7a | 3092 | struct rcu_state *rsp, int cpu, bool lazy) |
64db4cff PM |
3093 | { |
3094 | unsigned long flags; | |
3095 | struct rcu_data *rdp; | |
3096 | ||
b8f2ed53 PM |
3097 | /* Misaligned rcu_head! */ |
3098 | WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); | |
3099 | ||
ae150184 | 3100 | if (debug_rcu_head_queue(head)) { |
fa3c6647 PM |
3101 | /* |
3102 | * Probable double call_rcu(), so leak the callback. | |
3103 | * Use rcu:rcu_callback trace event to find the previous | |
3104 | * time callback was passed to __call_rcu(). | |
3105 | */ | |
3106 | WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pF()!!!\n", | |
3107 | head, head->func); | |
7d0ae808 | 3108 | WRITE_ONCE(head->func, rcu_leak_callback); |
ae150184 PM |
3109 | return; |
3110 | } | |
64db4cff PM |
3111 | head->func = func; |
3112 | head->next = NULL; | |
64db4cff | 3113 | local_irq_save(flags); |
394f99a9 | 3114 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
3115 | |
3116 | /* Add the callback to our list. */ | |
15fecf89 | 3117 | if (unlikely(!rcu_segcblist_is_enabled(&rdp->cblist)) || cpu != -1) { |
3fbfbf7a PM |
3118 | int offline; |
3119 | ||
3120 | if (cpu != -1) | |
3121 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
143da9c2 PM |
3122 | if (likely(rdp->mynode)) { |
3123 | /* Post-boot, so this should be for a no-CBs CPU. */ | |
3124 | offline = !__call_rcu_nocb(rdp, head, lazy, flags); | |
3125 | WARN_ON_ONCE(offline); | |
3126 | /* Offline CPU, _call_rcu() illegal, leak callback. */ | |
3127 | local_irq_restore(flags); | |
3128 | return; | |
3129 | } | |
3130 | /* | |
3131 | * Very early boot, before rcu_init(). Initialize if needed | |
3132 | * and then drop through to queue the callback. | |
3133 | */ | |
3134 | BUG_ON(cpu != -1); | |
34404ca8 | 3135 | WARN_ON_ONCE(!rcu_is_watching()); |
15fecf89 PM |
3136 | if (rcu_segcblist_empty(&rdp->cblist)) |
3137 | rcu_segcblist_init(&rdp->cblist); | |
0d8ee37e | 3138 | } |
15fecf89 PM |
3139 | rcu_segcblist_enqueue(&rdp->cblist, head, lazy); |
3140 | if (!lazy) | |
c57afe80 | 3141 | rcu_idle_count_callbacks_posted(); |
2655d57e | 3142 | |
d4c08f2a PM |
3143 | if (__is_kfree_rcu_offset((unsigned long)func)) |
3144 | trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, | |
15fecf89 PM |
3145 | rcu_segcblist_n_lazy_cbs(&rdp->cblist), |
3146 | rcu_segcblist_n_cbs(&rdp->cblist)); | |
d4c08f2a | 3147 | else |
15fecf89 PM |
3148 | trace_rcu_callback(rsp->name, head, |
3149 | rcu_segcblist_n_lazy_cbs(&rdp->cblist), | |
3150 | rcu_segcblist_n_cbs(&rdp->cblist)); | |
d4c08f2a | 3151 | |
29154c57 PM |
3152 | /* Go handle any RCU core processing required. */ |
3153 | __call_rcu_core(rsp, rdp, head, flags); | |
64db4cff PM |
3154 | local_irq_restore(flags); |
3155 | } | |
3156 | ||
a68a2bb2 PM |
3157 | /** |
3158 | * call_rcu_sched() - Queue an RCU for invocation after sched grace period. | |
3159 | * @head: structure to be used for queueing the RCU updates. | |
3160 | * @func: actual callback function to be invoked after the grace period | |
3161 | * | |
3162 | * The callback function will be invoked some time after a full grace | |
3163 | * period elapses, in other words after all currently executing RCU | |
3164 | * read-side critical sections have completed. call_rcu_sched() assumes | |
3165 | * that the read-side critical sections end on enabling of preemption | |
3166 | * or on voluntary preemption. | |
27fdb35f PM |
3167 | * RCU read-side critical sections are delimited by: |
3168 | * | |
3169 | * - rcu_read_lock_sched() and rcu_read_unlock_sched(), OR | |
3170 | * - anything that disables preemption. | |
a68a2bb2 PM |
3171 | * |
3172 | * These may be nested. | |
3173 | * | |
3174 | * See the description of call_rcu() for more detailed information on | |
3175 | * memory ordering guarantees. | |
64db4cff | 3176 | */ |
b6a4ae76 | 3177 | void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) |
64db4cff | 3178 | { |
3fbfbf7a | 3179 | __call_rcu(head, func, &rcu_sched_state, -1, 0); |
64db4cff | 3180 | } |
d6714c22 | 3181 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff | 3182 | |
a68a2bb2 PM |
3183 | /** |
3184 | * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. | |
3185 | * @head: structure to be used for queueing the RCU updates. | |
3186 | * @func: actual callback function to be invoked after the grace period | |
3187 | * | |
3188 | * The callback function will be invoked some time after a full grace | |
3189 | * period elapses, in other words after all currently executing RCU | |
3190 | * read-side critical sections have completed. call_rcu_bh() assumes | |
3191 | * that the read-side critical sections end on completion of a softirq | |
3192 | * handler. This means that read-side critical sections in process | |
3193 | * context must not be interrupted by softirqs. This interface is to be | |
3194 | * used when most of the read-side critical sections are in softirq context. | |
27fdb35f PM |
3195 | * RCU read-side critical sections are delimited by: |
3196 | * | |
3197 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context, OR | |
3198 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. | |
3199 | * | |
3200 | * These may be nested. | |
a68a2bb2 PM |
3201 | * |
3202 | * See the description of call_rcu() for more detailed information on | |
3203 | * memory ordering guarantees. | |
64db4cff | 3204 | */ |
b6a4ae76 | 3205 | void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) |
64db4cff | 3206 | { |
3fbfbf7a | 3207 | __call_rcu(head, func, &rcu_bh_state, -1, 0); |
64db4cff PM |
3208 | } |
3209 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
3210 | ||
495aa969 ACB |
3211 | /* |
3212 | * Queue an RCU callback for lazy invocation after a grace period. | |
3213 | * This will likely be later named something like "call_rcu_lazy()", | |
3214 | * but this change will require some way of tagging the lazy RCU | |
3215 | * callbacks in the list of pending callbacks. Until then, this | |
3216 | * function may only be called from __kfree_rcu(). | |
3217 | */ | |
3218 | void kfree_call_rcu(struct rcu_head *head, | |
b6a4ae76 | 3219 | rcu_callback_t func) |
495aa969 | 3220 | { |
e534165b | 3221 | __call_rcu(head, func, rcu_state_p, -1, 1); |
495aa969 ACB |
3222 | } |
3223 | EXPORT_SYMBOL_GPL(kfree_call_rcu); | |
3224 | ||
6d813391 PM |
3225 | /* |
3226 | * Because a context switch is a grace period for RCU-sched and RCU-bh, | |
3227 | * any blocking grace-period wait automatically implies a grace period | |
3228 | * if there is only one CPU online at any point time during execution | |
3229 | * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to | |
3230 | * occasionally incorrectly indicate that there are multiple CPUs online | |
3231 | * when there was in fact only one the whole time, as this just adds | |
3232 | * some overhead: RCU still operates correctly. | |
6d813391 PM |
3233 | */ |
3234 | static inline int rcu_blocking_is_gp(void) | |
3235 | { | |
95f0c1de PM |
3236 | int ret; |
3237 | ||
6d813391 | 3238 | might_sleep(); /* Check for RCU read-side critical section. */ |
95f0c1de PM |
3239 | preempt_disable(); |
3240 | ret = num_online_cpus() <= 1; | |
3241 | preempt_enable(); | |
3242 | return ret; | |
6d813391 PM |
3243 | } |
3244 | ||
6ebb237b PM |
3245 | /** |
3246 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
3247 | * | |
3248 | * Control will return to the caller some time after a full rcu-sched | |
3249 | * grace period has elapsed, in other words after all currently executing | |
3250 | * rcu-sched read-side critical sections have completed. These read-side | |
3251 | * critical sections are delimited by rcu_read_lock_sched() and | |
3252 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
3253 | * local_irq_disable(), and so on may be used in place of | |
3254 | * rcu_read_lock_sched(). | |
3255 | * | |
3256 | * This means that all preempt_disable code sequences, including NMI and | |
f0a0e6f2 PM |
3257 | * non-threaded hardware-interrupt handlers, in progress on entry will |
3258 | * have completed before this primitive returns. However, this does not | |
3259 | * guarantee that softirq handlers will have completed, since in some | |
3260 | * kernels, these handlers can run in process context, and can block. | |
3261 | * | |
3262 | * Note that this guarantee implies further memory-ordering guarantees. | |
3263 | * On systems with more than one CPU, when synchronize_sched() returns, | |
3264 | * each CPU is guaranteed to have executed a full memory barrier since the | |
3265 | * end of its last RCU-sched read-side critical section whose beginning | |
3266 | * preceded the call to synchronize_sched(). In addition, each CPU having | |
3267 | * an RCU read-side critical section that extends beyond the return from | |
3268 | * synchronize_sched() is guaranteed to have executed a full memory barrier | |
3269 | * after the beginning of synchronize_sched() and before the beginning of | |
3270 | * that RCU read-side critical section. Note that these guarantees include | |
3271 | * CPUs that are offline, idle, or executing in user mode, as well as CPUs | |
3272 | * that are executing in the kernel. | |
3273 | * | |
3274 | * Furthermore, if CPU A invoked synchronize_sched(), which returned | |
3275 | * to its caller on CPU B, then both CPU A and CPU B are guaranteed | |
3276 | * to have executed a full memory barrier during the execution of | |
3277 | * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but | |
3278 | * again only if the system has more than one CPU). | |
6ebb237b PM |
3279 | */ |
3280 | void synchronize_sched(void) | |
3281 | { | |
f78f5b90 PM |
3282 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
3283 | lock_is_held(&rcu_lock_map) || | |
3284 | lock_is_held(&rcu_sched_lock_map), | |
3285 | "Illegal synchronize_sched() in RCU-sched read-side critical section"); | |
6ebb237b PM |
3286 | if (rcu_blocking_is_gp()) |
3287 | return; | |
5afff48b | 3288 | if (rcu_gp_is_expedited()) |
3705b88d AM |
3289 | synchronize_sched_expedited(); |
3290 | else | |
3291 | wait_rcu_gp(call_rcu_sched); | |
6ebb237b PM |
3292 | } |
3293 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
3294 | ||
3295 | /** | |
3296 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
3297 | * | |
3298 | * Control will return to the caller some time after a full rcu_bh grace | |
3299 | * period has elapsed, in other words after all currently executing rcu_bh | |
3300 | * read-side critical sections have completed. RCU read-side critical | |
3301 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
3302 | * and may be nested. | |
f0a0e6f2 PM |
3303 | * |
3304 | * See the description of synchronize_sched() for more detailed information | |
3305 | * on memory ordering guarantees. | |
6ebb237b PM |
3306 | */ |
3307 | void synchronize_rcu_bh(void) | |
3308 | { | |
f78f5b90 PM |
3309 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
3310 | lock_is_held(&rcu_lock_map) || | |
3311 | lock_is_held(&rcu_sched_lock_map), | |
3312 | "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); | |
6ebb237b PM |
3313 | if (rcu_blocking_is_gp()) |
3314 | return; | |
5afff48b | 3315 | if (rcu_gp_is_expedited()) |
3705b88d AM |
3316 | synchronize_rcu_bh_expedited(); |
3317 | else | |
3318 | wait_rcu_gp(call_rcu_bh); | |
6ebb237b PM |
3319 | } |
3320 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
3321 | ||
765a3f4f PM |
3322 | /** |
3323 | * get_state_synchronize_rcu - Snapshot current RCU state | |
3324 | * | |
3325 | * Returns a cookie that is used by a later call to cond_synchronize_rcu() | |
3326 | * to determine whether or not a full grace period has elapsed in the | |
3327 | * meantime. | |
3328 | */ | |
3329 | unsigned long get_state_synchronize_rcu(void) | |
3330 | { | |
3331 | /* | |
3332 | * Any prior manipulation of RCU-protected data must happen | |
3333 | * before the load from ->gpnum. | |
3334 | */ | |
3335 | smp_mb(); /* ^^^ */ | |
3336 | ||
3337 | /* | |
3338 | * Make sure this load happens before the purportedly | |
3339 | * time-consuming work between get_state_synchronize_rcu() | |
3340 | * and cond_synchronize_rcu(). | |
3341 | */ | |
e534165b | 3342 | return smp_load_acquire(&rcu_state_p->gpnum); |
765a3f4f PM |
3343 | } |
3344 | EXPORT_SYMBOL_GPL(get_state_synchronize_rcu); | |
3345 | ||
3346 | /** | |
3347 | * cond_synchronize_rcu - Conditionally wait for an RCU grace period | |
3348 | * | |
3349 | * @oldstate: return value from earlier call to get_state_synchronize_rcu() | |
3350 | * | |
3351 | * If a full RCU grace period has elapsed since the earlier call to | |
3352 | * get_state_synchronize_rcu(), just return. Otherwise, invoke | |
3353 | * synchronize_rcu() to wait for a full grace period. | |
3354 | * | |
3355 | * Yes, this function does not take counter wrap into account. But | |
3356 | * counter wrap is harmless. If the counter wraps, we have waited for | |
3357 | * more than 2 billion grace periods (and way more on a 64-bit system!), | |
3358 | * so waiting for one additional grace period should be just fine. | |
3359 | */ | |
3360 | void cond_synchronize_rcu(unsigned long oldstate) | |
3361 | { | |
3362 | unsigned long newstate; | |
3363 | ||
3364 | /* | |
3365 | * Ensure that this load happens before any RCU-destructive | |
3366 | * actions the caller might carry out after we return. | |
3367 | */ | |
e534165b | 3368 | newstate = smp_load_acquire(&rcu_state_p->completed); |
765a3f4f PM |
3369 | if (ULONG_CMP_GE(oldstate, newstate)) |
3370 | synchronize_rcu(); | |
3371 | } | |
3372 | EXPORT_SYMBOL_GPL(cond_synchronize_rcu); | |
3373 | ||
24560056 PM |
3374 | /** |
3375 | * get_state_synchronize_sched - Snapshot current RCU-sched state | |
3376 | * | |
3377 | * Returns a cookie that is used by a later call to cond_synchronize_sched() | |
3378 | * to determine whether or not a full grace period has elapsed in the | |
3379 | * meantime. | |
3380 | */ | |
3381 | unsigned long get_state_synchronize_sched(void) | |
3382 | { | |
3383 | /* | |
3384 | * Any prior manipulation of RCU-protected data must happen | |
3385 | * before the load from ->gpnum. | |
3386 | */ | |
3387 | smp_mb(); /* ^^^ */ | |
3388 | ||
3389 | /* | |
3390 | * Make sure this load happens before the purportedly | |
3391 | * time-consuming work between get_state_synchronize_sched() | |
3392 | * and cond_synchronize_sched(). | |
3393 | */ | |
3394 | return smp_load_acquire(&rcu_sched_state.gpnum); | |
3395 | } | |
3396 | EXPORT_SYMBOL_GPL(get_state_synchronize_sched); | |
3397 | ||
3398 | /** | |
3399 | * cond_synchronize_sched - Conditionally wait for an RCU-sched grace period | |
3400 | * | |
3401 | * @oldstate: return value from earlier call to get_state_synchronize_sched() | |
3402 | * | |
3403 | * If a full RCU-sched grace period has elapsed since the earlier call to | |
3404 | * get_state_synchronize_sched(), just return. Otherwise, invoke | |
3405 | * synchronize_sched() to wait for a full grace period. | |
3406 | * | |
3407 | * Yes, this function does not take counter wrap into account. But | |
3408 | * counter wrap is harmless. If the counter wraps, we have waited for | |
3409 | * more than 2 billion grace periods (and way more on a 64-bit system!), | |
3410 | * so waiting for one additional grace period should be just fine. | |
3411 | */ | |
3412 | void cond_synchronize_sched(unsigned long oldstate) | |
3413 | { | |
3414 | unsigned long newstate; | |
3415 | ||
3416 | /* | |
3417 | * Ensure that this load happens before any RCU-destructive | |
3418 | * actions the caller might carry out after we return. | |
3419 | */ | |
3420 | newstate = smp_load_acquire(&rcu_sched_state.completed); | |
3421 | if (ULONG_CMP_GE(oldstate, newstate)) | |
3422 | synchronize_sched(); | |
3423 | } | |
3424 | EXPORT_SYMBOL_GPL(cond_synchronize_sched); | |
3425 | ||
64db4cff PM |
3426 | /* |
3427 | * Check to see if there is any immediate RCU-related work to be done | |
3428 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
3429 | * The checks are in order of increasing expense: checks that can be | |
3430 | * carried out against CPU-local state are performed first. However, | |
3431 | * we must check for CPU stalls first, else we might not get a chance. | |
3432 | */ | |
3433 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
3434 | { | |
2f51f988 PM |
3435 | struct rcu_node *rnp = rdp->mynode; |
3436 | ||
64db4cff PM |
3437 | rdp->n_rcu_pending++; |
3438 | ||
3439 | /* Check for CPU stalls, if enabled. */ | |
3440 | check_cpu_stall(rsp, rdp); | |
3441 | ||
a096932f PM |
3442 | /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */ |
3443 | if (rcu_nohz_full_cpu(rsp)) | |
3444 | return 0; | |
3445 | ||
64db4cff | 3446 | /* Is the RCU core waiting for a quiescent state from this CPU? */ |
5c51dd73 | 3447 | if (rcu_scheduler_fully_active && |
5b74c458 | 3448 | rdp->core_needs_qs && rdp->cpu_no_qs.b.norm && |
9577df9a | 3449 | rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_dynticks.rcu_qs_ctr)) { |
97c668b8 | 3450 | rdp->n_rp_core_needs_qs++; |
3a19b46a | 3451 | } else if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm) { |
d21670ac | 3452 | rdp->n_rp_report_qs++; |
64db4cff | 3453 | return 1; |
7ba5c840 | 3454 | } |
64db4cff PM |
3455 | |
3456 | /* Does this CPU have callbacks ready to invoke? */ | |
15fecf89 | 3457 | if (rcu_segcblist_ready_cbs(&rdp->cblist)) { |
7ba5c840 | 3458 | rdp->n_rp_cb_ready++; |
64db4cff | 3459 | return 1; |
7ba5c840 | 3460 | } |
64db4cff PM |
3461 | |
3462 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
3463 | if (cpu_needs_another_gp(rsp, rdp)) { |
3464 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 3465 | return 1; |
7ba5c840 | 3466 | } |
64db4cff PM |
3467 | |
3468 | /* Has another RCU grace period completed? */ | |
7d0ae808 | 3469 | if (READ_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 3470 | rdp->n_rp_gp_completed++; |
64db4cff | 3471 | return 1; |
7ba5c840 | 3472 | } |
64db4cff PM |
3473 | |
3474 | /* Has a new RCU grace period started? */ | |
7d0ae808 PM |
3475 | if (READ_ONCE(rnp->gpnum) != rdp->gpnum || |
3476 | unlikely(READ_ONCE(rdp->gpwrap))) { /* outside lock */ | |
7ba5c840 | 3477 | rdp->n_rp_gp_started++; |
64db4cff | 3478 | return 1; |
7ba5c840 | 3479 | } |
64db4cff | 3480 | |
96d3fd0d PM |
3481 | /* Does this CPU need a deferred NOCB wakeup? */ |
3482 | if (rcu_nocb_need_deferred_wakeup(rdp)) { | |
3483 | rdp->n_rp_nocb_defer_wakeup++; | |
3484 | return 1; | |
3485 | } | |
3486 | ||
64db4cff | 3487 | /* nothing to do */ |
7ba5c840 | 3488 | rdp->n_rp_need_nothing++; |
64db4cff PM |
3489 | return 0; |
3490 | } | |
3491 | ||
3492 | /* | |
3493 | * Check to see if there is any immediate RCU-related work to be done | |
3494 | * by the current CPU, returning 1 if so. This function is part of the | |
3495 | * RCU implementation; it is -not- an exported member of the RCU API. | |
3496 | */ | |
e3950ecd | 3497 | static int rcu_pending(void) |
64db4cff | 3498 | { |
6ce75a23 PM |
3499 | struct rcu_state *rsp; |
3500 | ||
3501 | for_each_rcu_flavor(rsp) | |
e3950ecd | 3502 | if (__rcu_pending(rsp, this_cpu_ptr(rsp->rda))) |
6ce75a23 PM |
3503 | return 1; |
3504 | return 0; | |
64db4cff PM |
3505 | } |
3506 | ||
3507 | /* | |
c0f4dfd4 PM |
3508 | * Return true if the specified CPU has any callback. If all_lazy is |
3509 | * non-NULL, store an indication of whether all callbacks are lazy. | |
3510 | * (If there are no callbacks, all of them are deemed to be lazy.) | |
64db4cff | 3511 | */ |
82072c4f | 3512 | static bool __maybe_unused rcu_cpu_has_callbacks(bool *all_lazy) |
64db4cff | 3513 | { |
c0f4dfd4 PM |
3514 | bool al = true; |
3515 | bool hc = false; | |
3516 | struct rcu_data *rdp; | |
6ce75a23 PM |
3517 | struct rcu_state *rsp; |
3518 | ||
c0f4dfd4 | 3519 | for_each_rcu_flavor(rsp) { |
aa6da514 | 3520 | rdp = this_cpu_ptr(rsp->rda); |
15fecf89 | 3521 | if (rcu_segcblist_empty(&rdp->cblist)) |
69c8d28c PM |
3522 | continue; |
3523 | hc = true; | |
15fecf89 | 3524 | if (rcu_segcblist_n_nonlazy_cbs(&rdp->cblist) || !all_lazy) { |
c0f4dfd4 | 3525 | al = false; |
69c8d28c PM |
3526 | break; |
3527 | } | |
c0f4dfd4 PM |
3528 | } |
3529 | if (all_lazy) | |
3530 | *all_lazy = al; | |
3531 | return hc; | |
64db4cff PM |
3532 | } |
3533 | ||
a83eff0a PM |
3534 | /* |
3535 | * Helper function for _rcu_barrier() tracing. If tracing is disabled, | |
3536 | * the compiler is expected to optimize this away. | |
3537 | */ | |
e66c33d5 | 3538 | static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s, |
a83eff0a PM |
3539 | int cpu, unsigned long done) |
3540 | { | |
3541 | trace_rcu_barrier(rsp->name, s, cpu, | |
3542 | atomic_read(&rsp->barrier_cpu_count), done); | |
3543 | } | |
3544 | ||
b1420f1c PM |
3545 | /* |
3546 | * RCU callback function for _rcu_barrier(). If we are last, wake | |
3547 | * up the task executing _rcu_barrier(). | |
3548 | */ | |
24ebbca8 | 3549 | static void rcu_barrier_callback(struct rcu_head *rhp) |
d0ec774c | 3550 | { |
24ebbca8 PM |
3551 | struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); |
3552 | struct rcu_state *rsp = rdp->rsp; | |
3553 | ||
a83eff0a | 3554 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { |
d8db2e86 PM |
3555 | _rcu_barrier_trace(rsp, TPS("LastCB"), -1, |
3556 | rsp->barrier_sequence); | |
7db74df8 | 3557 | complete(&rsp->barrier_completion); |
a83eff0a | 3558 | } else { |
d8db2e86 | 3559 | _rcu_barrier_trace(rsp, TPS("CB"), -1, rsp->barrier_sequence); |
a83eff0a | 3560 | } |
d0ec774c PM |
3561 | } |
3562 | ||
3563 | /* | |
3564 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
3565 | */ | |
3566 | static void rcu_barrier_func(void *type) | |
3567 | { | |
037b64ed | 3568 | struct rcu_state *rsp = type; |
fa07a58f | 3569 | struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); |
d0ec774c | 3570 | |
d8db2e86 | 3571 | _rcu_barrier_trace(rsp, TPS("IRQ"), -1, rsp->barrier_sequence); |
f92c734f PM |
3572 | rdp->barrier_head.func = rcu_barrier_callback; |
3573 | debug_rcu_head_queue(&rdp->barrier_head); | |
3574 | if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head, 0)) { | |
3575 | atomic_inc(&rsp->barrier_cpu_count); | |
3576 | } else { | |
3577 | debug_rcu_head_unqueue(&rdp->barrier_head); | |
d8db2e86 PM |
3578 | _rcu_barrier_trace(rsp, TPS("IRQNQ"), -1, |
3579 | rsp->barrier_sequence); | |
f92c734f | 3580 | } |
d0ec774c PM |
3581 | } |
3582 | ||
d0ec774c PM |
3583 | /* |
3584 | * Orchestrate the specified type of RCU barrier, waiting for all | |
3585 | * RCU callbacks of the specified type to complete. | |
3586 | */ | |
037b64ed | 3587 | static void _rcu_barrier(struct rcu_state *rsp) |
d0ec774c | 3588 | { |
b1420f1c | 3589 | int cpu; |
b1420f1c | 3590 | struct rcu_data *rdp; |
4f525a52 | 3591 | unsigned long s = rcu_seq_snap(&rsp->barrier_sequence); |
b1420f1c | 3592 | |
d8db2e86 | 3593 | _rcu_barrier_trace(rsp, TPS("Begin"), -1, s); |
b1420f1c | 3594 | |
e74f4c45 | 3595 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
7be7f0be | 3596 | mutex_lock(&rsp->barrier_mutex); |
b1420f1c | 3597 | |
4f525a52 PM |
3598 | /* Did someone else do our work for us? */ |
3599 | if (rcu_seq_done(&rsp->barrier_sequence, s)) { | |
d8db2e86 PM |
3600 | _rcu_barrier_trace(rsp, TPS("EarlyExit"), -1, |
3601 | rsp->barrier_sequence); | |
cf3a9c48 PM |
3602 | smp_mb(); /* caller's subsequent code after above check. */ |
3603 | mutex_unlock(&rsp->barrier_mutex); | |
3604 | return; | |
3605 | } | |
3606 | ||
4f525a52 PM |
3607 | /* Mark the start of the barrier operation. */ |
3608 | rcu_seq_start(&rsp->barrier_sequence); | |
d8db2e86 | 3609 | _rcu_barrier_trace(rsp, TPS("Inc1"), -1, rsp->barrier_sequence); |
b1420f1c | 3610 | |
d0ec774c | 3611 | /* |
b1420f1c PM |
3612 | * Initialize the count to one rather than to zero in order to |
3613 | * avoid a too-soon return to zero in case of a short grace period | |
1331e7a1 PM |
3614 | * (or preemption of this task). Exclude CPU-hotplug operations |
3615 | * to ensure that no offline CPU has callbacks queued. | |
d0ec774c | 3616 | */ |
7db74df8 | 3617 | init_completion(&rsp->barrier_completion); |
24ebbca8 | 3618 | atomic_set(&rsp->barrier_cpu_count, 1); |
1331e7a1 | 3619 | get_online_cpus(); |
b1420f1c PM |
3620 | |
3621 | /* | |
1331e7a1 PM |
3622 | * Force each CPU with callbacks to register a new callback. |
3623 | * When that callback is invoked, we will know that all of the | |
3624 | * corresponding CPU's preceding callbacks have been invoked. | |
b1420f1c | 3625 | */ |
3fbfbf7a | 3626 | for_each_possible_cpu(cpu) { |
d1e43fa5 | 3627 | if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) |
3fbfbf7a | 3628 | continue; |
b1420f1c | 3629 | rdp = per_cpu_ptr(rsp->rda, cpu); |
d1e43fa5 | 3630 | if (rcu_is_nocb_cpu(cpu)) { |
d7e29933 | 3631 | if (!rcu_nocb_cpu_needs_barrier(rsp, cpu)) { |
d8db2e86 | 3632 | _rcu_barrier_trace(rsp, TPS("OfflineNoCB"), cpu, |
4f525a52 | 3633 | rsp->barrier_sequence); |
d7e29933 | 3634 | } else { |
d8db2e86 | 3635 | _rcu_barrier_trace(rsp, TPS("OnlineNoCB"), cpu, |
4f525a52 | 3636 | rsp->barrier_sequence); |
41050a00 | 3637 | smp_mb__before_atomic(); |
d7e29933 PM |
3638 | atomic_inc(&rsp->barrier_cpu_count); |
3639 | __call_rcu(&rdp->barrier_head, | |
3640 | rcu_barrier_callback, rsp, cpu, 0); | |
3641 | } | |
15fecf89 | 3642 | } else if (rcu_segcblist_n_cbs(&rdp->cblist)) { |
d8db2e86 | 3643 | _rcu_barrier_trace(rsp, TPS("OnlineQ"), cpu, |
4f525a52 | 3644 | rsp->barrier_sequence); |
037b64ed | 3645 | smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); |
b1420f1c | 3646 | } else { |
d8db2e86 | 3647 | _rcu_barrier_trace(rsp, TPS("OnlineNQ"), cpu, |
4f525a52 | 3648 | rsp->barrier_sequence); |
b1420f1c PM |
3649 | } |
3650 | } | |
1331e7a1 | 3651 | put_online_cpus(); |
b1420f1c PM |
3652 | |
3653 | /* | |
3654 | * Now that we have an rcu_barrier_callback() callback on each | |
3655 | * CPU, and thus each counted, remove the initial count. | |
3656 | */ | |
24ebbca8 | 3657 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) |
7db74df8 | 3658 | complete(&rsp->barrier_completion); |
b1420f1c PM |
3659 | |
3660 | /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ | |
7db74df8 | 3661 | wait_for_completion(&rsp->barrier_completion); |
b1420f1c | 3662 | |
4f525a52 | 3663 | /* Mark the end of the barrier operation. */ |
d8db2e86 | 3664 | _rcu_barrier_trace(rsp, TPS("Inc2"), -1, rsp->barrier_sequence); |
4f525a52 PM |
3665 | rcu_seq_end(&rsp->barrier_sequence); |
3666 | ||
b1420f1c | 3667 | /* Other rcu_barrier() invocations can now safely proceed. */ |
7be7f0be | 3668 | mutex_unlock(&rsp->barrier_mutex); |
d0ec774c | 3669 | } |
d0ec774c PM |
3670 | |
3671 | /** | |
3672 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
3673 | */ | |
3674 | void rcu_barrier_bh(void) | |
3675 | { | |
037b64ed | 3676 | _rcu_barrier(&rcu_bh_state); |
d0ec774c PM |
3677 | } |
3678 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
3679 | ||
3680 | /** | |
3681 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
3682 | */ | |
3683 | void rcu_barrier_sched(void) | |
3684 | { | |
037b64ed | 3685 | _rcu_barrier(&rcu_sched_state); |
d0ec774c PM |
3686 | } |
3687 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
3688 | ||
0aa04b05 PM |
3689 | /* |
3690 | * Propagate ->qsinitmask bits up the rcu_node tree to account for the | |
3691 | * first CPU in a given leaf rcu_node structure coming online. The caller | |
3692 | * must hold the corresponding leaf rcu_node ->lock with interrrupts | |
3693 | * disabled. | |
3694 | */ | |
3695 | static void rcu_init_new_rnp(struct rcu_node *rnp_leaf) | |
3696 | { | |
3697 | long mask; | |
3698 | struct rcu_node *rnp = rnp_leaf; | |
3699 | ||
c0b334c5 | 3700 | lockdep_assert_held(&rnp->lock); |
0aa04b05 PM |
3701 | for (;;) { |
3702 | mask = rnp->grpmask; | |
3703 | rnp = rnp->parent; | |
3704 | if (rnp == NULL) | |
3705 | return; | |
6cf10081 | 3706 | raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */ |
0aa04b05 | 3707 | rnp->qsmaskinit |= mask; |
67c583a7 | 3708 | raw_spin_unlock_rcu_node(rnp); /* Interrupts remain disabled. */ |
0aa04b05 PM |
3709 | } |
3710 | } | |
3711 | ||
64db4cff | 3712 | /* |
27569620 | 3713 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 3714 | */ |
27569620 PM |
3715 | static void __init |
3716 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
3717 | { |
3718 | unsigned long flags; | |
394f99a9 | 3719 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
3720 | struct rcu_node *rnp = rcu_get_root(rsp); |
3721 | ||
3722 | /* Set up local state, ensuring consistent view of global state. */ | |
6cf10081 | 3723 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
bc75e999 | 3724 | rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu); |
27569620 | 3725 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
29e37d81 | 3726 | WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); |
02a5c550 | 3727 | WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp->dynticks))); |
27569620 | 3728 | rdp->cpu = cpu; |
d4c08f2a | 3729 | rdp->rsp = rsp; |
3fbfbf7a | 3730 | rcu_boot_init_nocb_percpu_data(rdp); |
67c583a7 | 3731 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
27569620 PM |
3732 | } |
3733 | ||
3734 | /* | |
3735 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
3736 | * offline event can be happening at a given time. Note also that we | |
3737 | * can accept some slop in the rsp->completed access due to the fact | |
3738 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 3739 | */ |
49fb4c62 | 3740 | static void |
9b67122a | 3741 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp) |
64db4cff PM |
3742 | { |
3743 | unsigned long flags; | |
394f99a9 | 3744 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
3745 | struct rcu_node *rnp = rcu_get_root(rsp); |
3746 | ||
3747 | /* Set up local state, ensuring consistent view of global state. */ | |
6cf10081 | 3748 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
37c72e56 PM |
3749 | rdp->qlen_last_fqs_check = 0; |
3750 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 3751 | rdp->blimit = blimit; |
15fecf89 PM |
3752 | if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */ |
3753 | !init_nocb_callback_list(rdp)) | |
3754 | rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */ | |
29e37d81 | 3755 | rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
2625d469 | 3756 | rcu_dynticks_eqs_online(); |
67c583a7 | 3757 | raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ |
64db4cff | 3758 | |
0aa04b05 PM |
3759 | /* |
3760 | * Add CPU to leaf rcu_node pending-online bitmask. Any needed | |
3761 | * propagation up the rcu_node tree will happen at the beginning | |
3762 | * of the next grace period. | |
3763 | */ | |
64db4cff | 3764 | rnp = rdp->mynode; |
2a67e741 | 3765 | raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ |
b9585e94 | 3766 | rdp->beenonline = true; /* We have now been online. */ |
0aa04b05 PM |
3767 | rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */ |
3768 | rdp->completed = rnp->completed; | |
5b74c458 | 3769 | rdp->cpu_no_qs.b.norm = true; |
9577df9a | 3770 | rdp->rcu_qs_ctr_snap = per_cpu(rcu_dynticks.rcu_qs_ctr, cpu); |
97c668b8 | 3771 | rdp->core_needs_qs = false; |
9b9500da PM |
3772 | rdp->rcu_iw_pending = false; |
3773 | rdp->rcu_iw_gpnum = rnp->gpnum - 1; | |
0aa04b05 | 3774 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl")); |
67c583a7 | 3775 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
64db4cff PM |
3776 | } |
3777 | ||
deb34f36 PM |
3778 | /* |
3779 | * Invoked early in the CPU-online process, when pretty much all | |
3780 | * services are available. The incoming CPU is not present. | |
3781 | */ | |
4df83742 | 3782 | int rcutree_prepare_cpu(unsigned int cpu) |
64db4cff | 3783 | { |
6ce75a23 PM |
3784 | struct rcu_state *rsp; |
3785 | ||
3786 | for_each_rcu_flavor(rsp) | |
9b67122a | 3787 | rcu_init_percpu_data(cpu, rsp); |
4df83742 TG |
3788 | |
3789 | rcu_prepare_kthreads(cpu); | |
3790 | rcu_spawn_all_nocb_kthreads(cpu); | |
3791 | ||
3792 | return 0; | |
3793 | } | |
3794 | ||
deb34f36 PM |
3795 | /* |
3796 | * Update RCU priority boot kthread affinity for CPU-hotplug changes. | |
3797 | */ | |
4df83742 TG |
3798 | static void rcutree_affinity_setting(unsigned int cpu, int outgoing) |
3799 | { | |
3800 | struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); | |
3801 | ||
3802 | rcu_boost_kthread_setaffinity(rdp->mynode, outgoing); | |
3803 | } | |
3804 | ||
deb34f36 PM |
3805 | /* |
3806 | * Near the end of the CPU-online process. Pretty much all services | |
3807 | * enabled, and the CPU is now very much alive. | |
3808 | */ | |
4df83742 TG |
3809 | int rcutree_online_cpu(unsigned int cpu) |
3810 | { | |
9b9500da PM |
3811 | unsigned long flags; |
3812 | struct rcu_data *rdp; | |
3813 | struct rcu_node *rnp; | |
3814 | struct rcu_state *rsp; | |
3815 | ||
3816 | for_each_rcu_flavor(rsp) { | |
3817 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
3818 | rnp = rdp->mynode; | |
3819 | raw_spin_lock_irqsave_rcu_node(rnp, flags); | |
3820 | rnp->ffmask |= rdp->grpmask; | |
3821 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); | |
3822 | } | |
da915ad5 PM |
3823 | if (IS_ENABLED(CONFIG_TREE_SRCU)) |
3824 | srcu_online_cpu(cpu); | |
9b9500da PM |
3825 | if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) |
3826 | return 0; /* Too early in boot for scheduler work. */ | |
3827 | sync_sched_exp_online_cleanup(cpu); | |
3828 | rcutree_affinity_setting(cpu, -1); | |
4df83742 TG |
3829 | return 0; |
3830 | } | |
3831 | ||
deb34f36 PM |
3832 | /* |
3833 | * Near the beginning of the process. The CPU is still very much alive | |
3834 | * with pretty much all services enabled. | |
3835 | */ | |
4df83742 TG |
3836 | int rcutree_offline_cpu(unsigned int cpu) |
3837 | { | |
9b9500da PM |
3838 | unsigned long flags; |
3839 | struct rcu_data *rdp; | |
3840 | struct rcu_node *rnp; | |
3841 | struct rcu_state *rsp; | |
3842 | ||
3843 | for_each_rcu_flavor(rsp) { | |
3844 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
3845 | rnp = rdp->mynode; | |
3846 | raw_spin_lock_irqsave_rcu_node(rnp, flags); | |
3847 | rnp->ffmask &= ~rdp->grpmask; | |
3848 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); | |
3849 | } | |
3850 | ||
4df83742 | 3851 | rcutree_affinity_setting(cpu, cpu); |
da915ad5 PM |
3852 | if (IS_ENABLED(CONFIG_TREE_SRCU)) |
3853 | srcu_offline_cpu(cpu); | |
4df83742 TG |
3854 | return 0; |
3855 | } | |
3856 | ||
deb34f36 PM |
3857 | /* |
3858 | * Near the end of the offline process. We do only tracing here. | |
3859 | */ | |
4df83742 TG |
3860 | int rcutree_dying_cpu(unsigned int cpu) |
3861 | { | |
3862 | struct rcu_state *rsp; | |
3863 | ||
3864 | for_each_rcu_flavor(rsp) | |
3865 | rcu_cleanup_dying_cpu(rsp); | |
3866 | return 0; | |
3867 | } | |
3868 | ||
deb34f36 PM |
3869 | /* |
3870 | * The outgoing CPU is gone and we are running elsewhere. | |
3871 | */ | |
4df83742 TG |
3872 | int rcutree_dead_cpu(unsigned int cpu) |
3873 | { | |
3874 | struct rcu_state *rsp; | |
3875 | ||
3876 | for_each_rcu_flavor(rsp) { | |
3877 | rcu_cleanup_dead_cpu(cpu, rsp); | |
3878 | do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu)); | |
3879 | } | |
3880 | return 0; | |
64db4cff PM |
3881 | } |
3882 | ||
7ec99de3 PM |
3883 | /* |
3884 | * Mark the specified CPU as being online so that subsequent grace periods | |
3885 | * (both expedited and normal) will wait on it. Note that this means that | |
3886 | * incoming CPUs are not allowed to use RCU read-side critical sections | |
3887 | * until this function is called. Failing to observe this restriction | |
3888 | * will result in lockdep splats. | |
deb34f36 PM |
3889 | * |
3890 | * Note that this function is special in that it is invoked directly | |
3891 | * from the incoming CPU rather than from the cpuhp_step mechanism. | |
3892 | * This is because this function must be invoked at a precise location. | |
7ec99de3 PM |
3893 | */ |
3894 | void rcu_cpu_starting(unsigned int cpu) | |
3895 | { | |
3896 | unsigned long flags; | |
3897 | unsigned long mask; | |
313517fc PM |
3898 | int nbits; |
3899 | unsigned long oldmask; | |
7ec99de3 PM |
3900 | struct rcu_data *rdp; |
3901 | struct rcu_node *rnp; | |
3902 | struct rcu_state *rsp; | |
3903 | ||
3904 | for_each_rcu_flavor(rsp) { | |
fdbb9b31 | 3905 | rdp = per_cpu_ptr(rsp->rda, cpu); |
7ec99de3 PM |
3906 | rnp = rdp->mynode; |
3907 | mask = rdp->grpmask; | |
3908 | raw_spin_lock_irqsave_rcu_node(rnp, flags); | |
3909 | rnp->qsmaskinitnext |= mask; | |
313517fc | 3910 | oldmask = rnp->expmaskinitnext; |
7ec99de3 | 3911 | rnp->expmaskinitnext |= mask; |
313517fc PM |
3912 | oldmask ^= rnp->expmaskinitnext; |
3913 | nbits = bitmap_weight(&oldmask, BITS_PER_LONG); | |
3914 | /* Allow lockless access for expedited grace periods. */ | |
3915 | smp_store_release(&rsp->ncpus, rsp->ncpus + nbits); /* ^^^ */ | |
7ec99de3 PM |
3916 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
3917 | } | |
313517fc | 3918 | smp_mb(); /* Ensure RCU read-side usage follows above initialization. */ |
7ec99de3 PM |
3919 | } |
3920 | ||
27d50c7e TG |
3921 | #ifdef CONFIG_HOTPLUG_CPU |
3922 | /* | |
3923 | * The CPU is exiting the idle loop into the arch_cpu_idle_dead() | |
3924 | * function. We now remove it from the rcu_node tree's ->qsmaskinit | |
3925 | * bit masks. | |
3926 | */ | |
3927 | static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp) | |
3928 | { | |
3929 | unsigned long flags; | |
3930 | unsigned long mask; | |
3931 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
3932 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ | |
3933 | ||
27d50c7e TG |
3934 | /* Remove outgoing CPU from mask in the leaf rcu_node structure. */ |
3935 | mask = rdp->grpmask; | |
3936 | raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */ | |
3937 | rnp->qsmaskinitnext &= ~mask; | |
710d60cb | 3938 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
27d50c7e TG |
3939 | } |
3940 | ||
deb34f36 PM |
3941 | /* |
3942 | * The outgoing function has no further need of RCU, so remove it from | |
3943 | * the list of CPUs that RCU must track. | |
3944 | * | |
3945 | * Note that this function is special in that it is invoked directly | |
3946 | * from the outgoing CPU rather than from the cpuhp_step mechanism. | |
3947 | * This is because this function must be invoked at a precise location. | |
3948 | */ | |
27d50c7e TG |
3949 | void rcu_report_dead(unsigned int cpu) |
3950 | { | |
3951 | struct rcu_state *rsp; | |
3952 | ||
3953 | /* QS for any half-done expedited RCU-sched GP. */ | |
3954 | preempt_disable(); | |
3955 | rcu_report_exp_rdp(&rcu_sched_state, | |
3956 | this_cpu_ptr(rcu_sched_state.rda), true); | |
3957 | preempt_enable(); | |
3958 | for_each_rcu_flavor(rsp) | |
3959 | rcu_cleanup_dying_idle_cpu(cpu, rsp); | |
3960 | } | |
a58163d8 | 3961 | |
f2dbe4a5 | 3962 | /* Migrate the dead CPU's callbacks to the current CPU. */ |
a58163d8 PM |
3963 | static void rcu_migrate_callbacks(int cpu, struct rcu_state *rsp) |
3964 | { | |
3965 | unsigned long flags; | |
b1a2d79f | 3966 | struct rcu_data *my_rdp; |
a58163d8 | 3967 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
9fa46fb8 | 3968 | struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); |
a58163d8 | 3969 | |
95335c03 PM |
3970 | if (rcu_is_nocb_cpu(cpu) || rcu_segcblist_empty(&rdp->cblist)) |
3971 | return; /* No callbacks to migrate. */ | |
3972 | ||
b1a2d79f PM |
3973 | local_irq_save(flags); |
3974 | my_rdp = this_cpu_ptr(rsp->rda); | |
3975 | if (rcu_nocb_adopt_orphan_cbs(my_rdp, rdp, flags)) { | |
3976 | local_irq_restore(flags); | |
3977 | return; | |
3978 | } | |
9fa46fb8 PM |
3979 | raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */ |
3980 | rcu_advance_cbs(rsp, rnp_root, rdp); /* Leverage recent GPs. */ | |
21cc2483 | 3981 | rcu_advance_cbs(rsp, rnp_root, my_rdp); /* Assign GP to pending CBs. */ |
f2dbe4a5 | 3982 | rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist); |
09efeeee PM |
3983 | WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) != |
3984 | !rcu_segcblist_n_cbs(&my_rdp->cblist)); | |
537b85c8 | 3985 | raw_spin_unlock_irqrestore_rcu_node(rnp_root, flags); |
a58163d8 PM |
3986 | WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 || |
3987 | !rcu_segcblist_empty(&rdp->cblist), | |
3988 | "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, 1stCB=%p\n", | |
3989 | cpu, rcu_segcblist_n_cbs(&rdp->cblist), | |
3990 | rcu_segcblist_first_cb(&rdp->cblist)); | |
3991 | } | |
3992 | ||
3993 | /* | |
3994 | * The outgoing CPU has just passed through the dying-idle state, | |
3995 | * and we are being invoked from the CPU that was IPIed to continue the | |
3996 | * offline operation. We need to migrate the outgoing CPU's callbacks. | |
3997 | */ | |
3998 | void rcutree_migrate_callbacks(int cpu) | |
3999 | { | |
4000 | struct rcu_state *rsp; | |
4001 | ||
4002 | for_each_rcu_flavor(rsp) | |
4003 | rcu_migrate_callbacks(cpu, rsp); | |
4004 | } | |
27d50c7e TG |
4005 | #endif |
4006 | ||
deb34f36 PM |
4007 | /* |
4008 | * On non-huge systems, use expedited RCU grace periods to make suspend | |
4009 | * and hibernation run faster. | |
4010 | */ | |
d1d74d14 BP |
4011 | static int rcu_pm_notify(struct notifier_block *self, |
4012 | unsigned long action, void *hcpu) | |
4013 | { | |
4014 | switch (action) { | |
4015 | case PM_HIBERNATION_PREPARE: | |
4016 | case PM_SUSPEND_PREPARE: | |
4017 | if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ | |
5afff48b | 4018 | rcu_expedite_gp(); |
d1d74d14 BP |
4019 | break; |
4020 | case PM_POST_HIBERNATION: | |
4021 | case PM_POST_SUSPEND: | |
5afff48b PM |
4022 | if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ |
4023 | rcu_unexpedite_gp(); | |
d1d74d14 BP |
4024 | break; |
4025 | default: | |
4026 | break; | |
4027 | } | |
4028 | return NOTIFY_OK; | |
4029 | } | |
4030 | ||
b3dbec76 | 4031 | /* |
9386c0b7 | 4032 | * Spawn the kthreads that handle each RCU flavor's grace periods. |
b3dbec76 PM |
4033 | */ |
4034 | static int __init rcu_spawn_gp_kthread(void) | |
4035 | { | |
4036 | unsigned long flags; | |
a94844b2 | 4037 | int kthread_prio_in = kthread_prio; |
b3dbec76 PM |
4038 | struct rcu_node *rnp; |
4039 | struct rcu_state *rsp; | |
a94844b2 | 4040 | struct sched_param sp; |
b3dbec76 PM |
4041 | struct task_struct *t; |
4042 | ||
a94844b2 PM |
4043 | /* Force priority into range. */ |
4044 | if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1) | |
4045 | kthread_prio = 1; | |
4046 | else if (kthread_prio < 0) | |
4047 | kthread_prio = 0; | |
4048 | else if (kthread_prio > 99) | |
4049 | kthread_prio = 99; | |
4050 | if (kthread_prio != kthread_prio_in) | |
4051 | pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n", | |
4052 | kthread_prio, kthread_prio_in); | |
4053 | ||
9386c0b7 | 4054 | rcu_scheduler_fully_active = 1; |
b3dbec76 | 4055 | for_each_rcu_flavor(rsp) { |
a94844b2 | 4056 | t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name); |
b3dbec76 PM |
4057 | BUG_ON(IS_ERR(t)); |
4058 | rnp = rcu_get_root(rsp); | |
6cf10081 | 4059 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
b3dbec76 | 4060 | rsp->gp_kthread = t; |
a94844b2 PM |
4061 | if (kthread_prio) { |
4062 | sp.sched_priority = kthread_prio; | |
4063 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); | |
4064 | } | |
67c583a7 | 4065 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
e11f1335 | 4066 | wake_up_process(t); |
b3dbec76 | 4067 | } |
35ce7f29 | 4068 | rcu_spawn_nocb_kthreads(); |
9386c0b7 | 4069 | rcu_spawn_boost_kthreads(); |
b3dbec76 PM |
4070 | return 0; |
4071 | } | |
4072 | early_initcall(rcu_spawn_gp_kthread); | |
4073 | ||
bbad9379 | 4074 | /* |
52d7e48b PM |
4075 | * This function is invoked towards the end of the scheduler's |
4076 | * initialization process. Before this is called, the idle task might | |
4077 | * contain synchronous grace-period primitives (during which time, this idle | |
4078 | * task is booting the system, and such primitives are no-ops). After this | |
4079 | * function is called, any synchronous grace-period primitives are run as | |
4080 | * expedited, with the requesting task driving the grace period forward. | |
900b1028 | 4081 | * A later core_initcall() rcu_set_runtime_mode() will switch to full |
52d7e48b | 4082 | * runtime RCU functionality. |
bbad9379 PM |
4083 | */ |
4084 | void rcu_scheduler_starting(void) | |
4085 | { | |
4086 | WARN_ON(num_online_cpus() != 1); | |
4087 | WARN_ON(nr_context_switches() > 0); | |
52d7e48b PM |
4088 | rcu_test_sync_prims(); |
4089 | rcu_scheduler_active = RCU_SCHEDULER_INIT; | |
4090 | rcu_test_sync_prims(); | |
bbad9379 PM |
4091 | } |
4092 | ||
64db4cff PM |
4093 | /* |
4094 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
4095 | */ | |
a87f203e | 4096 | static void __init rcu_init_one(struct rcu_state *rsp) |
64db4cff | 4097 | { |
cb007102 AG |
4098 | static const char * const buf[] = RCU_NODE_NAME_INIT; |
4099 | static const char * const fqs[] = RCU_FQS_NAME_INIT; | |
3dc5dbe9 PM |
4100 | static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; |
4101 | static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; | |
199977bf | 4102 | |
199977bf | 4103 | int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */ |
64db4cff PM |
4104 | int cpustride = 1; |
4105 | int i; | |
4106 | int j; | |
4107 | struct rcu_node *rnp; | |
4108 | ||
05b84aec | 4109 | BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
b6407e86 | 4110 | |
3eaaaf6c PM |
4111 | /* Silence gcc 4.8 false positive about array index out of range. */ |
4112 | if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS) | |
4113 | panic("rcu_init_one: rcu_num_lvls out of range"); | |
4930521a | 4114 | |
64db4cff PM |
4115 | /* Initialize the level-tracking arrays. */ |
4116 | ||
f885b7f2 | 4117 | for (i = 1; i < rcu_num_lvls; i++) |
41f5c631 PM |
4118 | rsp->level[i] = rsp->level[i - 1] + num_rcu_lvl[i - 1]; |
4119 | rcu_init_levelspread(levelspread, num_rcu_lvl); | |
64db4cff PM |
4120 | |
4121 | /* Initialize the elements themselves, starting from the leaves. */ | |
4122 | ||
f885b7f2 | 4123 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
199977bf | 4124 | cpustride *= levelspread[i]; |
64db4cff | 4125 | rnp = rsp->level[i]; |
41f5c631 | 4126 | for (j = 0; j < num_rcu_lvl[i]; j++, rnp++) { |
67c583a7 BF |
4127 | raw_spin_lock_init(&ACCESS_PRIVATE(rnp, lock)); |
4128 | lockdep_set_class_and_name(&ACCESS_PRIVATE(rnp, lock), | |
b6407e86 | 4129 | &rcu_node_class[i], buf[i]); |
394f2769 PM |
4130 | raw_spin_lock_init(&rnp->fqslock); |
4131 | lockdep_set_class_and_name(&rnp->fqslock, | |
4132 | &rcu_fqs_class[i], fqs[i]); | |
25d30cf4 PM |
4133 | rnp->gpnum = rsp->gpnum; |
4134 | rnp->completed = rsp->completed; | |
64db4cff PM |
4135 | rnp->qsmask = 0; |
4136 | rnp->qsmaskinit = 0; | |
4137 | rnp->grplo = j * cpustride; | |
4138 | rnp->grphi = (j + 1) * cpustride - 1; | |
595f3900 HS |
4139 | if (rnp->grphi >= nr_cpu_ids) |
4140 | rnp->grphi = nr_cpu_ids - 1; | |
64db4cff PM |
4141 | if (i == 0) { |
4142 | rnp->grpnum = 0; | |
4143 | rnp->grpmask = 0; | |
4144 | rnp->parent = NULL; | |
4145 | } else { | |
199977bf | 4146 | rnp->grpnum = j % levelspread[i - 1]; |
64db4cff PM |
4147 | rnp->grpmask = 1UL << rnp->grpnum; |
4148 | rnp->parent = rsp->level[i - 1] + | |
199977bf | 4149 | j / levelspread[i - 1]; |
64db4cff PM |
4150 | } |
4151 | rnp->level = i; | |
12f5f524 | 4152 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
dae6e64d | 4153 | rcu_init_one_nocb(rnp); |
f6a12f34 PM |
4154 | init_waitqueue_head(&rnp->exp_wq[0]); |
4155 | init_waitqueue_head(&rnp->exp_wq[1]); | |
3b5f668e PM |
4156 | init_waitqueue_head(&rnp->exp_wq[2]); |
4157 | init_waitqueue_head(&rnp->exp_wq[3]); | |
f6a12f34 | 4158 | spin_lock_init(&rnp->exp_lock); |
64db4cff PM |
4159 | } |
4160 | } | |
0c34029a | 4161 | |
abedf8e2 PG |
4162 | init_swait_queue_head(&rsp->gp_wq); |
4163 | init_swait_queue_head(&rsp->expedited_wq); | |
f885b7f2 | 4164 | rnp = rsp->level[rcu_num_lvls - 1]; |
0c34029a | 4165 | for_each_possible_cpu(i) { |
4a90a068 | 4166 | while (i > rnp->grphi) |
0c34029a | 4167 | rnp++; |
394f99a9 | 4168 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
4169 | rcu_boot_init_percpu_data(i, rsp); |
4170 | } | |
6ce75a23 | 4171 | list_add(&rsp->flavors, &rcu_struct_flavors); |
64db4cff PM |
4172 | } |
4173 | ||
f885b7f2 PM |
4174 | /* |
4175 | * Compute the rcu_node tree geometry from kernel parameters. This cannot | |
4102adab | 4176 | * replace the definitions in tree.h because those are needed to size |
f885b7f2 PM |
4177 | * the ->node array in the rcu_state structure. |
4178 | */ | |
4179 | static void __init rcu_init_geometry(void) | |
4180 | { | |
026ad283 | 4181 | ulong d; |
f885b7f2 | 4182 | int i; |
05b84aec | 4183 | int rcu_capacity[RCU_NUM_LVLS]; |
f885b7f2 | 4184 | |
026ad283 PM |
4185 | /* |
4186 | * Initialize any unspecified boot parameters. | |
4187 | * The default values of jiffies_till_first_fqs and | |
4188 | * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS | |
4189 | * value, which is a function of HZ, then adding one for each | |
4190 | * RCU_JIFFIES_FQS_DIV CPUs that might be on the system. | |
4191 | */ | |
4192 | d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; | |
4193 | if (jiffies_till_first_fqs == ULONG_MAX) | |
4194 | jiffies_till_first_fqs = d; | |
4195 | if (jiffies_till_next_fqs == ULONG_MAX) | |
4196 | jiffies_till_next_fqs = d; | |
4197 | ||
f885b7f2 | 4198 | /* If the compile-time values are accurate, just leave. */ |
47d631af | 4199 | if (rcu_fanout_leaf == RCU_FANOUT_LEAF && |
b17c7035 | 4200 | nr_cpu_ids == NR_CPUS) |
f885b7f2 | 4201 | return; |
9b130ad5 | 4202 | pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n", |
39479098 | 4203 | rcu_fanout_leaf, nr_cpu_ids); |
f885b7f2 | 4204 | |
f885b7f2 | 4205 | /* |
ee968ac6 PM |
4206 | * The boot-time rcu_fanout_leaf parameter must be at least two |
4207 | * and cannot exceed the number of bits in the rcu_node masks. | |
4208 | * Complain and fall back to the compile-time values if this | |
4209 | * limit is exceeded. | |
f885b7f2 | 4210 | */ |
ee968ac6 | 4211 | if (rcu_fanout_leaf < 2 || |
75cf15a4 | 4212 | rcu_fanout_leaf > sizeof(unsigned long) * 8) { |
13bd6494 | 4213 | rcu_fanout_leaf = RCU_FANOUT_LEAF; |
f885b7f2 PM |
4214 | WARN_ON(1); |
4215 | return; | |
4216 | } | |
4217 | ||
f885b7f2 PM |
4218 | /* |
4219 | * Compute number of nodes that can be handled an rcu_node tree | |
9618138b | 4220 | * with the given number of levels. |
f885b7f2 | 4221 | */ |
9618138b | 4222 | rcu_capacity[0] = rcu_fanout_leaf; |
05b84aec | 4223 | for (i = 1; i < RCU_NUM_LVLS; i++) |
05c5df31 | 4224 | rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT; |
f885b7f2 PM |
4225 | |
4226 | /* | |
75cf15a4 | 4227 | * The tree must be able to accommodate the configured number of CPUs. |
ee968ac6 | 4228 | * If this limit is exceeded, fall back to the compile-time values. |
f885b7f2 | 4229 | */ |
ee968ac6 PM |
4230 | if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1]) { |
4231 | rcu_fanout_leaf = RCU_FANOUT_LEAF; | |
4232 | WARN_ON(1); | |
4233 | return; | |
4234 | } | |
f885b7f2 | 4235 | |
679f9858 | 4236 | /* Calculate the number of levels in the tree. */ |
9618138b | 4237 | for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) { |
679f9858 | 4238 | } |
9618138b | 4239 | rcu_num_lvls = i + 1; |
679f9858 | 4240 | |
f885b7f2 | 4241 | /* Calculate the number of rcu_nodes at each level of the tree. */ |
679f9858 | 4242 | for (i = 0; i < rcu_num_lvls; i++) { |
9618138b | 4243 | int cap = rcu_capacity[(rcu_num_lvls - 1) - i]; |
679f9858 AG |
4244 | num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); |
4245 | } | |
f885b7f2 PM |
4246 | |
4247 | /* Calculate the total number of rcu_node structures. */ | |
4248 | rcu_num_nodes = 0; | |
679f9858 | 4249 | for (i = 0; i < rcu_num_lvls; i++) |
f885b7f2 | 4250 | rcu_num_nodes += num_rcu_lvl[i]; |
f885b7f2 PM |
4251 | } |
4252 | ||
a3dc2948 PM |
4253 | /* |
4254 | * Dump out the structure of the rcu_node combining tree associated | |
4255 | * with the rcu_state structure referenced by rsp. | |
4256 | */ | |
4257 | static void __init rcu_dump_rcu_node_tree(struct rcu_state *rsp) | |
4258 | { | |
4259 | int level = 0; | |
4260 | struct rcu_node *rnp; | |
4261 | ||
4262 | pr_info("rcu_node tree layout dump\n"); | |
4263 | pr_info(" "); | |
4264 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
4265 | if (rnp->level != level) { | |
4266 | pr_cont("\n"); | |
4267 | pr_info(" "); | |
4268 | level = rnp->level; | |
4269 | } | |
4270 | pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum); | |
4271 | } | |
4272 | pr_cont("\n"); | |
4273 | } | |
4274 | ||
9f680ab4 | 4275 | void __init rcu_init(void) |
64db4cff | 4276 | { |
017c4261 | 4277 | int cpu; |
9f680ab4 | 4278 | |
47627678 PM |
4279 | rcu_early_boot_tests(); |
4280 | ||
f41d911f | 4281 | rcu_bootup_announce(); |
f885b7f2 | 4282 | rcu_init_geometry(); |
a87f203e PM |
4283 | rcu_init_one(&rcu_bh_state); |
4284 | rcu_init_one(&rcu_sched_state); | |
a3dc2948 PM |
4285 | if (dump_tree) |
4286 | rcu_dump_rcu_node_tree(&rcu_sched_state); | |
f41d911f | 4287 | __rcu_init_preempt(); |
b5b39360 | 4288 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
4289 | |
4290 | /* | |
4291 | * We don't need protection against CPU-hotplug here because | |
4292 | * this is called early in boot, before either interrupts | |
4293 | * or the scheduler are operational. | |
4294 | */ | |
d1d74d14 | 4295 | pm_notifier(rcu_pm_notify, 0); |
7ec99de3 | 4296 | for_each_online_cpu(cpu) { |
4df83742 | 4297 | rcutree_prepare_cpu(cpu); |
7ec99de3 | 4298 | rcu_cpu_starting(cpu); |
9b9500da | 4299 | rcutree_online_cpu(cpu); |
7ec99de3 | 4300 | } |
64db4cff PM |
4301 | } |
4302 | ||
3549c2bc | 4303 | #include "tree_exp.h" |
4102adab | 4304 | #include "tree_plugin.h" |