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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 | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
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> | |
35 | #include <linux/rcupdate.h> | |
36 | #include <linux/interrupt.h> | |
37 | #include <linux/sched.h> | |
c1dc0b9c | 38 | #include <linux/nmi.h> |
8826f3b0 | 39 | #include <linux/atomic.h> |
64db4cff | 40 | #include <linux/bitops.h> |
9984de1a | 41 | #include <linux/export.h> |
64db4cff PM |
42 | #include <linux/completion.h> |
43 | #include <linux/moduleparam.h> | |
44 | #include <linux/percpu.h> | |
45 | #include <linux/notifier.h> | |
46 | #include <linux/cpu.h> | |
47 | #include <linux/mutex.h> | |
48 | #include <linux/time.h> | |
bbad9379 | 49 | #include <linux/kernel_stat.h> |
a26ac245 PM |
50 | #include <linux/wait.h> |
51 | #include <linux/kthread.h> | |
268bb0ce | 52 | #include <linux/prefetch.h> |
3d3b7db0 PM |
53 | #include <linux/delay.h> |
54 | #include <linux/stop_machine.h> | |
64db4cff | 55 | |
9f77da9f | 56 | #include "rcutree.h" |
29c00b4a PM |
57 | #include <trace/events/rcu.h> |
58 | ||
59 | #include "rcu.h" | |
9f77da9f | 60 | |
64db4cff PM |
61 | /* Data structures. */ |
62 | ||
f885b7f2 | 63 | static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; |
88b91c7c | 64 | |
037b64ed | 65 | #define RCU_STATE_INITIALIZER(sname, cr) { \ |
6c90cc7b | 66 | .level = { &sname##_state.node[0] }, \ |
037b64ed | 67 | .call = cr, \ |
af446b70 | 68 | .fqs_state = RCU_GP_IDLE, \ |
64db4cff PM |
69 | .gpnum = -300, \ |
70 | .completed = -300, \ | |
6c90cc7b PM |
71 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.onofflock), \ |
72 | .orphan_nxttail = &sname##_state.orphan_nxtlist, \ | |
73 | .orphan_donetail = &sname##_state.orphan_donelist, \ | |
74 | .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.fqslock), \ | |
64db4cff PM |
75 | .n_force_qs = 0, \ |
76 | .n_force_qs_ngp = 0, \ | |
6c90cc7b | 77 | .name = #sname, \ |
64db4cff PM |
78 | } |
79 | ||
037b64ed PM |
80 | struct rcu_state rcu_sched_state = |
81 | RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched); | |
d6714c22 | 82 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
64db4cff | 83 | |
037b64ed | 84 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh); |
6258c4fb | 85 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
b1f77b05 | 86 | |
27f4d280 PM |
87 | static struct rcu_state *rcu_state; |
88 | ||
f885b7f2 PM |
89 | /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ |
90 | static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; | |
91 | module_param(rcu_fanout_leaf, int, 0); | |
92 | int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; | |
93 | static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */ | |
94 | NUM_RCU_LVL_0, | |
95 | NUM_RCU_LVL_1, | |
96 | NUM_RCU_LVL_2, | |
97 | NUM_RCU_LVL_3, | |
98 | NUM_RCU_LVL_4, | |
99 | }; | |
100 | int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ | |
101 | ||
b0d30417 PM |
102 | /* |
103 | * The rcu_scheduler_active variable transitions from zero to one just | |
104 | * before the first task is spawned. So when this variable is zero, RCU | |
105 | * can assume that there is but one task, allowing RCU to (for example) | |
106 | * optimized synchronize_sched() to a simple barrier(). When this variable | |
107 | * is one, RCU must actually do all the hard work required to detect real | |
108 | * grace periods. This variable is also used to suppress boot-time false | |
109 | * positives from lockdep-RCU error checking. | |
110 | */ | |
bbad9379 PM |
111 | int rcu_scheduler_active __read_mostly; |
112 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
113 | ||
b0d30417 PM |
114 | /* |
115 | * The rcu_scheduler_fully_active variable transitions from zero to one | |
116 | * during the early_initcall() processing, which is after the scheduler | |
117 | * is capable of creating new tasks. So RCU processing (for example, | |
118 | * creating tasks for RCU priority boosting) must be delayed until after | |
119 | * rcu_scheduler_fully_active transitions from zero to one. We also | |
120 | * currently delay invocation of any RCU callbacks until after this point. | |
121 | * | |
122 | * It might later prove better for people registering RCU callbacks during | |
123 | * early boot to take responsibility for these callbacks, but one step at | |
124 | * a time. | |
125 | */ | |
126 | static int rcu_scheduler_fully_active __read_mostly; | |
127 | ||
a46e0899 PM |
128 | #ifdef CONFIG_RCU_BOOST |
129 | ||
a26ac245 PM |
130 | /* |
131 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
132 | * handle all flavors of RCU. | |
133 | */ | |
134 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
d71df90e | 135 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
15ba0ba8 | 136 | DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu); |
5ece5bab | 137 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
d71df90e | 138 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
a26ac245 | 139 | |
a46e0899 PM |
140 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
141 | ||
0f962a5e | 142 | static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
a46e0899 PM |
143 | static void invoke_rcu_core(void); |
144 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); | |
a26ac245 | 145 | |
4a298656 PM |
146 | /* |
147 | * Track the rcutorture test sequence number and the update version | |
148 | * number within a given test. The rcutorture_testseq is incremented | |
149 | * on every rcutorture module load and unload, so has an odd value | |
150 | * when a test is running. The rcutorture_vernum is set to zero | |
151 | * when rcutorture starts and is incremented on each rcutorture update. | |
152 | * These variables enable correlating rcutorture output with the | |
153 | * RCU tracing information. | |
154 | */ | |
155 | unsigned long rcutorture_testseq; | |
156 | unsigned long rcutorture_vernum; | |
157 | ||
b1420f1c PM |
158 | /* State information for rcu_barrier() and friends. */ |
159 | ||
b1420f1c | 160 | static DEFINE_MUTEX(rcu_barrier_mutex); |
b1420f1c | 161 | |
fc2219d4 PM |
162 | /* |
163 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
164 | * permit this function to be invoked without holding the root rcu_node | |
165 | * structure's ->lock, but of course results can be subject to change. | |
166 | */ | |
167 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
168 | { | |
169 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
170 | } | |
171 | ||
b1f77b05 | 172 | /* |
d6714c22 | 173 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 174 | * how many quiescent states passed, just if there was at least |
d6714c22 | 175 | * one since the start of the grace period, this just sets a flag. |
e4cc1f22 | 176 | * The caller must have disabled preemption. |
b1f77b05 | 177 | */ |
d6714c22 | 178 | void rcu_sched_qs(int cpu) |
b1f77b05 | 179 | { |
25502a6c | 180 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
f41d911f | 181 | |
e4cc1f22 | 182 | rdp->passed_quiesce_gpnum = rdp->gpnum; |
c3422bea | 183 | barrier(); |
e4cc1f22 | 184 | if (rdp->passed_quiesce == 0) |
d4c08f2a | 185 | trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs"); |
e4cc1f22 | 186 | rdp->passed_quiesce = 1; |
b1f77b05 IM |
187 | } |
188 | ||
d6714c22 | 189 | void rcu_bh_qs(int cpu) |
b1f77b05 | 190 | { |
25502a6c | 191 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
f41d911f | 192 | |
e4cc1f22 | 193 | rdp->passed_quiesce_gpnum = rdp->gpnum; |
c3422bea | 194 | barrier(); |
e4cc1f22 | 195 | if (rdp->passed_quiesce == 0) |
d4c08f2a | 196 | trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs"); |
e4cc1f22 | 197 | rdp->passed_quiesce = 1; |
b1f77b05 | 198 | } |
64db4cff | 199 | |
25502a6c PM |
200 | /* |
201 | * Note a context switch. This is a quiescent state for RCU-sched, | |
202 | * and requires special handling for preemptible RCU. | |
e4cc1f22 | 203 | * The caller must have disabled preemption. |
25502a6c PM |
204 | */ |
205 | void rcu_note_context_switch(int cpu) | |
206 | { | |
300df91c | 207 | trace_rcu_utilization("Start context switch"); |
25502a6c | 208 | rcu_sched_qs(cpu); |
cba6d0d6 | 209 | rcu_preempt_note_context_switch(cpu); |
300df91c | 210 | trace_rcu_utilization("End context switch"); |
25502a6c | 211 | } |
29ce8310 | 212 | EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
25502a6c | 213 | |
90a4d2c0 | 214 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
29e37d81 | 215 | .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, |
23b5c8fa | 216 | .dynticks = ATOMIC_INIT(1), |
90a4d2c0 | 217 | }; |
64db4cff | 218 | |
e0f23060 | 219 | static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */ |
64db4cff PM |
220 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
221 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
222 | ||
3d76c082 PM |
223 | module_param(blimit, int, 0); |
224 | module_param(qhimark, int, 0); | |
225 | module_param(qlowmark, int, 0); | |
226 | ||
13cfcca0 PM |
227 | int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ |
228 | int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; | |
229 | ||
f2e0dd70 | 230 | module_param(rcu_cpu_stall_suppress, int, 0644); |
13cfcca0 | 231 | module_param(rcu_cpu_stall_timeout, int, 0644); |
742734ee | 232 | |
64db4cff | 233 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
a157229c | 234 | static int rcu_pending(int cpu); |
64db4cff PM |
235 | |
236 | /* | |
d6714c22 | 237 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 238 | */ |
d6714c22 | 239 | long rcu_batches_completed_sched(void) |
64db4cff | 240 | { |
d6714c22 | 241 | return rcu_sched_state.completed; |
64db4cff | 242 | } |
d6714c22 | 243 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
244 | |
245 | /* | |
246 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
247 | */ | |
248 | long rcu_batches_completed_bh(void) | |
249 | { | |
250 | return rcu_bh_state.completed; | |
251 | } | |
252 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
253 | ||
bf66f18e PM |
254 | /* |
255 | * Force a quiescent state for RCU BH. | |
256 | */ | |
257 | void rcu_bh_force_quiescent_state(void) | |
258 | { | |
259 | force_quiescent_state(&rcu_bh_state, 0); | |
260 | } | |
261 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
262 | ||
4a298656 PM |
263 | /* |
264 | * Record the number of times rcutorture tests have been initiated and | |
265 | * terminated. This information allows the debugfs tracing stats to be | |
266 | * correlated to the rcutorture messages, even when the rcutorture module | |
267 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
268 | * store this state in rcutorture itself. | |
269 | */ | |
270 | void rcutorture_record_test_transition(void) | |
271 | { | |
272 | rcutorture_testseq++; | |
273 | rcutorture_vernum = 0; | |
274 | } | |
275 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
276 | ||
277 | /* | |
278 | * Record the number of writer passes through the current rcutorture test. | |
279 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
280 | * messages. | |
281 | */ | |
282 | void rcutorture_record_progress(unsigned long vernum) | |
283 | { | |
284 | rcutorture_vernum++; | |
285 | } | |
286 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
287 | ||
bf66f18e PM |
288 | /* |
289 | * Force a quiescent state for RCU-sched. | |
290 | */ | |
291 | void rcu_sched_force_quiescent_state(void) | |
292 | { | |
293 | force_quiescent_state(&rcu_sched_state, 0); | |
294 | } | |
295 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
296 | ||
64db4cff PM |
297 | /* |
298 | * Does the CPU have callbacks ready to be invoked? | |
299 | */ | |
300 | static int | |
301 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
302 | { | |
303 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
304 | } | |
305 | ||
306 | /* | |
307 | * Does the current CPU require a yet-as-unscheduled grace period? | |
308 | */ | |
309 | static int | |
310 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
311 | { | |
fc2219d4 | 312 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
64db4cff PM |
313 | } |
314 | ||
315 | /* | |
316 | * Return the root node of the specified rcu_state structure. | |
317 | */ | |
318 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
319 | { | |
320 | return &rsp->node[0]; | |
321 | } | |
322 | ||
64db4cff PM |
323 | /* |
324 | * If the specified CPU is offline, tell the caller that it is in | |
325 | * a quiescent state. Otherwise, whack it with a reschedule IPI. | |
326 | * Grace periods can end up waiting on an offline CPU when that | |
327 | * CPU is in the process of coming online -- it will be added to the | |
328 | * rcu_node bitmasks before it actually makes it online. The same thing | |
329 | * can happen while a CPU is in the process of coming online. Because this | |
330 | * race is quite rare, we check for it after detecting that the grace | |
331 | * period has been delayed rather than checking each and every CPU | |
332 | * each and every time we start a new grace period. | |
333 | */ | |
334 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) | |
335 | { | |
336 | /* | |
2036d94a PM |
337 | * If the CPU is offline for more than a jiffy, it is in a quiescent |
338 | * state. We can trust its state not to change because interrupts | |
339 | * are disabled. The reason for the jiffy's worth of slack is to | |
340 | * handle CPUs initializing on the way up and finding their way | |
341 | * to the idle loop on the way down. | |
64db4cff | 342 | */ |
2036d94a PM |
343 | if (cpu_is_offline(rdp->cpu) && |
344 | ULONG_CMP_LT(rdp->rsp->gp_start + 2, jiffies)) { | |
d4c08f2a | 345 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl"); |
64db4cff PM |
346 | rdp->offline_fqs++; |
347 | return 1; | |
348 | } | |
64db4cff PM |
349 | return 0; |
350 | } | |
351 | ||
9b2e4f18 PM |
352 | /* |
353 | * rcu_idle_enter_common - inform RCU that current CPU is moving towards idle | |
354 | * | |
355 | * If the new value of the ->dynticks_nesting counter now is zero, | |
356 | * we really have entered idle, and must do the appropriate accounting. | |
357 | * The caller must have disabled interrupts. | |
358 | */ | |
4145fa7f | 359 | static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval) |
9b2e4f18 | 360 | { |
facc4e15 | 361 | trace_rcu_dyntick("Start", oldval, 0); |
99745b6a | 362 | if (!is_idle_task(current)) { |
0989cb46 PM |
363 | struct task_struct *idle = idle_task(smp_processor_id()); |
364 | ||
facc4e15 | 365 | trace_rcu_dyntick("Error on entry: not idle task", oldval, 0); |
9b2e4f18 | 366 | ftrace_dump(DUMP_ALL); |
0989cb46 PM |
367 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
368 | current->pid, current->comm, | |
369 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 | 370 | } |
aea1b35e | 371 | rcu_prepare_for_idle(smp_processor_id()); |
9b2e4f18 PM |
372 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
373 | smp_mb__before_atomic_inc(); /* See above. */ | |
374 | atomic_inc(&rdtp->dynticks); | |
375 | smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ | |
376 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
c44e2cdd PM |
377 | |
378 | /* | |
379 | * The idle task is not permitted to enter the idle loop while | |
380 | * in an RCU read-side critical section. | |
381 | */ | |
382 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), | |
383 | "Illegal idle entry in RCU read-side critical section."); | |
384 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), | |
385 | "Illegal idle entry in RCU-bh read-side critical section."); | |
386 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), | |
387 | "Illegal idle entry in RCU-sched read-side critical section."); | |
9b2e4f18 | 388 | } |
64db4cff PM |
389 | |
390 | /** | |
9b2e4f18 | 391 | * rcu_idle_enter - inform RCU that current CPU is entering idle |
64db4cff | 392 | * |
9b2e4f18 | 393 | * Enter idle mode, in other words, -leave- the mode in which RCU |
64db4cff | 394 | * read-side critical sections can occur. (Though RCU read-side |
9b2e4f18 PM |
395 | * critical sections can occur in irq handlers in idle, a possibility |
396 | * handled by irq_enter() and irq_exit().) | |
397 | * | |
398 | * We crowbar the ->dynticks_nesting field to zero to allow for | |
399 | * the possibility of usermode upcalls having messed up our count | |
400 | * of interrupt nesting level during the prior busy period. | |
64db4cff | 401 | */ |
9b2e4f18 | 402 | void rcu_idle_enter(void) |
64db4cff PM |
403 | { |
404 | unsigned long flags; | |
4145fa7f | 405 | long long oldval; |
64db4cff PM |
406 | struct rcu_dynticks *rdtp; |
407 | ||
64db4cff PM |
408 | local_irq_save(flags); |
409 | rdtp = &__get_cpu_var(rcu_dynticks); | |
4145fa7f | 410 | oldval = rdtp->dynticks_nesting; |
29e37d81 PM |
411 | WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); |
412 | if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) | |
413 | rdtp->dynticks_nesting = 0; | |
414 | else | |
415 | rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; | |
4145fa7f | 416 | rcu_idle_enter_common(rdtp, oldval); |
64db4cff PM |
417 | local_irq_restore(flags); |
418 | } | |
8a2ecf47 | 419 | EXPORT_SYMBOL_GPL(rcu_idle_enter); |
64db4cff | 420 | |
9b2e4f18 PM |
421 | /** |
422 | * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle | |
423 | * | |
424 | * Exit from an interrupt handler, which might possibly result in entering | |
425 | * idle mode, in other words, leaving the mode in which read-side critical | |
426 | * sections can occur. | |
64db4cff | 427 | * |
9b2e4f18 PM |
428 | * This code assumes that the idle loop never does anything that might |
429 | * result in unbalanced calls to irq_enter() and irq_exit(). If your | |
430 | * architecture violates this assumption, RCU will give you what you | |
431 | * deserve, good and hard. But very infrequently and irreproducibly. | |
432 | * | |
433 | * Use things like work queues to work around this limitation. | |
434 | * | |
435 | * You have been warned. | |
64db4cff | 436 | */ |
9b2e4f18 | 437 | void rcu_irq_exit(void) |
64db4cff PM |
438 | { |
439 | unsigned long flags; | |
4145fa7f | 440 | long long oldval; |
64db4cff PM |
441 | struct rcu_dynticks *rdtp; |
442 | ||
443 | local_irq_save(flags); | |
444 | rdtp = &__get_cpu_var(rcu_dynticks); | |
4145fa7f | 445 | oldval = rdtp->dynticks_nesting; |
9b2e4f18 PM |
446 | rdtp->dynticks_nesting--; |
447 | WARN_ON_ONCE(rdtp->dynticks_nesting < 0); | |
b6fc6020 FW |
448 | if (rdtp->dynticks_nesting) |
449 | trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); | |
450 | else | |
451 | rcu_idle_enter_common(rdtp, oldval); | |
9b2e4f18 PM |
452 | local_irq_restore(flags); |
453 | } | |
454 | ||
455 | /* | |
456 | * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle | |
457 | * | |
458 | * If the new value of the ->dynticks_nesting counter was previously zero, | |
459 | * we really have exited idle, and must do the appropriate accounting. | |
460 | * The caller must have disabled interrupts. | |
461 | */ | |
462 | static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval) | |
463 | { | |
23b5c8fa PM |
464 | smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ |
465 | atomic_inc(&rdtp->dynticks); | |
466 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
467 | smp_mb__after_atomic_inc(); /* See above. */ | |
468 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
7cb92499 | 469 | rcu_cleanup_after_idle(smp_processor_id()); |
4145fa7f | 470 | trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting); |
99745b6a | 471 | if (!is_idle_task(current)) { |
0989cb46 PM |
472 | struct task_struct *idle = idle_task(smp_processor_id()); |
473 | ||
4145fa7f PM |
474 | trace_rcu_dyntick("Error on exit: not idle task", |
475 | oldval, rdtp->dynticks_nesting); | |
9b2e4f18 | 476 | ftrace_dump(DUMP_ALL); |
0989cb46 PM |
477 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
478 | current->pid, current->comm, | |
479 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 PM |
480 | } |
481 | } | |
482 | ||
483 | /** | |
484 | * rcu_idle_exit - inform RCU that current CPU is leaving idle | |
485 | * | |
486 | * Exit idle mode, in other words, -enter- the mode in which RCU | |
487 | * read-side critical sections can occur. | |
488 | * | |
29e37d81 | 489 | * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to |
4145fa7f | 490 | * allow for the possibility of usermode upcalls messing up our count |
9b2e4f18 PM |
491 | * of interrupt nesting level during the busy period that is just |
492 | * now starting. | |
493 | */ | |
494 | void rcu_idle_exit(void) | |
495 | { | |
496 | unsigned long flags; | |
497 | struct rcu_dynticks *rdtp; | |
498 | long long oldval; | |
499 | ||
500 | local_irq_save(flags); | |
501 | rdtp = &__get_cpu_var(rcu_dynticks); | |
502 | oldval = rdtp->dynticks_nesting; | |
29e37d81 PM |
503 | WARN_ON_ONCE(oldval < 0); |
504 | if (oldval & DYNTICK_TASK_NEST_MASK) | |
505 | rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; | |
506 | else | |
507 | rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; | |
9b2e4f18 PM |
508 | rcu_idle_exit_common(rdtp, oldval); |
509 | local_irq_restore(flags); | |
510 | } | |
8a2ecf47 | 511 | EXPORT_SYMBOL_GPL(rcu_idle_exit); |
9b2e4f18 PM |
512 | |
513 | /** | |
514 | * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle | |
515 | * | |
516 | * Enter an interrupt handler, which might possibly result in exiting | |
517 | * idle mode, in other words, entering the mode in which read-side critical | |
518 | * sections can occur. | |
519 | * | |
520 | * Note that the Linux kernel is fully capable of entering an interrupt | |
521 | * handler that it never exits, for example when doing upcalls to | |
522 | * user mode! This code assumes that the idle loop never does upcalls to | |
523 | * user mode. If your architecture does do upcalls from the idle loop (or | |
524 | * does anything else that results in unbalanced calls to the irq_enter() | |
525 | * and irq_exit() functions), RCU will give you what you deserve, good | |
526 | * and hard. But very infrequently and irreproducibly. | |
527 | * | |
528 | * Use things like work queues to work around this limitation. | |
529 | * | |
530 | * You have been warned. | |
531 | */ | |
532 | void rcu_irq_enter(void) | |
533 | { | |
534 | unsigned long flags; | |
535 | struct rcu_dynticks *rdtp; | |
536 | long long oldval; | |
537 | ||
538 | local_irq_save(flags); | |
539 | rdtp = &__get_cpu_var(rcu_dynticks); | |
540 | oldval = rdtp->dynticks_nesting; | |
541 | rdtp->dynticks_nesting++; | |
542 | WARN_ON_ONCE(rdtp->dynticks_nesting == 0); | |
b6fc6020 FW |
543 | if (oldval) |
544 | trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); | |
545 | else | |
546 | rcu_idle_exit_common(rdtp, oldval); | |
64db4cff | 547 | local_irq_restore(flags); |
64db4cff PM |
548 | } |
549 | ||
550 | /** | |
551 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
552 | * | |
553 | * If the CPU was idle with dynamic ticks active, and there is no | |
554 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
555 | * RCU grace-period handling know that the CPU is active. | |
556 | */ | |
557 | void rcu_nmi_enter(void) | |
558 | { | |
559 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
560 | ||
23b5c8fa PM |
561 | if (rdtp->dynticks_nmi_nesting == 0 && |
562 | (atomic_read(&rdtp->dynticks) & 0x1)) | |
64db4cff | 563 | return; |
23b5c8fa PM |
564 | rdtp->dynticks_nmi_nesting++; |
565 | smp_mb__before_atomic_inc(); /* Force delay from prior write. */ | |
566 | atomic_inc(&rdtp->dynticks); | |
567 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
568 | smp_mb__after_atomic_inc(); /* See above. */ | |
569 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
64db4cff PM |
570 | } |
571 | ||
572 | /** | |
573 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
574 | * | |
575 | * If the CPU was idle with dynamic ticks active, and there is no | |
576 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
577 | * RCU grace-period handling know that the CPU is no longer active. | |
578 | */ | |
579 | void rcu_nmi_exit(void) | |
580 | { | |
581 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
582 | ||
23b5c8fa PM |
583 | if (rdtp->dynticks_nmi_nesting == 0 || |
584 | --rdtp->dynticks_nmi_nesting != 0) | |
64db4cff | 585 | return; |
23b5c8fa PM |
586 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
587 | smp_mb__before_atomic_inc(); /* See above. */ | |
588 | atomic_inc(&rdtp->dynticks); | |
589 | smp_mb__after_atomic_inc(); /* Force delay to next write. */ | |
590 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
64db4cff PM |
591 | } |
592 | ||
9b2e4f18 PM |
593 | #ifdef CONFIG_PROVE_RCU |
594 | ||
64db4cff | 595 | /** |
9b2e4f18 | 596 | * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle |
64db4cff | 597 | * |
9b2e4f18 | 598 | * If the current CPU is in its idle loop and is neither in an interrupt |
34240697 | 599 | * or NMI handler, return true. |
64db4cff | 600 | */ |
9b2e4f18 | 601 | int rcu_is_cpu_idle(void) |
64db4cff | 602 | { |
34240697 PM |
603 | int ret; |
604 | ||
605 | preempt_disable(); | |
606 | ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0; | |
607 | preempt_enable(); | |
608 | return ret; | |
64db4cff | 609 | } |
e6b80a3b | 610 | EXPORT_SYMBOL(rcu_is_cpu_idle); |
64db4cff | 611 | |
c0d6d01b PM |
612 | #ifdef CONFIG_HOTPLUG_CPU |
613 | ||
614 | /* | |
615 | * Is the current CPU online? Disable preemption to avoid false positives | |
616 | * that could otherwise happen due to the current CPU number being sampled, | |
617 | * this task being preempted, its old CPU being taken offline, resuming | |
618 | * on some other CPU, then determining that its old CPU is now offline. | |
619 | * It is OK to use RCU on an offline processor during initial boot, hence | |
2036d94a PM |
620 | * the check for rcu_scheduler_fully_active. Note also that it is OK |
621 | * for a CPU coming online to use RCU for one jiffy prior to marking itself | |
622 | * online in the cpu_online_mask. Similarly, it is OK for a CPU going | |
623 | * offline to continue to use RCU for one jiffy after marking itself | |
624 | * offline in the cpu_online_mask. This leniency is necessary given the | |
625 | * non-atomic nature of the online and offline processing, for example, | |
626 | * the fact that a CPU enters the scheduler after completing the CPU_DYING | |
627 | * notifiers. | |
628 | * | |
629 | * This is also why RCU internally marks CPUs online during the | |
630 | * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. | |
c0d6d01b PM |
631 | * |
632 | * Disable checking if in an NMI handler because we cannot safely report | |
633 | * errors from NMI handlers anyway. | |
634 | */ | |
635 | bool rcu_lockdep_current_cpu_online(void) | |
636 | { | |
2036d94a PM |
637 | struct rcu_data *rdp; |
638 | struct rcu_node *rnp; | |
c0d6d01b PM |
639 | bool ret; |
640 | ||
641 | if (in_nmi()) | |
642 | return 1; | |
643 | preempt_disable(); | |
2036d94a PM |
644 | rdp = &__get_cpu_var(rcu_sched_data); |
645 | rnp = rdp->mynode; | |
646 | ret = (rdp->grpmask & rnp->qsmaskinit) || | |
c0d6d01b PM |
647 | !rcu_scheduler_fully_active; |
648 | preempt_enable(); | |
649 | return ret; | |
650 | } | |
651 | EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); | |
652 | ||
653 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ | |
654 | ||
9b2e4f18 PM |
655 | #endif /* #ifdef CONFIG_PROVE_RCU */ |
656 | ||
64db4cff | 657 | /** |
9b2e4f18 | 658 | * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle |
64db4cff | 659 | * |
9b2e4f18 PM |
660 | * If the current CPU is idle or running at a first-level (not nested) |
661 | * interrupt from idle, return true. The caller must have at least | |
662 | * disabled preemption. | |
64db4cff | 663 | */ |
9b2e4f18 | 664 | int rcu_is_cpu_rrupt_from_idle(void) |
64db4cff | 665 | { |
9b2e4f18 | 666 | return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; |
64db4cff PM |
667 | } |
668 | ||
64db4cff PM |
669 | /* |
670 | * Snapshot the specified CPU's dynticks counter so that we can later | |
671 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 672 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
673 | */ |
674 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
675 | { | |
23b5c8fa | 676 | rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
f0e7c19d | 677 | return (rdp->dynticks_snap & 0x1) == 0; |
64db4cff PM |
678 | } |
679 | ||
680 | /* | |
681 | * Return true if the specified CPU has passed through a quiescent | |
682 | * state by virtue of being in or having passed through an dynticks | |
683 | * idle state since the last call to dyntick_save_progress_counter() | |
684 | * for this same CPU. | |
685 | */ | |
686 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
687 | { | |
7eb4f455 PM |
688 | unsigned int curr; |
689 | unsigned int snap; | |
64db4cff | 690 | |
7eb4f455 PM |
691 | curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); |
692 | snap = (unsigned int)rdp->dynticks_snap; | |
64db4cff PM |
693 | |
694 | /* | |
695 | * If the CPU passed through or entered a dynticks idle phase with | |
696 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
697 | * already acknowledged the request to pass through a quiescent | |
698 | * state. Either way, that CPU cannot possibly be in an RCU | |
699 | * read-side critical section that started before the beginning | |
700 | * of the current RCU grace period. | |
701 | */ | |
7eb4f455 | 702 | if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { |
d4c08f2a | 703 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti"); |
64db4cff PM |
704 | rdp->dynticks_fqs++; |
705 | return 1; | |
706 | } | |
707 | ||
708 | /* Go check for the CPU being offline. */ | |
709 | return rcu_implicit_offline_qs(rdp); | |
710 | } | |
711 | ||
13cfcca0 PM |
712 | static int jiffies_till_stall_check(void) |
713 | { | |
714 | int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout); | |
715 | ||
716 | /* | |
717 | * Limit check must be consistent with the Kconfig limits | |
718 | * for CONFIG_RCU_CPU_STALL_TIMEOUT. | |
719 | */ | |
720 | if (till_stall_check < 3) { | |
721 | ACCESS_ONCE(rcu_cpu_stall_timeout) = 3; | |
722 | till_stall_check = 3; | |
723 | } else if (till_stall_check > 300) { | |
724 | ACCESS_ONCE(rcu_cpu_stall_timeout) = 300; | |
725 | till_stall_check = 300; | |
726 | } | |
727 | return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; | |
728 | } | |
729 | ||
64db4cff PM |
730 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
731 | { | |
732 | rsp->gp_start = jiffies; | |
13cfcca0 | 733 | rsp->jiffies_stall = jiffies + jiffies_till_stall_check(); |
64db4cff PM |
734 | } |
735 | ||
736 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
737 | { | |
738 | int cpu; | |
739 | long delta; | |
740 | unsigned long flags; | |
9bc8b558 | 741 | int ndetected; |
64db4cff | 742 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff PM |
743 | |
744 | /* Only let one CPU complain about others per time interval. */ | |
745 | ||
1304afb2 | 746 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 747 | delta = jiffies - rsp->jiffies_stall; |
fc2219d4 | 748 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 749 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
750 | return; |
751 | } | |
13cfcca0 | 752 | rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3; |
1304afb2 | 753 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 754 | |
8cdd32a9 PM |
755 | /* |
756 | * OK, time to rat on our buddy... | |
757 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
758 | * RCU CPU stall warnings. | |
759 | */ | |
a858af28 | 760 | printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:", |
4300aa64 | 761 | rsp->name); |
a858af28 | 762 | print_cpu_stall_info_begin(); |
a0b6c9a7 | 763 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 764 | raw_spin_lock_irqsave(&rnp->lock, flags); |
9bc8b558 | 765 | ndetected += rcu_print_task_stall(rnp); |
3acd9eb3 | 766 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
a0b6c9a7 | 767 | if (rnp->qsmask == 0) |
64db4cff | 768 | continue; |
a0b6c9a7 | 769 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
9bc8b558 | 770 | if (rnp->qsmask & (1UL << cpu)) { |
a858af28 | 771 | print_cpu_stall_info(rsp, rnp->grplo + cpu); |
9bc8b558 PM |
772 | ndetected++; |
773 | } | |
64db4cff | 774 | } |
a858af28 PM |
775 | |
776 | /* | |
777 | * Now rat on any tasks that got kicked up to the root rcu_node | |
778 | * due to CPU offlining. | |
779 | */ | |
780 | rnp = rcu_get_root(rsp); | |
781 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
782 | ndetected = rcu_print_task_stall(rnp); | |
783 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
784 | ||
785 | print_cpu_stall_info_end(); | |
786 | printk(KERN_CONT "(detected by %d, t=%ld jiffies)\n", | |
64db4cff | 787 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
9bc8b558 PM |
788 | if (ndetected == 0) |
789 | printk(KERN_ERR "INFO: Stall ended before state dump start\n"); | |
790 | else if (!trigger_all_cpu_backtrace()) | |
4627e240 | 791 | dump_stack(); |
c1dc0b9c | 792 | |
1ed509a2 PM |
793 | /* If so configured, complain about tasks blocking the grace period. */ |
794 | ||
795 | rcu_print_detail_task_stall(rsp); | |
796 | ||
64db4cff PM |
797 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
798 | } | |
799 | ||
800 | static void print_cpu_stall(struct rcu_state *rsp) | |
801 | { | |
802 | unsigned long flags; | |
803 | struct rcu_node *rnp = rcu_get_root(rsp); | |
804 | ||
8cdd32a9 PM |
805 | /* |
806 | * OK, time to rat on ourselves... | |
807 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
808 | * RCU CPU stall warnings. | |
809 | */ | |
a858af28 PM |
810 | printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name); |
811 | print_cpu_stall_info_begin(); | |
812 | print_cpu_stall_info(rsp, smp_processor_id()); | |
813 | print_cpu_stall_info_end(); | |
814 | printk(KERN_CONT " (t=%lu jiffies)\n", jiffies - rsp->gp_start); | |
4627e240 PM |
815 | if (!trigger_all_cpu_backtrace()) |
816 | dump_stack(); | |
c1dc0b9c | 817 | |
1304afb2 | 818 | raw_spin_lock_irqsave(&rnp->lock, flags); |
20133cfc | 819 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
13cfcca0 PM |
820 | rsp->jiffies_stall = jiffies + |
821 | 3 * jiffies_till_stall_check() + 3; | |
1304afb2 | 822 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 823 | |
64db4cff PM |
824 | set_need_resched(); /* kick ourselves to get things going. */ |
825 | } | |
826 | ||
827 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
828 | { | |
bad6e139 PM |
829 | unsigned long j; |
830 | unsigned long js; | |
64db4cff PM |
831 | struct rcu_node *rnp; |
832 | ||
742734ee | 833 | if (rcu_cpu_stall_suppress) |
c68de209 | 834 | return; |
bad6e139 PM |
835 | j = ACCESS_ONCE(jiffies); |
836 | js = ACCESS_ONCE(rsp->jiffies_stall); | |
64db4cff | 837 | rnp = rdp->mynode; |
bad6e139 | 838 | if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { |
64db4cff PM |
839 | |
840 | /* We haven't checked in, so go dump stack. */ | |
841 | print_cpu_stall(rsp); | |
842 | ||
bad6e139 PM |
843 | } else if (rcu_gp_in_progress(rsp) && |
844 | ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { | |
64db4cff | 845 | |
bad6e139 | 846 | /* They had a few time units to dump stack, so complain. */ |
64db4cff PM |
847 | print_other_cpu_stall(rsp); |
848 | } | |
849 | } | |
850 | ||
c68de209 PM |
851 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
852 | { | |
742734ee | 853 | rcu_cpu_stall_suppress = 1; |
c68de209 PM |
854 | return NOTIFY_DONE; |
855 | } | |
856 | ||
53d84e00 PM |
857 | /** |
858 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
859 | * | |
860 | * Set the stall-warning timeout way off into the future, thus preventing | |
861 | * any RCU CPU stall-warning messages from appearing in the current set of | |
862 | * RCU grace periods. | |
863 | * | |
864 | * The caller must disable hard irqs. | |
865 | */ | |
866 | void rcu_cpu_stall_reset(void) | |
867 | { | |
868 | rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2; | |
869 | rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2; | |
870 | rcu_preempt_stall_reset(); | |
871 | } | |
872 | ||
c68de209 PM |
873 | static struct notifier_block rcu_panic_block = { |
874 | .notifier_call = rcu_panic, | |
875 | }; | |
876 | ||
877 | static void __init check_cpu_stall_init(void) | |
878 | { | |
879 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); | |
880 | } | |
881 | ||
64db4cff PM |
882 | /* |
883 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
884 | * This is used both when we started the grace period and when we notice | |
9160306e PM |
885 | * that someone else started the grace period. The caller must hold the |
886 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, | |
887 | * and must have irqs disabled. | |
64db4cff | 888 | */ |
9160306e PM |
889 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
890 | { | |
891 | if (rdp->gpnum != rnp->gpnum) { | |
121dfc4b PM |
892 | /* |
893 | * If the current grace period is waiting for this CPU, | |
894 | * set up to detect a quiescent state, otherwise don't | |
895 | * go looking for one. | |
896 | */ | |
9160306e | 897 | rdp->gpnum = rnp->gpnum; |
d4c08f2a | 898 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart"); |
121dfc4b PM |
899 | if (rnp->qsmask & rdp->grpmask) { |
900 | rdp->qs_pending = 1; | |
e4cc1f22 | 901 | rdp->passed_quiesce = 0; |
121dfc4b PM |
902 | } else |
903 | rdp->qs_pending = 0; | |
a858af28 | 904 | zero_cpu_stall_ticks(rdp); |
9160306e PM |
905 | } |
906 | } | |
907 | ||
64db4cff PM |
908 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
909 | { | |
9160306e PM |
910 | unsigned long flags; |
911 | struct rcu_node *rnp; | |
912 | ||
913 | local_irq_save(flags); | |
914 | rnp = rdp->mynode; | |
915 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ | |
1304afb2 | 916 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
9160306e PM |
917 | local_irq_restore(flags); |
918 | return; | |
919 | } | |
920 | __note_new_gpnum(rsp, rnp, rdp); | |
1304afb2 | 921 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
922 | } |
923 | ||
924 | /* | |
925 | * Did someone else start a new RCU grace period start since we last | |
926 | * checked? Update local state appropriately if so. Must be called | |
927 | * on the CPU corresponding to rdp. | |
928 | */ | |
929 | static int | |
930 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
931 | { | |
932 | unsigned long flags; | |
933 | int ret = 0; | |
934 | ||
935 | local_irq_save(flags); | |
936 | if (rdp->gpnum != rsp->gpnum) { | |
937 | note_new_gpnum(rsp, rdp); | |
938 | ret = 1; | |
939 | } | |
940 | local_irq_restore(flags); | |
941 | return ret; | |
942 | } | |
943 | ||
d09b62df PM |
944 | /* |
945 | * Advance this CPU's callbacks, but only if the current grace period | |
946 | * has ended. This may be called only from the CPU to whom the rdp | |
947 | * belongs. In addition, the corresponding leaf rcu_node structure's | |
948 | * ->lock must be held by the caller, with irqs disabled. | |
949 | */ | |
950 | static void | |
951 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
952 | { | |
953 | /* Did another grace period end? */ | |
954 | if (rdp->completed != rnp->completed) { | |
955 | ||
956 | /* Advance callbacks. No harm if list empty. */ | |
957 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
958 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
959 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
960 | ||
961 | /* Remember that we saw this grace-period completion. */ | |
962 | rdp->completed = rnp->completed; | |
d4c08f2a | 963 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend"); |
20377f32 | 964 | |
5ff8e6f0 FW |
965 | /* |
966 | * If we were in an extended quiescent state, we may have | |
121dfc4b | 967 | * missed some grace periods that others CPUs handled on |
5ff8e6f0 | 968 | * our behalf. Catch up with this state to avoid noting |
121dfc4b PM |
969 | * spurious new grace periods. If another grace period |
970 | * has started, then rnp->gpnum will have advanced, so | |
971 | * we will detect this later on. | |
5ff8e6f0 | 972 | */ |
121dfc4b | 973 | if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) |
5ff8e6f0 FW |
974 | rdp->gpnum = rdp->completed; |
975 | ||
20377f32 | 976 | /* |
121dfc4b PM |
977 | * If RCU does not need a quiescent state from this CPU, |
978 | * then make sure that this CPU doesn't go looking for one. | |
20377f32 | 979 | */ |
121dfc4b | 980 | if ((rnp->qsmask & rdp->grpmask) == 0) |
20377f32 | 981 | rdp->qs_pending = 0; |
d09b62df PM |
982 | } |
983 | } | |
984 | ||
985 | /* | |
986 | * Advance this CPU's callbacks, but only if the current grace period | |
987 | * has ended. This may be called only from the CPU to whom the rdp | |
988 | * belongs. | |
989 | */ | |
990 | static void | |
991 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
992 | { | |
993 | unsigned long flags; | |
994 | struct rcu_node *rnp; | |
995 | ||
996 | local_irq_save(flags); | |
997 | rnp = rdp->mynode; | |
998 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ | |
1304afb2 | 999 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
d09b62df PM |
1000 | local_irq_restore(flags); |
1001 | return; | |
1002 | } | |
1003 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1304afb2 | 1004 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d09b62df PM |
1005 | } |
1006 | ||
1007 | /* | |
1008 | * Do per-CPU grace-period initialization for running CPU. The caller | |
1009 | * must hold the lock of the leaf rcu_node structure corresponding to | |
1010 | * this CPU. | |
1011 | */ | |
1012 | static void | |
1013 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
1014 | { | |
1015 | /* Prior grace period ended, so advance callbacks for current CPU. */ | |
1016 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1017 | ||
1018 | /* | |
1019 | * Because this CPU just now started the new grace period, we know | |
1020 | * that all of its callbacks will be covered by this upcoming grace | |
1021 | * period, even the ones that were registered arbitrarily recently. | |
1022 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. | |
1023 | * | |
1024 | * Other CPUs cannot be sure exactly when the grace period started. | |
1025 | * Therefore, their recently registered callbacks must pass through | |
1026 | * an additional RCU_NEXT_READY stage, so that they will be handled | |
1027 | * by the next RCU grace period. | |
1028 | */ | |
1029 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
1030 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
9160306e PM |
1031 | |
1032 | /* Set state so that this CPU will detect the next quiescent state. */ | |
1033 | __note_new_gpnum(rsp, rnp, rdp); | |
d09b62df PM |
1034 | } |
1035 | ||
64db4cff PM |
1036 | /* |
1037 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
1038 | * in preparation for detecting the next grace period. The caller must hold | |
1039 | * the root node's ->lock, which is released before return. Hard irqs must | |
1040 | * be disabled. | |
e5601400 PM |
1041 | * |
1042 | * Note that it is legal for a dying CPU (which is marked as offline) to | |
1043 | * invoke this function. This can happen when the dying CPU reports its | |
1044 | * quiescent state. | |
64db4cff PM |
1045 | */ |
1046 | static void | |
1047 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
1048 | __releases(rcu_get_root(rsp)->lock) | |
1049 | { | |
394f99a9 | 1050 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
64db4cff | 1051 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 1052 | |
037067a1 | 1053 | if (!rcu_scheduler_fully_active || |
afe24b12 PM |
1054 | !cpu_needs_another_gp(rsp, rdp)) { |
1055 | /* | |
1056 | * Either the scheduler hasn't yet spawned the first | |
1057 | * non-idle task or this CPU does not need another | |
1058 | * grace period. Either way, don't start a new grace | |
1059 | * period. | |
1060 | */ | |
1061 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1062 | return; | |
1063 | } | |
b32e9eb6 | 1064 | |
afe24b12 | 1065 | if (rsp->fqs_active) { |
b32e9eb6 | 1066 | /* |
afe24b12 PM |
1067 | * This CPU needs a grace period, but force_quiescent_state() |
1068 | * is running. Tell it to start one on this CPU's behalf. | |
b32e9eb6 | 1069 | */ |
afe24b12 PM |
1070 | rsp->fqs_need_gp = 1; |
1071 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
64db4cff PM |
1072 | return; |
1073 | } | |
1074 | ||
1075 | /* Advance to a new grace period and initialize state. */ | |
1076 | rsp->gpnum++; | |
d4c08f2a | 1077 | trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); |
af446b70 PM |
1078 | WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT); |
1079 | rsp->fqs_state = RCU_GP_INIT; /* Hold off force_quiescent_state. */ | |
64db4cff | 1080 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
64db4cff | 1081 | record_gp_stall_check_time(rsp); |
1304afb2 | 1082 | raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
64db4cff | 1083 | |
64db4cff | 1084 | /* Exclude any concurrent CPU-hotplug operations. */ |
1304afb2 | 1085 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
1086 | |
1087 | /* | |
b835db1f PM |
1088 | * Set the quiescent-state-needed bits in all the rcu_node |
1089 | * structures for all currently online CPUs in breadth-first | |
1090 | * order, starting from the root rcu_node structure. This | |
1091 | * operation relies on the layout of the hierarchy within the | |
1092 | * rsp->node[] array. Note that other CPUs will access only | |
1093 | * the leaves of the hierarchy, which still indicate that no | |
1094 | * grace period is in progress, at least until the corresponding | |
1095 | * leaf node has been initialized. In addition, we have excluded | |
1096 | * CPU-hotplug operations. | |
64db4cff PM |
1097 | * |
1098 | * Note that the grace period cannot complete until we finish | |
1099 | * the initialization process, as there will be at least one | |
1100 | * qsmask bit set in the root node until that time, namely the | |
b835db1f PM |
1101 | * one corresponding to this CPU, due to the fact that we have |
1102 | * irqs disabled. | |
64db4cff | 1103 | */ |
a0b6c9a7 | 1104 | rcu_for_each_node_breadth_first(rsp, rnp) { |
1304afb2 | 1105 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
b0e165c0 | 1106 | rcu_preempt_check_blocked_tasks(rnp); |
49e29126 | 1107 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 1108 | rnp->gpnum = rsp->gpnum; |
d09b62df PM |
1109 | rnp->completed = rsp->completed; |
1110 | if (rnp == rdp->mynode) | |
1111 | rcu_start_gp_per_cpu(rsp, rnp, rdp); | |
27f4d280 | 1112 | rcu_preempt_boost_start_gp(rnp); |
d4c08f2a PM |
1113 | trace_rcu_grace_period_init(rsp->name, rnp->gpnum, |
1114 | rnp->level, rnp->grplo, | |
1115 | rnp->grphi, rnp->qsmask); | |
1304afb2 | 1116 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
1117 | } |
1118 | ||
83f5b01f | 1119 | rnp = rcu_get_root(rsp); |
1304afb2 | 1120 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
af446b70 | 1121 | rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
1304afb2 PM |
1122 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
1123 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); | |
64db4cff PM |
1124 | } |
1125 | ||
f41d911f | 1126 | /* |
d3f6bad3 PM |
1127 | * Report a full set of quiescent states to the specified rcu_state |
1128 | * data structure. This involves cleaning up after the prior grace | |
1129 | * period and letting rcu_start_gp() start up the next grace period | |
1130 | * if one is needed. Note that the caller must hold rnp->lock, as | |
1131 | * required by rcu_start_gp(), which will release it. | |
f41d911f | 1132 | */ |
d3f6bad3 | 1133 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 1134 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 1135 | { |
15ba0ba8 | 1136 | unsigned long gp_duration; |
afe24b12 PM |
1137 | struct rcu_node *rnp = rcu_get_root(rsp); |
1138 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
15ba0ba8 | 1139 | |
fc2219d4 | 1140 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
0bbcc529 PM |
1141 | |
1142 | /* | |
1143 | * Ensure that all grace-period and pre-grace-period activity | |
1144 | * is seen before the assignment to rsp->completed. | |
1145 | */ | |
1146 | smp_mb(); /* See above block comment. */ | |
15ba0ba8 PM |
1147 | gp_duration = jiffies - rsp->gp_start; |
1148 | if (gp_duration > rsp->gp_max) | |
1149 | rsp->gp_max = gp_duration; | |
afe24b12 PM |
1150 | |
1151 | /* | |
1152 | * We know the grace period is complete, but to everyone else | |
1153 | * it appears to still be ongoing. But it is also the case | |
1154 | * that to everyone else it looks like there is nothing that | |
1155 | * they can do to advance the grace period. It is therefore | |
1156 | * safe for us to drop the lock in order to mark the grace | |
1157 | * period as completed in all of the rcu_node structures. | |
1158 | * | |
1159 | * But if this CPU needs another grace period, it will take | |
1160 | * care of this while initializing the next grace period. | |
1161 | * We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL | |
1162 | * because the callbacks have not yet been advanced: Those | |
1163 | * callbacks are waiting on the grace period that just now | |
1164 | * completed. | |
1165 | */ | |
1166 | if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) { | |
1167 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1168 | ||
1169 | /* | |
1170 | * Propagate new ->completed value to rcu_node structures | |
1171 | * so that other CPUs don't have to wait until the start | |
1172 | * of the next grace period to process their callbacks. | |
1173 | */ | |
1174 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
1175 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1176 | rnp->completed = rsp->gpnum; | |
1177 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1178 | } | |
1179 | rnp = rcu_get_root(rsp); | |
1180 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1181 | } | |
1182 | ||
1183 | rsp->completed = rsp->gpnum; /* Declare the grace period complete. */ | |
d4c08f2a | 1184 | trace_rcu_grace_period(rsp->name, rsp->completed, "end"); |
af446b70 | 1185 | rsp->fqs_state = RCU_GP_IDLE; |
f41d911f PM |
1186 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
1187 | } | |
1188 | ||
64db4cff | 1189 | /* |
d3f6bad3 PM |
1190 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
1191 | * Allows quiescent states for a group of CPUs to be reported at one go | |
1192 | * to the specified rcu_node structure, though all the CPUs in the group | |
1193 | * must be represented by the same rcu_node structure (which need not be | |
1194 | * a leaf rcu_node structure, though it often will be). That structure's | |
1195 | * lock must be held upon entry, and it is released before return. | |
64db4cff PM |
1196 | */ |
1197 | static void | |
d3f6bad3 PM |
1198 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
1199 | struct rcu_node *rnp, unsigned long flags) | |
64db4cff PM |
1200 | __releases(rnp->lock) |
1201 | { | |
28ecd580 PM |
1202 | struct rcu_node *rnp_c; |
1203 | ||
64db4cff PM |
1204 | /* Walk up the rcu_node hierarchy. */ |
1205 | for (;;) { | |
1206 | if (!(rnp->qsmask & mask)) { | |
1207 | ||
1208 | /* Our bit has already been cleared, so done. */ | |
1304afb2 | 1209 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1210 | return; |
1211 | } | |
1212 | rnp->qsmask &= ~mask; | |
d4c08f2a PM |
1213 | trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, |
1214 | mask, rnp->qsmask, rnp->level, | |
1215 | rnp->grplo, rnp->grphi, | |
1216 | !!rnp->gp_tasks); | |
27f4d280 | 1217 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
1218 | |
1219 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 1220 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1221 | return; |
1222 | } | |
1223 | mask = rnp->grpmask; | |
1224 | if (rnp->parent == NULL) { | |
1225 | ||
1226 | /* No more levels. Exit loop holding root lock. */ | |
1227 | ||
1228 | break; | |
1229 | } | |
1304afb2 | 1230 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 1231 | rnp_c = rnp; |
64db4cff | 1232 | rnp = rnp->parent; |
1304afb2 | 1233 | raw_spin_lock_irqsave(&rnp->lock, flags); |
28ecd580 | 1234 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
1235 | } |
1236 | ||
1237 | /* | |
1238 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 1239 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 1240 | * to clean up and start the next grace period if one is needed. |
64db4cff | 1241 | */ |
d3f6bad3 | 1242 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
1243 | } |
1244 | ||
1245 | /* | |
d3f6bad3 PM |
1246 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
1247 | * structure. This must be either called from the specified CPU, or | |
1248 | * called when the specified CPU is known to be offline (and when it is | |
1249 | * also known that no other CPU is concurrently trying to help the offline | |
1250 | * CPU). The lastcomp argument is used to make sure we are still in the | |
1251 | * grace period of interest. We don't want to end the current grace period | |
1252 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
1253 | */ |
1254 | static void | |
e4cc1f22 | 1255 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp) |
64db4cff PM |
1256 | { |
1257 | unsigned long flags; | |
1258 | unsigned long mask; | |
1259 | struct rcu_node *rnp; | |
1260 | ||
1261 | rnp = rdp->mynode; | |
1304afb2 | 1262 | raw_spin_lock_irqsave(&rnp->lock, flags); |
e4cc1f22 | 1263 | if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) { |
64db4cff PM |
1264 | |
1265 | /* | |
e4cc1f22 PM |
1266 | * The grace period in which this quiescent state was |
1267 | * recorded has ended, so don't report it upwards. | |
1268 | * We will instead need a new quiescent state that lies | |
1269 | * within the current grace period. | |
64db4cff | 1270 | */ |
e4cc1f22 | 1271 | rdp->passed_quiesce = 0; /* need qs for new gp. */ |
1304afb2 | 1272 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1273 | return; |
1274 | } | |
1275 | mask = rdp->grpmask; | |
1276 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 1277 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1278 | } else { |
1279 | rdp->qs_pending = 0; | |
1280 | ||
1281 | /* | |
1282 | * This GP can't end until cpu checks in, so all of our | |
1283 | * callbacks can be processed during the next GP. | |
1284 | */ | |
64db4cff PM |
1285 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
1286 | ||
d3f6bad3 | 1287 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
64db4cff PM |
1288 | } |
1289 | } | |
1290 | ||
1291 | /* | |
1292 | * Check to see if there is a new grace period of which this CPU | |
1293 | * is not yet aware, and if so, set up local rcu_data state for it. | |
1294 | * Otherwise, see if this CPU has just passed through its first | |
1295 | * quiescent state for this grace period, and record that fact if so. | |
1296 | */ | |
1297 | static void | |
1298 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
1299 | { | |
1300 | /* If there is now a new grace period, record and return. */ | |
1301 | if (check_for_new_grace_period(rsp, rdp)) | |
1302 | return; | |
1303 | ||
1304 | /* | |
1305 | * Does this CPU still need to do its part for current grace period? | |
1306 | * If no, return and let the other CPUs do their part as well. | |
1307 | */ | |
1308 | if (!rdp->qs_pending) | |
1309 | return; | |
1310 | ||
1311 | /* | |
1312 | * Was there a quiescent state since the beginning of the grace | |
1313 | * period? If no, then exit and wait for the next call. | |
1314 | */ | |
e4cc1f22 | 1315 | if (!rdp->passed_quiesce) |
64db4cff PM |
1316 | return; |
1317 | ||
d3f6bad3 PM |
1318 | /* |
1319 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
1320 | * judge of that). | |
1321 | */ | |
e4cc1f22 | 1322 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum); |
64db4cff PM |
1323 | } |
1324 | ||
1325 | #ifdef CONFIG_HOTPLUG_CPU | |
1326 | ||
e74f4c45 | 1327 | /* |
b1420f1c PM |
1328 | * Send the specified CPU's RCU callbacks to the orphanage. The |
1329 | * specified CPU must be offline, and the caller must hold the | |
1330 | * ->onofflock. | |
e74f4c45 | 1331 | */ |
b1420f1c PM |
1332 | static void |
1333 | rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, | |
1334 | struct rcu_node *rnp, struct rcu_data *rdp) | |
e74f4c45 PM |
1335 | { |
1336 | int i; | |
e5601400 | 1337 | |
b1420f1c PM |
1338 | /* |
1339 | * Orphan the callbacks. First adjust the counts. This is safe | |
1340 | * because ->onofflock excludes _rcu_barrier()'s adoption of | |
1341 | * the callbacks, thus no memory barrier is required. | |
1342 | */ | |
a50c3af9 | 1343 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
1344 | rsp->qlen_lazy += rdp->qlen_lazy; |
1345 | rsp->qlen += rdp->qlen; | |
1346 | rdp->n_cbs_orphaned += rdp->qlen; | |
a50c3af9 PM |
1347 | rdp->qlen_lazy = 0; |
1348 | rdp->qlen = 0; | |
1349 | } | |
1350 | ||
1351 | /* | |
b1420f1c PM |
1352 | * Next, move those callbacks still needing a grace period to |
1353 | * the orphanage, where some other CPU will pick them up. | |
1354 | * Some of the callbacks might have gone partway through a grace | |
1355 | * period, but that is too bad. They get to start over because we | |
1356 | * cannot assume that grace periods are synchronized across CPUs. | |
1357 | * We don't bother updating the ->nxttail[] array yet, instead | |
1358 | * we just reset the whole thing later on. | |
a50c3af9 | 1359 | */ |
b1420f1c PM |
1360 | if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { |
1361 | *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; | |
1362 | rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; | |
1363 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
a50c3af9 PM |
1364 | } |
1365 | ||
1366 | /* | |
b1420f1c PM |
1367 | * Then move the ready-to-invoke callbacks to the orphanage, |
1368 | * where some other CPU will pick them up. These will not be | |
1369 | * required to pass though another grace period: They are done. | |
a50c3af9 | 1370 | */ |
e5601400 | 1371 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
1372 | *rsp->orphan_donetail = rdp->nxtlist; |
1373 | rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; | |
e5601400 | 1374 | } |
e74f4c45 | 1375 | |
b1420f1c PM |
1376 | /* Finally, initialize the rcu_data structure's list to empty. */ |
1377 | rdp->nxtlist = NULL; | |
1378 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1379 | rdp->nxttail[i] = &rdp->nxtlist; | |
1380 | } | |
1381 | ||
1382 | /* | |
1383 | * Adopt the RCU callbacks from the specified rcu_state structure's | |
1384 | * orphanage. The caller must hold the ->onofflock. | |
1385 | */ | |
1386 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) | |
1387 | { | |
1388 | int i; | |
1389 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); | |
1390 | ||
a50c3af9 | 1391 | /* |
b1420f1c PM |
1392 | * If there is an rcu_barrier() operation in progress, then |
1393 | * only the task doing that operation is permitted to adopt | |
1394 | * callbacks. To do otherwise breaks rcu_barrier() and friends | |
1395 | * by causing them to fail to wait for the callbacks in the | |
1396 | * orphanage. | |
a50c3af9 | 1397 | */ |
b1420f1c PM |
1398 | if (rsp->rcu_barrier_in_progress && |
1399 | rsp->rcu_barrier_in_progress != current) | |
1400 | return; | |
1401 | ||
1402 | /* Do the accounting first. */ | |
1403 | rdp->qlen_lazy += rsp->qlen_lazy; | |
1404 | rdp->qlen += rsp->qlen; | |
1405 | rdp->n_cbs_adopted += rsp->qlen; | |
8f5af6f1 PM |
1406 | if (rsp->qlen_lazy != rsp->qlen) |
1407 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
1408 | rsp->qlen_lazy = 0; |
1409 | rsp->qlen = 0; | |
1410 | ||
1411 | /* | |
1412 | * We do not need a memory barrier here because the only way we | |
1413 | * can get here if there is an rcu_barrier() in flight is if | |
1414 | * we are the task doing the rcu_barrier(). | |
1415 | */ | |
1416 | ||
1417 | /* First adopt the ready-to-invoke callbacks. */ | |
1418 | if (rsp->orphan_donelist != NULL) { | |
1419 | *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; | |
1420 | *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; | |
1421 | for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) | |
1422 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
1423 | rdp->nxttail[i] = rsp->orphan_donetail; | |
1424 | rsp->orphan_donelist = NULL; | |
1425 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
1426 | } | |
1427 | ||
1428 | /* And then adopt the callbacks that still need a grace period. */ | |
1429 | if (rsp->orphan_nxtlist != NULL) { | |
1430 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; | |
1431 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; | |
1432 | rsp->orphan_nxtlist = NULL; | |
1433 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
1434 | } | |
1435 | } | |
1436 | ||
1437 | /* | |
1438 | * Trace the fact that this CPU is going offline. | |
1439 | */ | |
1440 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) | |
1441 | { | |
1442 | RCU_TRACE(unsigned long mask); | |
1443 | RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); | |
1444 | RCU_TRACE(struct rcu_node *rnp = rdp->mynode); | |
1445 | ||
1446 | RCU_TRACE(mask = rdp->grpmask); | |
e5601400 PM |
1447 | trace_rcu_grace_period(rsp->name, |
1448 | rnp->gpnum + 1 - !!(rnp->qsmask & mask), | |
1449 | "cpuofl"); | |
64db4cff PM |
1450 | } |
1451 | ||
1452 | /* | |
e5601400 | 1453 | * The CPU has been completely removed, and some other CPU is reporting |
b1420f1c PM |
1454 | * this fact from process context. Do the remainder of the cleanup, |
1455 | * including orphaning the outgoing CPU's RCU callbacks, and also | |
1456 | * adopting them, if there is no _rcu_barrier() instance running. | |
e5601400 PM |
1457 | * There can only be one CPU hotplug operation at a time, so no other |
1458 | * CPU can be attempting to update rcu_cpu_kthread_task. | |
64db4cff | 1459 | */ |
e5601400 | 1460 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff | 1461 | { |
2036d94a PM |
1462 | unsigned long flags; |
1463 | unsigned long mask; | |
1464 | int need_report = 0; | |
e5601400 | 1465 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
b1420f1c | 1466 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
e5601400 | 1467 | |
2036d94a | 1468 | /* Adjust any no-longer-needed kthreads. */ |
e5601400 PM |
1469 | rcu_stop_cpu_kthread(cpu); |
1470 | rcu_node_kthread_setaffinity(rnp, -1); | |
2036d94a | 1471 | |
b1420f1c | 1472 | /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */ |
2036d94a PM |
1473 | |
1474 | /* Exclude any attempts to start a new grace period. */ | |
1475 | raw_spin_lock_irqsave(&rsp->onofflock, flags); | |
1476 | ||
b1420f1c PM |
1477 | /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ |
1478 | rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); | |
1479 | rcu_adopt_orphan_cbs(rsp); | |
1480 | ||
2036d94a PM |
1481 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
1482 | mask = rdp->grpmask; /* rnp->grplo is constant. */ | |
1483 | do { | |
1484 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1485 | rnp->qsmaskinit &= ~mask; | |
1486 | if (rnp->qsmaskinit != 0) { | |
1487 | if (rnp != rdp->mynode) | |
1488 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1489 | break; | |
1490 | } | |
1491 | if (rnp == rdp->mynode) | |
1492 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); | |
1493 | else | |
1494 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1495 | mask = rnp->grpmask; | |
1496 | rnp = rnp->parent; | |
1497 | } while (rnp != NULL); | |
1498 | ||
1499 | /* | |
1500 | * We still hold the leaf rcu_node structure lock here, and | |
1501 | * irqs are still disabled. The reason for this subterfuge is | |
1502 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock | |
1503 | * held leads to deadlock. | |
1504 | */ | |
1505 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ | |
1506 | rnp = rdp->mynode; | |
1507 | if (need_report & RCU_OFL_TASKS_NORM_GP) | |
1508 | rcu_report_unblock_qs_rnp(rnp, flags); | |
1509 | else | |
1510 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1511 | if (need_report & RCU_OFL_TASKS_EXP_GP) | |
1512 | rcu_report_exp_rnp(rsp, rnp, true); | |
64db4cff PM |
1513 | } |
1514 | ||
1515 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1516 | ||
b1420f1c PM |
1517 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
1518 | { | |
1519 | } | |
1520 | ||
e5601400 | 1521 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) |
e74f4c45 PM |
1522 | { |
1523 | } | |
1524 | ||
e5601400 | 1525 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff PM |
1526 | { |
1527 | } | |
1528 | ||
1529 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
1530 | ||
1531 | /* | |
1532 | * Invoke any RCU callbacks that have made it to the end of their grace | |
1533 | * period. Thottle as specified by rdp->blimit. | |
1534 | */ | |
37c72e56 | 1535 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1536 | { |
1537 | unsigned long flags; | |
1538 | struct rcu_head *next, *list, **tail; | |
b41772ab | 1539 | int bl, count, count_lazy, i; |
64db4cff PM |
1540 | |
1541 | /* If no callbacks are ready, just return.*/ | |
29c00b4a | 1542 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) { |
486e2593 | 1543 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); |
4968c300 PM |
1544 | trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), |
1545 | need_resched(), is_idle_task(current), | |
1546 | rcu_is_callbacks_kthread()); | |
64db4cff | 1547 | return; |
29c00b4a | 1548 | } |
64db4cff PM |
1549 | |
1550 | /* | |
1551 | * Extract the list of ready callbacks, disabling to prevent | |
1552 | * races with call_rcu() from interrupt handlers. | |
1553 | */ | |
1554 | local_irq_save(flags); | |
8146c4e2 | 1555 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
29c00b4a | 1556 | bl = rdp->blimit; |
486e2593 | 1557 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); |
64db4cff PM |
1558 | list = rdp->nxtlist; |
1559 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
1560 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
1561 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
b41772ab PM |
1562 | for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) |
1563 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
1564 | rdp->nxttail[i] = &rdp->nxtlist; | |
64db4cff PM |
1565 | local_irq_restore(flags); |
1566 | ||
1567 | /* Invoke callbacks. */ | |
486e2593 | 1568 | count = count_lazy = 0; |
64db4cff PM |
1569 | while (list) { |
1570 | next = list->next; | |
1571 | prefetch(next); | |
551d55a9 | 1572 | debug_rcu_head_unqueue(list); |
486e2593 PM |
1573 | if (__rcu_reclaim(rsp->name, list)) |
1574 | count_lazy++; | |
64db4cff | 1575 | list = next; |
dff1672d PM |
1576 | /* Stop only if limit reached and CPU has something to do. */ |
1577 | if (++count >= bl && | |
1578 | (need_resched() || | |
1579 | (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) | |
64db4cff PM |
1580 | break; |
1581 | } | |
1582 | ||
1583 | local_irq_save(flags); | |
4968c300 PM |
1584 | trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), |
1585 | is_idle_task(current), | |
1586 | rcu_is_callbacks_kthread()); | |
64db4cff PM |
1587 | |
1588 | /* Update count, and requeue any remaining callbacks. */ | |
64db4cff PM |
1589 | if (list != NULL) { |
1590 | *tail = rdp->nxtlist; | |
1591 | rdp->nxtlist = list; | |
b41772ab PM |
1592 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
1593 | if (&rdp->nxtlist == rdp->nxttail[i]) | |
1594 | rdp->nxttail[i] = tail; | |
64db4cff PM |
1595 | else |
1596 | break; | |
1597 | } | |
b1420f1c PM |
1598 | smp_mb(); /* List handling before counting for rcu_barrier(). */ |
1599 | rdp->qlen_lazy -= count_lazy; | |
1600 | rdp->qlen -= count; | |
1601 | rdp->n_cbs_invoked += count; | |
64db4cff PM |
1602 | |
1603 | /* Reinstate batch limit if we have worked down the excess. */ | |
1604 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
1605 | rdp->blimit = blimit; | |
1606 | ||
37c72e56 PM |
1607 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1608 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
1609 | rdp->qlen_last_fqs_check = 0; | |
1610 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1611 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
1612 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1613 | ||
64db4cff PM |
1614 | local_irq_restore(flags); |
1615 | ||
e0f23060 | 1616 | /* Re-invoke RCU core processing if there are callbacks remaining. */ |
64db4cff | 1617 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 1618 | invoke_rcu_core(); |
64db4cff PM |
1619 | } |
1620 | ||
1621 | /* | |
1622 | * Check to see if this CPU is in a non-context-switch quiescent state | |
1623 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
e0f23060 | 1624 | * Also schedule RCU core processing. |
64db4cff | 1625 | * |
9b2e4f18 | 1626 | * This function must be called from hardirq context. It is normally |
64db4cff PM |
1627 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
1628 | * false, there is no point in invoking rcu_check_callbacks(). | |
1629 | */ | |
1630 | void rcu_check_callbacks(int cpu, int user) | |
1631 | { | |
300df91c | 1632 | trace_rcu_utilization("Start scheduler-tick"); |
a858af28 | 1633 | increment_cpu_stall_ticks(); |
9b2e4f18 | 1634 | if (user || rcu_is_cpu_rrupt_from_idle()) { |
64db4cff PM |
1635 | |
1636 | /* | |
1637 | * Get here if this CPU took its interrupt from user | |
1638 | * mode or from the idle loop, and if this is not a | |
1639 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1640 | * a quiescent state, so note it. |
64db4cff PM |
1641 | * |
1642 | * No memory barrier is required here because both | |
d6714c22 PM |
1643 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1644 | * variables that other CPUs neither access nor modify, | |
1645 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1646 | */ |
1647 | ||
d6714c22 PM |
1648 | rcu_sched_qs(cpu); |
1649 | rcu_bh_qs(cpu); | |
64db4cff PM |
1650 | |
1651 | } else if (!in_softirq()) { | |
1652 | ||
1653 | /* | |
1654 | * Get here if this CPU did not take its interrupt from | |
1655 | * softirq, in other words, if it is not interrupting | |
1656 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1657 | * critical section, so note it. |
64db4cff PM |
1658 | */ |
1659 | ||
d6714c22 | 1660 | rcu_bh_qs(cpu); |
64db4cff | 1661 | } |
f41d911f | 1662 | rcu_preempt_check_callbacks(cpu); |
d21670ac | 1663 | if (rcu_pending(cpu)) |
a46e0899 | 1664 | invoke_rcu_core(); |
300df91c | 1665 | trace_rcu_utilization("End scheduler-tick"); |
64db4cff PM |
1666 | } |
1667 | ||
64db4cff PM |
1668 | /* |
1669 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1670 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
1671 | * Also initiate boosting for any threads blocked on the root rcu_node. |
1672 | * | |
ee47eb9f | 1673 | * The caller must have suppressed start of new grace periods. |
64db4cff | 1674 | */ |
45f014c5 | 1675 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
64db4cff PM |
1676 | { |
1677 | unsigned long bit; | |
1678 | int cpu; | |
1679 | unsigned long flags; | |
1680 | unsigned long mask; | |
a0b6c9a7 | 1681 | struct rcu_node *rnp; |
64db4cff | 1682 | |
a0b6c9a7 | 1683 | rcu_for_each_leaf_node(rsp, rnp) { |
64db4cff | 1684 | mask = 0; |
1304afb2 | 1685 | raw_spin_lock_irqsave(&rnp->lock, flags); |
ee47eb9f | 1686 | if (!rcu_gp_in_progress(rsp)) { |
1304afb2 | 1687 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
0f10dc82 | 1688 | return; |
64db4cff | 1689 | } |
a0b6c9a7 | 1690 | if (rnp->qsmask == 0) { |
1217ed1b | 1691 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
64db4cff PM |
1692 | continue; |
1693 | } | |
a0b6c9a7 | 1694 | cpu = rnp->grplo; |
64db4cff | 1695 | bit = 1; |
a0b6c9a7 | 1696 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
394f99a9 LJ |
1697 | if ((rnp->qsmask & bit) != 0 && |
1698 | f(per_cpu_ptr(rsp->rda, cpu))) | |
64db4cff PM |
1699 | mask |= bit; |
1700 | } | |
45f014c5 | 1701 | if (mask != 0) { |
64db4cff | 1702 | |
d3f6bad3 PM |
1703 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
1704 | rcu_report_qs_rnp(mask, rsp, rnp, flags); | |
64db4cff PM |
1705 | continue; |
1706 | } | |
1304afb2 | 1707 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 1708 | } |
27f4d280 | 1709 | rnp = rcu_get_root(rsp); |
1217ed1b PM |
1710 | if (rnp->qsmask == 0) { |
1711 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
1712 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ | |
1713 | } | |
64db4cff PM |
1714 | } |
1715 | ||
1716 | /* | |
1717 | * Force quiescent states on reluctant CPUs, and also detect which | |
1718 | * CPUs are in dyntick-idle mode. | |
1719 | */ | |
1720 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1721 | { | |
1722 | unsigned long flags; | |
64db4cff | 1723 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 1724 | |
300df91c PM |
1725 | trace_rcu_utilization("Start fqs"); |
1726 | if (!rcu_gp_in_progress(rsp)) { | |
1727 | trace_rcu_utilization("End fqs"); | |
64db4cff | 1728 | return; /* No grace period in progress, nothing to force. */ |
300df91c | 1729 | } |
1304afb2 | 1730 | if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { |
64db4cff | 1731 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
300df91c | 1732 | trace_rcu_utilization("End fqs"); |
64db4cff PM |
1733 | return; /* Someone else is already on the job. */ |
1734 | } | |
20133cfc | 1735 | if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) |
f96e9232 | 1736 | goto unlock_fqs_ret; /* no emergency and done recently. */ |
64db4cff | 1737 | rsp->n_force_qs++; |
1304afb2 | 1738 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
64db4cff | 1739 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
560d4bc0 | 1740 | if(!rcu_gp_in_progress(rsp)) { |
64db4cff | 1741 | rsp->n_force_qs_ngp++; |
1304afb2 | 1742 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
f96e9232 | 1743 | goto unlock_fqs_ret; /* no GP in progress, time updated. */ |
64db4cff | 1744 | } |
07079d53 | 1745 | rsp->fqs_active = 1; |
af446b70 | 1746 | switch (rsp->fqs_state) { |
83f5b01f | 1747 | case RCU_GP_IDLE: |
64db4cff PM |
1748 | case RCU_GP_INIT: |
1749 | ||
83f5b01f | 1750 | break; /* grace period idle or initializing, ignore. */ |
64db4cff PM |
1751 | |
1752 | case RCU_SAVE_DYNTICK: | |
64db4cff PM |
1753 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
1754 | break; /* So gcc recognizes the dead code. */ | |
1755 | ||
f261414f LJ |
1756 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1757 | ||
64db4cff | 1758 | /* Record dyntick-idle state. */ |
45f014c5 | 1759 | force_qs_rnp(rsp, dyntick_save_progress_counter); |
1304afb2 | 1760 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
ee47eb9f | 1761 | if (rcu_gp_in_progress(rsp)) |
af446b70 | 1762 | rsp->fqs_state = RCU_FORCE_QS; |
ee47eb9f | 1763 | break; |
64db4cff PM |
1764 | |
1765 | case RCU_FORCE_QS: | |
1766 | ||
1767 | /* Check dyntick-idle state, send IPI to laggarts. */ | |
1304afb2 | 1768 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
45f014c5 | 1769 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
64db4cff PM |
1770 | |
1771 | /* Leave state in case more forcing is required. */ | |
1772 | ||
1304afb2 | 1773 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
f96e9232 | 1774 | break; |
64db4cff | 1775 | } |
07079d53 | 1776 | rsp->fqs_active = 0; |
46a1e34e | 1777 | if (rsp->fqs_need_gp) { |
1304afb2 | 1778 | raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ |
46a1e34e PM |
1779 | rsp->fqs_need_gp = 0; |
1780 | rcu_start_gp(rsp, flags); /* releases rnp->lock */ | |
300df91c | 1781 | trace_rcu_utilization("End fqs"); |
46a1e34e PM |
1782 | return; |
1783 | } | |
1304afb2 | 1784 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
f96e9232 | 1785 | unlock_fqs_ret: |
1304afb2 | 1786 | raw_spin_unlock_irqrestore(&rsp->fqslock, flags); |
300df91c | 1787 | trace_rcu_utilization("End fqs"); |
64db4cff PM |
1788 | } |
1789 | ||
64db4cff | 1790 | /* |
e0f23060 PM |
1791 | * This does the RCU core processing work for the specified rcu_state |
1792 | * and rcu_data structures. This may be called only from the CPU to | |
1793 | * whom the rdp belongs. | |
64db4cff PM |
1794 | */ |
1795 | static void | |
1796 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) | |
1797 | { | |
1798 | unsigned long flags; | |
1799 | ||
2e597558 PM |
1800 | WARN_ON_ONCE(rdp->beenonline == 0); |
1801 | ||
64db4cff PM |
1802 | /* |
1803 | * If an RCU GP has gone long enough, go check for dyntick | |
1804 | * idle CPUs and, if needed, send resched IPIs. | |
1805 | */ | |
20133cfc | 1806 | if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
64db4cff PM |
1807 | force_quiescent_state(rsp, 1); |
1808 | ||
1809 | /* | |
1810 | * Advance callbacks in response to end of earlier grace | |
1811 | * period that some other CPU ended. | |
1812 | */ | |
1813 | rcu_process_gp_end(rsp, rdp); | |
1814 | ||
1815 | /* Update RCU state based on any recent quiescent states. */ | |
1816 | rcu_check_quiescent_state(rsp, rdp); | |
1817 | ||
1818 | /* Does this CPU require a not-yet-started grace period? */ | |
1819 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1304afb2 | 1820 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
64db4cff PM |
1821 | rcu_start_gp(rsp, flags); /* releases above lock */ |
1822 | } | |
1823 | ||
1824 | /* If there are callbacks ready, invoke them. */ | |
09223371 | 1825 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 1826 | invoke_rcu_callbacks(rsp, rdp); |
09223371 SL |
1827 | } |
1828 | ||
64db4cff | 1829 | /* |
e0f23060 | 1830 | * Do RCU core processing for the current CPU. |
64db4cff | 1831 | */ |
09223371 | 1832 | static void rcu_process_callbacks(struct softirq_action *unused) |
64db4cff | 1833 | { |
300df91c | 1834 | trace_rcu_utilization("Start RCU core"); |
d6714c22 PM |
1835 | __rcu_process_callbacks(&rcu_sched_state, |
1836 | &__get_cpu_var(rcu_sched_data)); | |
64db4cff | 1837 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
f41d911f | 1838 | rcu_preempt_process_callbacks(); |
300df91c | 1839 | trace_rcu_utilization("End RCU core"); |
64db4cff PM |
1840 | } |
1841 | ||
a26ac245 | 1842 | /* |
e0f23060 PM |
1843 | * Schedule RCU callback invocation. If the specified type of RCU |
1844 | * does not support RCU priority boosting, just do a direct call, | |
1845 | * otherwise wake up the per-CPU kernel kthread. Note that because we | |
1846 | * are running on the current CPU with interrupts disabled, the | |
1847 | * rcu_cpu_kthread_task cannot disappear out from under us. | |
a26ac245 | 1848 | */ |
a46e0899 | 1849 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
a26ac245 | 1850 | { |
b0d30417 PM |
1851 | if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) |
1852 | return; | |
a46e0899 PM |
1853 | if (likely(!rsp->boost)) { |
1854 | rcu_do_batch(rsp, rdp); | |
a26ac245 PM |
1855 | return; |
1856 | } | |
a46e0899 | 1857 | invoke_rcu_callbacks_kthread(); |
a26ac245 PM |
1858 | } |
1859 | ||
a46e0899 | 1860 | static void invoke_rcu_core(void) |
09223371 SL |
1861 | { |
1862 | raise_softirq(RCU_SOFTIRQ); | |
1863 | } | |
1864 | ||
64db4cff PM |
1865 | static void |
1866 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
486e2593 | 1867 | struct rcu_state *rsp, bool lazy) |
64db4cff PM |
1868 | { |
1869 | unsigned long flags; | |
1870 | struct rcu_data *rdp; | |
1871 | ||
0bb7b59d | 1872 | WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ |
551d55a9 | 1873 | debug_rcu_head_queue(head); |
64db4cff PM |
1874 | head->func = func; |
1875 | head->next = NULL; | |
1876 | ||
1877 | smp_mb(); /* Ensure RCU update seen before callback registry. */ | |
1878 | ||
1879 | /* | |
1880 | * Opportunistically note grace-period endings and beginnings. | |
1881 | * Note that we might see a beginning right after we see an | |
1882 | * end, but never vice versa, since this CPU has to pass through | |
1883 | * a quiescent state betweentimes. | |
1884 | */ | |
1885 | local_irq_save(flags); | |
394f99a9 | 1886 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
1887 | |
1888 | /* Add the callback to our list. */ | |
2655d57e | 1889 | rdp->qlen++; |
486e2593 PM |
1890 | if (lazy) |
1891 | rdp->qlen_lazy++; | |
c57afe80 PM |
1892 | else |
1893 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
1894 | smp_mb(); /* Count before adding callback for rcu_barrier(). */ |
1895 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
1896 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
2655d57e | 1897 | |
d4c08f2a PM |
1898 | if (__is_kfree_rcu_offset((unsigned long)func)) |
1899 | trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, | |
486e2593 | 1900 | rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 1901 | else |
486e2593 | 1902 | trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 1903 | |
2655d57e PM |
1904 | /* If interrupts were disabled, don't dive into RCU core. */ |
1905 | if (irqs_disabled_flags(flags)) { | |
1906 | local_irq_restore(flags); | |
1907 | return; | |
1908 | } | |
64db4cff | 1909 | |
37c72e56 PM |
1910 | /* |
1911 | * Force the grace period if too many callbacks or too long waiting. | |
1912 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
1913 | * if some other CPU has recently done so. Also, don't bother | |
1914 | * invoking force_quiescent_state() if the newly enqueued callback | |
1915 | * is the only one waiting for a grace period to complete. | |
1916 | */ | |
2655d57e | 1917 | if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
b52573d2 PM |
1918 | |
1919 | /* Are we ignoring a completed grace period? */ | |
1920 | rcu_process_gp_end(rsp, rdp); | |
1921 | check_for_new_grace_period(rsp, rdp); | |
1922 | ||
1923 | /* Start a new grace period if one not already started. */ | |
1924 | if (!rcu_gp_in_progress(rsp)) { | |
1925 | unsigned long nestflag; | |
1926 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
1927 | ||
1928 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); | |
1929 | rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */ | |
1930 | } else { | |
1931 | /* Give the grace period a kick. */ | |
1932 | rdp->blimit = LONG_MAX; | |
1933 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
1934 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
1935 | force_quiescent_state(rsp, 0); | |
1936 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1937 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1938 | } | |
20133cfc | 1939 | } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
64db4cff PM |
1940 | force_quiescent_state(rsp, 1); |
1941 | local_irq_restore(flags); | |
1942 | } | |
1943 | ||
1944 | /* | |
d6714c22 | 1945 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 1946 | */ |
d6714c22 | 1947 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 1948 | { |
486e2593 | 1949 | __call_rcu(head, func, &rcu_sched_state, 0); |
64db4cff | 1950 | } |
d6714c22 | 1951 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
1952 | |
1953 | /* | |
486e2593 | 1954 | * Queue an RCU callback for invocation after a quicker grace period. |
64db4cff PM |
1955 | */ |
1956 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1957 | { | |
486e2593 | 1958 | __call_rcu(head, func, &rcu_bh_state, 0); |
64db4cff PM |
1959 | } |
1960 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
1961 | ||
6d813391 PM |
1962 | /* |
1963 | * Because a context switch is a grace period for RCU-sched and RCU-bh, | |
1964 | * any blocking grace-period wait automatically implies a grace period | |
1965 | * if there is only one CPU online at any point time during execution | |
1966 | * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to | |
1967 | * occasionally incorrectly indicate that there are multiple CPUs online | |
1968 | * when there was in fact only one the whole time, as this just adds | |
1969 | * some overhead: RCU still operates correctly. | |
1970 | * | |
1971 | * Of course, sampling num_online_cpus() with preemption enabled can | |
1972 | * give erroneous results if there are concurrent CPU-hotplug operations. | |
1973 | * For example, given a demonic sequence of preemptions in num_online_cpus() | |
1974 | * and CPU-hotplug operations, there could be two or more CPUs online at | |
1975 | * all times, but num_online_cpus() might well return one (or even zero). | |
1976 | * | |
1977 | * However, all such demonic sequences require at least one CPU-offline | |
1978 | * operation. Furthermore, rcu_blocking_is_gp() giving the wrong answer | |
1979 | * is only a problem if there is an RCU read-side critical section executing | |
1980 | * throughout. But RCU-sched and RCU-bh read-side critical sections | |
1981 | * disable either preemption or bh, which prevents a CPU from going offline. | |
1982 | * Therefore, the only way that rcu_blocking_is_gp() can incorrectly return | |
1983 | * that there is only one CPU when in fact there was more than one throughout | |
1984 | * is when there were no RCU readers in the system. If there are no | |
1985 | * RCU readers, the grace period by definition can be of zero length, | |
1986 | * regardless of the number of online CPUs. | |
1987 | */ | |
1988 | static inline int rcu_blocking_is_gp(void) | |
1989 | { | |
1990 | might_sleep(); /* Check for RCU read-side critical section. */ | |
1991 | return num_online_cpus() <= 1; | |
1992 | } | |
1993 | ||
6ebb237b PM |
1994 | /** |
1995 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
1996 | * | |
1997 | * Control will return to the caller some time after a full rcu-sched | |
1998 | * grace period has elapsed, in other words after all currently executing | |
1999 | * rcu-sched read-side critical sections have completed. These read-side | |
2000 | * critical sections are delimited by rcu_read_lock_sched() and | |
2001 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
2002 | * local_irq_disable(), and so on may be used in place of | |
2003 | * rcu_read_lock_sched(). | |
2004 | * | |
2005 | * This means that all preempt_disable code sequences, including NMI and | |
2006 | * hardware-interrupt handlers, in progress on entry will have completed | |
2007 | * before this primitive returns. However, this does not guarantee that | |
2008 | * softirq handlers will have completed, since in some kernels, these | |
2009 | * handlers can run in process context, and can block. | |
2010 | * | |
2011 | * This primitive provides the guarantees made by the (now removed) | |
2012 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
2013 | * guarantees that rcu_read_lock() sections will have completed. | |
2014 | * In "classic RCU", these two guarantees happen to be one and | |
2015 | * the same, but can differ in realtime RCU implementations. | |
2016 | */ | |
2017 | void synchronize_sched(void) | |
2018 | { | |
fe15d706 PM |
2019 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2020 | !lock_is_held(&rcu_lock_map) && | |
2021 | !lock_is_held(&rcu_sched_lock_map), | |
2022 | "Illegal synchronize_sched() in RCU-sched read-side critical section"); | |
6ebb237b PM |
2023 | if (rcu_blocking_is_gp()) |
2024 | return; | |
2c42818e | 2025 | wait_rcu_gp(call_rcu_sched); |
6ebb237b PM |
2026 | } |
2027 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
2028 | ||
2029 | /** | |
2030 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
2031 | * | |
2032 | * Control will return to the caller some time after a full rcu_bh grace | |
2033 | * period has elapsed, in other words after all currently executing rcu_bh | |
2034 | * read-side critical sections have completed. RCU read-side critical | |
2035 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
2036 | * and may be nested. | |
2037 | */ | |
2038 | void synchronize_rcu_bh(void) | |
2039 | { | |
fe15d706 PM |
2040 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2041 | !lock_is_held(&rcu_lock_map) && | |
2042 | !lock_is_held(&rcu_sched_lock_map), | |
2043 | "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); | |
6ebb237b PM |
2044 | if (rcu_blocking_is_gp()) |
2045 | return; | |
2c42818e | 2046 | wait_rcu_gp(call_rcu_bh); |
6ebb237b PM |
2047 | } |
2048 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
2049 | ||
3d3b7db0 PM |
2050 | static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0); |
2051 | static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0); | |
2052 | ||
2053 | static int synchronize_sched_expedited_cpu_stop(void *data) | |
2054 | { | |
2055 | /* | |
2056 | * There must be a full memory barrier on each affected CPU | |
2057 | * between the time that try_stop_cpus() is called and the | |
2058 | * time that it returns. | |
2059 | * | |
2060 | * In the current initial implementation of cpu_stop, the | |
2061 | * above condition is already met when the control reaches | |
2062 | * this point and the following smp_mb() is not strictly | |
2063 | * necessary. Do smp_mb() anyway for documentation and | |
2064 | * robustness against future implementation changes. | |
2065 | */ | |
2066 | smp_mb(); /* See above comment block. */ | |
2067 | return 0; | |
2068 | } | |
2069 | ||
236fefaf PM |
2070 | /** |
2071 | * synchronize_sched_expedited - Brute-force RCU-sched grace period | |
2072 | * | |
2073 | * Wait for an RCU-sched grace period to elapse, but use a "big hammer" | |
2074 | * approach to force the grace period to end quickly. This consumes | |
2075 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
2076 | * so is thus not recommended for any sort of common-case code. In fact, | |
2077 | * if you are using synchronize_sched_expedited() in a loop, please | |
2078 | * restructure your code to batch your updates, and then use a single | |
2079 | * synchronize_sched() instead. | |
3d3b7db0 | 2080 | * |
236fefaf PM |
2081 | * Note that it is illegal to call this function while holding any lock |
2082 | * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal | |
2083 | * to call this function from a CPU-hotplug notifier. Failing to observe | |
2084 | * these restriction will result in deadlock. | |
3d3b7db0 PM |
2085 | * |
2086 | * This implementation can be thought of as an application of ticket | |
2087 | * locking to RCU, with sync_sched_expedited_started and | |
2088 | * sync_sched_expedited_done taking on the roles of the halves | |
2089 | * of the ticket-lock word. Each task atomically increments | |
2090 | * sync_sched_expedited_started upon entry, snapshotting the old value, | |
2091 | * then attempts to stop all the CPUs. If this succeeds, then each | |
2092 | * CPU will have executed a context switch, resulting in an RCU-sched | |
2093 | * grace period. We are then done, so we use atomic_cmpxchg() to | |
2094 | * update sync_sched_expedited_done to match our snapshot -- but | |
2095 | * only if someone else has not already advanced past our snapshot. | |
2096 | * | |
2097 | * On the other hand, if try_stop_cpus() fails, we check the value | |
2098 | * of sync_sched_expedited_done. If it has advanced past our | |
2099 | * initial snapshot, then someone else must have forced a grace period | |
2100 | * some time after we took our snapshot. In this case, our work is | |
2101 | * done for us, and we can simply return. Otherwise, we try again, | |
2102 | * but keep our initial snapshot for purposes of checking for someone | |
2103 | * doing our work for us. | |
2104 | * | |
2105 | * If we fail too many times in a row, we fall back to synchronize_sched(). | |
2106 | */ | |
2107 | void synchronize_sched_expedited(void) | |
2108 | { | |
2109 | int firstsnap, s, snap, trycount = 0; | |
2110 | ||
2111 | /* Note that atomic_inc_return() implies full memory barrier. */ | |
2112 | firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started); | |
2113 | get_online_cpus(); | |
1cc85961 | 2114 | WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); |
3d3b7db0 PM |
2115 | |
2116 | /* | |
2117 | * Each pass through the following loop attempts to force a | |
2118 | * context switch on each CPU. | |
2119 | */ | |
2120 | while (try_stop_cpus(cpu_online_mask, | |
2121 | synchronize_sched_expedited_cpu_stop, | |
2122 | NULL) == -EAGAIN) { | |
2123 | put_online_cpus(); | |
2124 | ||
2125 | /* No joy, try again later. Or just synchronize_sched(). */ | |
2126 | if (trycount++ < 10) | |
2127 | udelay(trycount * num_online_cpus()); | |
2128 | else { | |
2129 | synchronize_sched(); | |
2130 | return; | |
2131 | } | |
2132 | ||
2133 | /* Check to see if someone else did our work for us. */ | |
2134 | s = atomic_read(&sync_sched_expedited_done); | |
2135 | if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) { | |
2136 | smp_mb(); /* ensure test happens before caller kfree */ | |
2137 | return; | |
2138 | } | |
2139 | ||
2140 | /* | |
2141 | * Refetching sync_sched_expedited_started allows later | |
2142 | * callers to piggyback on our grace period. We subtract | |
2143 | * 1 to get the same token that the last incrementer got. | |
2144 | * We retry after they started, so our grace period works | |
2145 | * for them, and they started after our first try, so their | |
2146 | * grace period works for us. | |
2147 | */ | |
2148 | get_online_cpus(); | |
2149 | snap = atomic_read(&sync_sched_expedited_started); | |
2150 | smp_mb(); /* ensure read is before try_stop_cpus(). */ | |
2151 | } | |
2152 | ||
2153 | /* | |
2154 | * Everyone up to our most recent fetch is covered by our grace | |
2155 | * period. Update the counter, but only if our work is still | |
2156 | * relevant -- which it won't be if someone who started later | |
2157 | * than we did beat us to the punch. | |
2158 | */ | |
2159 | do { | |
2160 | s = atomic_read(&sync_sched_expedited_done); | |
2161 | if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) { | |
2162 | smp_mb(); /* ensure test happens before caller kfree */ | |
2163 | break; | |
2164 | } | |
2165 | } while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s); | |
2166 | ||
2167 | put_online_cpus(); | |
2168 | } | |
2169 | EXPORT_SYMBOL_GPL(synchronize_sched_expedited); | |
2170 | ||
64db4cff PM |
2171 | /* |
2172 | * Check to see if there is any immediate RCU-related work to be done | |
2173 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
2174 | * The checks are in order of increasing expense: checks that can be | |
2175 | * carried out against CPU-local state are performed first. However, | |
2176 | * we must check for CPU stalls first, else we might not get a chance. | |
2177 | */ | |
2178 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
2179 | { | |
2f51f988 PM |
2180 | struct rcu_node *rnp = rdp->mynode; |
2181 | ||
64db4cff PM |
2182 | rdp->n_rcu_pending++; |
2183 | ||
2184 | /* Check for CPU stalls, if enabled. */ | |
2185 | check_cpu_stall(rsp, rdp); | |
2186 | ||
2187 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
5c51dd73 PM |
2188 | if (rcu_scheduler_fully_active && |
2189 | rdp->qs_pending && !rdp->passed_quiesce) { | |
d25eb944 PM |
2190 | |
2191 | /* | |
2192 | * If force_quiescent_state() coming soon and this CPU | |
2193 | * needs a quiescent state, and this is either RCU-sched | |
2194 | * or RCU-bh, force a local reschedule. | |
2195 | */ | |
d21670ac | 2196 | rdp->n_rp_qs_pending++; |
6cc68793 | 2197 | if (!rdp->preemptible && |
d25eb944 PM |
2198 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, |
2199 | jiffies)) | |
2200 | set_need_resched(); | |
e4cc1f22 | 2201 | } else if (rdp->qs_pending && rdp->passed_quiesce) { |
d21670ac | 2202 | rdp->n_rp_report_qs++; |
64db4cff | 2203 | return 1; |
7ba5c840 | 2204 | } |
64db4cff PM |
2205 | |
2206 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
2207 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
2208 | rdp->n_rp_cb_ready++; | |
64db4cff | 2209 | return 1; |
7ba5c840 | 2210 | } |
64db4cff PM |
2211 | |
2212 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
2213 | if (cpu_needs_another_gp(rsp, rdp)) { |
2214 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 2215 | return 1; |
7ba5c840 | 2216 | } |
64db4cff PM |
2217 | |
2218 | /* Has another RCU grace period completed? */ | |
2f51f988 | 2219 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 2220 | rdp->n_rp_gp_completed++; |
64db4cff | 2221 | return 1; |
7ba5c840 | 2222 | } |
64db4cff PM |
2223 | |
2224 | /* Has a new RCU grace period started? */ | |
2f51f988 | 2225 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 2226 | rdp->n_rp_gp_started++; |
64db4cff | 2227 | return 1; |
7ba5c840 | 2228 | } |
64db4cff PM |
2229 | |
2230 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ | |
fc2219d4 | 2231 | if (rcu_gp_in_progress(rsp) && |
20133cfc | 2232 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { |
7ba5c840 | 2233 | rdp->n_rp_need_fqs++; |
64db4cff | 2234 | return 1; |
7ba5c840 | 2235 | } |
64db4cff PM |
2236 | |
2237 | /* nothing to do */ | |
7ba5c840 | 2238 | rdp->n_rp_need_nothing++; |
64db4cff PM |
2239 | return 0; |
2240 | } | |
2241 | ||
2242 | /* | |
2243 | * Check to see if there is any immediate RCU-related work to be done | |
2244 | * by the current CPU, returning 1 if so. This function is part of the | |
2245 | * RCU implementation; it is -not- an exported member of the RCU API. | |
2246 | */ | |
a157229c | 2247 | static int rcu_pending(int cpu) |
64db4cff | 2248 | { |
d6714c22 | 2249 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
f41d911f PM |
2250 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
2251 | rcu_preempt_pending(cpu); | |
64db4cff PM |
2252 | } |
2253 | ||
2254 | /* | |
2255 | * Check to see if any future RCU-related work will need to be done | |
2256 | * by the current CPU, even if none need be done immediately, returning | |
8bd93a2c | 2257 | * 1 if so. |
64db4cff | 2258 | */ |
aea1b35e | 2259 | static int rcu_cpu_has_callbacks(int cpu) |
64db4cff PM |
2260 | { |
2261 | /* RCU callbacks either ready or pending? */ | |
d6714c22 | 2262 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
f41d911f | 2263 | per_cpu(rcu_bh_data, cpu).nxtlist || |
30fbcc90 | 2264 | rcu_preempt_cpu_has_callbacks(cpu); |
64db4cff PM |
2265 | } |
2266 | ||
b1420f1c PM |
2267 | /* |
2268 | * RCU callback function for _rcu_barrier(). If we are last, wake | |
2269 | * up the task executing _rcu_barrier(). | |
2270 | */ | |
24ebbca8 | 2271 | static void rcu_barrier_callback(struct rcu_head *rhp) |
d0ec774c | 2272 | { |
24ebbca8 PM |
2273 | struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); |
2274 | struct rcu_state *rsp = rdp->rsp; | |
2275 | ||
2276 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) | |
7db74df8 | 2277 | complete(&rsp->barrier_completion); |
d0ec774c PM |
2278 | } |
2279 | ||
2280 | /* | |
2281 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
2282 | */ | |
2283 | static void rcu_barrier_func(void *type) | |
2284 | { | |
037b64ed | 2285 | struct rcu_state *rsp = type; |
06668efa | 2286 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
d0ec774c | 2287 | |
24ebbca8 | 2288 | atomic_inc(&rsp->barrier_cpu_count); |
06668efa | 2289 | rsp->call(&rdp->barrier_head, rcu_barrier_callback); |
d0ec774c PM |
2290 | } |
2291 | ||
d0ec774c PM |
2292 | /* |
2293 | * Orchestrate the specified type of RCU barrier, waiting for all | |
2294 | * RCU callbacks of the specified type to complete. | |
2295 | */ | |
037b64ed | 2296 | static void _rcu_barrier(struct rcu_state *rsp) |
d0ec774c | 2297 | { |
b1420f1c PM |
2298 | int cpu; |
2299 | unsigned long flags; | |
2300 | struct rcu_data *rdp; | |
24ebbca8 | 2301 | struct rcu_data rd; |
b1420f1c | 2302 | |
24ebbca8 | 2303 | init_rcu_head_on_stack(&rd.barrier_head); |
b1420f1c | 2304 | |
e74f4c45 | 2305 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
d0ec774c | 2306 | mutex_lock(&rcu_barrier_mutex); |
b1420f1c PM |
2307 | |
2308 | smp_mb(); /* Prevent any prior operations from leaking in. */ | |
2309 | ||
d0ec774c | 2310 | /* |
b1420f1c PM |
2311 | * Initialize the count to one rather than to zero in order to |
2312 | * avoid a too-soon return to zero in case of a short grace period | |
2313 | * (or preemption of this task). Also flag this task as doing | |
2314 | * an rcu_barrier(). This will prevent anyone else from adopting | |
2315 | * orphaned callbacks, which could cause otherwise failure if a | |
2316 | * CPU went offline and quickly came back online. To see this, | |
2317 | * consider the following sequence of events: | |
2318 | * | |
2319 | * 1. We cause CPU 0 to post an rcu_barrier_callback() callback. | |
2320 | * 2. CPU 1 goes offline, orphaning its callbacks. | |
2321 | * 3. CPU 0 adopts CPU 1's orphaned callbacks. | |
2322 | * 4. CPU 1 comes back online. | |
2323 | * 5. We cause CPU 1 to post an rcu_barrier_callback() callback. | |
2324 | * 6. Both rcu_barrier_callback() callbacks are invoked, awakening | |
2325 | * us -- but before CPU 1's orphaned callbacks are invoked!!! | |
d0ec774c | 2326 | */ |
7db74df8 | 2327 | init_completion(&rsp->barrier_completion); |
24ebbca8 | 2328 | atomic_set(&rsp->barrier_cpu_count, 1); |
b1420f1c PM |
2329 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
2330 | rsp->rcu_barrier_in_progress = current; | |
2331 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); | |
2332 | ||
2333 | /* | |
2334 | * Force every CPU with callbacks to register a new callback | |
2335 | * that will tell us when all the preceding callbacks have | |
2336 | * been invoked. If an offline CPU has callbacks, wait for | |
2337 | * it to either come back online or to finish orphaning those | |
2338 | * callbacks. | |
2339 | */ | |
2340 | for_each_possible_cpu(cpu) { | |
2341 | preempt_disable(); | |
2342 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
2343 | if (cpu_is_offline(cpu)) { | |
2344 | preempt_enable(); | |
2345 | while (cpu_is_offline(cpu) && ACCESS_ONCE(rdp->qlen)) | |
2346 | schedule_timeout_interruptible(1); | |
2347 | } else if (ACCESS_ONCE(rdp->qlen)) { | |
037b64ed | 2348 | smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); |
b1420f1c PM |
2349 | preempt_enable(); |
2350 | } else { | |
2351 | preempt_enable(); | |
2352 | } | |
2353 | } | |
2354 | ||
2355 | /* | |
2356 | * Now that all online CPUs have rcu_barrier_callback() callbacks | |
2357 | * posted, we can adopt all of the orphaned callbacks and place | |
2358 | * an rcu_barrier_callback() callback after them. When that is done, | |
2359 | * we are guaranteed to have an rcu_barrier_callback() callback | |
2360 | * following every callback that could possibly have been | |
2361 | * registered before _rcu_barrier() was called. | |
2362 | */ | |
2363 | raw_spin_lock_irqsave(&rsp->onofflock, flags); | |
2364 | rcu_adopt_orphan_cbs(rsp); | |
2365 | rsp->rcu_barrier_in_progress = NULL; | |
2366 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); | |
24ebbca8 | 2367 | atomic_inc(&rsp->barrier_cpu_count); |
b1420f1c | 2368 | smp_mb__after_atomic_inc(); /* Ensure atomic_inc() before callback. */ |
24ebbca8 PM |
2369 | rd.rsp = rsp; |
2370 | rsp->call(&rd.barrier_head, rcu_barrier_callback); | |
b1420f1c PM |
2371 | |
2372 | /* | |
2373 | * Now that we have an rcu_barrier_callback() callback on each | |
2374 | * CPU, and thus each counted, remove the initial count. | |
2375 | */ | |
24ebbca8 | 2376 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) |
7db74df8 | 2377 | complete(&rsp->barrier_completion); |
b1420f1c PM |
2378 | |
2379 | /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ | |
7db74df8 | 2380 | wait_for_completion(&rsp->barrier_completion); |
b1420f1c PM |
2381 | |
2382 | /* Other rcu_barrier() invocations can now safely proceed. */ | |
d0ec774c | 2383 | mutex_unlock(&rcu_barrier_mutex); |
b1420f1c | 2384 | |
24ebbca8 | 2385 | destroy_rcu_head_on_stack(&rd.barrier_head); |
d0ec774c | 2386 | } |
d0ec774c PM |
2387 | |
2388 | /** | |
2389 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
2390 | */ | |
2391 | void rcu_barrier_bh(void) | |
2392 | { | |
037b64ed | 2393 | _rcu_barrier(&rcu_bh_state); |
d0ec774c PM |
2394 | } |
2395 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
2396 | ||
2397 | /** | |
2398 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
2399 | */ | |
2400 | void rcu_barrier_sched(void) | |
2401 | { | |
037b64ed | 2402 | _rcu_barrier(&rcu_sched_state); |
d0ec774c PM |
2403 | } |
2404 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
2405 | ||
64db4cff | 2406 | /* |
27569620 | 2407 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 2408 | */ |
27569620 PM |
2409 | static void __init |
2410 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
2411 | { |
2412 | unsigned long flags; | |
2413 | int i; | |
394f99a9 | 2414 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
2415 | struct rcu_node *rnp = rcu_get_root(rsp); |
2416 | ||
2417 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2418 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 PM |
2419 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
2420 | rdp->nxtlist = NULL; | |
2421 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
2422 | rdp->nxttail[i] = &rdp->nxtlist; | |
486e2593 | 2423 | rdp->qlen_lazy = 0; |
27569620 | 2424 | rdp->qlen = 0; |
27569620 | 2425 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
29e37d81 | 2426 | WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); |
9b2e4f18 | 2427 | WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); |
27569620 | 2428 | rdp->cpu = cpu; |
d4c08f2a | 2429 | rdp->rsp = rsp; |
1304afb2 | 2430 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
2431 | } |
2432 | ||
2433 | /* | |
2434 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
2435 | * offline event can be happening at a given time. Note also that we | |
2436 | * can accept some slop in the rsp->completed access due to the fact | |
2437 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 2438 | */ |
e4fa4c97 | 2439 | static void __cpuinit |
6cc68793 | 2440 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) |
64db4cff PM |
2441 | { |
2442 | unsigned long flags; | |
64db4cff | 2443 | unsigned long mask; |
394f99a9 | 2444 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
2445 | struct rcu_node *rnp = rcu_get_root(rsp); |
2446 | ||
2447 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2448 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 2449 | rdp->beenonline = 1; /* We have now been online. */ |
6cc68793 | 2450 | rdp->preemptible = preemptible; |
37c72e56 PM |
2451 | rdp->qlen_last_fqs_check = 0; |
2452 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 2453 | rdp->blimit = blimit; |
29e37d81 | 2454 | rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
c92b131b PM |
2455 | atomic_set(&rdp->dynticks->dynticks, |
2456 | (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); | |
7cb92499 | 2457 | rcu_prepare_for_idle_init(cpu); |
1304afb2 | 2458 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
2459 | |
2460 | /* | |
2461 | * A new grace period might start here. If so, we won't be part | |
2462 | * of it, but that is OK, as we are currently in a quiescent state. | |
2463 | */ | |
2464 | ||
2465 | /* Exclude any attempts to start a new GP on large systems. */ | |
1304afb2 | 2466 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
2467 | |
2468 | /* Add CPU to rcu_node bitmasks. */ | |
2469 | rnp = rdp->mynode; | |
2470 | mask = rdp->grpmask; | |
2471 | do { | |
2472 | /* Exclude any attempts to start a new GP on small systems. */ | |
1304afb2 | 2473 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2474 | rnp->qsmaskinit |= mask; |
2475 | mask = rnp->grpmask; | |
d09b62df | 2476 | if (rnp == rdp->mynode) { |
06ae115a PM |
2477 | /* |
2478 | * If there is a grace period in progress, we will | |
2479 | * set up to wait for it next time we run the | |
2480 | * RCU core code. | |
2481 | */ | |
2482 | rdp->gpnum = rnp->completed; | |
d09b62df | 2483 | rdp->completed = rnp->completed; |
06ae115a PM |
2484 | rdp->passed_quiesce = 0; |
2485 | rdp->qs_pending = 0; | |
e4cc1f22 | 2486 | rdp->passed_quiesce_gpnum = rnp->gpnum - 1; |
d4c08f2a | 2487 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl"); |
d09b62df | 2488 | } |
1304afb2 | 2489 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2490 | rnp = rnp->parent; |
2491 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
2492 | ||
1304afb2 | 2493 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
64db4cff PM |
2494 | } |
2495 | ||
d72bce0e | 2496 | static void __cpuinit rcu_prepare_cpu(int cpu) |
64db4cff | 2497 | { |
f41d911f PM |
2498 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
2499 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); | |
2500 | rcu_preempt_init_percpu_data(cpu); | |
64db4cff PM |
2501 | } |
2502 | ||
2503 | /* | |
f41d911f | 2504 | * Handle CPU online/offline notification events. |
64db4cff | 2505 | */ |
9f680ab4 PM |
2506 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
2507 | unsigned long action, void *hcpu) | |
64db4cff PM |
2508 | { |
2509 | long cpu = (long)hcpu; | |
27f4d280 | 2510 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
a26ac245 | 2511 | struct rcu_node *rnp = rdp->mynode; |
64db4cff | 2512 | |
300df91c | 2513 | trace_rcu_utilization("Start CPU hotplug"); |
64db4cff PM |
2514 | switch (action) { |
2515 | case CPU_UP_PREPARE: | |
2516 | case CPU_UP_PREPARE_FROZEN: | |
d72bce0e PZ |
2517 | rcu_prepare_cpu(cpu); |
2518 | rcu_prepare_kthreads(cpu); | |
a26ac245 PM |
2519 | break; |
2520 | case CPU_ONLINE: | |
0f962a5e PM |
2521 | case CPU_DOWN_FAILED: |
2522 | rcu_node_kthread_setaffinity(rnp, -1); | |
e3995a25 | 2523 | rcu_cpu_kthread_setrt(cpu, 1); |
0f962a5e PM |
2524 | break; |
2525 | case CPU_DOWN_PREPARE: | |
2526 | rcu_node_kthread_setaffinity(rnp, cpu); | |
e3995a25 | 2527 | rcu_cpu_kthread_setrt(cpu, 0); |
64db4cff | 2528 | break; |
d0ec774c PM |
2529 | case CPU_DYING: |
2530 | case CPU_DYING_FROZEN: | |
2531 | /* | |
2d999e03 PM |
2532 | * The whole machine is "stopped" except this CPU, so we can |
2533 | * touch any data without introducing corruption. We send the | |
2534 | * dying CPU's callbacks to an arbitrarily chosen online CPU. | |
d0ec774c | 2535 | */ |
e5601400 PM |
2536 | rcu_cleanup_dying_cpu(&rcu_bh_state); |
2537 | rcu_cleanup_dying_cpu(&rcu_sched_state); | |
2538 | rcu_preempt_cleanup_dying_cpu(); | |
7cb92499 | 2539 | rcu_cleanup_after_idle(cpu); |
d0ec774c | 2540 | break; |
64db4cff PM |
2541 | case CPU_DEAD: |
2542 | case CPU_DEAD_FROZEN: | |
2543 | case CPU_UP_CANCELED: | |
2544 | case CPU_UP_CANCELED_FROZEN: | |
e5601400 PM |
2545 | rcu_cleanup_dead_cpu(cpu, &rcu_bh_state); |
2546 | rcu_cleanup_dead_cpu(cpu, &rcu_sched_state); | |
2547 | rcu_preempt_cleanup_dead_cpu(cpu); | |
64db4cff PM |
2548 | break; |
2549 | default: | |
2550 | break; | |
2551 | } | |
300df91c | 2552 | trace_rcu_utilization("End CPU hotplug"); |
64db4cff PM |
2553 | return NOTIFY_OK; |
2554 | } | |
2555 | ||
bbad9379 PM |
2556 | /* |
2557 | * This function is invoked towards the end of the scheduler's initialization | |
2558 | * process. Before this is called, the idle task might contain | |
2559 | * RCU read-side critical sections (during which time, this idle | |
2560 | * task is booting the system). After this function is called, the | |
2561 | * idle tasks are prohibited from containing RCU read-side critical | |
2562 | * sections. This function also enables RCU lockdep checking. | |
2563 | */ | |
2564 | void rcu_scheduler_starting(void) | |
2565 | { | |
2566 | WARN_ON(num_online_cpus() != 1); | |
2567 | WARN_ON(nr_context_switches() > 0); | |
2568 | rcu_scheduler_active = 1; | |
2569 | } | |
2570 | ||
64db4cff PM |
2571 | /* |
2572 | * Compute the per-level fanout, either using the exact fanout specified | |
2573 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
2574 | */ | |
2575 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
2576 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
2577 | { | |
2578 | int i; | |
2579 | ||
f885b7f2 | 2580 | for (i = rcu_num_lvls - 1; i > 0; i--) |
64db4cff | 2581 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
f885b7f2 | 2582 | rsp->levelspread[0] = rcu_fanout_leaf; |
64db4cff PM |
2583 | } |
2584 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2585 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
2586 | { | |
2587 | int ccur; | |
2588 | int cprv; | |
2589 | int i; | |
2590 | ||
2591 | cprv = NR_CPUS; | |
f885b7f2 | 2592 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
2593 | ccur = rsp->levelcnt[i]; |
2594 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
2595 | cprv = ccur; | |
2596 | } | |
2597 | } | |
2598 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2599 | ||
2600 | /* | |
2601 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
2602 | */ | |
394f99a9 LJ |
2603 | static void __init rcu_init_one(struct rcu_state *rsp, |
2604 | struct rcu_data __percpu *rda) | |
64db4cff | 2605 | { |
b6407e86 PM |
2606 | static char *buf[] = { "rcu_node_level_0", |
2607 | "rcu_node_level_1", | |
2608 | "rcu_node_level_2", | |
2609 | "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ | |
64db4cff PM |
2610 | int cpustride = 1; |
2611 | int i; | |
2612 | int j; | |
2613 | struct rcu_node *rnp; | |
2614 | ||
b6407e86 PM |
2615 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
2616 | ||
64db4cff PM |
2617 | /* Initialize the level-tracking arrays. */ |
2618 | ||
f885b7f2 PM |
2619 | for (i = 0; i < rcu_num_lvls; i++) |
2620 | rsp->levelcnt[i] = num_rcu_lvl[i]; | |
2621 | for (i = 1; i < rcu_num_lvls; i++) | |
64db4cff PM |
2622 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
2623 | rcu_init_levelspread(rsp); | |
2624 | ||
2625 | /* Initialize the elements themselves, starting from the leaves. */ | |
2626 | ||
f885b7f2 | 2627 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
2628 | cpustride *= rsp->levelspread[i]; |
2629 | rnp = rsp->level[i]; | |
2630 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1304afb2 | 2631 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
2632 | lockdep_set_class_and_name(&rnp->lock, |
2633 | &rcu_node_class[i], buf[i]); | |
f41d911f | 2634 | rnp->gpnum = 0; |
64db4cff PM |
2635 | rnp->qsmask = 0; |
2636 | rnp->qsmaskinit = 0; | |
2637 | rnp->grplo = j * cpustride; | |
2638 | rnp->grphi = (j + 1) * cpustride - 1; | |
2639 | if (rnp->grphi >= NR_CPUS) | |
2640 | rnp->grphi = NR_CPUS - 1; | |
2641 | if (i == 0) { | |
2642 | rnp->grpnum = 0; | |
2643 | rnp->grpmask = 0; | |
2644 | rnp->parent = NULL; | |
2645 | } else { | |
2646 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
2647 | rnp->grpmask = 1UL << rnp->grpnum; | |
2648 | rnp->parent = rsp->level[i - 1] + | |
2649 | j / rsp->levelspread[i - 1]; | |
2650 | } | |
2651 | rnp->level = i; | |
12f5f524 | 2652 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
64db4cff PM |
2653 | } |
2654 | } | |
0c34029a | 2655 | |
394f99a9 | 2656 | rsp->rda = rda; |
f885b7f2 | 2657 | rnp = rsp->level[rcu_num_lvls - 1]; |
0c34029a | 2658 | for_each_possible_cpu(i) { |
4a90a068 | 2659 | while (i > rnp->grphi) |
0c34029a | 2660 | rnp++; |
394f99a9 | 2661 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
2662 | rcu_boot_init_percpu_data(i, rsp); |
2663 | } | |
64db4cff PM |
2664 | } |
2665 | ||
f885b7f2 PM |
2666 | /* |
2667 | * Compute the rcu_node tree geometry from kernel parameters. This cannot | |
2668 | * replace the definitions in rcutree.h because those are needed to size | |
2669 | * the ->node array in the rcu_state structure. | |
2670 | */ | |
2671 | static void __init rcu_init_geometry(void) | |
2672 | { | |
2673 | int i; | |
2674 | int j; | |
cca6f393 | 2675 | int n = nr_cpu_ids; |
f885b7f2 PM |
2676 | int rcu_capacity[MAX_RCU_LVLS + 1]; |
2677 | ||
2678 | /* If the compile-time values are accurate, just leave. */ | |
2679 | if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF) | |
2680 | return; | |
2681 | ||
2682 | /* | |
2683 | * Compute number of nodes that can be handled an rcu_node tree | |
2684 | * with the given number of levels. Setting rcu_capacity[0] makes | |
2685 | * some of the arithmetic easier. | |
2686 | */ | |
2687 | rcu_capacity[0] = 1; | |
2688 | rcu_capacity[1] = rcu_fanout_leaf; | |
2689 | for (i = 2; i <= MAX_RCU_LVLS; i++) | |
2690 | rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; | |
2691 | ||
2692 | /* | |
2693 | * The boot-time rcu_fanout_leaf parameter is only permitted | |
2694 | * to increase the leaf-level fanout, not decrease it. Of course, | |
2695 | * the leaf-level fanout cannot exceed the number of bits in | |
2696 | * the rcu_node masks. Finally, the tree must be able to accommodate | |
2697 | * the configured number of CPUs. Complain and fall back to the | |
2698 | * compile-time values if these limits are exceeded. | |
2699 | */ | |
2700 | if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || | |
2701 | rcu_fanout_leaf > sizeof(unsigned long) * 8 || | |
2702 | n > rcu_capacity[MAX_RCU_LVLS]) { | |
2703 | WARN_ON(1); | |
2704 | return; | |
2705 | } | |
2706 | ||
2707 | /* Calculate the number of rcu_nodes at each level of the tree. */ | |
2708 | for (i = 1; i <= MAX_RCU_LVLS; i++) | |
2709 | if (n <= rcu_capacity[i]) { | |
2710 | for (j = 0; j <= i; j++) | |
2711 | num_rcu_lvl[j] = | |
2712 | DIV_ROUND_UP(n, rcu_capacity[i - j]); | |
2713 | rcu_num_lvls = i; | |
2714 | for (j = i + 1; j <= MAX_RCU_LVLS; j++) | |
2715 | num_rcu_lvl[j] = 0; | |
2716 | break; | |
2717 | } | |
2718 | ||
2719 | /* Calculate the total number of rcu_node structures. */ | |
2720 | rcu_num_nodes = 0; | |
2721 | for (i = 0; i <= MAX_RCU_LVLS; i++) | |
2722 | rcu_num_nodes += num_rcu_lvl[i]; | |
2723 | rcu_num_nodes -= n; | |
2724 | } | |
2725 | ||
9f680ab4 | 2726 | void __init rcu_init(void) |
64db4cff | 2727 | { |
017c4261 | 2728 | int cpu; |
9f680ab4 | 2729 | |
f41d911f | 2730 | rcu_bootup_announce(); |
f885b7f2 | 2731 | rcu_init_geometry(); |
394f99a9 LJ |
2732 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
2733 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); | |
f41d911f | 2734 | __rcu_init_preempt(); |
09223371 | 2735 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
2736 | |
2737 | /* | |
2738 | * We don't need protection against CPU-hotplug here because | |
2739 | * this is called early in boot, before either interrupts | |
2740 | * or the scheduler are operational. | |
2741 | */ | |
2742 | cpu_notifier(rcu_cpu_notify, 0); | |
017c4261 PM |
2743 | for_each_online_cpu(cpu) |
2744 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
c68de209 | 2745 | check_cpu_stall_init(); |
64db4cff PM |
2746 | } |
2747 | ||
1eba8f84 | 2748 | #include "rcutree_plugin.h" |