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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
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15 * along with this program; if not, you can access it online at
16 * http://www.gnu.org/licenses/gpl-2.0.html.
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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
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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>
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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>
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50#include <linux/wait.h>
51#include <linux/kthread.h>
268bb0ce 52#include <linux/prefetch.h>
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53#include <linux/delay.h>
54#include <linux/stop_machine.h>
661a85dc 55#include <linux/random.h>
af658dca 56#include <linux/trace_events.h>
d1d74d14 57#include <linux/suspend.h>
64db4cff 58
4102adab 59#include "tree.h"
29c00b4a 60#include "rcu.h"
9f77da9f 61
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62#ifdef MODULE_PARAM_PREFIX
63#undef MODULE_PARAM_PREFIX
64#endif
65#define MODULE_PARAM_PREFIX "rcutree."
66
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67/* Data structures. */
68
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69/*
70 * In order to export the rcu_state name to the tracing tools, it
71 * needs to be added in the __tracepoint_string section.
72 * This requires defining a separate variable tp_<sname>_varname
73 * that points to the string being used, and this will allow
74 * the tracing userspace tools to be able to decipher the string
75 * address to the matching string.
76 */
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77#ifdef CONFIG_TRACING
78# define DEFINE_RCU_TPS(sname) \
f7f7bac9 79static char sname##_varname[] = #sname; \
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80static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname;
81# define RCU_STATE_NAME(sname) sname##_varname
82#else
83# define DEFINE_RCU_TPS(sname)
84# define RCU_STATE_NAME(sname) __stringify(sname)
85#endif
86
87#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \
88DEFINE_RCU_TPS(sname) \
c92fb057 89static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data); \
a41bfeb2 90struct rcu_state sname##_state = { \
6c90cc7b 91 .level = { &sname##_state.node[0] }, \
2723249a 92 .rda = &sname##_data, \
037b64ed 93 .call = cr, \
77f81fe0 94 .gp_state = RCU_GP_IDLE, \
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95 .gpnum = 0UL - 300UL, \
96 .completed = 0UL - 300UL, \
7b2e6011 97 .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \
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98 .orphan_nxttail = &sname##_state.orphan_nxtlist, \
99 .orphan_donetail = &sname##_state.orphan_donelist, \
7be7f0be 100 .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
a8a29b3b 101 .name = RCU_STATE_NAME(sname), \
a4889858 102 .abbr = sabbr, \
f6a12f34 103 .exp_mutex = __MUTEX_INITIALIZER(sname##_state.exp_mutex), \
3b5f668e 104 .exp_wake_mutex = __MUTEX_INITIALIZER(sname##_state.exp_wake_mutex), \
2723249a 105}
64db4cff 106
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107RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
108RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
b1f77b05 109
b28a7c01 110static struct rcu_state *const rcu_state_p;
6ce75a23 111LIST_HEAD(rcu_struct_flavors);
27f4d280 112
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113/* Dump rcu_node combining tree at boot to verify correct setup. */
114static bool dump_tree;
115module_param(dump_tree, bool, 0444);
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116/* Control rcu_node-tree auto-balancing at boot time. */
117static bool rcu_fanout_exact;
118module_param(rcu_fanout_exact, bool, 0444);
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119/* Increase (but not decrease) the RCU_FANOUT_LEAF at boot time. */
120static int rcu_fanout_leaf = RCU_FANOUT_LEAF;
7e5c2dfb 121module_param(rcu_fanout_leaf, int, 0444);
f885b7f2 122int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
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123/* Number of rcu_nodes at specified level. */
124static int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
f885b7f2 125int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
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126/* panic() on RCU Stall sysctl. */
127int sysctl_panic_on_rcu_stall __read_mostly;
f885b7f2 128
b0d30417 129/*
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130 * The rcu_scheduler_active variable is initialized to the value
131 * RCU_SCHEDULER_INACTIVE and transitions RCU_SCHEDULER_INIT just before the
132 * first task is spawned. So when this variable is RCU_SCHEDULER_INACTIVE,
133 * RCU can assume that there is but one task, allowing RCU to (for example)
0d95092c 134 * optimize synchronize_rcu() to a simple barrier(). When this variable
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135 * is RCU_SCHEDULER_INIT, RCU must actually do all the hard work required
136 * to detect real grace periods. This variable is also used to suppress
137 * boot-time false positives from lockdep-RCU error checking. Finally, it
138 * transitions from RCU_SCHEDULER_INIT to RCU_SCHEDULER_RUNNING after RCU
139 * is fully initialized, including all of its kthreads having been spawned.
b0d30417 140 */
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141int rcu_scheduler_active __read_mostly;
142EXPORT_SYMBOL_GPL(rcu_scheduler_active);
143
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144/*
145 * The rcu_scheduler_fully_active variable transitions from zero to one
146 * during the early_initcall() processing, which is after the scheduler
147 * is capable of creating new tasks. So RCU processing (for example,
148 * creating tasks for RCU priority boosting) must be delayed until after
149 * rcu_scheduler_fully_active transitions from zero to one. We also
150 * currently delay invocation of any RCU callbacks until after this point.
151 *
152 * It might later prove better for people registering RCU callbacks during
153 * early boot to take responsibility for these callbacks, but one step at
154 * a time.
155 */
156static int rcu_scheduler_fully_active __read_mostly;
157
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158static void rcu_init_new_rnp(struct rcu_node *rnp_leaf);
159static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf);
5d01bbd1 160static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
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161static void invoke_rcu_core(void);
162static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
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163static void rcu_report_exp_rdp(struct rcu_state *rsp,
164 struct rcu_data *rdp, bool wake);
3549c2bc 165static void sync_sched_exp_online_cleanup(int cpu);
a26ac245 166
a94844b2 167/* rcuc/rcub kthread realtime priority */
26730f55 168#ifdef CONFIG_RCU_KTHREAD_PRIO
a94844b2 169static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
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170#else /* #ifdef CONFIG_RCU_KTHREAD_PRIO */
171static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0;
172#endif /* #else #ifdef CONFIG_RCU_KTHREAD_PRIO */
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173module_param(kthread_prio, int, 0644);
174
8d7dc928 175/* Delay in jiffies for grace-period initialization delays, debug only. */
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176
177#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT
178static int gp_preinit_delay = CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT_DELAY;
179module_param(gp_preinit_delay, int, 0644);
180#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT */
181static const int gp_preinit_delay;
182#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT */
183
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184#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT
185static int gp_init_delay = CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY;
37745d28 186module_param(gp_init_delay, int, 0644);
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187#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */
188static const int gp_init_delay;
189#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */
eab128e8 190
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191#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP
192static int gp_cleanup_delay = CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY;
193module_param(gp_cleanup_delay, int, 0644);
194#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP */
195static const int gp_cleanup_delay;
196#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP */
197
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198/*
199 * Number of grace periods between delays, normalized by the duration of
200 * the delay. The longer the the delay, the more the grace periods between
201 * each delay. The reason for this normalization is that it means that,
202 * for non-zero delays, the overall slowdown of grace periods is constant
203 * regardless of the duration of the delay. This arrangement balances
204 * the need for long delays to increase some race probabilities with the
205 * need for fast grace periods to increase other race probabilities.
206 */
207#define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */
37745d28 208
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209/*
210 * Track the rcutorture test sequence number and the update version
211 * number within a given test. The rcutorture_testseq is incremented
212 * on every rcutorture module load and unload, so has an odd value
213 * when a test is running. The rcutorture_vernum is set to zero
214 * when rcutorture starts and is incremented on each rcutorture update.
215 * These variables enable correlating rcutorture output with the
216 * RCU tracing information.
217 */
218unsigned long rcutorture_testseq;
219unsigned long rcutorture_vernum;
220
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221/*
222 * Compute the mask of online CPUs for the specified rcu_node structure.
223 * This will not be stable unless the rcu_node structure's ->lock is
224 * held, but the bit corresponding to the current CPU will be stable
225 * in most contexts.
226 */
227unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
228{
7d0ae808 229 return READ_ONCE(rnp->qsmaskinitnext);
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230}
231
fc2219d4 232/*
7d0ae808 233 * Return true if an RCU grace period is in progress. The READ_ONCE()s
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234 * permit this function to be invoked without holding the root rcu_node
235 * structure's ->lock, but of course results can be subject to change.
236 */
237static int rcu_gp_in_progress(struct rcu_state *rsp)
238{
7d0ae808 239 return READ_ONCE(rsp->completed) != READ_ONCE(rsp->gpnum);
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240}
241
b1f77b05 242/*
d6714c22 243 * Note a quiescent state. Because we do not need to know
b1f77b05 244 * how many quiescent states passed, just if there was at least
d6714c22 245 * one since the start of the grace period, this just sets a flag.
e4cc1f22 246 * The caller must have disabled preemption.
b1f77b05 247 */
284a8c93 248void rcu_sched_qs(void)
b1f77b05 249{
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250 if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.s))
251 return;
252 trace_rcu_grace_period(TPS("rcu_sched"),
253 __this_cpu_read(rcu_sched_data.gpnum),
254 TPS("cpuqs"));
255 __this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false);
256 if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
257 return;
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258 __this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, false);
259 rcu_report_exp_rdp(&rcu_sched_state,
260 this_cpu_ptr(&rcu_sched_data), true);
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261}
262
284a8c93 263void rcu_bh_qs(void)
b1f77b05 264{
5b74c458 265 if (__this_cpu_read(rcu_bh_data.cpu_no_qs.s)) {
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266 trace_rcu_grace_period(TPS("rcu_bh"),
267 __this_cpu_read(rcu_bh_data.gpnum),
268 TPS("cpuqs"));
5b74c458 269 __this_cpu_write(rcu_bh_data.cpu_no_qs.b.norm, false);
284a8c93 270 }
b1f77b05 271}
64db4cff 272
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273static DEFINE_PER_CPU(int, rcu_sched_qs_mask);
274
275static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
276 .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
277 .dynticks = ATOMIC_INIT(1),
278#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
279 .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE,
280 .dynticks_idle = ATOMIC_INIT(1),
281#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
282};
283
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284DEFINE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr);
285EXPORT_PER_CPU_SYMBOL_GPL(rcu_qs_ctr);
286
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287/*
288 * Let the RCU core know that this CPU has gone through the scheduler,
289 * which is a quiescent state. This is called when the need for a
290 * quiescent state is urgent, so we burn an atomic operation and full
291 * memory barriers to let the RCU core know about it, regardless of what
292 * this CPU might (or might not) do in the near future.
293 *
294 * We inform the RCU core by emulating a zero-duration dyntick-idle
295 * period, which we in turn do by incrementing the ->dynticks counter
296 * by two.
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297 *
298 * The caller must have disabled interrupts.
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299 */
300static void rcu_momentary_dyntick_idle(void)
301{
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302 struct rcu_data *rdp;
303 struct rcu_dynticks *rdtp;
304 int resched_mask;
305 struct rcu_state *rsp;
306
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307 /*
308 * Yes, we can lose flag-setting operations. This is OK, because
309 * the flag will be set again after some delay.
310 */
311 resched_mask = raw_cpu_read(rcu_sched_qs_mask);
312 raw_cpu_write(rcu_sched_qs_mask, 0);
313
314 /* Find the flavor that needs a quiescent state. */
315 for_each_rcu_flavor(rsp) {
316 rdp = raw_cpu_ptr(rsp->rda);
317 if (!(resched_mask & rsp->flavor_mask))
318 continue;
319 smp_mb(); /* rcu_sched_qs_mask before cond_resched_completed. */
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320 if (READ_ONCE(rdp->mynode->completed) !=
321 READ_ONCE(rdp->cond_resched_completed))
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322 continue;
323
324 /*
325 * Pretend to be momentarily idle for the quiescent state.
326 * This allows the grace-period kthread to record the
327 * quiescent state, with no need for this CPU to do anything
328 * further.
329 */
330 rdtp = this_cpu_ptr(&rcu_dynticks);
331 smp_mb__before_atomic(); /* Earlier stuff before QS. */
332 atomic_add(2, &rdtp->dynticks); /* QS. */
333 smp_mb__after_atomic(); /* Later stuff after QS. */
334 break;
335 }
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336}
337
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338/*
339 * Note a context switch. This is a quiescent state for RCU-sched,
340 * and requires special handling for preemptible RCU.
46a5d164 341 * The caller must have disabled interrupts.
25502a6c 342 */
38200cf2 343void rcu_note_context_switch(void)
25502a6c 344{
bb73c52b 345 barrier(); /* Avoid RCU read-side critical sections leaking down. */
f7f7bac9 346 trace_rcu_utilization(TPS("Start context switch"));
284a8c93 347 rcu_sched_qs();
38200cf2 348 rcu_preempt_note_context_switch();
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349 if (unlikely(raw_cpu_read(rcu_sched_qs_mask)))
350 rcu_momentary_dyntick_idle();
f7f7bac9 351 trace_rcu_utilization(TPS("End context switch"));
bb73c52b 352 barrier(); /* Avoid RCU read-side critical sections leaking up. */
25502a6c 353}
29ce8310 354EXPORT_SYMBOL_GPL(rcu_note_context_switch);
25502a6c 355
5cd37193 356/*
1925d196 357 * Register a quiescent state for all RCU flavors. If there is an
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358 * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight
359 * dyntick-idle quiescent state visible to other CPUs (but only for those
1925d196 360 * RCU flavors in desperate need of a quiescent state, which will normally
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361 * be none of them). Either way, do a lightweight quiescent state for
362 * all RCU flavors.
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363 *
364 * The barrier() calls are redundant in the common case when this is
365 * called externally, but just in case this is called from within this
366 * file.
367 *
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368 */
369void rcu_all_qs(void)
370{
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371 unsigned long flags;
372
bb73c52b 373 barrier(); /* Avoid RCU read-side critical sections leaking down. */
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374 if (unlikely(raw_cpu_read(rcu_sched_qs_mask))) {
375 local_irq_save(flags);
5cd37193 376 rcu_momentary_dyntick_idle();
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377 local_irq_restore(flags);
378 }
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379 if (unlikely(raw_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))) {
380 /*
381 * Yes, we just checked a per-CPU variable with preemption
382 * enabled, so we might be migrated to some other CPU at
383 * this point. That is OK because in that case, the
384 * migration will supply the needed quiescent state.
385 * We might end up needlessly disabling preemption and
386 * invoking rcu_sched_qs() on the destination CPU, but
387 * the probability and cost are both quite low, so this
388 * should not be a problem in practice.
389 */
390 preempt_disable();
391 rcu_sched_qs();
392 preempt_enable();
393 }
5cd37193 394 this_cpu_inc(rcu_qs_ctr);
bb73c52b 395 barrier(); /* Avoid RCU read-side critical sections leaking up. */
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396}
397EXPORT_SYMBOL_GPL(rcu_all_qs);
398
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399static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */
400static long qhimark = 10000; /* If this many pending, ignore blimit. */
401static long qlowmark = 100; /* Once only this many pending, use blimit. */
64db4cff 402
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403module_param(blimit, long, 0444);
404module_param(qhimark, long, 0444);
405module_param(qlowmark, long, 0444);
3d76c082 406
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407static ulong jiffies_till_first_fqs = ULONG_MAX;
408static ulong jiffies_till_next_fqs = ULONG_MAX;
8c7c4829 409static bool rcu_kick_kthreads;
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410
411module_param(jiffies_till_first_fqs, ulong, 0644);
412module_param(jiffies_till_next_fqs, ulong, 0644);
8c7c4829 413module_param(rcu_kick_kthreads, bool, 0644);
d40011f6 414
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415/*
416 * How long the grace period must be before we start recruiting
417 * quiescent-state help from rcu_note_context_switch().
418 */
419static ulong jiffies_till_sched_qs = HZ / 20;
420module_param(jiffies_till_sched_qs, ulong, 0644);
421
48a7639c 422static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
910ee45d 423 struct rcu_data *rdp);
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424static void force_qs_rnp(struct rcu_state *rsp,
425 int (*f)(struct rcu_data *rsp, bool *isidle,
426 unsigned long *maxj),
427 bool *isidle, unsigned long *maxj);
4cdfc175 428static void force_quiescent_state(struct rcu_state *rsp);
e3950ecd 429static int rcu_pending(void);
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430
431/*
917963d0 432 * Return the number of RCU batches started thus far for debug & stats.
64db4cff 433 */
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434unsigned long rcu_batches_started(void)
435{
436 return rcu_state_p->gpnum;
437}
438EXPORT_SYMBOL_GPL(rcu_batches_started);
439
440/*
441 * Return the number of RCU-sched batches started thus far for debug & stats.
64db4cff 442 */
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443unsigned long rcu_batches_started_sched(void)
444{
445 return rcu_sched_state.gpnum;
446}
447EXPORT_SYMBOL_GPL(rcu_batches_started_sched);
448
449/*
450 * Return the number of RCU BH batches started thus far for debug & stats.
451 */
452unsigned long rcu_batches_started_bh(void)
453{
454 return rcu_bh_state.gpnum;
455}
456EXPORT_SYMBOL_GPL(rcu_batches_started_bh);
457
458/*
459 * Return the number of RCU batches completed thus far for debug & stats.
460 */
461unsigned long rcu_batches_completed(void)
462{
463 return rcu_state_p->completed;
464}
465EXPORT_SYMBOL_GPL(rcu_batches_completed);
466
467/*
468 * Return the number of RCU-sched batches completed thus far for debug & stats.
64db4cff 469 */
9733e4f0 470unsigned long rcu_batches_completed_sched(void)
64db4cff 471{
d6714c22 472 return rcu_sched_state.completed;
64db4cff 473}
d6714c22 474EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
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475
476/*
917963d0 477 * Return the number of RCU BH batches completed thus far for debug & stats.
64db4cff 478 */
9733e4f0 479unsigned long rcu_batches_completed_bh(void)
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480{
481 return rcu_bh_state.completed;
482}
483EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
484
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485/*
486 * Return the number of RCU expedited batches completed thus far for
487 * debug & stats. Odd numbers mean that a batch is in progress, even
488 * numbers mean idle. The value returned will thus be roughly double
489 * the cumulative batches since boot.
490 */
491unsigned long rcu_exp_batches_completed(void)
492{
493 return rcu_state_p->expedited_sequence;
494}
495EXPORT_SYMBOL_GPL(rcu_exp_batches_completed);
496
497/*
498 * Return the number of RCU-sched expedited batches completed thus far
499 * for debug & stats. Similar to rcu_exp_batches_completed().
500 */
501unsigned long rcu_exp_batches_completed_sched(void)
502{
503 return rcu_sched_state.expedited_sequence;
504}
505EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched);
506
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507/*
508 * Force a quiescent state.
509 */
510void rcu_force_quiescent_state(void)
511{
e534165b 512 force_quiescent_state(rcu_state_p);
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513}
514EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
515
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516/*
517 * Force a quiescent state for RCU BH.
518 */
519void rcu_bh_force_quiescent_state(void)
520{
4cdfc175 521 force_quiescent_state(&rcu_bh_state);
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522}
523EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
524
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525/*
526 * Force a quiescent state for RCU-sched.
527 */
528void rcu_sched_force_quiescent_state(void)
529{
530 force_quiescent_state(&rcu_sched_state);
531}
532EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
533
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534/*
535 * Show the state of the grace-period kthreads.
536 */
537void show_rcu_gp_kthreads(void)
538{
539 struct rcu_state *rsp;
540
541 for_each_rcu_flavor(rsp) {
542 pr_info("%s: wait state: %d ->state: %#lx\n",
543 rsp->name, rsp->gp_state, rsp->gp_kthread->state);
544 /* sched_show_task(rsp->gp_kthread); */
545 }
546}
547EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);
548
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549/*
550 * Record the number of times rcutorture tests have been initiated and
551 * terminated. This information allows the debugfs tracing stats to be
552 * correlated to the rcutorture messages, even when the rcutorture module
553 * is being repeatedly loaded and unloaded. In other words, we cannot
554 * store this state in rcutorture itself.
555 */
556void rcutorture_record_test_transition(void)
557{
558 rcutorture_testseq++;
559 rcutorture_vernum = 0;
560}
561EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
562
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563/*
564 * Send along grace-period-related data for rcutorture diagnostics.
565 */
566void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
567 unsigned long *gpnum, unsigned long *completed)
568{
569 struct rcu_state *rsp = NULL;
570
571 switch (test_type) {
572 case RCU_FLAVOR:
e534165b 573 rsp = rcu_state_p;
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574 break;
575 case RCU_BH_FLAVOR:
576 rsp = &rcu_bh_state;
577 break;
578 case RCU_SCHED_FLAVOR:
579 rsp = &rcu_sched_state;
580 break;
581 default:
582 break;
583 }
584 if (rsp != NULL) {
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585 *flags = READ_ONCE(rsp->gp_flags);
586 *gpnum = READ_ONCE(rsp->gpnum);
587 *completed = READ_ONCE(rsp->completed);
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588 return;
589 }
590 *flags = 0;
591 *gpnum = 0;
592 *completed = 0;
593}
594EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
595
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596/*
597 * Record the number of writer passes through the current rcutorture test.
598 * This is also used to correlate debugfs tracing stats with the rcutorture
599 * messages.
600 */
601void rcutorture_record_progress(unsigned long vernum)
602{
603 rcutorture_vernum++;
604}
605EXPORT_SYMBOL_GPL(rcutorture_record_progress);
606
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607/*
608 * Does the CPU have callbacks ready to be invoked?
609 */
610static int
611cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
612{
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613 return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] &&
614 rdp->nxttail[RCU_DONE_TAIL] != NULL;
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615}
616
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617/*
618 * Return the root node of the specified rcu_state structure.
619 */
620static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
621{
622 return &rsp->node[0];
623}
624
625/*
626 * Is there any need for future grace periods?
627 * Interrupts must be disabled. If the caller does not hold the root
628 * rnp_node structure's ->lock, the results are advisory only.
629 */
630static int rcu_future_needs_gp(struct rcu_state *rsp)
631{
632 struct rcu_node *rnp = rcu_get_root(rsp);
7d0ae808 633 int idx = (READ_ONCE(rnp->completed) + 1) & 0x1;
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634 int *fp = &rnp->need_future_gp[idx];
635
7d0ae808 636 return READ_ONCE(*fp);
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637}
638
64db4cff 639/*
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640 * Does the current CPU require a not-yet-started grace period?
641 * The caller must have disabled interrupts to prevent races with
642 * normal callback registry.
64db4cff 643 */
d117c8aa 644static bool
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645cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
646{
dc35c893 647 int i;
3fbfbf7a 648
dc35c893 649 if (rcu_gp_in_progress(rsp))
d117c8aa 650 return false; /* No, a grace period is already in progress. */
365187fb 651 if (rcu_future_needs_gp(rsp))
d117c8aa 652 return true; /* Yes, a no-CBs CPU needs one. */
dc35c893 653 if (!rdp->nxttail[RCU_NEXT_TAIL])
d117c8aa 654 return false; /* No, this is a no-CBs (or offline) CPU. */
dc35c893 655 if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
d117c8aa 656 return true; /* Yes, CPU has newly registered callbacks. */
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657 for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
658 if (rdp->nxttail[i - 1] != rdp->nxttail[i] &&
7d0ae808 659 ULONG_CMP_LT(READ_ONCE(rsp->completed),
dc35c893 660 rdp->nxtcompleted[i]))
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661 return true; /* Yes, CBs for future grace period. */
662 return false; /* No grace period needed. */
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663}
664
9b2e4f18 665/*
adf5091e 666 * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state
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667 *
668 * If the new value of the ->dynticks_nesting counter now is zero,
669 * we really have entered idle, and must do the appropriate accounting.
670 * The caller must have disabled interrupts.
671 */
28ced795 672static void rcu_eqs_enter_common(long long oldval, bool user)
9b2e4f18 673{
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674 struct rcu_state *rsp;
675 struct rcu_data *rdp;
28ced795 676 struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
96d3fd0d 677
f7f7bac9 678 trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting);
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679 if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
680 !user && !is_idle_task(current)) {
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681 struct task_struct *idle __maybe_unused =
682 idle_task(smp_processor_id());
0989cb46 683
f7f7bac9 684 trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0);
274529ba 685 rcu_ftrace_dump(DUMP_ORIG);
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686 WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
687 current->pid, current->comm,
688 idle->pid, idle->comm); /* must be idle task! */
9b2e4f18 689 }
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690 for_each_rcu_flavor(rsp) {
691 rdp = this_cpu_ptr(rsp->rda);
692 do_nocb_deferred_wakeup(rdp);
693 }
198bbf81 694 rcu_prepare_for_idle();
9b2e4f18 695 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
4e857c58 696 smp_mb__before_atomic(); /* See above. */
9b2e4f18 697 atomic_inc(&rdtp->dynticks);
4e857c58 698 smp_mb__after_atomic(); /* Force ordering with next sojourn. */
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699 WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
700 atomic_read(&rdtp->dynticks) & 0x1);
176f8f7a 701 rcu_dynticks_task_enter();
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702
703 /*
adf5091e 704 * It is illegal to enter an extended quiescent state while
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705 * in an RCU read-side critical section.
706 */
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707 RCU_LOCKDEP_WARN(lock_is_held(&rcu_lock_map),
708 "Illegal idle entry in RCU read-side critical section.");
709 RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map),
710 "Illegal idle entry in RCU-bh read-side critical section.");
711 RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map),
712 "Illegal idle entry in RCU-sched read-side critical section.");
9b2e4f18 713}
64db4cff 714
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715/*
716 * Enter an RCU extended quiescent state, which can be either the
717 * idle loop or adaptive-tickless usermode execution.
64db4cff 718 */
adf5091e 719static void rcu_eqs_enter(bool user)
64db4cff 720{
4145fa7f 721 long long oldval;
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722 struct rcu_dynticks *rdtp;
723
c9d4b0af 724 rdtp = this_cpu_ptr(&rcu_dynticks);
4145fa7f 725 oldval = rdtp->dynticks_nesting;
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726 WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
727 (oldval & DYNTICK_TASK_NEST_MASK) == 0);
3a592405 728 if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) {
29e37d81 729 rdtp->dynticks_nesting = 0;
28ced795 730 rcu_eqs_enter_common(oldval, user);
3a592405 731 } else {
29e37d81 732 rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
3a592405 733 }
64db4cff 734}
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735
736/**
737 * rcu_idle_enter - inform RCU that current CPU is entering idle
738 *
739 * Enter idle mode, in other words, -leave- the mode in which RCU
740 * read-side critical sections can occur. (Though RCU read-side
741 * critical sections can occur in irq handlers in idle, a possibility
742 * handled by irq_enter() and irq_exit().)
743 *
744 * We crowbar the ->dynticks_nesting field to zero to allow for
745 * the possibility of usermode upcalls having messed up our count
746 * of interrupt nesting level during the prior busy period.
747 */
748void rcu_idle_enter(void)
749{
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750 unsigned long flags;
751
752 local_irq_save(flags);
cb349ca9 753 rcu_eqs_enter(false);
28ced795 754 rcu_sysidle_enter(0);
c5d900bf 755 local_irq_restore(flags);
adf5091e 756}
8a2ecf47 757EXPORT_SYMBOL_GPL(rcu_idle_enter);
64db4cff 758
d1ec4c34 759#ifdef CONFIG_NO_HZ_FULL
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760/**
761 * rcu_user_enter - inform RCU that we are resuming userspace.
762 *
763 * Enter RCU idle mode right before resuming userspace. No use of RCU
764 * is permitted between this call and rcu_user_exit(). This way the
765 * CPU doesn't need to maintain the tick for RCU maintenance purposes
766 * when the CPU runs in userspace.
767 */
768void rcu_user_enter(void)
769{
91d1aa43 770 rcu_eqs_enter(1);
adf5091e 771}
d1ec4c34 772#endif /* CONFIG_NO_HZ_FULL */
19dd1591 773
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774/**
775 * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
776 *
777 * Exit from an interrupt handler, which might possibly result in entering
778 * idle mode, in other words, leaving the mode in which read-side critical
7c9906ca 779 * sections can occur. The caller must have disabled interrupts.
64db4cff 780 *
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781 * This code assumes that the idle loop never does anything that might
782 * result in unbalanced calls to irq_enter() and irq_exit(). If your
783 * architecture violates this assumption, RCU will give you what you
784 * deserve, good and hard. But very infrequently and irreproducibly.
785 *
786 * Use things like work queues to work around this limitation.
787 *
788 * You have been warned.
64db4cff 789 */
9b2e4f18 790void rcu_irq_exit(void)
64db4cff 791{
4145fa7f 792 long long oldval;
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793 struct rcu_dynticks *rdtp;
794
7c9906ca 795 RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_irq_exit() invoked with irqs enabled!!!");
c9d4b0af 796 rdtp = this_cpu_ptr(&rcu_dynticks);
4145fa7f 797 oldval = rdtp->dynticks_nesting;
9b2e4f18 798 rdtp->dynticks_nesting--;
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799 WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
800 rdtp->dynticks_nesting < 0);
b6fc6020 801 if (rdtp->dynticks_nesting)
f7f7bac9 802 trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting);
b6fc6020 803 else
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804 rcu_eqs_enter_common(oldval, true);
805 rcu_sysidle_enter(1);
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806}
807
808/*
809 * Wrapper for rcu_irq_exit() where interrupts are enabled.
810 */
811void rcu_irq_exit_irqson(void)
812{
813 unsigned long flags;
814
815 local_irq_save(flags);
816 rcu_irq_exit();
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817 local_irq_restore(flags);
818}
819
820/*
adf5091e 821 * rcu_eqs_exit_common - current CPU moving away from extended quiescent state
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822 *
823 * If the new value of the ->dynticks_nesting counter was previously zero,
824 * we really have exited idle, and must do the appropriate accounting.
825 * The caller must have disabled interrupts.
826 */
28ced795 827static void rcu_eqs_exit_common(long long oldval, int user)
9b2e4f18 828{
28ced795
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829 struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
830
176f8f7a 831 rcu_dynticks_task_exit();
4e857c58 832 smp_mb__before_atomic(); /* Force ordering w/previous sojourn. */
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833 atomic_inc(&rdtp->dynticks);
834 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
4e857c58 835 smp_mb__after_atomic(); /* See above. */
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836 WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
837 !(atomic_read(&rdtp->dynticks) & 0x1));
8fa7845d 838 rcu_cleanup_after_idle();
f7f7bac9 839 trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting);
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840 if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
841 !user && !is_idle_task(current)) {
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842 struct task_struct *idle __maybe_unused =
843 idle_task(smp_processor_id());
0989cb46 844
f7f7bac9 845 trace_rcu_dyntick(TPS("Error on exit: not idle task"),
4145fa7f 846 oldval, rdtp->dynticks_nesting);
274529ba 847 rcu_ftrace_dump(DUMP_ORIG);
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848 WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
849 current->pid, current->comm,
850 idle->pid, idle->comm); /* must be idle task! */
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851 }
852}
853
adf5091e
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854/*
855 * Exit an RCU extended quiescent state, which can be either the
856 * idle loop or adaptive-tickless usermode execution.
9b2e4f18 857 */
adf5091e 858static void rcu_eqs_exit(bool user)
9b2e4f18 859{
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860 struct rcu_dynticks *rdtp;
861 long long oldval;
862
c9d4b0af 863 rdtp = this_cpu_ptr(&rcu_dynticks);
9b2e4f18 864 oldval = rdtp->dynticks_nesting;
1ce46ee5 865 WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
3a592405 866 if (oldval & DYNTICK_TASK_NEST_MASK) {
29e37d81 867 rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
3a592405 868 } else {
29e37d81 869 rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
28ced795 870 rcu_eqs_exit_common(oldval, user);
3a592405 871 }
9b2e4f18 872}
adf5091e
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873
874/**
875 * rcu_idle_exit - inform RCU that current CPU is leaving idle
876 *
877 * Exit idle mode, in other words, -enter- the mode in which RCU
878 * read-side critical sections can occur.
879 *
880 * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to
881 * allow for the possibility of usermode upcalls messing up our count
882 * of interrupt nesting level during the busy period that is just
883 * now starting.
884 */
885void rcu_idle_exit(void)
886{
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887 unsigned long flags;
888
889 local_irq_save(flags);
cb349ca9 890 rcu_eqs_exit(false);
28ced795 891 rcu_sysidle_exit(0);
c5d900bf 892 local_irq_restore(flags);
adf5091e 893}
8a2ecf47 894EXPORT_SYMBOL_GPL(rcu_idle_exit);
9b2e4f18 895
d1ec4c34 896#ifdef CONFIG_NO_HZ_FULL
adf5091e
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897/**
898 * rcu_user_exit - inform RCU that we are exiting userspace.
899 *
900 * Exit RCU idle mode while entering the kernel because it can
901 * run a RCU read side critical section anytime.
902 */
903void rcu_user_exit(void)
904{
91d1aa43 905 rcu_eqs_exit(1);
adf5091e 906}
d1ec4c34 907#endif /* CONFIG_NO_HZ_FULL */
19dd1591 908
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909/**
910 * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
911 *
912 * Enter an interrupt handler, which might possibly result in exiting
913 * idle mode, in other words, entering the mode in which read-side critical
7c9906ca 914 * sections can occur. The caller must have disabled interrupts.
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915 *
916 * Note that the Linux kernel is fully capable of entering an interrupt
917 * handler that it never exits, for example when doing upcalls to
918 * user mode! This code assumes that the idle loop never does upcalls to
919 * user mode. If your architecture does do upcalls from the idle loop (or
920 * does anything else that results in unbalanced calls to the irq_enter()
921 * and irq_exit() functions), RCU will give you what you deserve, good
922 * and hard. But very infrequently and irreproducibly.
923 *
924 * Use things like work queues to work around this limitation.
925 *
926 * You have been warned.
927 */
928void rcu_irq_enter(void)
929{
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930 struct rcu_dynticks *rdtp;
931 long long oldval;
932
7c9906ca 933 RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_irq_enter() invoked with irqs enabled!!!");
c9d4b0af 934 rdtp = this_cpu_ptr(&rcu_dynticks);
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935 oldval = rdtp->dynticks_nesting;
936 rdtp->dynticks_nesting++;
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937 WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
938 rdtp->dynticks_nesting == 0);
b6fc6020 939 if (oldval)
f7f7bac9 940 trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting);
b6fc6020 941 else
28ced795
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942 rcu_eqs_exit_common(oldval, true);
943 rcu_sysidle_exit(1);
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944}
945
946/*
947 * Wrapper for rcu_irq_enter() where interrupts are enabled.
948 */
949void rcu_irq_enter_irqson(void)
950{
951 unsigned long flags;
952
953 local_irq_save(flags);
954 rcu_irq_enter();
64db4cff 955 local_irq_restore(flags);
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956}
957
958/**
959 * rcu_nmi_enter - inform RCU of entry to NMI context
960 *
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961 * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and
962 * rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know
963 * that the CPU is active. This implementation permits nested NMIs, as
964 * long as the nesting level does not overflow an int. (You will probably
965 * run out of stack space first.)
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966 */
967void rcu_nmi_enter(void)
968{
c9d4b0af 969 struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
734d1680 970 int incby = 2;
64db4cff 971
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972 /* Complain about underflow. */
973 WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0);
974
975 /*
976 * If idle from RCU viewpoint, atomically increment ->dynticks
977 * to mark non-idle and increment ->dynticks_nmi_nesting by one.
978 * Otherwise, increment ->dynticks_nmi_nesting by two. This means
979 * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
980 * to be in the outermost NMI handler that interrupted an RCU-idle
981 * period (observation due to Andy Lutomirski).
982 */
983 if (!(atomic_read(&rdtp->dynticks) & 0x1)) {
984 smp_mb__before_atomic(); /* Force delay from prior write. */
985 atomic_inc(&rdtp->dynticks);
986 /* atomic_inc() before later RCU read-side crit sects */
987 smp_mb__after_atomic(); /* See above. */
988 WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
989 incby = 1;
990 }
991 rdtp->dynticks_nmi_nesting += incby;
992 barrier();
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993}
994
995/**
996 * rcu_nmi_exit - inform RCU of exit from NMI context
997 *
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998 * If we are returning from the outermost NMI handler that interrupted an
999 * RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting
1000 * to let the RCU grace-period handling know that the CPU is back to
1001 * being RCU-idle.
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1002 */
1003void rcu_nmi_exit(void)
1004{
c9d4b0af 1005 struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
64db4cff 1006
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1007 /*
1008 * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
1009 * (We are exiting an NMI handler, so RCU better be paying attention
1010 * to us!)
1011 */
1012 WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0);
1013 WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
1014
1015 /*
1016 * If the nesting level is not 1, the CPU wasn't RCU-idle, so
1017 * leave it in non-RCU-idle state.
1018 */
1019 if (rdtp->dynticks_nmi_nesting != 1) {
1020 rdtp->dynticks_nmi_nesting -= 2;
64db4cff 1021 return;
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1022 }
1023
1024 /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
1025 rdtp->dynticks_nmi_nesting = 0;
23b5c8fa 1026 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
4e857c58 1027 smp_mb__before_atomic(); /* See above. */
23b5c8fa 1028 atomic_inc(&rdtp->dynticks);
4e857c58 1029 smp_mb__after_atomic(); /* Force delay to next write. */
23b5c8fa 1030 WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
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1031}
1032
1033/**
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1034 * __rcu_is_watching - are RCU read-side critical sections safe?
1035 *
1036 * Return true if RCU is watching the running CPU, which means that
1037 * this CPU can safely enter RCU read-side critical sections. Unlike
1038 * rcu_is_watching(), the caller of __rcu_is_watching() must have at
1039 * least disabled preemption.
1040 */
9418fb20 1041bool notrace __rcu_is_watching(void)
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1042{
1043 return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1;
1044}
1045
1046/**
1047 * rcu_is_watching - see if RCU thinks that the current CPU is idle
64db4cff 1048 *
9b2e4f18 1049 * If the current CPU is in its idle loop and is neither in an interrupt
34240697 1050 * or NMI handler, return true.
64db4cff 1051 */
9418fb20 1052bool notrace rcu_is_watching(void)
64db4cff 1053{
f534ed1f 1054 bool ret;
34240697 1055
46f00d18 1056 preempt_disable_notrace();
5c173eb8 1057 ret = __rcu_is_watching();
46f00d18 1058 preempt_enable_notrace();
34240697 1059 return ret;
64db4cff 1060}
5c173eb8 1061EXPORT_SYMBOL_GPL(rcu_is_watching);
64db4cff 1062
62fde6ed 1063#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
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1064
1065/*
1066 * Is the current CPU online? Disable preemption to avoid false positives
1067 * that could otherwise happen due to the current CPU number being sampled,
1068 * this task being preempted, its old CPU being taken offline, resuming
1069 * on some other CPU, then determining that its old CPU is now offline.
1070 * It is OK to use RCU on an offline processor during initial boot, hence
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1071 * the check for rcu_scheduler_fully_active. Note also that it is OK
1072 * for a CPU coming online to use RCU for one jiffy prior to marking itself
1073 * online in the cpu_online_mask. Similarly, it is OK for a CPU going
1074 * offline to continue to use RCU for one jiffy after marking itself
1075 * offline in the cpu_online_mask. This leniency is necessary given the
1076 * non-atomic nature of the online and offline processing, for example,
4df83742
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1077 * the fact that a CPU enters the scheduler after completing the teardown
1078 * of the CPU.
2036d94a 1079 *
4df83742
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1080 * This is also why RCU internally marks CPUs online during in the
1081 * preparation phase and offline after the CPU has been taken down.
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1082 *
1083 * Disable checking if in an NMI handler because we cannot safely report
1084 * errors from NMI handlers anyway.
1085 */
1086bool rcu_lockdep_current_cpu_online(void)
1087{
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1088 struct rcu_data *rdp;
1089 struct rcu_node *rnp;
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1090 bool ret;
1091
1092 if (in_nmi())
f6f7ee9a 1093 return true;
c0d6d01b 1094 preempt_disable();
c9d4b0af 1095 rdp = this_cpu_ptr(&rcu_sched_data);
2036d94a 1096 rnp = rdp->mynode;
0aa04b05 1097 ret = (rdp->grpmask & rcu_rnp_online_cpus(rnp)) ||
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1098 !rcu_scheduler_fully_active;
1099 preempt_enable();
1100 return ret;
1101}
1102EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
1103
62fde6ed 1104#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
9b2e4f18 1105
64db4cff 1106/**
9b2e4f18 1107 * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
64db4cff 1108 *
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1109 * If the current CPU is idle or running at a first-level (not nested)
1110 * interrupt from idle, return true. The caller must have at least
1111 * disabled preemption.
64db4cff 1112 */
62e3cb14 1113static int rcu_is_cpu_rrupt_from_idle(void)
64db4cff 1114{
c9d4b0af 1115 return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 1;
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1116}
1117
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1118/*
1119 * Snapshot the specified CPU's dynticks counter so that we can later
1120 * credit them with an implicit quiescent state. Return 1 if this CPU
1eba8f84 1121 * is in dynticks idle mode, which is an extended quiescent state.
64db4cff 1122 */
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1123static int dyntick_save_progress_counter(struct rcu_data *rdp,
1124 bool *isidle, unsigned long *maxj)
64db4cff 1125{
23b5c8fa 1126 rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
0edd1b17 1127 rcu_sysidle_check_cpu(rdp, isidle, maxj);
7941dbde
ACB
1128 if ((rdp->dynticks_snap & 0x1) == 0) {
1129 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
7d0ae808 1130 if (ULONG_CMP_LT(READ_ONCE(rdp->gpnum) + ULONG_MAX / 4,
e3663b10 1131 rdp->mynode->gpnum))
7d0ae808 1132 WRITE_ONCE(rdp->gpwrap, true);
23a9bacd 1133 return 1;
7941dbde 1134 }
23a9bacd 1135 return 0;
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1136}
1137
1138/*
1139 * Return true if the specified CPU has passed through a quiescent
1140 * state by virtue of being in or having passed through an dynticks
1141 * idle state since the last call to dyntick_save_progress_counter()
a82dcc76 1142 * for this same CPU, or by virtue of having been offline.
64db4cff 1143 */
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1144static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
1145 bool *isidle, unsigned long *maxj)
64db4cff 1146{
7eb4f455 1147 unsigned int curr;
4a81e832 1148 int *rcrmp;
7eb4f455 1149 unsigned int snap;
64db4cff 1150
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1151 curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
1152 snap = (unsigned int)rdp->dynticks_snap;
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1153
1154 /*
1155 * If the CPU passed through or entered a dynticks idle phase with
1156 * no active irq/NMI handlers, then we can safely pretend that the CPU
1157 * already acknowledged the request to pass through a quiescent
1158 * state. Either way, that CPU cannot possibly be in an RCU
1159 * read-side critical section that started before the beginning
1160 * of the current RCU grace period.
1161 */
7eb4f455 1162 if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
f7f7bac9 1163 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
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1164 rdp->dynticks_fqs++;
1165 return 1;
1166 }
1167
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1168 /*
1169 * Check for the CPU being offline, but only if the grace period
1170 * is old enough. We don't need to worry about the CPU changing
1171 * state: If we see it offline even once, it has been through a
1172 * quiescent state.
1173 *
1174 * The reason for insisting that the grace period be at least
1175 * one jiffy old is that CPUs that are not quite online and that
1176 * have just gone offline can still execute RCU read-side critical
1177 * sections.
1178 */
1179 if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies))
1180 return 0; /* Grace period is not old enough. */
1181 barrier();
1182 if (cpu_is_offline(rdp->cpu)) {
f7f7bac9 1183 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl"));
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1184 rdp->offline_fqs++;
1185 return 1;
1186 }
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1187
1188 /*
4a81e832
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1189 * A CPU running for an extended time within the kernel can
1190 * delay RCU grace periods. When the CPU is in NO_HZ_FULL mode,
1191 * even context-switching back and forth between a pair of
1192 * in-kernel CPU-bound tasks cannot advance grace periods.
1193 * So if the grace period is old enough, make the CPU pay attention.
1194 * Note that the unsynchronized assignments to the per-CPU
1195 * rcu_sched_qs_mask variable are safe. Yes, setting of
1196 * bits can be lost, but they will be set again on the next
1197 * force-quiescent-state pass. So lost bit sets do not result
1198 * in incorrect behavior, merely in a grace period lasting
1199 * a few jiffies longer than it might otherwise. Because
1200 * there are at most four threads involved, and because the
1201 * updates are only once every few jiffies, the probability of
1202 * lossage (and thus of slight grace-period extension) is
1203 * quite low.
1204 *
1205 * Note that if the jiffies_till_sched_qs boot/sysfs parameter
1206 * is set too high, we override with half of the RCU CPU stall
1207 * warning delay.
6193c76a 1208 */
4a81e832
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1209 rcrmp = &per_cpu(rcu_sched_qs_mask, rdp->cpu);
1210 if (ULONG_CMP_GE(jiffies,
1211 rdp->rsp->gp_start + jiffies_till_sched_qs) ||
cb1e78cf 1212 ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) {
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1213 if (!(READ_ONCE(*rcrmp) & rdp->rsp->flavor_mask)) {
1214 WRITE_ONCE(rdp->cond_resched_completed,
1215 READ_ONCE(rdp->mynode->completed));
4a81e832 1216 smp_mb(); /* ->cond_resched_completed before *rcrmp. */
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1217 WRITE_ONCE(*rcrmp,
1218 READ_ONCE(*rcrmp) + rdp->rsp->flavor_mask);
4a81e832 1219 }
4914950a 1220 rdp->rsp->jiffies_resched += 5; /* Re-enable beating. */
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PM
1221 }
1222
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1223 /* And if it has been a really long time, kick the CPU as well. */
1224 if (ULONG_CMP_GE(jiffies,
1225 rdp->rsp->gp_start + 2 * jiffies_till_sched_qs) ||
1226 ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs))
1227 resched_cpu(rdp->cpu); /* Force CPU into scheduler. */
1228
a82dcc76 1229 return 0;
64db4cff
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1230}
1231
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1232static void record_gp_stall_check_time(struct rcu_state *rsp)
1233{
cb1e78cf 1234 unsigned long j = jiffies;
6193c76a 1235 unsigned long j1;
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1236
1237 rsp->gp_start = j;
1238 smp_wmb(); /* Record start time before stall time. */
6193c76a 1239 j1 = rcu_jiffies_till_stall_check();
7d0ae808 1240 WRITE_ONCE(rsp->jiffies_stall, j + j1);
6193c76a 1241 rsp->jiffies_resched = j + j1 / 2;
7d0ae808 1242 rsp->n_force_qs_gpstart = READ_ONCE(rsp->n_force_qs);
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1243}
1244
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1245/*
1246 * Convert a ->gp_state value to a character string.
1247 */
1248static const char *gp_state_getname(short gs)
1249{
1250 if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
1251 return "???";
1252 return gp_state_names[gs];
1253}
1254
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1255/*
1256 * Complain about starvation of grace-period kthread.
1257 */
1258static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
1259{
1260 unsigned long gpa;
1261 unsigned long j;
1262
1263 j = jiffies;
7d0ae808 1264 gpa = READ_ONCE(rsp->gp_activity);
b1adb3e2 1265 if (j - gpa > 2 * HZ) {
6b50e119 1266 pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx\n",
81e701e4 1267 rsp->name, j - gpa,
319362c9 1268 rsp->gpnum, rsp->completed,
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1269 rsp->gp_flags,
1270 gp_state_getname(rsp->gp_state), rsp->gp_state,
a0e3a3aa 1271 rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
86057b80 1272 if (rsp->gp_kthread) {
b1adb3e2 1273 sched_show_task(rsp->gp_kthread);
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1274 wake_up_process(rsp->gp_kthread);
1275 }
b1adb3e2 1276 }
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1277}
1278
b637a328 1279/*
bc1dce51 1280 * Dump stacks of all tasks running on stalled CPUs.
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1281 */
1282static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
1283{
1284 int cpu;
1285 unsigned long flags;
1286 struct rcu_node *rnp;
1287
1288 rcu_for_each_leaf_node(rsp, rnp) {
6cf10081 1289 raw_spin_lock_irqsave_rcu_node(rnp, flags);
b637a328 1290 if (rnp->qsmask != 0) {
bc75e999
MR
1291 for_each_leaf_node_possible_cpu(rnp, cpu)
1292 if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))
1293 dump_cpu_task(cpu);
b637a328 1294 }
67c583a7 1295 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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1296 }
1297}
1298
8c7c4829
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1299/*
1300 * If too much time has passed in the current grace period, and if
1301 * so configured, go kick the relevant kthreads.
1302 */
1303static void rcu_stall_kick_kthreads(struct rcu_state *rsp)
1304{
1305 unsigned long j;
1306
1307 if (!rcu_kick_kthreads)
1308 return;
1309 j = READ_ONCE(rsp->jiffies_kick_kthreads);
aa3e0bf1
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1310 if (time_after(jiffies, j) && rsp->gp_kthread &&
1311 (rcu_gp_in_progress(rsp) || READ_ONCE(rsp->gp_flags))) {
8c7c4829 1312 WARN_ONCE(1, "Kicking %s grace-period kthread\n", rsp->name);
5dffed1e 1313 rcu_ftrace_dump(DUMP_ALL);
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1314 wake_up_process(rsp->gp_kthread);
1315 WRITE_ONCE(rsp->jiffies_kick_kthreads, j + HZ);
1316 }
1317}
1318
088e9d25
DBO
1319static inline void panic_on_rcu_stall(void)
1320{
1321 if (sysctl_panic_on_rcu_stall)
1322 panic("RCU Stall\n");
1323}
1324
6ccd2ecd 1325static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
64db4cff
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1326{
1327 int cpu;
1328 long delta;
1329 unsigned long flags;
6ccd2ecd
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1330 unsigned long gpa;
1331 unsigned long j;
285fe294 1332 int ndetected = 0;
64db4cff 1333 struct rcu_node *rnp = rcu_get_root(rsp);
53bb857c 1334 long totqlen = 0;
64db4cff 1335
8c7c4829
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1336 /* Kick and suppress, if so configured. */
1337 rcu_stall_kick_kthreads(rsp);
1338 if (rcu_cpu_stall_suppress)
1339 return;
1340
64db4cff
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1341 /* Only let one CPU complain about others per time interval. */
1342
6cf10081 1343 raw_spin_lock_irqsave_rcu_node(rnp, flags);
7d0ae808 1344 delta = jiffies - READ_ONCE(rsp->jiffies_stall);
fc2219d4 1345 if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
67c583a7 1346 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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1347 return;
1348 }
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1349 WRITE_ONCE(rsp->jiffies_stall,
1350 jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
67c583a7 1351 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
64db4cff 1352
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1353 /*
1354 * OK, time to rat on our buddy...
1355 * See Documentation/RCU/stallwarn.txt for info on how to debug
1356 * RCU CPU stall warnings.
1357 */
d7f3e207 1358 pr_err("INFO: %s detected stalls on CPUs/tasks:",
4300aa64 1359 rsp->name);
a858af28 1360 print_cpu_stall_info_begin();
a0b6c9a7 1361 rcu_for_each_leaf_node(rsp, rnp) {
6cf10081 1362 raw_spin_lock_irqsave_rcu_node(rnp, flags);
9bc8b558 1363 ndetected += rcu_print_task_stall(rnp);
c8020a67 1364 if (rnp->qsmask != 0) {
bc75e999
MR
1365 for_each_leaf_node_possible_cpu(rnp, cpu)
1366 if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) {
1367 print_cpu_stall_info(rsp, cpu);
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1368 ndetected++;
1369 }
1370 }
67c583a7 1371 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
64db4cff 1372 }
a858af28 1373
a858af28 1374 print_cpu_stall_info_end();
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1375 for_each_possible_cpu(cpu)
1376 totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
83ebe63e 1377 pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n",
eee05882 1378 smp_processor_id(), (long)(jiffies - rsp->gp_start),
83ebe63e 1379 (long)rsp->gpnum, (long)rsp->completed, totqlen);
6ccd2ecd 1380 if (ndetected) {
b637a328 1381 rcu_dump_cpu_stacks(rsp);
6ccd2ecd 1382 } else {
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1383 if (READ_ONCE(rsp->gpnum) != gpnum ||
1384 READ_ONCE(rsp->completed) == gpnum) {
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1385 pr_err("INFO: Stall ended before state dump start\n");
1386 } else {
1387 j = jiffies;
7d0ae808 1388 gpa = READ_ONCE(rsp->gp_activity);
237a0f21 1389 pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n",
6ccd2ecd 1390 rsp->name, j - gpa, j, gpa,
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1391 jiffies_till_next_fqs,
1392 rcu_get_root(rsp)->qsmask);
6ccd2ecd
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1393 /* In this case, the current CPU might be at fault. */
1394 sched_show_task(current);
1395 }
1396 }
c1dc0b9c 1397
4cdfc175 1398 /* Complain about tasks blocking the grace period. */
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1399 rcu_print_detail_task_stall(rsp);
1400
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1401 rcu_check_gp_kthread_starvation(rsp);
1402
088e9d25
DBO
1403 panic_on_rcu_stall();
1404
4cdfc175 1405 force_quiescent_state(rsp); /* Kick them all. */
64db4cff
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1406}
1407
1408static void print_cpu_stall(struct rcu_state *rsp)
1409{
53bb857c 1410 int cpu;
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1411 unsigned long flags;
1412 struct rcu_node *rnp = rcu_get_root(rsp);
53bb857c 1413 long totqlen = 0;
64db4cff 1414
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1415 /* Kick and suppress, if so configured. */
1416 rcu_stall_kick_kthreads(rsp);
1417 if (rcu_cpu_stall_suppress)
1418 return;
1419
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1420 /*
1421 * OK, time to rat on ourselves...
1422 * See Documentation/RCU/stallwarn.txt for info on how to debug
1423 * RCU CPU stall warnings.
1424 */
d7f3e207 1425 pr_err("INFO: %s self-detected stall on CPU", rsp->name);
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1426 print_cpu_stall_info_begin();
1427 print_cpu_stall_info(rsp, smp_processor_id());
1428 print_cpu_stall_info_end();
53bb857c
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1429 for_each_possible_cpu(cpu)
1430 totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
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1431 pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n",
1432 jiffies - rsp->gp_start,
1433 (long)rsp->gpnum, (long)rsp->completed, totqlen);
fb81a44b
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1434
1435 rcu_check_gp_kthread_starvation(rsp);
1436
bc1dce51 1437 rcu_dump_cpu_stacks(rsp);
c1dc0b9c 1438
6cf10081 1439 raw_spin_lock_irqsave_rcu_node(rnp, flags);
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1440 if (ULONG_CMP_GE(jiffies, READ_ONCE(rsp->jiffies_stall)))
1441 WRITE_ONCE(rsp->jiffies_stall,
1442 jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
67c583a7 1443 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
c1dc0b9c 1444
088e9d25
DBO
1445 panic_on_rcu_stall();
1446
b021fe3e
PZ
1447 /*
1448 * Attempt to revive the RCU machinery by forcing a context switch.
1449 *
1450 * A context switch would normally allow the RCU state machine to make
1451 * progress and it could be we're stuck in kernel space without context
1452 * switches for an entirely unreasonable amount of time.
1453 */
1454 resched_cpu(smp_processor_id());
64db4cff
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1455}
1456
1457static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
1458{
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1459 unsigned long completed;
1460 unsigned long gpnum;
1461 unsigned long gps;
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1462 unsigned long j;
1463 unsigned long js;
64db4cff
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1464 struct rcu_node *rnp;
1465
8c7c4829
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1466 if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) ||
1467 !rcu_gp_in_progress(rsp))
c68de209 1468 return;
8c7c4829 1469 rcu_stall_kick_kthreads(rsp);
cb1e78cf 1470 j = jiffies;
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1471
1472 /*
1473 * Lots of memory barriers to reject false positives.
1474 *
1475 * The idea is to pick up rsp->gpnum, then rsp->jiffies_stall,
1476 * then rsp->gp_start, and finally rsp->completed. These values
1477 * are updated in the opposite order with memory barriers (or
1478 * equivalent) during grace-period initialization and cleanup.
1479 * Now, a false positive can occur if we get an new value of
1480 * rsp->gp_start and a old value of rsp->jiffies_stall. But given
1481 * the memory barriers, the only way that this can happen is if one
1482 * grace period ends and another starts between these two fetches.
1483 * Detect this by comparing rsp->completed with the previous fetch
1484 * from rsp->gpnum.
1485 *
1486 * Given this check, comparisons of jiffies, rsp->jiffies_stall,
1487 * and rsp->gp_start suffice to forestall false positives.
1488 */
7d0ae808 1489 gpnum = READ_ONCE(rsp->gpnum);
26cdfedf 1490 smp_rmb(); /* Pick up ->gpnum first... */
7d0ae808 1491 js = READ_ONCE(rsp->jiffies_stall);
26cdfedf 1492 smp_rmb(); /* ...then ->jiffies_stall before the rest... */
7d0ae808 1493 gps = READ_ONCE(rsp->gp_start);
26cdfedf 1494 smp_rmb(); /* ...and finally ->gp_start before ->completed. */
7d0ae808 1495 completed = READ_ONCE(rsp->completed);
26cdfedf
PM
1496 if (ULONG_CMP_GE(completed, gpnum) ||
1497 ULONG_CMP_LT(j, js) ||
1498 ULONG_CMP_GE(gps, js))
1499 return; /* No stall or GP completed since entering function. */
64db4cff 1500 rnp = rdp->mynode;
c96ea7cf 1501 if (rcu_gp_in_progress(rsp) &&
7d0ae808 1502 (READ_ONCE(rnp->qsmask) & rdp->grpmask)) {
64db4cff
PM
1503
1504 /* We haven't checked in, so go dump stack. */
1505 print_cpu_stall(rsp);
1506
bad6e139
PM
1507 } else if (rcu_gp_in_progress(rsp) &&
1508 ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
64db4cff 1509
bad6e139 1510 /* They had a few time units to dump stack, so complain. */
6ccd2ecd 1511 print_other_cpu_stall(rsp, gpnum);
64db4cff
PM
1512 }
1513}
1514
53d84e00
PM
1515/**
1516 * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
1517 *
1518 * Set the stall-warning timeout way off into the future, thus preventing
1519 * any RCU CPU stall-warning messages from appearing in the current set of
1520 * RCU grace periods.
1521 *
1522 * The caller must disable hard irqs.
1523 */
1524void rcu_cpu_stall_reset(void)
1525{
6ce75a23
PM
1526 struct rcu_state *rsp;
1527
1528 for_each_rcu_flavor(rsp)
7d0ae808 1529 WRITE_ONCE(rsp->jiffies_stall, jiffies + ULONG_MAX / 2);
53d84e00
PM
1530}
1531
3f5d3ea6 1532/*
d3f3f3f2
PM
1533 * Initialize the specified rcu_data structure's default callback list
1534 * to empty. The default callback list is the one that is not used by
1535 * no-callbacks CPUs.
3f5d3ea6 1536 */
d3f3f3f2 1537static void init_default_callback_list(struct rcu_data *rdp)
3f5d3ea6
PM
1538{
1539 int i;
1540
1541 rdp->nxtlist = NULL;
1542 for (i = 0; i < RCU_NEXT_SIZE; i++)
1543 rdp->nxttail[i] = &rdp->nxtlist;
1544}
1545
d3f3f3f2
PM
1546/*
1547 * Initialize the specified rcu_data structure's callback list to empty.
1548 */
1549static void init_callback_list(struct rcu_data *rdp)
1550{
1551 if (init_nocb_callback_list(rdp))
1552 return;
1553 init_default_callback_list(rdp);
1554}
1555
dc35c893
PM
1556/*
1557 * Determine the value that ->completed will have at the end of the
1558 * next subsequent grace period. This is used to tag callbacks so that
1559 * a CPU can invoke callbacks in a timely fashion even if that CPU has
1560 * been dyntick-idle for an extended period with callbacks under the
1561 * influence of RCU_FAST_NO_HZ.
1562 *
1563 * The caller must hold rnp->lock with interrupts disabled.
1564 */
1565static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
1566 struct rcu_node *rnp)
1567{
1568 /*
1569 * If RCU is idle, we just wait for the next grace period.
1570 * But we can only be sure that RCU is idle if we are looking
1571 * at the root rcu_node structure -- otherwise, a new grace
1572 * period might have started, but just not yet gotten around
1573 * to initializing the current non-root rcu_node structure.
1574 */
1575 if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed)
1576 return rnp->completed + 1;
1577
1578 /*
1579 * Otherwise, wait for a possible partial grace period and
1580 * then the subsequent full grace period.
1581 */
1582 return rnp->completed + 2;
1583}
1584
0446be48
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1585/*
1586 * Trace-event helper function for rcu_start_future_gp() and
1587 * rcu_nocb_wait_gp().
1588 */
1589static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
e66c33d5 1590 unsigned long c, const char *s)
0446be48
PM
1591{
1592 trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
1593 rnp->completed, c, rnp->level,
1594 rnp->grplo, rnp->grphi, s);
1595}
1596
1597/*
1598 * Start some future grace period, as needed to handle newly arrived
1599 * callbacks. The required future grace periods are recorded in each
48a7639c
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1600 * rcu_node structure's ->need_future_gp field. Returns true if there
1601 * is reason to awaken the grace-period kthread.
0446be48
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1602 *
1603 * The caller must hold the specified rcu_node structure's ->lock.
1604 */
48a7639c
PM
1605static bool __maybe_unused
1606rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
1607 unsigned long *c_out)
0446be48
PM
1608{
1609 unsigned long c;
1610 int i;
48a7639c 1611 bool ret = false;
0446be48
PM
1612 struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
1613
1614 /*
1615 * Pick up grace-period number for new callbacks. If this
1616 * grace period is already marked as needed, return to the caller.
1617 */
1618 c = rcu_cbs_completed(rdp->rsp, rnp);
f7f7bac9 1619 trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf"));
0446be48 1620 if (rnp->need_future_gp[c & 0x1]) {
f7f7bac9 1621 trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf"));
48a7639c 1622 goto out;
0446be48
PM
1623 }
1624
1625 /*
1626 * If either this rcu_node structure or the root rcu_node structure
1627 * believe that a grace period is in progress, then we must wait
1628 * for the one following, which is in "c". Because our request
1629 * will be noticed at the end of the current grace period, we don't
48bd8e9b
PK
1630 * need to explicitly start one. We only do the lockless check
1631 * of rnp_root's fields if the current rcu_node structure thinks
1632 * there is no grace period in flight, and because we hold rnp->lock,
1633 * the only possible change is when rnp_root's two fields are
1634 * equal, in which case rnp_root->gpnum might be concurrently
1635 * incremented. But that is OK, as it will just result in our
1636 * doing some extra useless work.
0446be48
PM
1637 */
1638 if (rnp->gpnum != rnp->completed ||
7d0ae808 1639 READ_ONCE(rnp_root->gpnum) != READ_ONCE(rnp_root->completed)) {
0446be48 1640 rnp->need_future_gp[c & 0x1]++;
f7f7bac9 1641 trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf"));
48a7639c 1642 goto out;
0446be48
PM
1643 }
1644
1645 /*
1646 * There might be no grace period in progress. If we don't already
1647 * hold it, acquire the root rcu_node structure's lock in order to
1648 * start one (if needed).
1649 */
2a67e741
PZ
1650 if (rnp != rnp_root)
1651 raw_spin_lock_rcu_node(rnp_root);
0446be48
PM
1652
1653 /*
1654 * Get a new grace-period number. If there really is no grace
1655 * period in progress, it will be smaller than the one we obtained
1656 * earlier. Adjust callbacks as needed. Note that even no-CBs
1657 * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed.
1658 */
1659 c = rcu_cbs_completed(rdp->rsp, rnp_root);
1660 for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++)
1661 if (ULONG_CMP_LT(c, rdp->nxtcompleted[i]))
1662 rdp->nxtcompleted[i] = c;
1663
1664 /*
1665 * If the needed for the required grace period is already
1666 * recorded, trace and leave.
1667 */
1668 if (rnp_root->need_future_gp[c & 0x1]) {
f7f7bac9 1669 trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot"));
0446be48
PM
1670 goto unlock_out;
1671 }
1672
1673 /* Record the need for the future grace period. */
1674 rnp_root->need_future_gp[c & 0x1]++;
1675
1676 /* If a grace period is not already in progress, start one. */
1677 if (rnp_root->gpnum != rnp_root->completed) {
f7f7bac9 1678 trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot"));
0446be48 1679 } else {
f7f7bac9 1680 trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot"));
48a7639c 1681 ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp);
0446be48
PM
1682 }
1683unlock_out:
1684 if (rnp != rnp_root)
67c583a7 1685 raw_spin_unlock_rcu_node(rnp_root);
48a7639c
PM
1686out:
1687 if (c_out != NULL)
1688 *c_out = c;
1689 return ret;
0446be48
PM
1690}
1691
1692/*
1693 * Clean up any old requests for the just-ended grace period. Also return
1694 * whether any additional grace periods have been requested. Also invoke
1695 * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads
1696 * waiting for this grace period to complete.
1697 */
1698static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
1699{
1700 int c = rnp->completed;
1701 int needmore;
1702 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
1703
0446be48
PM
1704 rnp->need_future_gp[c & 0x1] = 0;
1705 needmore = rnp->need_future_gp[(c + 1) & 0x1];
f7f7bac9
SRRH
1706 trace_rcu_future_gp(rnp, rdp, c,
1707 needmore ? TPS("CleanupMore") : TPS("Cleanup"));
0446be48
PM
1708 return needmore;
1709}
1710
48a7639c
PM
1711/*
1712 * Awaken the grace-period kthread for the specified flavor of RCU.
1713 * Don't do a self-awaken, and don't bother awakening when there is
1714 * nothing for the grace-period kthread to do (as in several CPUs
1715 * raced to awaken, and we lost), and finally don't try to awaken
1716 * a kthread that has not yet been created.
1717 */
1718static void rcu_gp_kthread_wake(struct rcu_state *rsp)
1719{
1720 if (current == rsp->gp_kthread ||
7d0ae808 1721 !READ_ONCE(rsp->gp_flags) ||
48a7639c
PM
1722 !rsp->gp_kthread)
1723 return;
abedf8e2 1724 swake_up(&rsp->gp_wq);
48a7639c
PM
1725}
1726
dc35c893
PM
1727/*
1728 * If there is room, assign a ->completed number to any callbacks on
1729 * this CPU that have not already been assigned. Also accelerate any
1730 * callbacks that were previously assigned a ->completed number that has
1731 * since proven to be too conservative, which can happen if callbacks get
1732 * assigned a ->completed number while RCU is idle, but with reference to
1733 * a non-root rcu_node structure. This function is idempotent, so it does
48a7639c
PM
1734 * not hurt to call it repeatedly. Returns an flag saying that we should
1735 * awaken the RCU grace-period kthread.
dc35c893
PM
1736 *
1737 * The caller must hold rnp->lock with interrupts disabled.
1738 */
48a7639c 1739static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
dc35c893
PM
1740 struct rcu_data *rdp)
1741{
1742 unsigned long c;
1743 int i;
48a7639c 1744 bool ret;
dc35c893
PM
1745
1746 /* If the CPU has no callbacks, nothing to do. */
1747 if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
48a7639c 1748 return false;
dc35c893
PM
1749
1750 /*
1751 * Starting from the sublist containing the callbacks most
1752 * recently assigned a ->completed number and working down, find the
1753 * first sublist that is not assignable to an upcoming grace period.
1754 * Such a sublist has something in it (first two tests) and has
1755 * a ->completed number assigned that will complete sooner than
1756 * the ->completed number for newly arrived callbacks (last test).
1757 *
1758 * The key point is that any later sublist can be assigned the
1759 * same ->completed number as the newly arrived callbacks, which
1760 * means that the callbacks in any of these later sublist can be
1761 * grouped into a single sublist, whether or not they have already
1762 * been assigned a ->completed number.
1763 */
1764 c = rcu_cbs_completed(rsp, rnp);
1765 for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--)
1766 if (rdp->nxttail[i] != rdp->nxttail[i - 1] &&
1767 !ULONG_CMP_GE(rdp->nxtcompleted[i], c))
1768 break;
1769
1770 /*
1771 * If there are no sublist for unassigned callbacks, leave.
1772 * At the same time, advance "i" one sublist, so that "i" will
1773 * index into the sublist where all the remaining callbacks should
1774 * be grouped into.
1775 */
1776 if (++i >= RCU_NEXT_TAIL)
48a7639c 1777 return false;
dc35c893
PM
1778
1779 /*
1780 * Assign all subsequent callbacks' ->completed number to the next
1781 * full grace period and group them all in the sublist initially
1782 * indexed by "i".
1783 */
1784 for (; i <= RCU_NEXT_TAIL; i++) {
1785 rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL];
1786 rdp->nxtcompleted[i] = c;
1787 }
910ee45d 1788 /* Record any needed additional grace periods. */
48a7639c 1789 ret = rcu_start_future_gp(rnp, rdp, NULL);
6d4b418c
PM
1790
1791 /* Trace depending on how much we were able to accelerate. */
1792 if (!*rdp->nxttail[RCU_WAIT_TAIL])
f7f7bac9 1793 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB"));
6d4b418c 1794 else
f7f7bac9 1795 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB"));
48a7639c 1796 return ret;
dc35c893
PM
1797}
1798
1799/*
1800 * Move any callbacks whose grace period has completed to the
1801 * RCU_DONE_TAIL sublist, then compact the remaining sublists and
1802 * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL
1803 * sublist. This function is idempotent, so it does not hurt to
1804 * invoke it repeatedly. As long as it is not invoked -too- often...
48a7639c 1805 * Returns true if the RCU grace-period kthread needs to be awakened.
dc35c893
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1806 *
1807 * The caller must hold rnp->lock with interrupts disabled.
1808 */
48a7639c 1809static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
dc35c893
PM
1810 struct rcu_data *rdp)
1811{
1812 int i, j;
1813
1814 /* If the CPU has no callbacks, nothing to do. */
1815 if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
48a7639c 1816 return false;
dc35c893
PM
1817
1818 /*
1819 * Find all callbacks whose ->completed numbers indicate that they
1820 * are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
1821 */
1822 for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
1823 if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i]))
1824 break;
1825 rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i];
1826 }
1827 /* Clean up any sublist tail pointers that were misordered above. */
1828 for (j = RCU_WAIT_TAIL; j < i; j++)
1829 rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL];
1830
1831 /* Copy down callbacks to fill in empty sublists. */
1832 for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
1833 if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL])
1834 break;
1835 rdp->nxttail[j] = rdp->nxttail[i];
1836 rdp->nxtcompleted[j] = rdp->nxtcompleted[i];
1837 }
1838
1839 /* Classify any remaining callbacks. */
48a7639c 1840 return rcu_accelerate_cbs(rsp, rnp, rdp);
dc35c893
PM
1841}
1842
d09b62df 1843/*
ba9fbe95
PM
1844 * Update CPU-local rcu_data state to record the beginnings and ends of
1845 * grace periods. The caller must hold the ->lock of the leaf rcu_node
1846 * structure corresponding to the current CPU, and must have irqs disabled.
48a7639c 1847 * Returns true if the grace-period kthread needs to be awakened.
d09b62df 1848 */
48a7639c
PM
1849static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
1850 struct rcu_data *rdp)
d09b62df 1851{
48a7639c 1852 bool ret;
3563a438 1853 bool need_gp;
48a7639c 1854
ba9fbe95 1855 /* Handle the ends of any preceding grace periods first. */
e3663b10 1856 if (rdp->completed == rnp->completed &&
7d0ae808 1857 !unlikely(READ_ONCE(rdp->gpwrap))) {
d09b62df 1858
ba9fbe95 1859 /* No grace period end, so just accelerate recent callbacks. */
48a7639c 1860 ret = rcu_accelerate_cbs(rsp, rnp, rdp);
d09b62df 1861
dc35c893
PM
1862 } else {
1863
1864 /* Advance callbacks. */
48a7639c 1865 ret = rcu_advance_cbs(rsp, rnp, rdp);
d09b62df
PM
1866
1867 /* Remember that we saw this grace-period completion. */
1868 rdp->completed = rnp->completed;
f7f7bac9 1869 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend"));
d09b62df 1870 }
398ebe60 1871
7d0ae808 1872 if (rdp->gpnum != rnp->gpnum || unlikely(READ_ONCE(rdp->gpwrap))) {
6eaef633
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1873 /*
1874 * If the current grace period is waiting for this CPU,
1875 * set up to detect a quiescent state, otherwise don't
1876 * go looking for one.
1877 */
1878 rdp->gpnum = rnp->gpnum;
f7f7bac9 1879 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart"));
3563a438
PM
1880 need_gp = !!(rnp->qsmask & rdp->grpmask);
1881 rdp->cpu_no_qs.b.norm = need_gp;
5cd37193 1882 rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
3563a438 1883 rdp->core_needs_qs = need_gp;
6eaef633 1884 zero_cpu_stall_ticks(rdp);
7d0ae808 1885 WRITE_ONCE(rdp->gpwrap, false);
6eaef633 1886 }
48a7639c 1887 return ret;
6eaef633
PM
1888}
1889
d34ea322 1890static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
6eaef633
PM
1891{
1892 unsigned long flags;
48a7639c 1893 bool needwake;
6eaef633
PM
1894 struct rcu_node *rnp;
1895
1896 local_irq_save(flags);
1897 rnp = rdp->mynode;
7d0ae808
PM
1898 if ((rdp->gpnum == READ_ONCE(rnp->gpnum) &&
1899 rdp->completed == READ_ONCE(rnp->completed) &&
1900 !unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */
2a67e741 1901 !raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */
6eaef633
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1902 local_irq_restore(flags);
1903 return;
1904 }
48a7639c 1905 needwake = __note_gp_changes(rsp, rnp, rdp);
67c583a7 1906 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
48a7639c
PM
1907 if (needwake)
1908 rcu_gp_kthread_wake(rsp);
6eaef633
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1909}
1910
0f41c0dd
PM
1911static void rcu_gp_slow(struct rcu_state *rsp, int delay)
1912{
1913 if (delay > 0 &&
1914 !(rsp->gpnum % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
1915 schedule_timeout_uninterruptible(delay);
1916}
1917
b3dbec76 1918/*
45fed3e7 1919 * Initialize a new grace period. Return false if no grace period required.
b3dbec76 1920 */
45fed3e7 1921static bool rcu_gp_init(struct rcu_state *rsp)
b3dbec76 1922{
0aa04b05 1923 unsigned long oldmask;
b3dbec76 1924 struct rcu_data *rdp;
7fdefc10 1925 struct rcu_node *rnp = rcu_get_root(rsp);
b3dbec76 1926
7d0ae808 1927 WRITE_ONCE(rsp->gp_activity, jiffies);
2a67e741 1928 raw_spin_lock_irq_rcu_node(rnp);
7d0ae808 1929 if (!READ_ONCE(rsp->gp_flags)) {
f7be8209 1930 /* Spurious wakeup, tell caller to go back to sleep. */
67c583a7 1931 raw_spin_unlock_irq_rcu_node(rnp);
45fed3e7 1932 return false;
f7be8209 1933 }
7d0ae808 1934 WRITE_ONCE(rsp->gp_flags, 0); /* Clear all flags: New grace period. */
b3dbec76 1935
f7be8209
PM
1936 if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) {
1937 /*
1938 * Grace period already in progress, don't start another.
1939 * Not supposed to be able to happen.
1940 */
67c583a7 1941 raw_spin_unlock_irq_rcu_node(rnp);
45fed3e7 1942 return false;
7fdefc10
PM
1943 }
1944
7fdefc10 1945 /* Advance to a new grace period and initialize state. */
26cdfedf 1946 record_gp_stall_check_time(rsp);
765a3f4f
PM
1947 /* Record GP times before starting GP, hence smp_store_release(). */
1948 smp_store_release(&rsp->gpnum, rsp->gpnum + 1);
f7f7bac9 1949 trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start"));
67c583a7 1950 raw_spin_unlock_irq_rcu_node(rnp);
7fdefc10 1951
0aa04b05
PM
1952 /*
1953 * Apply per-leaf buffered online and offline operations to the
1954 * rcu_node tree. Note that this new grace period need not wait
1955 * for subsequent online CPUs, and that quiescent-state forcing
1956 * will handle subsequent offline CPUs.
1957 */
1958 rcu_for_each_leaf_node(rsp, rnp) {
0f41c0dd 1959 rcu_gp_slow(rsp, gp_preinit_delay);
2a67e741 1960 raw_spin_lock_irq_rcu_node(rnp);
0aa04b05
PM
1961 if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
1962 !rnp->wait_blkd_tasks) {
1963 /* Nothing to do on this leaf rcu_node structure. */
67c583a7 1964 raw_spin_unlock_irq_rcu_node(rnp);
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1965 continue;
1966 }
1967
1968 /* Record old state, apply changes to ->qsmaskinit field. */
1969 oldmask = rnp->qsmaskinit;
1970 rnp->qsmaskinit = rnp->qsmaskinitnext;
1971
1972 /* If zero-ness of ->qsmaskinit changed, propagate up tree. */
1973 if (!oldmask != !rnp->qsmaskinit) {
1974 if (!oldmask) /* First online CPU for this rcu_node. */
1975 rcu_init_new_rnp(rnp);
1976 else if (rcu_preempt_has_tasks(rnp)) /* blocked tasks */
1977 rnp->wait_blkd_tasks = true;
1978 else /* Last offline CPU and can propagate. */
1979 rcu_cleanup_dead_rnp(rnp);
1980 }
1981
1982 /*
1983 * If all waited-on tasks from prior grace period are
1984 * done, and if all this rcu_node structure's CPUs are
1985 * still offline, propagate up the rcu_node tree and
1986 * clear ->wait_blkd_tasks. Otherwise, if one of this
1987 * rcu_node structure's CPUs has since come back online,
1988 * simply clear ->wait_blkd_tasks (but rcu_cleanup_dead_rnp()
1989 * checks for this, so just call it unconditionally).
1990 */
1991 if (rnp->wait_blkd_tasks &&
1992 (!rcu_preempt_has_tasks(rnp) ||
1993 rnp->qsmaskinit)) {
1994 rnp->wait_blkd_tasks = false;
1995 rcu_cleanup_dead_rnp(rnp);
1996 }
1997
67c583a7 1998 raw_spin_unlock_irq_rcu_node(rnp);
0aa04b05 1999 }
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2000
2001 /*
2002 * Set the quiescent-state-needed bits in all the rcu_node
2003 * structures for all currently online CPUs in breadth-first order,
2004 * starting from the root rcu_node structure, relying on the layout
2005 * of the tree within the rsp->node[] array. Note that other CPUs
2006 * will access only the leaves of the hierarchy, thus seeing that no
2007 * grace period is in progress, at least until the corresponding
590d1757 2008 * leaf node has been initialized.
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2009 *
2010 * The grace period cannot complete until the initialization
2011 * process finishes, because this kthread handles both.
2012 */
2013 rcu_for_each_node_breadth_first(rsp, rnp) {
0f41c0dd 2014 rcu_gp_slow(rsp, gp_init_delay);
2a67e741 2015 raw_spin_lock_irq_rcu_node(rnp);
b3dbec76 2016 rdp = this_cpu_ptr(rsp->rda);
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2017 rcu_preempt_check_blocked_tasks(rnp);
2018 rnp->qsmask = rnp->qsmaskinit;
7d0ae808 2019 WRITE_ONCE(rnp->gpnum, rsp->gpnum);
3f47da0f 2020 if (WARN_ON_ONCE(rnp->completed != rsp->completed))
7d0ae808 2021 WRITE_ONCE(rnp->completed, rsp->completed);
7fdefc10 2022 if (rnp == rdp->mynode)
48a7639c 2023 (void)__note_gp_changes(rsp, rnp, rdp);
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2024 rcu_preempt_boost_start_gp(rnp);
2025 trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
2026 rnp->level, rnp->grplo,
2027 rnp->grphi, rnp->qsmask);
67c583a7 2028 raw_spin_unlock_irq_rcu_node(rnp);
bde6c3aa 2029 cond_resched_rcu_qs();
7d0ae808 2030 WRITE_ONCE(rsp->gp_activity, jiffies);
7fdefc10 2031 }
b3dbec76 2032
45fed3e7 2033 return true;
7fdefc10 2034}
b3dbec76 2035
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2036/*
2037 * Helper function for wait_event_interruptible_timeout() wakeup
2038 * at force-quiescent-state time.
2039 */
2040static bool rcu_gp_fqs_check_wake(struct rcu_state *rsp, int *gfp)
2041{
2042 struct rcu_node *rnp = rcu_get_root(rsp);
2043
2044 /* Someone like call_rcu() requested a force-quiescent-state scan. */
2045 *gfp = READ_ONCE(rsp->gp_flags);
2046 if (*gfp & RCU_GP_FLAG_FQS)
2047 return true;
2048
2049 /* The current grace period has completed. */
2050 if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp))
2051 return true;
2052
2053 return false;
2054}
2055
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2056/*
2057 * Do one round of quiescent-state forcing.
2058 */
77f81fe0 2059static void rcu_gp_fqs(struct rcu_state *rsp, bool first_time)
4cdfc175 2060{
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2061 bool isidle = false;
2062 unsigned long maxj;
4cdfc175
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2063 struct rcu_node *rnp = rcu_get_root(rsp);
2064
7d0ae808 2065 WRITE_ONCE(rsp->gp_activity, jiffies);
4cdfc175 2066 rsp->n_force_qs++;
77f81fe0 2067 if (first_time) {
4cdfc175 2068 /* Collect dyntick-idle snapshots. */
0edd1b17 2069 if (is_sysidle_rcu_state(rsp)) {
e02b2edf 2070 isidle = true;
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2071 maxj = jiffies - ULONG_MAX / 4;
2072 }
217af2a2
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2073 force_qs_rnp(rsp, dyntick_save_progress_counter,
2074 &isidle, &maxj);
0edd1b17 2075 rcu_sysidle_report_gp(rsp, isidle, maxj);
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2076 } else {
2077 /* Handle dyntick-idle and offline CPUs. */
675da67f 2078 isidle = true;
217af2a2 2079 force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj);
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2080 }
2081 /* Clear flag to prevent immediate re-entry. */
7d0ae808 2082 if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
2a67e741 2083 raw_spin_lock_irq_rcu_node(rnp);
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2084 WRITE_ONCE(rsp->gp_flags,
2085 READ_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS);
67c583a7 2086 raw_spin_unlock_irq_rcu_node(rnp);
4cdfc175 2087 }
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2088}
2089
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2090/*
2091 * Clean up after the old grace period.
2092 */
4cdfc175 2093static void rcu_gp_cleanup(struct rcu_state *rsp)
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2094{
2095 unsigned long gp_duration;
48a7639c 2096 bool needgp = false;
dae6e64d 2097 int nocb = 0;
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2098 struct rcu_data *rdp;
2099 struct rcu_node *rnp = rcu_get_root(rsp);
abedf8e2 2100 struct swait_queue_head *sq;
b3dbec76 2101
7d0ae808 2102 WRITE_ONCE(rsp->gp_activity, jiffies);
2a67e741 2103 raw_spin_lock_irq_rcu_node(rnp);
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2104 gp_duration = jiffies - rsp->gp_start;
2105 if (gp_duration > rsp->gp_max)
2106 rsp->gp_max = gp_duration;
b3dbec76 2107
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2108 /*
2109 * We know the grace period is complete, but to everyone else
2110 * it appears to still be ongoing. But it is also the case
2111 * that to everyone else it looks like there is nothing that
2112 * they can do to advance the grace period. It is therefore
2113 * safe for us to drop the lock in order to mark the grace
2114 * period as completed in all of the rcu_node structures.
7fdefc10 2115 */
67c583a7 2116 raw_spin_unlock_irq_rcu_node(rnp);
b3dbec76 2117
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2118 /*
2119 * Propagate new ->completed value to rcu_node structures so
2120 * that other CPUs don't have to wait until the start of the next
2121 * grace period to process their callbacks. This also avoids
2122 * some nasty RCU grace-period initialization races by forcing
2123 * the end of the current grace period to be completely recorded in
2124 * all of the rcu_node structures before the beginning of the next
2125 * grace period is recorded in any of the rcu_node structures.
2126 */
2127 rcu_for_each_node_breadth_first(rsp, rnp) {
2a67e741 2128 raw_spin_lock_irq_rcu_node(rnp);
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2129 WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
2130 WARN_ON_ONCE(rnp->qsmask);
7d0ae808 2131 WRITE_ONCE(rnp->completed, rsp->gpnum);
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2132 rdp = this_cpu_ptr(rsp->rda);
2133 if (rnp == rdp->mynode)
48a7639c 2134 needgp = __note_gp_changes(rsp, rnp, rdp) || needgp;
78e4bc34 2135 /* smp_mb() provided by prior unlock-lock pair. */
0446be48 2136 nocb += rcu_future_gp_cleanup(rsp, rnp);
065bb78c 2137 sq = rcu_nocb_gp_get(rnp);
67c583a7 2138 raw_spin_unlock_irq_rcu_node(rnp);
065bb78c 2139 rcu_nocb_gp_cleanup(sq);
bde6c3aa 2140 cond_resched_rcu_qs();
7d0ae808 2141 WRITE_ONCE(rsp->gp_activity, jiffies);
0f41c0dd 2142 rcu_gp_slow(rsp, gp_cleanup_delay);
7fdefc10 2143 }
5d4b8659 2144 rnp = rcu_get_root(rsp);
2a67e741 2145 raw_spin_lock_irq_rcu_node(rnp); /* Order GP before ->completed update. */
dae6e64d 2146 rcu_nocb_gp_set(rnp, nocb);
7fdefc10 2147
765a3f4f 2148 /* Declare grace period done. */
7d0ae808 2149 WRITE_ONCE(rsp->completed, rsp->gpnum);
f7f7bac9 2150 trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end"));
77f81fe0 2151 rsp->gp_state = RCU_GP_IDLE;
5d4b8659 2152 rdp = this_cpu_ptr(rsp->rda);
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PM
2153 /* Advance CBs to reduce false positives below. */
2154 needgp = rcu_advance_cbs(rsp, rnp, rdp) || needgp;
2155 if (needgp || cpu_needs_another_gp(rsp, rdp)) {
7d0ae808 2156 WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT);
bb311ecc 2157 trace_rcu_grace_period(rsp->name,
7d0ae808 2158 READ_ONCE(rsp->gpnum),
bb311ecc
PM
2159 TPS("newreq"));
2160 }
67c583a7 2161 raw_spin_unlock_irq_rcu_node(rnp);
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2162}
2163
2164/*
2165 * Body of kthread that handles grace periods.
2166 */
2167static int __noreturn rcu_gp_kthread(void *arg)
2168{
77f81fe0 2169 bool first_gp_fqs;
88d6df61 2170 int gf;
d40011f6 2171 unsigned long j;
4cdfc175 2172 int ret;
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2173 struct rcu_state *rsp = arg;
2174 struct rcu_node *rnp = rcu_get_root(rsp);
2175
5871968d 2176 rcu_bind_gp_kthread();
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2177 for (;;) {
2178
2179 /* Handle grace-period start. */
2180 for (;;) {
63c4db78 2181 trace_rcu_grace_period(rsp->name,
7d0ae808 2182 READ_ONCE(rsp->gpnum),
63c4db78 2183 TPS("reqwait"));
afea227f 2184 rsp->gp_state = RCU_GP_WAIT_GPS;
abedf8e2 2185 swait_event_interruptible(rsp->gp_wq,
7d0ae808 2186 READ_ONCE(rsp->gp_flags) &
4cdfc175 2187 RCU_GP_FLAG_INIT);
319362c9 2188 rsp->gp_state = RCU_GP_DONE_GPS;
78e4bc34 2189 /* Locking provides needed memory barrier. */
f7be8209 2190 if (rcu_gp_init(rsp))
7fdefc10 2191 break;
bde6c3aa 2192 cond_resched_rcu_qs();
7d0ae808 2193 WRITE_ONCE(rsp->gp_activity, jiffies);
73a860cd 2194 WARN_ON(signal_pending(current));
63c4db78 2195 trace_rcu_grace_period(rsp->name,
7d0ae808 2196 READ_ONCE(rsp->gpnum),
63c4db78 2197 TPS("reqwaitsig"));
7fdefc10 2198 }
cabc49c1 2199
4cdfc175 2200 /* Handle quiescent-state forcing. */
77f81fe0 2201 first_gp_fqs = true;
d40011f6
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2202 j = jiffies_till_first_fqs;
2203 if (j > HZ) {
2204 j = HZ;
2205 jiffies_till_first_fqs = HZ;
2206 }
88d6df61 2207 ret = 0;
cabc49c1 2208 for (;;) {
8c7c4829 2209 if (!ret) {
88d6df61 2210 rsp->jiffies_force_qs = jiffies + j;
8c7c4829
PM
2211 WRITE_ONCE(rsp->jiffies_kick_kthreads,
2212 jiffies + 3 * j);
2213 }
63c4db78 2214 trace_rcu_grace_period(rsp->name,
7d0ae808 2215 READ_ONCE(rsp->gpnum),
63c4db78 2216 TPS("fqswait"));
afea227f 2217 rsp->gp_state = RCU_GP_WAIT_FQS;
abedf8e2 2218 ret = swait_event_interruptible_timeout(rsp->gp_wq,
b9a425cf 2219 rcu_gp_fqs_check_wake(rsp, &gf), j);
32bb1c79 2220 rsp->gp_state = RCU_GP_DOING_FQS;
78e4bc34 2221 /* Locking provides needed memory barriers. */
4cdfc175 2222 /* If grace period done, leave loop. */
7d0ae808 2223 if (!READ_ONCE(rnp->qsmask) &&
4cdfc175 2224 !rcu_preempt_blocked_readers_cgp(rnp))
cabc49c1 2225 break;
4cdfc175 2226 /* If time for quiescent-state forcing, do it. */
88d6df61
PM
2227 if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) ||
2228 (gf & RCU_GP_FLAG_FQS)) {
63c4db78 2229 trace_rcu_grace_period(rsp->name,
7d0ae808 2230 READ_ONCE(rsp->gpnum),
63c4db78 2231 TPS("fqsstart"));
77f81fe0
PM
2232 rcu_gp_fqs(rsp, first_gp_fqs);
2233 first_gp_fqs = false;
63c4db78 2234 trace_rcu_grace_period(rsp->name,
7d0ae808 2235 READ_ONCE(rsp->gpnum),
63c4db78 2236 TPS("fqsend"));
bde6c3aa 2237 cond_resched_rcu_qs();
7d0ae808 2238 WRITE_ONCE(rsp->gp_activity, jiffies);
fcfd0a23
PM
2239 ret = 0; /* Force full wait till next FQS. */
2240 j = jiffies_till_next_fqs;
2241 if (j > HZ) {
2242 j = HZ;
2243 jiffies_till_next_fqs = HZ;
2244 } else if (j < 1) {
2245 j = 1;
2246 jiffies_till_next_fqs = 1;
2247 }
4cdfc175
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2248 } else {
2249 /* Deal with stray signal. */
bde6c3aa 2250 cond_resched_rcu_qs();
7d0ae808 2251 WRITE_ONCE(rsp->gp_activity, jiffies);
73a860cd 2252 WARN_ON(signal_pending(current));
63c4db78 2253 trace_rcu_grace_period(rsp->name,
7d0ae808 2254 READ_ONCE(rsp->gpnum),
63c4db78 2255 TPS("fqswaitsig"));
fcfd0a23
PM
2256 ret = 1; /* Keep old FQS timing. */
2257 j = jiffies;
2258 if (time_after(jiffies, rsp->jiffies_force_qs))
2259 j = 1;
2260 else
2261 j = rsp->jiffies_force_qs - j;
d40011f6 2262 }
cabc49c1 2263 }
4cdfc175
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2264
2265 /* Handle grace-period end. */
319362c9 2266 rsp->gp_state = RCU_GP_CLEANUP;
4cdfc175 2267 rcu_gp_cleanup(rsp);
319362c9 2268 rsp->gp_state = RCU_GP_CLEANED;
b3dbec76 2269 }
b3dbec76
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2270}
2271
64db4cff
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2272/*
2273 * Start a new RCU grace period if warranted, re-initializing the hierarchy
2274 * in preparation for detecting the next grace period. The caller must hold
b8462084 2275 * the root node's ->lock and hard irqs must be disabled.
e5601400
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2276 *
2277 * Note that it is legal for a dying CPU (which is marked as offline) to
2278 * invoke this function. This can happen when the dying CPU reports its
2279 * quiescent state.
48a7639c
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2280 *
2281 * Returns true if the grace-period kthread must be awakened.
64db4cff 2282 */
48a7639c 2283static bool
910ee45d
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2284rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
2285 struct rcu_data *rdp)
64db4cff 2286{
b8462084 2287 if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) {
afe24b12 2288 /*
b3dbec76 2289 * Either we have not yet spawned the grace-period
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2290 * task, this CPU does not need another grace period,
2291 * or a grace period is already in progress.
b3dbec76 2292 * Either way, don't start a new grace period.
afe24b12 2293 */
48a7639c 2294 return false;
afe24b12 2295 }
7d0ae808
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2296 WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT);
2297 trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum),
bb311ecc 2298 TPS("newreq"));
62da1921 2299
016a8d5b
SR
2300 /*
2301 * We can't do wakeups while holding the rnp->lock, as that
1eafd31c 2302 * could cause possible deadlocks with the rq->lock. Defer
48a7639c 2303 * the wakeup to our caller.
016a8d5b 2304 */
48a7639c 2305 return true;
64db4cff
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2306}
2307
910ee45d
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2308/*
2309 * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's
2310 * callbacks. Note that rcu_start_gp_advanced() cannot do this because it
2311 * is invoked indirectly from rcu_advance_cbs(), which would result in
2312 * endless recursion -- or would do so if it wasn't for the self-deadlock
2313 * that is encountered beforehand.
48a7639c
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2314 *
2315 * Returns true if the grace-period kthread needs to be awakened.
910ee45d 2316 */
48a7639c 2317static bool rcu_start_gp(struct rcu_state *rsp)
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2318{
2319 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
2320 struct rcu_node *rnp = rcu_get_root(rsp);
48a7639c 2321 bool ret = false;
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2322
2323 /*
2324 * If there is no grace period in progress right now, any
2325 * callbacks we have up to this point will be satisfied by the
2326 * next grace period. Also, advancing the callbacks reduces the
2327 * probability of false positives from cpu_needs_another_gp()
2328 * resulting in pointless grace periods. So, advance callbacks
2329 * then start the grace period!
2330 */
48a7639c
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2331 ret = rcu_advance_cbs(rsp, rnp, rdp) || ret;
2332 ret = rcu_start_gp_advanced(rsp, rnp, rdp) || ret;
2333 return ret;
910ee45d
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2334}
2335
f41d911f 2336/*
8994515c
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2337 * Report a full set of quiescent states to the specified rcu_state data
2338 * structure. Invoke rcu_gp_kthread_wake() to awaken the grace-period
2339 * kthread if another grace period is required. Whether we wake
2340 * the grace-period kthread or it awakens itself for the next round
2341 * of quiescent-state forcing, that kthread will clean up after the
2342 * just-completed grace period. Note that the caller must hold rnp->lock,
2343 * which is released before return.
f41d911f 2344 */
d3f6bad3 2345static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
fc2219d4 2346 __releases(rcu_get_root(rsp)->lock)
f41d911f 2347{
fc2219d4 2348 WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
cd73ca21 2349 WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS);
67c583a7 2350 raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(rsp), flags);
94d44776 2351 rcu_gp_kthread_wake(rsp);
f41d911f
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2352}
2353
64db4cff 2354/*
d3f6bad3
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2355 * Similar to rcu_report_qs_rdp(), for which it is a helper function.
2356 * Allows quiescent states for a group of CPUs to be reported at one go
2357 * to the specified rcu_node structure, though all the CPUs in the group
654e9533
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2358 * must be represented by the same rcu_node structure (which need not be a
2359 * leaf rcu_node structure, though it often will be). The gps parameter
2360 * is the grace-period snapshot, which means that the quiescent states
2361 * are valid only if rnp->gpnum is equal to gps. That structure's lock
2362 * must be held upon entry, and it is released before return.
64db4cff
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2363 */
2364static void
d3f6bad3 2365rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
654e9533 2366 struct rcu_node *rnp, unsigned long gps, unsigned long flags)
64db4cff
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2367 __releases(rnp->lock)
2368{
654e9533 2369 unsigned long oldmask = 0;
28ecd580
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2370 struct rcu_node *rnp_c;
2371
64db4cff
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2372 /* Walk up the rcu_node hierarchy. */
2373 for (;;) {
654e9533 2374 if (!(rnp->qsmask & mask) || rnp->gpnum != gps) {
64db4cff 2375
654e9533
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2376 /*
2377 * Our bit has already been cleared, or the
2378 * relevant grace period is already over, so done.
2379 */
67c583a7 2380 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
64db4cff
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2381 return;
2382 }
654e9533 2383 WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */
64db4cff 2384 rnp->qsmask &= ~mask;
d4c08f2a
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2385 trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
2386 mask, rnp->qsmask, rnp->level,
2387 rnp->grplo, rnp->grphi,
2388 !!rnp->gp_tasks);
27f4d280 2389 if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
64db4cff
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2390
2391 /* Other bits still set at this level, so done. */
67c583a7 2392 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
64db4cff
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2393 return;
2394 }
2395 mask = rnp->grpmask;
2396 if (rnp->parent == NULL) {
2397
2398 /* No more levels. Exit loop holding root lock. */
2399
2400 break;
2401 }
67c583a7 2402 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
28ecd580 2403 rnp_c = rnp;
64db4cff 2404 rnp = rnp->parent;
2a67e741 2405 raw_spin_lock_irqsave_rcu_node(rnp, flags);
654e9533 2406 oldmask = rnp_c->qsmask;
64db4cff
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2407 }
2408
2409 /*
2410 * Get here if we are the last CPU to pass through a quiescent
d3f6bad3 2411 * state for this grace period. Invoke rcu_report_qs_rsp()
f41d911f 2412 * to clean up and start the next grace period if one is needed.
64db4cff 2413 */
d3f6bad3 2414 rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
64db4cff
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2415}
2416
cc99a310
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2417/*
2418 * Record a quiescent state for all tasks that were previously queued
2419 * on the specified rcu_node structure and that were blocking the current
2420 * RCU grace period. The caller must hold the specified rnp->lock with
2421 * irqs disabled, and this lock is released upon return, but irqs remain
2422 * disabled.
2423 */
0aa04b05 2424static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
cc99a310
PM
2425 struct rcu_node *rnp, unsigned long flags)
2426 __releases(rnp->lock)
2427{
654e9533 2428 unsigned long gps;
cc99a310
PM
2429 unsigned long mask;
2430 struct rcu_node *rnp_p;
2431
a77da14c
PM
2432 if (rcu_state_p == &rcu_sched_state || rsp != rcu_state_p ||
2433 rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
67c583a7 2434 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
cc99a310
PM
2435 return; /* Still need more quiescent states! */
2436 }
2437
2438 rnp_p = rnp->parent;
2439 if (rnp_p == NULL) {
2440 /*
a77da14c
PM
2441 * Only one rcu_node structure in the tree, so don't
2442 * try to report up to its nonexistent parent!
cc99a310
PM
2443 */
2444 rcu_report_qs_rsp(rsp, flags);
2445 return;
2446 }
2447
654e9533
PM
2448 /* Report up the rest of the hierarchy, tracking current ->gpnum. */
2449 gps = rnp->gpnum;
cc99a310 2450 mask = rnp->grpmask;
67c583a7 2451 raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
2a67e741 2452 raw_spin_lock_rcu_node(rnp_p); /* irqs already disabled. */
654e9533 2453 rcu_report_qs_rnp(mask, rsp, rnp_p, gps, flags);
cc99a310
PM
2454}
2455
64db4cff 2456/*
d3f6bad3 2457 * Record a quiescent state for the specified CPU to that CPU's rcu_data
4b455dc3 2458 * structure. This must be called from the specified CPU.
64db4cff
PM
2459 */
2460static void
d7d6a11e 2461rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
64db4cff
PM
2462{
2463 unsigned long flags;
2464 unsigned long mask;
48a7639c 2465 bool needwake;
64db4cff
PM
2466 struct rcu_node *rnp;
2467
2468 rnp = rdp->mynode;
2a67e741 2469 raw_spin_lock_irqsave_rcu_node(rnp, flags);
5b74c458 2470 if ((rdp->cpu_no_qs.b.norm &&
5cd37193
PM
2471 rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) ||
2472 rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum ||
2473 rdp->gpwrap) {
64db4cff
PM
2474
2475 /*
e4cc1f22
PM
2476 * The grace period in which this quiescent state was
2477 * recorded has ended, so don't report it upwards.
2478 * We will instead need a new quiescent state that lies
2479 * within the current grace period.
64db4cff 2480 */
5b74c458 2481 rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */
5cd37193 2482 rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
67c583a7 2483 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
64db4cff
PM
2484 return;
2485 }
2486 mask = rdp->grpmask;
2487 if ((rnp->qsmask & mask) == 0) {
67c583a7 2488 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
64db4cff 2489 } else {
bb53e416 2490 rdp->core_needs_qs = false;
64db4cff
PM
2491
2492 /*
2493 * This GP can't end until cpu checks in, so all of our
2494 * callbacks can be processed during the next GP.
2495 */
48a7639c 2496 needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
64db4cff 2497
654e9533
PM
2498 rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags);
2499 /* ^^^ Released rnp->lock */
48a7639c
PM
2500 if (needwake)
2501 rcu_gp_kthread_wake(rsp);
64db4cff
PM
2502 }
2503}
2504
2505/*
2506 * Check to see if there is a new grace period of which this CPU
2507 * is not yet aware, and if so, set up local rcu_data state for it.
2508 * Otherwise, see if this CPU has just passed through its first
2509 * quiescent state for this grace period, and record that fact if so.
2510 */
2511static void
2512rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
2513{
05eb552b
PM
2514 /* Check for grace-period ends and beginnings. */
2515 note_gp_changes(rsp, rdp);
64db4cff
PM
2516
2517 /*
2518 * Does this CPU still need to do its part for current grace period?
2519 * If no, return and let the other CPUs do their part as well.
2520 */
97c668b8 2521 if (!rdp->core_needs_qs)
64db4cff
PM
2522 return;
2523
2524 /*
2525 * Was there a quiescent state since the beginning of the grace
2526 * period? If no, then exit and wait for the next call.
2527 */
5b74c458 2528 if (rdp->cpu_no_qs.b.norm &&
5cd37193 2529 rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr))
64db4cff
PM
2530 return;
2531
d3f6bad3
PM
2532 /*
2533 * Tell RCU we are done (but rcu_report_qs_rdp() will be the
2534 * judge of that).
2535 */
d7d6a11e 2536 rcu_report_qs_rdp(rdp->cpu, rsp, rdp);
64db4cff
PM
2537}
2538
e74f4c45 2539/*
b1420f1c
PM
2540 * Send the specified CPU's RCU callbacks to the orphanage. The
2541 * specified CPU must be offline, and the caller must hold the
7b2e6011 2542 * ->orphan_lock.
e74f4c45 2543 */
b1420f1c
PM
2544static void
2545rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
2546 struct rcu_node *rnp, struct rcu_data *rdp)
e74f4c45 2547{
3fbfbf7a 2548 /* No-CBs CPUs do not have orphanable callbacks. */
ea46351c 2549 if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || rcu_is_nocb_cpu(rdp->cpu))
3fbfbf7a
PM
2550 return;
2551
b1420f1c
PM
2552 /*
2553 * Orphan the callbacks. First adjust the counts. This is safe
abfd6e58
PM
2554 * because _rcu_barrier() excludes CPU-hotplug operations, so it
2555 * cannot be running now. Thus no memory barrier is required.
b1420f1c 2556 */
a50c3af9 2557 if (rdp->nxtlist != NULL) {
b1420f1c
PM
2558 rsp->qlen_lazy += rdp->qlen_lazy;
2559 rsp->qlen += rdp->qlen;
2560 rdp->n_cbs_orphaned += rdp->qlen;
a50c3af9 2561 rdp->qlen_lazy = 0;
7d0ae808 2562 WRITE_ONCE(rdp->qlen, 0);
a50c3af9
PM
2563 }
2564
2565 /*
b1420f1c
PM
2566 * Next, move those callbacks still needing a grace period to
2567 * the orphanage, where some other CPU will pick them up.
2568 * Some of the callbacks might have gone partway through a grace
2569 * period, but that is too bad. They get to start over because we
2570 * cannot assume that grace periods are synchronized across CPUs.
2571 * We don't bother updating the ->nxttail[] array yet, instead
2572 * we just reset the whole thing later on.
a50c3af9 2573 */
b1420f1c
PM
2574 if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) {
2575 *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL];
2576 rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL];
2577 *rdp->nxttail[RCU_DONE_TAIL] = NULL;
a50c3af9
PM
2578 }
2579
2580 /*
b1420f1c
PM
2581 * Then move the ready-to-invoke callbacks to the orphanage,
2582 * where some other CPU will pick them up. These will not be
2583 * required to pass though another grace period: They are done.
a50c3af9 2584 */
e5601400 2585 if (rdp->nxtlist != NULL) {
b1420f1c
PM
2586 *rsp->orphan_donetail = rdp->nxtlist;
2587 rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL];
e5601400 2588 }
e74f4c45 2589
b33078b6
PM
2590 /*
2591 * Finally, initialize the rcu_data structure's list to empty and
2592 * disallow further callbacks on this CPU.
2593 */
3f5d3ea6 2594 init_callback_list(rdp);
b33078b6 2595 rdp->nxttail[RCU_NEXT_TAIL] = NULL;
b1420f1c
PM
2596}
2597
2598/*
2599 * Adopt the RCU callbacks from the specified rcu_state structure's
7b2e6011 2600 * orphanage. The caller must hold the ->orphan_lock.
b1420f1c 2601 */
96d3fd0d 2602static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)
b1420f1c
PM
2603{
2604 int i;
fa07a58f 2605 struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);
b1420f1c 2606
3fbfbf7a 2607 /* No-CBs CPUs are handled specially. */
ea46351c
PM
2608 if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) ||
2609 rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags))
3fbfbf7a
PM
2610 return;
2611
b1420f1c
PM
2612 /* Do the accounting first. */
2613 rdp->qlen_lazy += rsp->qlen_lazy;
2614 rdp->qlen += rsp->qlen;
2615 rdp->n_cbs_adopted += rsp->qlen;
8f5af6f1
PM
2616 if (rsp->qlen_lazy != rsp->qlen)
2617 rcu_idle_count_callbacks_posted();
b1420f1c
PM
2618 rsp->qlen_lazy = 0;
2619 rsp->qlen = 0;
2620
2621 /*
2622 * We do not need a memory barrier here because the only way we
2623 * can get here if there is an rcu_barrier() in flight is if
2624 * we are the task doing the rcu_barrier().
2625 */
2626
2627 /* First adopt the ready-to-invoke callbacks. */
2628 if (rsp->orphan_donelist != NULL) {
2629 *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL];
2630 *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist;
2631 for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--)
2632 if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
2633 rdp->nxttail[i] = rsp->orphan_donetail;
2634 rsp->orphan_donelist = NULL;
2635 rsp->orphan_donetail = &rsp->orphan_donelist;
2636 }
2637
2638 /* And then adopt the callbacks that still need a grace period. */
2639 if (rsp->orphan_nxtlist != NULL) {
2640 *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist;
2641 rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail;
2642 rsp->orphan_nxtlist = NULL;
2643 rsp->orphan_nxttail = &rsp->orphan_nxtlist;
2644 }
2645}
2646
2647/*
2648 * Trace the fact that this CPU is going offline.
2649 */
2650static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
2651{
2652 RCU_TRACE(unsigned long mask);
2653 RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda));
2654 RCU_TRACE(struct rcu_node *rnp = rdp->mynode);
2655
ea46351c
PM
2656 if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
2657 return;
2658
b1420f1c 2659 RCU_TRACE(mask = rdp->grpmask);
e5601400
PM
2660 trace_rcu_grace_period(rsp->name,
2661 rnp->gpnum + 1 - !!(rnp->qsmask & mask),
f7f7bac9 2662 TPS("cpuofl"));
64db4cff
PM
2663}
2664
8af3a5e7
PM
2665/*
2666 * All CPUs for the specified rcu_node structure have gone offline,
2667 * and all tasks that were preempted within an RCU read-side critical
2668 * section while running on one of those CPUs have since exited their RCU
2669 * read-side critical section. Some other CPU is reporting this fact with
2670 * the specified rcu_node structure's ->lock held and interrupts disabled.
2671 * This function therefore goes up the tree of rcu_node structures,
2672 * clearing the corresponding bits in the ->qsmaskinit fields. Note that
2673 * the leaf rcu_node structure's ->qsmaskinit field has already been
2674 * updated
2675 *
2676 * This function does check that the specified rcu_node structure has
2677 * all CPUs offline and no blocked tasks, so it is OK to invoke it
2678 * prematurely. That said, invoking it after the fact will cost you
2679 * a needless lock acquisition. So once it has done its work, don't
2680 * invoke it again.
2681 */
2682static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
2683{
2684 long mask;
2685 struct rcu_node *rnp = rnp_leaf;
2686
ea46351c
PM
2687 if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) ||
2688 rnp->qsmaskinit || rcu_preempt_has_tasks(rnp))
8af3a5e7
PM
2689 return;
2690 for (;;) {
2691 mask = rnp->grpmask;
2692 rnp = rnp->parent;
2693 if (!rnp)
2694 break;
2a67e741 2695 raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
8af3a5e7 2696 rnp->qsmaskinit &= ~mask;
0aa04b05 2697 rnp->qsmask &= ~mask;
8af3a5e7 2698 if (rnp->qsmaskinit) {
67c583a7
BF
2699 raw_spin_unlock_rcu_node(rnp);
2700 /* irqs remain disabled. */
8af3a5e7
PM
2701 return;
2702 }
67c583a7 2703 raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
8af3a5e7
PM
2704 }
2705}
2706
64db4cff 2707/*
e5601400 2708 * The CPU has been completely removed, and some other CPU is reporting
b1420f1c
PM
2709 * this fact from process context. Do the remainder of the cleanup,
2710 * including orphaning the outgoing CPU's RCU callbacks, and also
1331e7a1
PM
2711 * adopting them. There can only be one CPU hotplug operation at a time,
2712 * so no other CPU can be attempting to update rcu_cpu_kthread_task.
64db4cff 2713 */
e5601400 2714static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
64db4cff 2715{
2036d94a 2716 unsigned long flags;
e5601400 2717 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
b1420f1c 2718 struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
e5601400 2719
ea46351c
PM
2720 if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
2721 return;
2722
2036d94a 2723 /* Adjust any no-longer-needed kthreads. */
5d01bbd1 2724 rcu_boost_kthread_setaffinity(rnp, -1);
2036d94a 2725
b1420f1c 2726 /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
78043c46 2727 raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
b1420f1c 2728 rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
96d3fd0d 2729 rcu_adopt_orphan_cbs(rsp, flags);
a8f4cbad 2730 raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags);
b1420f1c 2731
cf01537e
PM
2732 WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
2733 "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
2734 cpu, rdp->qlen, rdp->nxtlist);
64db4cff
PM
2735}
2736
64db4cff
PM
2737/*
2738 * Invoke any RCU callbacks that have made it to the end of their grace
2739 * period. Thottle as specified by rdp->blimit.
2740 */
37c72e56 2741static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
64db4cff
PM
2742{
2743 unsigned long flags;
2744 struct rcu_head *next, *list, **tail;
878d7439
ED
2745 long bl, count, count_lazy;
2746 int i;
64db4cff 2747
dc35c893 2748 /* If no callbacks are ready, just return. */
29c00b4a 2749 if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
486e2593 2750 trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0);
7d0ae808 2751 trace_rcu_batch_end(rsp->name, 0, !!READ_ONCE(rdp->nxtlist),
4968c300
PM
2752 need_resched(), is_idle_task(current),
2753 rcu_is_callbacks_kthread());
64db4cff 2754 return;
29c00b4a 2755 }
64db4cff
PM
2756
2757 /*
2758 * Extract the list of ready callbacks, disabling to prevent
2759 * races with call_rcu() from interrupt handlers.
2760 */
2761 local_irq_save(flags);
8146c4e2 2762 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
29c00b4a 2763 bl = rdp->blimit;
486e2593 2764 trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
64db4cff
PM
2765 list = rdp->nxtlist;
2766 rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
2767 *rdp->nxttail[RCU_DONE_TAIL] = NULL;
2768 tail = rdp->nxttail[RCU_DONE_TAIL];
b41772ab
PM
2769 for (i = RCU_NEXT_SIZE - 1; i >= 0; i--)
2770 if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
2771 rdp->nxttail[i] = &rdp->nxtlist;
64db4cff
PM
2772 local_irq_restore(flags);
2773
2774 /* Invoke callbacks. */
486e2593 2775 count = count_lazy = 0;
64db4cff
PM
2776 while (list) {
2777 next = list->next;
2778 prefetch(next);
551d55a9 2779 debug_rcu_head_unqueue(list);
486e2593
PM
2780 if (__rcu_reclaim(rsp->name, list))
2781 count_lazy++;
64db4cff 2782 list = next;
dff1672d
PM
2783 /* Stop only if limit reached and CPU has something to do. */
2784 if (++count >= bl &&
2785 (need_resched() ||
2786 (!is_idle_task(current) && !rcu_is_callbacks_kthread())))
64db4cff
PM
2787 break;
2788 }
2789
2790 local_irq_save(flags);
4968c300
PM
2791 trace_rcu_batch_end(rsp->name, count, !!list, need_resched(),
2792 is_idle_task(current),
2793 rcu_is_callbacks_kthread());
64db4cff
PM
2794
2795 /* Update count, and requeue any remaining callbacks. */
64db4cff
PM
2796 if (list != NULL) {
2797 *tail = rdp->nxtlist;
2798 rdp->nxtlist = list;
b41772ab
PM
2799 for (i = 0; i < RCU_NEXT_SIZE; i++)
2800 if (&rdp->nxtlist == rdp->nxttail[i])
2801 rdp->nxttail[i] = tail;
64db4cff
PM
2802 else
2803 break;
2804 }
b1420f1c
PM
2805 smp_mb(); /* List handling before counting for rcu_barrier(). */
2806 rdp->qlen_lazy -= count_lazy;
7d0ae808 2807 WRITE_ONCE(rdp->qlen, rdp->qlen - count);
b1420f1c 2808 rdp->n_cbs_invoked += count;
64db4cff
PM
2809
2810 /* Reinstate batch limit if we have worked down the excess. */
2811 if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
2812 rdp->blimit = blimit;
2813
37c72e56
PM
2814 /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
2815 if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
2816 rdp->qlen_last_fqs_check = 0;
2817 rdp->n_force_qs_snap = rsp->n_force_qs;
2818 } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
2819 rdp->qlen_last_fqs_check = rdp->qlen;
cfca9279 2820 WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0));
37c72e56 2821
64db4cff
PM
2822 local_irq_restore(flags);
2823
e0f23060 2824 /* Re-invoke RCU core processing if there are callbacks remaining. */
64db4cff 2825 if (cpu_has_callbacks_ready_to_invoke(rdp))
a46e0899 2826 invoke_rcu_core();
64db4cff
PM
2827}
2828
2829/*
2830 * Check to see if this CPU is in a non-context-switch quiescent state
2831 * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
e0f23060 2832 * Also schedule RCU core processing.
64db4cff 2833 *
9b2e4f18 2834 * This function must be called from hardirq context. It is normally
5403d367 2835 * invoked from the scheduling-clock interrupt.
64db4cff 2836 */
c3377c2d 2837void rcu_check_callbacks(int user)
64db4cff 2838{
f7f7bac9 2839 trace_rcu_utilization(TPS("Start scheduler-tick"));
a858af28 2840 increment_cpu_stall_ticks();
9b2e4f18 2841 if (user || rcu_is_cpu_rrupt_from_idle()) {
64db4cff
PM
2842
2843 /*
2844 * Get here if this CPU took its interrupt from user
2845 * mode or from the idle loop, and if this is not a
2846 * nested interrupt. In this case, the CPU is in
d6714c22 2847 * a quiescent state, so note it.
64db4cff
PM
2848 *
2849 * No memory barrier is required here because both
d6714c22
PM
2850 * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
2851 * variables that other CPUs neither access nor modify,
2852 * at least not while the corresponding CPU is online.
64db4cff
PM
2853 */
2854
284a8c93
PM
2855 rcu_sched_qs();
2856 rcu_bh_qs();
64db4cff
PM
2857
2858 } else if (!in_softirq()) {
2859
2860 /*
2861 * Get here if this CPU did not take its interrupt from
2862 * softirq, in other words, if it is not interrupting
2863 * a rcu_bh read-side critical section. This is an _bh
d6714c22 2864 * critical section, so note it.
64db4cff
PM
2865 */
2866
284a8c93 2867 rcu_bh_qs();
64db4cff 2868 }
86aea0e6 2869 rcu_preempt_check_callbacks();
e3950ecd 2870 if (rcu_pending())
a46e0899 2871 invoke_rcu_core();
8315f422
PM
2872 if (user)
2873 rcu_note_voluntary_context_switch(current);
f7f7bac9 2874 trace_rcu_utilization(TPS("End scheduler-tick"));
64db4cff
PM
2875}
2876
64db4cff
PM
2877/*
2878 * Scan the leaf rcu_node structures, processing dyntick state for any that
2879 * have not yet encountered a quiescent state, using the function specified.
27f4d280
PM
2880 * Also initiate boosting for any threads blocked on the root rcu_node.
2881 *
ee47eb9f 2882 * The caller must have suppressed start of new grace periods.
64db4cff 2883 */
217af2a2
PM
2884static void force_qs_rnp(struct rcu_state *rsp,
2885 int (*f)(struct rcu_data *rsp, bool *isidle,
2886 unsigned long *maxj),
2887 bool *isidle, unsigned long *maxj)
64db4cff 2888{
64db4cff
PM
2889 int cpu;
2890 unsigned long flags;
2891 unsigned long mask;
a0b6c9a7 2892 struct rcu_node *rnp;
64db4cff 2893
a0b6c9a7 2894 rcu_for_each_leaf_node(rsp, rnp) {
bde6c3aa 2895 cond_resched_rcu_qs();
64db4cff 2896 mask = 0;
2a67e741 2897 raw_spin_lock_irqsave_rcu_node(rnp, flags);
a0b6c9a7 2898 if (rnp->qsmask == 0) {
a77da14c
PM
2899 if (rcu_state_p == &rcu_sched_state ||
2900 rsp != rcu_state_p ||
2901 rcu_preempt_blocked_readers_cgp(rnp)) {
2902 /*
2903 * No point in scanning bits because they
2904 * are all zero. But we might need to
2905 * priority-boost blocked readers.
2906 */
2907 rcu_initiate_boost(rnp, flags);
2908 /* rcu_initiate_boost() releases rnp->lock */
2909 continue;
2910 }
2911 if (rnp->parent &&
2912 (rnp->parent->qsmask & rnp->grpmask)) {
2913 /*
2914 * Race between grace-period
2915 * initialization and task exiting RCU
2916 * read-side critical section: Report.
2917 */
2918 rcu_report_unblock_qs_rnp(rsp, rnp, flags);
2919 /* rcu_report_unblock_qs_rnp() rlses ->lock */
2920 continue;
2921 }
64db4cff 2922 }
bc75e999
MR
2923 for_each_leaf_node_possible_cpu(rnp, cpu) {
2924 unsigned long bit = leaf_node_cpu_bit(rnp, cpu);
0edd1b17 2925 if ((rnp->qsmask & bit) != 0) {
0edd1b17
PM
2926 if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj))
2927 mask |= bit;
2928 }
64db4cff 2929 }
45f014c5 2930 if (mask != 0) {
654e9533
PM
2931 /* Idle/offline CPUs, report (releases rnp->lock. */
2932 rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags);
0aa04b05
PM
2933 } else {
2934 /* Nothing to do here, so just drop the lock. */
67c583a7 2935 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
64db4cff 2936 }
64db4cff 2937 }
64db4cff
PM
2938}
2939
2940/*
2941 * Force quiescent states on reluctant CPUs, and also detect which
2942 * CPUs are in dyntick-idle mode.
2943 */
4cdfc175 2944static void force_quiescent_state(struct rcu_state *rsp)
64db4cff
PM
2945{
2946 unsigned long flags;
394f2769
PM
2947 bool ret;
2948 struct rcu_node *rnp;
2949 struct rcu_node *rnp_old = NULL;
2950
2951 /* Funnel through hierarchy to reduce memory contention. */
d860d403 2952 rnp = __this_cpu_read(rsp->rda->mynode);
394f2769 2953 for (; rnp != NULL; rnp = rnp->parent) {
7d0ae808 2954 ret = (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) ||
394f2769
PM
2955 !raw_spin_trylock(&rnp->fqslock);
2956 if (rnp_old != NULL)
2957 raw_spin_unlock(&rnp_old->fqslock);
2958 if (ret) {
a792563b 2959 rsp->n_force_qs_lh++;
394f2769
PM
2960 return;
2961 }
2962 rnp_old = rnp;
2963 }
2964 /* rnp_old == rcu_get_root(rsp), rnp == NULL. */
64db4cff 2965
394f2769 2966 /* Reached the root of the rcu_node tree, acquire lock. */
2a67e741 2967 raw_spin_lock_irqsave_rcu_node(rnp_old, flags);
394f2769 2968 raw_spin_unlock(&rnp_old->fqslock);
7d0ae808 2969 if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
a792563b 2970 rsp->n_force_qs_lh++;
67c583a7 2971 raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
4cdfc175 2972 return; /* Someone beat us to it. */
46a1e34e 2973 }
7d0ae808 2974 WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS);
67c583a7 2975 raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
94d44776 2976 rcu_gp_kthread_wake(rsp);
64db4cff
PM
2977}
2978
64db4cff 2979/*
e0f23060
PM
2980 * This does the RCU core processing work for the specified rcu_state
2981 * and rcu_data structures. This may be called only from the CPU to
2982 * whom the rdp belongs.
64db4cff
PM
2983 */
2984static void
1bca8cf1 2985__rcu_process_callbacks(struct rcu_state *rsp)
64db4cff
PM
2986{
2987 unsigned long flags;
48a7639c 2988 bool needwake;
fa07a58f 2989 struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);
64db4cff 2990
2e597558
PM
2991 WARN_ON_ONCE(rdp->beenonline == 0);
2992
64db4cff
PM
2993 /* Update RCU state based on any recent quiescent states. */
2994 rcu_check_quiescent_state(rsp, rdp);
2995
2996 /* Does this CPU require a not-yet-started grace period? */
dc35c893 2997 local_irq_save(flags);
64db4cff 2998 if (cpu_needs_another_gp(rsp, rdp)) {
6cf10081 2999 raw_spin_lock_rcu_node(rcu_get_root(rsp)); /* irqs disabled. */
48a7639c 3000 needwake = rcu_start_gp(rsp);
67c583a7 3001 raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(rsp), flags);
48a7639c
PM
3002 if (needwake)
3003 rcu_gp_kthread_wake(rsp);
dc35c893
PM
3004 } else {
3005 local_irq_restore(flags);
64db4cff
PM
3006 }
3007
3008 /* If there are callbacks ready, invoke them. */
09223371 3009 if (cpu_has_callbacks_ready_to_invoke(rdp))
a46e0899 3010 invoke_rcu_callbacks(rsp, rdp);
96d3fd0d
PM
3011
3012 /* Do any needed deferred wakeups of rcuo kthreads. */
3013 do_nocb_deferred_wakeup(rdp);
09223371
SL
3014}
3015
64db4cff 3016/*
e0f23060 3017 * Do RCU core processing for the current CPU.
64db4cff 3018 */
0766f788 3019static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
64db4cff 3020{
6ce75a23
PM
3021 struct rcu_state *rsp;
3022
bfa00b4c
PM
3023 if (cpu_is_offline(smp_processor_id()))
3024 return;
f7f7bac9 3025 trace_rcu_utilization(TPS("Start RCU core"));
6ce75a23
PM
3026 for_each_rcu_flavor(rsp)
3027 __rcu_process_callbacks(rsp);
f7f7bac9 3028 trace_rcu_utilization(TPS("End RCU core"));
64db4cff
PM
3029}
3030
a26ac245 3031/*
e0f23060
PM
3032 * Schedule RCU callback invocation. If the specified type of RCU
3033 * does not support RCU priority boosting, just do a direct call,
3034 * otherwise wake up the per-CPU kernel kthread. Note that because we
924df8a0 3035 * are running on the current CPU with softirqs disabled, the
e0f23060 3036 * rcu_cpu_kthread_task cannot disappear out from under us.
a26ac245 3037 */
a46e0899 3038static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
a26ac245 3039{
7d0ae808 3040 if (unlikely(!READ_ONCE(rcu_scheduler_fully_active)))
b0d30417 3041 return;
a46e0899
PM
3042 if (likely(!rsp->boost)) {
3043 rcu_do_batch(rsp, rdp);
a26ac245
PM
3044 return;
3045 }
a46e0899 3046 invoke_rcu_callbacks_kthread();
a26ac245
PM
3047}
3048
a46e0899 3049static void invoke_rcu_core(void)
09223371 3050{
b0f74036
PM
3051 if (cpu_online(smp_processor_id()))
3052 raise_softirq(RCU_SOFTIRQ);
09223371
SL
3053}
3054
29154c57
PM
3055/*
3056 * Handle any core-RCU processing required by a call_rcu() invocation.
3057 */
3058static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
3059 struct rcu_head *head, unsigned long flags)
64db4cff 3060{
48a7639c
PM
3061 bool needwake;
3062
62fde6ed
PM
3063 /*
3064 * If called from an extended quiescent state, invoke the RCU
3065 * core in order to force a re-evaluation of RCU's idleness.
3066 */
9910affa 3067 if (!rcu_is_watching())
62fde6ed
PM
3068 invoke_rcu_core();
3069
a16b7a69 3070 /* If interrupts were disabled or CPU offline, don't invoke RCU core. */
29154c57 3071 if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id()))
2655d57e 3072 return;
64db4cff 3073
37c72e56
PM
3074 /*
3075 * Force the grace period if too many callbacks or too long waiting.
3076 * Enforce hysteresis, and don't invoke force_quiescent_state()
3077 * if some other CPU has recently done so. Also, don't bother
3078 * invoking force_quiescent_state() if the newly enqueued callback
3079 * is the only one waiting for a grace period to complete.
3080 */
2655d57e 3081 if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
b52573d2
PM
3082
3083 /* Are we ignoring a completed grace period? */
470716fc 3084 note_gp_changes(rsp, rdp);
b52573d2
PM
3085
3086 /* Start a new grace period if one not already started. */
3087 if (!rcu_gp_in_progress(rsp)) {
b52573d2
PM
3088 struct rcu_node *rnp_root = rcu_get_root(rsp);
3089
2a67e741 3090 raw_spin_lock_rcu_node(rnp_root);
48a7639c 3091 needwake = rcu_start_gp(rsp);
67c583a7 3092 raw_spin_unlock_rcu_node(rnp_root);
48a7639c
PM
3093 if (needwake)
3094 rcu_gp_kthread_wake(rsp);
b52573d2
PM
3095 } else {
3096 /* Give the grace period a kick. */
3097 rdp->blimit = LONG_MAX;
3098 if (rsp->n_force_qs == rdp->n_force_qs_snap &&
3099 *rdp->nxttail[RCU_DONE_TAIL] != head)
4cdfc175 3100 force_quiescent_state(rsp);
b52573d2
PM
3101 rdp->n_force_qs_snap = rsp->n_force_qs;
3102 rdp->qlen_last_fqs_check = rdp->qlen;
3103 }
4cdfc175 3104 }
29154c57
PM
3105}
3106
ae150184
PM
3107/*
3108 * RCU callback function to leak a callback.
3109 */
3110static void rcu_leak_callback(struct rcu_head *rhp)
3111{
3112}
3113
3fbfbf7a
PM
3114/*
3115 * Helper function for call_rcu() and friends. The cpu argument will
3116 * normally be -1, indicating "currently running CPU". It may specify
3117 * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier()
3118 * is expected to specify a CPU.
3119 */
64db4cff 3120static void
b6a4ae76 3121__call_rcu(struct rcu_head *head, rcu_callback_t func,
3fbfbf7a 3122 struct rcu_state *rsp, int cpu, bool lazy)
64db4cff
PM
3123{
3124 unsigned long flags;
3125 struct rcu_data *rdp;
3126
b8f2ed53
PM
3127 /* Misaligned rcu_head! */
3128 WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1));
3129
ae150184
PM
3130 if (debug_rcu_head_queue(head)) {
3131 /* Probable double call_rcu(), so leak the callback. */
7d0ae808 3132 WRITE_ONCE(head->func, rcu_leak_callback);
ae150184
PM
3133 WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n");
3134 return;
3135 }
64db4cff
PM
3136 head->func = func;
3137 head->next = NULL;
64db4cff 3138 local_irq_save(flags);
394f99a9 3139 rdp = this_cpu_ptr(rsp->rda);
64db4cff
PM
3140
3141 /* Add the callback to our list. */
3fbfbf7a
PM
3142 if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) {
3143 int offline;
3144
3145 if (cpu != -1)
3146 rdp = per_cpu_ptr(rsp->rda, cpu);
143da9c2
PM
3147 if (likely(rdp->mynode)) {
3148 /* Post-boot, so this should be for a no-CBs CPU. */
3149 offline = !__call_rcu_nocb(rdp, head, lazy, flags);
3150 WARN_ON_ONCE(offline);
3151 /* Offline CPU, _call_rcu() illegal, leak callback. */
3152 local_irq_restore(flags);
3153 return;
3154 }
3155 /*
3156 * Very early boot, before rcu_init(). Initialize if needed
3157 * and then drop through to queue the callback.
3158 */
3159 BUG_ON(cpu != -1);
34404ca8 3160 WARN_ON_ONCE(!rcu_is_watching());
143da9c2
PM
3161 if (!likely(rdp->nxtlist))
3162 init_default_callback_list(rdp);
0d8ee37e 3163 }
7d0ae808 3164 WRITE_ONCE(rdp->qlen, rdp->qlen + 1);
486e2593
PM
3165 if (lazy)
3166 rdp->qlen_lazy++;
c57afe80
PM
3167 else
3168 rcu_idle_count_callbacks_posted();
b1420f1c
PM
3169 smp_mb(); /* Count before adding callback for rcu_barrier(). */
3170 *rdp->nxttail[RCU_NEXT_TAIL] = head;
3171 rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
2655d57e 3172
d4c08f2a
PM
3173 if (__is_kfree_rcu_offset((unsigned long)func))
3174 trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
486e2593 3175 rdp->qlen_lazy, rdp->qlen);
d4c08f2a 3176 else
486e2593 3177 trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
d4c08f2a 3178
29154c57
PM
3179 /* Go handle any RCU core processing required. */
3180 __call_rcu_core(rsp, rdp, head, flags);
64db4cff
PM
3181 local_irq_restore(flags);
3182}
3183
3184/*
d6714c22 3185 * Queue an RCU-sched callback for invocation after a grace period.
64db4cff 3186 */
b6a4ae76 3187void call_rcu_sched(struct rcu_head *head, rcu_callback_t func)
64db4cff 3188{
3fbfbf7a 3189 __call_rcu(head, func, &rcu_sched_state, -1, 0);
64db4cff 3190}
d6714c22 3191EXPORT_SYMBOL_GPL(call_rcu_sched);
64db4cff
PM
3192
3193/*
486e2593 3194 * Queue an RCU callback for invocation after a quicker grace period.
64db4cff 3195 */
b6a4ae76 3196void call_rcu_bh(struct rcu_head *head, rcu_callback_t func)
64db4cff 3197{
3fbfbf7a 3198 __call_rcu(head, func, &rcu_bh_state, -1, 0);
64db4cff
PM
3199}
3200EXPORT_SYMBOL_GPL(call_rcu_bh);
3201
495aa969
ACB
3202/*
3203 * Queue an RCU callback for lazy invocation after a grace period.
3204 * This will likely be later named something like "call_rcu_lazy()",
3205 * but this change will require some way of tagging the lazy RCU
3206 * callbacks in the list of pending callbacks. Until then, this
3207 * function may only be called from __kfree_rcu().
3208 */
3209void kfree_call_rcu(struct rcu_head *head,
b6a4ae76 3210 rcu_callback_t func)
495aa969 3211{
e534165b 3212 __call_rcu(head, func, rcu_state_p, -1, 1);
495aa969
ACB
3213}
3214EXPORT_SYMBOL_GPL(kfree_call_rcu);
3215
6d813391
PM
3216/*
3217 * Because a context switch is a grace period for RCU-sched and RCU-bh,
3218 * any blocking grace-period wait automatically implies a grace period
3219 * if there is only one CPU online at any point time during execution
3220 * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
3221 * occasionally incorrectly indicate that there are multiple CPUs online
3222 * when there was in fact only one the whole time, as this just adds
3223 * some overhead: RCU still operates correctly.
6d813391
PM
3224 */
3225static inline int rcu_blocking_is_gp(void)
3226{
95f0c1de
PM
3227 int ret;
3228
6d813391 3229 might_sleep(); /* Check for RCU read-side critical section. */
95f0c1de
PM
3230 preempt_disable();
3231 ret = num_online_cpus() <= 1;
3232 preempt_enable();
3233 return ret;
6d813391
PM
3234}
3235
6ebb237b
PM
3236/**
3237 * synchronize_sched - wait until an rcu-sched grace period has elapsed.
3238 *
3239 * Control will return to the caller some time after a full rcu-sched
3240 * grace period has elapsed, in other words after all currently executing
3241 * rcu-sched read-side critical sections have completed. These read-side
3242 * critical sections are delimited by rcu_read_lock_sched() and
3243 * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
3244 * local_irq_disable(), and so on may be used in place of
3245 * rcu_read_lock_sched().
3246 *
3247 * This means that all preempt_disable code sequences, including NMI and
f0a0e6f2
PM
3248 * non-threaded hardware-interrupt handlers, in progress on entry will
3249 * have completed before this primitive returns. However, this does not
3250 * guarantee that softirq handlers will have completed, since in some
3251 * kernels, these handlers can run in process context, and can block.
3252 *
3253 * Note that this guarantee implies further memory-ordering guarantees.
3254 * On systems with more than one CPU, when synchronize_sched() returns,
3255 * each CPU is guaranteed to have executed a full memory barrier since the
3256 * end of its last RCU-sched read-side critical section whose beginning
3257 * preceded the call to synchronize_sched(). In addition, each CPU having
3258 * an RCU read-side critical section that extends beyond the return from
3259 * synchronize_sched() is guaranteed to have executed a full memory barrier
3260 * after the beginning of synchronize_sched() and before the beginning of
3261 * that RCU read-side critical section. Note that these guarantees include
3262 * CPUs that are offline, idle, or executing in user mode, as well as CPUs
3263 * that are executing in the kernel.
3264 *
3265 * Furthermore, if CPU A invoked synchronize_sched(), which returned
3266 * to its caller on CPU B, then both CPU A and CPU B are guaranteed
3267 * to have executed a full memory barrier during the execution of
3268 * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but
3269 * again only if the system has more than one CPU).
6ebb237b
PM
3270 *
3271 * This primitive provides the guarantees made by the (now removed)
3272 * synchronize_kernel() API. In contrast, synchronize_rcu() only
3273 * guarantees that rcu_read_lock() sections will have completed.
3274 * In "classic RCU", these two guarantees happen to be one and
3275 * the same, but can differ in realtime RCU implementations.
3276 */
3277void synchronize_sched(void)
3278{
f78f5b90
PM
3279 RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
3280 lock_is_held(&rcu_lock_map) ||
3281 lock_is_held(&rcu_sched_lock_map),
3282 "Illegal synchronize_sched() in RCU-sched read-side critical section");
6ebb237b
PM
3283 if (rcu_blocking_is_gp())
3284 return;
5afff48b 3285 if (rcu_gp_is_expedited())
3705b88d
AM
3286 synchronize_sched_expedited();
3287 else
3288 wait_rcu_gp(call_rcu_sched);
6ebb237b
PM
3289}
3290EXPORT_SYMBOL_GPL(synchronize_sched);
3291
3292/**
3293 * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
3294 *
3295 * Control will return to the caller some time after a full rcu_bh grace
3296 * period has elapsed, in other words after all currently executing rcu_bh
3297 * read-side critical sections have completed. RCU read-side critical
3298 * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
3299 * and may be nested.
f0a0e6f2
PM
3300 *
3301 * See the description of synchronize_sched() for more detailed information
3302 * on memory ordering guarantees.
6ebb237b
PM
3303 */
3304void synchronize_rcu_bh(void)
3305{
f78f5b90
PM
3306 RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
3307 lock_is_held(&rcu_lock_map) ||
3308 lock_is_held(&rcu_sched_lock_map),
3309 "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
6ebb237b
PM
3310 if (rcu_blocking_is_gp())
3311 return;
5afff48b 3312 if (rcu_gp_is_expedited())
3705b88d
AM
3313 synchronize_rcu_bh_expedited();
3314 else
3315 wait_rcu_gp(call_rcu_bh);
6ebb237b
PM
3316}
3317EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
3318
765a3f4f
PM
3319/**
3320 * get_state_synchronize_rcu - Snapshot current RCU state
3321 *
3322 * Returns a cookie that is used by a later call to cond_synchronize_rcu()
3323 * to determine whether or not a full grace period has elapsed in the
3324 * meantime.
3325 */
3326unsigned long get_state_synchronize_rcu(void)
3327{
3328 /*
3329 * Any prior manipulation of RCU-protected data must happen
3330 * before the load from ->gpnum.
3331 */
3332 smp_mb(); /* ^^^ */
3333
3334 /*
3335 * Make sure this load happens before the purportedly
3336 * time-consuming work between get_state_synchronize_rcu()
3337 * and cond_synchronize_rcu().
3338 */
e534165b 3339 return smp_load_acquire(&rcu_state_p->gpnum);
765a3f4f
PM
3340}
3341EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
3342
3343/**
3344 * cond_synchronize_rcu - Conditionally wait for an RCU grace period
3345 *
3346 * @oldstate: return value from earlier call to get_state_synchronize_rcu()
3347 *
3348 * If a full RCU grace period has elapsed since the earlier call to
3349 * get_state_synchronize_rcu(), just return. Otherwise, invoke
3350 * synchronize_rcu() to wait for a full grace period.
3351 *
3352 * Yes, this function does not take counter wrap into account. But
3353 * counter wrap is harmless. If the counter wraps, we have waited for
3354 * more than 2 billion grace periods (and way more on a 64-bit system!),
3355 * so waiting for one additional grace period should be just fine.
3356 */
3357void cond_synchronize_rcu(unsigned long oldstate)
3358{
3359 unsigned long newstate;
3360
3361 /*
3362 * Ensure that this load happens before any RCU-destructive
3363 * actions the caller might carry out after we return.
3364 */
e534165b 3365 newstate = smp_load_acquire(&rcu_state_p->completed);
765a3f4f
PM
3366 if (ULONG_CMP_GE(oldstate, newstate))
3367 synchronize_rcu();
3368}
3369EXPORT_SYMBOL_GPL(cond_synchronize_rcu);
3370
24560056
PM
3371/**
3372 * get_state_synchronize_sched - Snapshot current RCU-sched state
3373 *
3374 * Returns a cookie that is used by a later call to cond_synchronize_sched()
3375 * to determine whether or not a full grace period has elapsed in the
3376 * meantime.
3377 */
3378unsigned long get_state_synchronize_sched(void)
3379{
3380 /*
3381 * Any prior manipulation of RCU-protected data must happen
3382 * before the load from ->gpnum.
3383 */
3384 smp_mb(); /* ^^^ */
3385
3386 /*
3387 * Make sure this load happens before the purportedly
3388 * time-consuming work between get_state_synchronize_sched()
3389 * and cond_synchronize_sched().
3390 */
3391 return smp_load_acquire(&rcu_sched_state.gpnum);
3392}
3393EXPORT_SYMBOL_GPL(get_state_synchronize_sched);
3394
3395/**
3396 * cond_synchronize_sched - Conditionally wait for an RCU-sched grace period
3397 *
3398 * @oldstate: return value from earlier call to get_state_synchronize_sched()
3399 *
3400 * If a full RCU-sched grace period has elapsed since the earlier call to
3401 * get_state_synchronize_sched(), just return. Otherwise, invoke
3402 * synchronize_sched() to wait for a full grace period.
3403 *
3404 * Yes, this function does not take counter wrap into account. But
3405 * counter wrap is harmless. If the counter wraps, we have waited for
3406 * more than 2 billion grace periods (and way more on a 64-bit system!),
3407 * so waiting for one additional grace period should be just fine.
3408 */
3409void cond_synchronize_sched(unsigned long oldstate)
3410{
3411 unsigned long newstate;
3412
3413 /*
3414 * Ensure that this load happens before any RCU-destructive
3415 * actions the caller might carry out after we return.
3416 */
3417 newstate = smp_load_acquire(&rcu_sched_state.completed);
3418 if (ULONG_CMP_GE(oldstate, newstate))
3419 synchronize_sched();
3420}
3421EXPORT_SYMBOL_GPL(cond_synchronize_sched);
3422
28f00767
PM
3423/* Adjust sequence number for start of update-side operation. */
3424static void rcu_seq_start(unsigned long *sp)
3425{
3426 WRITE_ONCE(*sp, *sp + 1);
3427 smp_mb(); /* Ensure update-side operation after counter increment. */
3428 WARN_ON_ONCE(!(*sp & 0x1));
3429}
3430
3431/* Adjust sequence number for end of update-side operation. */
3432static void rcu_seq_end(unsigned long *sp)
3433{
3434 smp_mb(); /* Ensure update-side operation before counter increment. */
3435 WRITE_ONCE(*sp, *sp + 1);
3436 WARN_ON_ONCE(*sp & 0x1);
3437}
3438
3439/* Take a snapshot of the update side's sequence number. */
3440static unsigned long rcu_seq_snap(unsigned long *sp)
3441{
3442 unsigned long s;
3443
28f00767
PM
3444 s = (READ_ONCE(*sp) + 3) & ~0x1;
3445 smp_mb(); /* Above access must not bleed into critical section. */
3446 return s;
3447}
3448
3449/*
3450 * Given a snapshot from rcu_seq_snap(), determine whether or not a
3451 * full update-side operation has occurred.
3452 */
3453static bool rcu_seq_done(unsigned long *sp, unsigned long s)
3454{
3455 return ULONG_CMP_GE(READ_ONCE(*sp), s);
3456}
3457
64db4cff
PM
3458/*
3459 * Check to see if there is any immediate RCU-related work to be done
3460 * by the current CPU, for the specified type of RCU, returning 1 if so.
3461 * The checks are in order of increasing expense: checks that can be
3462 * carried out against CPU-local state are performed first. However,
3463 * we must check for CPU stalls first, else we might not get a chance.
3464 */
3465static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
3466{
2f51f988
PM
3467 struct rcu_node *rnp = rdp->mynode;
3468
64db4cff
PM
3469 rdp->n_rcu_pending++;
3470
3471 /* Check for CPU stalls, if enabled. */
3472 check_cpu_stall(rsp, rdp);
3473
a096932f
PM
3474 /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */
3475 if (rcu_nohz_full_cpu(rsp))
3476 return 0;
3477
64db4cff 3478 /* Is the RCU core waiting for a quiescent state from this CPU? */
5c51dd73 3479 if (rcu_scheduler_fully_active &&
5b74c458 3480 rdp->core_needs_qs && rdp->cpu_no_qs.b.norm &&
5cd37193 3481 rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) {
97c668b8
PM
3482 rdp->n_rp_core_needs_qs++;
3483 } else if (rdp->core_needs_qs &&
5b74c458 3484 (!rdp->cpu_no_qs.b.norm ||
5cd37193 3485 rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) {
d21670ac 3486 rdp->n_rp_report_qs++;
64db4cff 3487 return 1;
7ba5c840 3488 }
64db4cff
PM
3489
3490 /* Does this CPU have callbacks ready to invoke? */
7ba5c840
PM
3491 if (cpu_has_callbacks_ready_to_invoke(rdp)) {
3492 rdp->n_rp_cb_ready++;
64db4cff 3493 return 1;
7ba5c840 3494 }
64db4cff
PM
3495
3496 /* Has RCU gone idle with this CPU needing another grace period? */
7ba5c840
PM
3497 if (cpu_needs_another_gp(rsp, rdp)) {
3498 rdp->n_rp_cpu_needs_gp++;
64db4cff 3499 return 1;
7ba5c840 3500 }
64db4cff
PM
3501
3502 /* Has another RCU grace period completed? */
7d0ae808 3503 if (READ_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
7ba5c840 3504 rdp->n_rp_gp_completed++;
64db4cff 3505 return 1;
7ba5c840 3506 }
64db4cff
PM
3507
3508 /* Has a new RCU grace period started? */
7d0ae808
PM
3509 if (READ_ONCE(rnp->gpnum) != rdp->gpnum ||
3510 unlikely(READ_ONCE(rdp->gpwrap))) { /* outside lock */
7ba5c840 3511 rdp->n_rp_gp_started++;
64db4cff 3512 return 1;
7ba5c840 3513 }
64db4cff 3514
96d3fd0d
PM
3515 /* Does this CPU need a deferred NOCB wakeup? */
3516 if (rcu_nocb_need_deferred_wakeup(rdp)) {
3517 rdp->n_rp_nocb_defer_wakeup++;
3518 return 1;
3519 }
3520
64db4cff 3521 /* nothing to do */
7ba5c840 3522 rdp->n_rp_need_nothing++;
64db4cff
PM
3523 return 0;
3524}
3525
3526/*
3527 * Check to see if there is any immediate RCU-related work to be done
3528 * by the current CPU, returning 1 if so. This function is part of the
3529 * RCU implementation; it is -not- an exported member of the RCU API.
3530 */
e3950ecd 3531static int rcu_pending(void)
64db4cff 3532{
6ce75a23
PM
3533 struct rcu_state *rsp;
3534
3535 for_each_rcu_flavor(rsp)
e3950ecd 3536 if (__rcu_pending(rsp, this_cpu_ptr(rsp->rda)))
6ce75a23
PM
3537 return 1;
3538 return 0;
64db4cff
PM
3539}
3540
3541/*
c0f4dfd4
PM
3542 * Return true if the specified CPU has any callback. If all_lazy is
3543 * non-NULL, store an indication of whether all callbacks are lazy.
3544 * (If there are no callbacks, all of them are deemed to be lazy.)
64db4cff 3545 */
82072c4f 3546static bool __maybe_unused rcu_cpu_has_callbacks(bool *all_lazy)
64db4cff 3547{
c0f4dfd4
PM
3548 bool al = true;
3549 bool hc = false;
3550 struct rcu_data *rdp;
6ce75a23
PM
3551 struct rcu_state *rsp;
3552
c0f4dfd4 3553 for_each_rcu_flavor(rsp) {
aa6da514 3554 rdp = this_cpu_ptr(rsp->rda);
69c8d28c
PM
3555 if (!rdp->nxtlist)
3556 continue;
3557 hc = true;
3558 if (rdp->qlen != rdp->qlen_lazy || !all_lazy) {
c0f4dfd4 3559 al = false;
69c8d28c
PM
3560 break;
3561 }
c0f4dfd4
PM
3562 }
3563 if (all_lazy)
3564 *all_lazy = al;
3565 return hc;
64db4cff
PM
3566}
3567
a83eff0a
PM
3568/*
3569 * Helper function for _rcu_barrier() tracing. If tracing is disabled,
3570 * the compiler is expected to optimize this away.
3571 */
e66c33d5 3572static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s,
a83eff0a
PM
3573 int cpu, unsigned long done)
3574{
3575 trace_rcu_barrier(rsp->name, s, cpu,
3576 atomic_read(&rsp->barrier_cpu_count), done);
3577}
3578
b1420f1c
PM
3579/*
3580 * RCU callback function for _rcu_barrier(). If we are last, wake
3581 * up the task executing _rcu_barrier().
3582 */
24ebbca8 3583static void rcu_barrier_callback(struct rcu_head *rhp)
d0ec774c 3584{
24ebbca8
PM
3585 struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head);
3586 struct rcu_state *rsp = rdp->rsp;
3587
a83eff0a 3588 if (atomic_dec_and_test(&rsp->barrier_cpu_count)) {
4f525a52 3589 _rcu_barrier_trace(rsp, "LastCB", -1, rsp->barrier_sequence);
7db74df8 3590 complete(&rsp->barrier_completion);
a83eff0a 3591 } else {
4f525a52 3592 _rcu_barrier_trace(rsp, "CB", -1, rsp->barrier_sequence);
a83eff0a 3593 }
d0ec774c
PM
3594}
3595
3596/*
3597 * Called with preemption disabled, and from cross-cpu IRQ context.
3598 */
3599static void rcu_barrier_func(void *type)
3600{
037b64ed 3601 struct rcu_state *rsp = type;
fa07a58f 3602 struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);
d0ec774c 3603
4f525a52 3604 _rcu_barrier_trace(rsp, "IRQ", -1, rsp->barrier_sequence);
24ebbca8 3605 atomic_inc(&rsp->barrier_cpu_count);
06668efa 3606 rsp->call(&rdp->barrier_head, rcu_barrier_callback);
d0ec774c
PM
3607}
3608
d0ec774c
PM
3609/*
3610 * Orchestrate the specified type of RCU barrier, waiting for all
3611 * RCU callbacks of the specified type to complete.
3612 */
037b64ed 3613static void _rcu_barrier(struct rcu_state *rsp)
d0ec774c 3614{
b1420f1c 3615 int cpu;
b1420f1c 3616 struct rcu_data *rdp;
4f525a52 3617 unsigned long s = rcu_seq_snap(&rsp->barrier_sequence);
b1420f1c 3618
4f525a52 3619 _rcu_barrier_trace(rsp, "Begin", -1, s);
b1420f1c 3620
e74f4c45 3621 /* Take mutex to serialize concurrent rcu_barrier() requests. */
7be7f0be 3622 mutex_lock(&rsp->barrier_mutex);
b1420f1c 3623
4f525a52
PM
3624 /* Did someone else do our work for us? */
3625 if (rcu_seq_done(&rsp->barrier_sequence, s)) {
3626 _rcu_barrier_trace(rsp, "EarlyExit", -1, rsp->barrier_sequence);
cf3a9c48
PM
3627 smp_mb(); /* caller's subsequent code after above check. */
3628 mutex_unlock(&rsp->barrier_mutex);
3629 return;
3630 }
3631
4f525a52
PM
3632 /* Mark the start of the barrier operation. */
3633 rcu_seq_start(&rsp->barrier_sequence);
3634 _rcu_barrier_trace(rsp, "Inc1", -1, rsp->barrier_sequence);
b1420f1c 3635
d0ec774c 3636 /*
b1420f1c
PM
3637 * Initialize the count to one rather than to zero in order to
3638 * avoid a too-soon return to zero in case of a short grace period
1331e7a1
PM
3639 * (or preemption of this task). Exclude CPU-hotplug operations
3640 * to ensure that no offline CPU has callbacks queued.
d0ec774c 3641 */
7db74df8 3642 init_completion(&rsp->barrier_completion);
24ebbca8 3643 atomic_set(&rsp->barrier_cpu_count, 1);
1331e7a1 3644 get_online_cpus();
b1420f1c
PM
3645
3646 /*
1331e7a1
PM
3647 * Force each CPU with callbacks to register a new callback.
3648 * When that callback is invoked, we will know that all of the
3649 * corresponding CPU's preceding callbacks have been invoked.
b1420f1c 3650 */
3fbfbf7a 3651 for_each_possible_cpu(cpu) {
d1e43fa5 3652 if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu))
3fbfbf7a 3653 continue;
b1420f1c 3654 rdp = per_cpu_ptr(rsp->rda, cpu);
d1e43fa5 3655 if (rcu_is_nocb_cpu(cpu)) {
d7e29933
PM
3656 if (!rcu_nocb_cpu_needs_barrier(rsp, cpu)) {
3657 _rcu_barrier_trace(rsp, "OfflineNoCB", cpu,
4f525a52 3658 rsp->barrier_sequence);
d7e29933
PM
3659 } else {
3660 _rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
4f525a52 3661 rsp->barrier_sequence);
41050a00 3662 smp_mb__before_atomic();
d7e29933
PM
3663 atomic_inc(&rsp->barrier_cpu_count);
3664 __call_rcu(&rdp->barrier_head,
3665 rcu_barrier_callback, rsp, cpu, 0);
3666 }
7d0ae808 3667 } else if (READ_ONCE(rdp->qlen)) {
a83eff0a 3668 _rcu_barrier_trace(rsp, "OnlineQ", cpu,
4f525a52 3669 rsp->barrier_sequence);
037b64ed 3670 smp_call_function_single(cpu, rcu_barrier_func, rsp, 1);
b1420f1c 3671 } else {
a83eff0a 3672 _rcu_barrier_trace(rsp, "OnlineNQ", cpu,
4f525a52 3673 rsp->barrier_sequence);
b1420f1c
PM
3674 }
3675 }
1331e7a1 3676 put_online_cpus();
b1420f1c
PM
3677
3678 /*
3679 * Now that we have an rcu_barrier_callback() callback on each
3680 * CPU, and thus each counted, remove the initial count.
3681 */
24ebbca8 3682 if (atomic_dec_and_test(&rsp->barrier_cpu_count))
7db74df8 3683 complete(&rsp->barrier_completion);
b1420f1c
PM
3684
3685 /* Wait for all rcu_barrier_callback() callbacks to be invoked. */
7db74df8 3686 wait_for_completion(&rsp->barrier_completion);
b1420f1c 3687
4f525a52
PM
3688 /* Mark the end of the barrier operation. */
3689 _rcu_barrier_trace(rsp, "Inc2", -1, rsp->barrier_sequence);
3690 rcu_seq_end(&rsp->barrier_sequence);
3691
b1420f1c 3692 /* Other rcu_barrier() invocations can now safely proceed. */
7be7f0be 3693 mutex_unlock(&rsp->barrier_mutex);
d0ec774c 3694}
d0ec774c
PM
3695
3696/**
3697 * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
3698 */
3699void rcu_barrier_bh(void)
3700{
037b64ed 3701 _rcu_barrier(&rcu_bh_state);
d0ec774c
PM
3702}
3703EXPORT_SYMBOL_GPL(rcu_barrier_bh);
3704
3705/**
3706 * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
3707 */
3708void rcu_barrier_sched(void)
3709{
037b64ed 3710 _rcu_barrier(&rcu_sched_state);
d0ec774c
PM
3711}
3712EXPORT_SYMBOL_GPL(rcu_barrier_sched);
3713
0aa04b05
PM
3714/*
3715 * Propagate ->qsinitmask bits up the rcu_node tree to account for the
3716 * first CPU in a given leaf rcu_node structure coming online. The caller
3717 * must hold the corresponding leaf rcu_node ->lock with interrrupts
3718 * disabled.
3719 */
3720static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
3721{
3722 long mask;
3723 struct rcu_node *rnp = rnp_leaf;
3724
3725 for (;;) {
3726 mask = rnp->grpmask;
3727 rnp = rnp->parent;
3728 if (rnp == NULL)
3729 return;
6cf10081 3730 raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */
0aa04b05 3731 rnp->qsmaskinit |= mask;
67c583a7 3732 raw_spin_unlock_rcu_node(rnp); /* Interrupts remain disabled. */
0aa04b05
PM
3733 }
3734}
3735
64db4cff 3736/*
27569620 3737 * Do boot-time initialization of a CPU's per-CPU RCU data.
64db4cff 3738 */
27569620
PM
3739static void __init
3740rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
64db4cff
PM
3741{
3742 unsigned long flags;
394f99a9 3743 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
27569620
PM
3744 struct rcu_node *rnp = rcu_get_root(rsp);
3745
3746 /* Set up local state, ensuring consistent view of global state. */
6cf10081 3747 raw_spin_lock_irqsave_rcu_node(rnp, flags);
bc75e999 3748 rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
27569620 3749 rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
29e37d81 3750 WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
9b2e4f18 3751 WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
27569620 3752 rdp->cpu = cpu;
d4c08f2a 3753 rdp->rsp = rsp;
3fbfbf7a 3754 rcu_boot_init_nocb_percpu_data(rdp);
67c583a7 3755 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
27569620
PM
3756}
3757
3758/*
3759 * Initialize a CPU's per-CPU RCU data. Note that only one online or
3760 * offline event can be happening at a given time. Note also that we
3761 * can accept some slop in the rsp->completed access due to the fact
3762 * that this CPU cannot possibly have any RCU callbacks in flight yet.
64db4cff 3763 */
49fb4c62 3764static void
9b67122a 3765rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
64db4cff
PM
3766{
3767 unsigned long flags;
64db4cff 3768 unsigned long mask;
394f99a9 3769 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
64db4cff
PM
3770 struct rcu_node *rnp = rcu_get_root(rsp);
3771
3772 /* Set up local state, ensuring consistent view of global state. */
6cf10081 3773 raw_spin_lock_irqsave_rcu_node(rnp, flags);
37c72e56
PM
3774 rdp->qlen_last_fqs_check = 0;
3775 rdp->n_force_qs_snap = rsp->n_force_qs;
64db4cff 3776 rdp->blimit = blimit;
39c8d313
PM
3777 if (!rdp->nxtlist)
3778 init_callback_list(rdp); /* Re-enable callbacks on this CPU. */
29e37d81 3779 rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
2333210b 3780 rcu_sysidle_init_percpu_data(rdp->dynticks);
c92b131b
PM
3781 atomic_set(&rdp->dynticks->dynticks,
3782 (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
67c583a7 3783 raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
64db4cff 3784
0aa04b05
PM
3785 /*
3786 * Add CPU to leaf rcu_node pending-online bitmask. Any needed
3787 * propagation up the rcu_node tree will happen at the beginning
3788 * of the next grace period.
3789 */
64db4cff
PM
3790 rnp = rdp->mynode;
3791 mask = rdp->grpmask;
2a67e741 3792 raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
b9585e94
PM
3793 if (!rdp->beenonline)
3794 WRITE_ONCE(rsp->ncpus, READ_ONCE(rsp->ncpus) + 1);
3795 rdp->beenonline = true; /* We have now been online. */
0aa04b05
PM
3796 rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */
3797 rdp->completed = rnp->completed;
5b74c458 3798 rdp->cpu_no_qs.b.norm = true;
a738eec6 3799 rdp->rcu_qs_ctr_snap = per_cpu(rcu_qs_ctr, cpu);
97c668b8 3800 rdp->core_needs_qs = false;
0aa04b05 3801 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
67c583a7 3802 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
64db4cff
PM
3803}
3804
4df83742 3805int rcutree_prepare_cpu(unsigned int cpu)
64db4cff 3806{
6ce75a23
PM
3807 struct rcu_state *rsp;
3808
3809 for_each_rcu_flavor(rsp)
9b67122a 3810 rcu_init_percpu_data(cpu, rsp);
4df83742
TG
3811
3812 rcu_prepare_kthreads(cpu);
3813 rcu_spawn_all_nocb_kthreads(cpu);
3814
3815 return 0;
3816}
3817
3818static void rcutree_affinity_setting(unsigned int cpu, int outgoing)
3819{
3820 struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu);
3821
3822 rcu_boost_kthread_setaffinity(rdp->mynode, outgoing);
3823}
3824
3825int rcutree_online_cpu(unsigned int cpu)
3826{
3827 sync_sched_exp_online_cleanup(cpu);
3828 rcutree_affinity_setting(cpu, -1);
3829 return 0;
3830}
3831
3832int rcutree_offline_cpu(unsigned int cpu)
3833{
3834 rcutree_affinity_setting(cpu, cpu);
3835 return 0;
3836}
3837
3838
3839int rcutree_dying_cpu(unsigned int cpu)
3840{
3841 struct rcu_state *rsp;
3842
3843 for_each_rcu_flavor(rsp)
3844 rcu_cleanup_dying_cpu(rsp);
3845 return 0;
3846}
3847
3848int rcutree_dead_cpu(unsigned int cpu)
3849{
3850 struct rcu_state *rsp;
3851
3852 for_each_rcu_flavor(rsp) {
3853 rcu_cleanup_dead_cpu(cpu, rsp);
3854 do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu));
3855 }
3856 return 0;
64db4cff
PM
3857}
3858
7ec99de3
PM
3859/*
3860 * Mark the specified CPU as being online so that subsequent grace periods
3861 * (both expedited and normal) will wait on it. Note that this means that
3862 * incoming CPUs are not allowed to use RCU read-side critical sections
3863 * until this function is called. Failing to observe this restriction
3864 * will result in lockdep splats.
3865 */
3866void rcu_cpu_starting(unsigned int cpu)
3867{
3868 unsigned long flags;
3869 unsigned long mask;
3870 struct rcu_data *rdp;
3871 struct rcu_node *rnp;
3872 struct rcu_state *rsp;
3873
3874 for_each_rcu_flavor(rsp) {
3875 rdp = this_cpu_ptr(rsp->rda);
3876 rnp = rdp->mynode;
3877 mask = rdp->grpmask;
3878 raw_spin_lock_irqsave_rcu_node(rnp, flags);
3879 rnp->qsmaskinitnext |= mask;
3880 rnp->expmaskinitnext |= mask;
3881 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
3882 }
3883}
3884
27d50c7e
TG
3885#ifdef CONFIG_HOTPLUG_CPU
3886/*
710d60cb
LT
3887 * The CPU is exiting the idle loop into the arch_cpu_idle_dead()
3888 * function. We now remove it from the rcu_node tree's ->qsmaskinit
3889 * bit masks.
27d50c7e
TG
3890 * The CPU is exiting the idle loop into the arch_cpu_idle_dead()
3891 * function. We now remove it from the rcu_node tree's ->qsmaskinit
3892 * bit masks.
3893 */
3894static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
3895{
3896 unsigned long flags;
3897 unsigned long mask;
3898 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
3899 struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
3900
27d50c7e
TG
3901 /* Remove outgoing CPU from mask in the leaf rcu_node structure. */
3902 mask = rdp->grpmask;
3903 raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
3904 rnp->qsmaskinitnext &= ~mask;
710d60cb 3905 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
27d50c7e
TG
3906}
3907
3908void rcu_report_dead(unsigned int cpu)
3909{
3910 struct rcu_state *rsp;
3911
3912 /* QS for any half-done expedited RCU-sched GP. */
3913 preempt_disable();
3914 rcu_report_exp_rdp(&rcu_sched_state,
3915 this_cpu_ptr(rcu_sched_state.rda), true);
3916 preempt_enable();
3917 for_each_rcu_flavor(rsp)
3918 rcu_cleanup_dying_idle_cpu(cpu, rsp);
3919}
3920#endif
3921
d1d74d14
BP
3922static int rcu_pm_notify(struct notifier_block *self,
3923 unsigned long action, void *hcpu)
3924{
3925 switch (action) {
3926 case PM_HIBERNATION_PREPARE:
3927 case PM_SUSPEND_PREPARE:
3928 if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */
5afff48b 3929 rcu_expedite_gp();
d1d74d14
BP
3930 break;
3931 case PM_POST_HIBERNATION:
3932 case PM_POST_SUSPEND:
5afff48b
PM
3933 if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */
3934 rcu_unexpedite_gp();
d1d74d14
BP
3935 break;
3936 default:
3937 break;
3938 }
3939 return NOTIFY_OK;
3940}
3941
b3dbec76 3942/*
9386c0b7 3943 * Spawn the kthreads that handle each RCU flavor's grace periods.
b3dbec76
PM
3944 */
3945static int __init rcu_spawn_gp_kthread(void)
3946{
3947 unsigned long flags;
a94844b2 3948 int kthread_prio_in = kthread_prio;
b3dbec76
PM
3949 struct rcu_node *rnp;
3950 struct rcu_state *rsp;
a94844b2 3951 struct sched_param sp;
b3dbec76
PM
3952 struct task_struct *t;
3953
a94844b2
PM
3954 /* Force priority into range. */
3955 if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
3956 kthread_prio = 1;
3957 else if (kthread_prio < 0)
3958 kthread_prio = 0;
3959 else if (kthread_prio > 99)
3960 kthread_prio = 99;
3961 if (kthread_prio != kthread_prio_in)
3962 pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n",
3963 kthread_prio, kthread_prio_in);
3964
9386c0b7 3965 rcu_scheduler_fully_active = 1;
b3dbec76 3966 for_each_rcu_flavor(rsp) {
a94844b2 3967 t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name);
b3dbec76
PM
3968 BUG_ON(IS_ERR(t));
3969 rnp = rcu_get_root(rsp);
6cf10081 3970 raw_spin_lock_irqsave_rcu_node(rnp, flags);
b3dbec76 3971 rsp->gp_kthread = t;
a94844b2
PM
3972 if (kthread_prio) {
3973 sp.sched_priority = kthread_prio;
3974 sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
3975 }
67c583a7 3976 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
e11f1335 3977 wake_up_process(t);
b3dbec76 3978 }
35ce7f29 3979 rcu_spawn_nocb_kthreads();
9386c0b7 3980 rcu_spawn_boost_kthreads();
b3dbec76
PM
3981 return 0;
3982}
3983early_initcall(rcu_spawn_gp_kthread);
3984
bbad9379 3985/*
52d7e48b
PM
3986 * This function is invoked towards the end of the scheduler's
3987 * initialization process. Before this is called, the idle task might
3988 * contain synchronous grace-period primitives (during which time, this idle
3989 * task is booting the system, and such primitives are no-ops). After this
3990 * function is called, any synchronous grace-period primitives are run as
3991 * expedited, with the requesting task driving the grace period forward.
3992 * A later core_initcall() rcu_exp_runtime_mode() will switch to full
3993 * runtime RCU functionality.
bbad9379
PM
3994 */
3995void rcu_scheduler_starting(void)
3996{
3997 WARN_ON(num_online_cpus() != 1);
3998 WARN_ON(nr_context_switches() > 0);
52d7e48b
PM
3999 rcu_test_sync_prims();
4000 rcu_scheduler_active = RCU_SCHEDULER_INIT;
4001 rcu_test_sync_prims();
bbad9379
PM
4002}
4003
64db4cff
PM
4004/*
4005 * Compute the per-level fanout, either using the exact fanout specified
7fa27001 4006 * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
64db4cff 4007 */
199977bf 4008static void __init rcu_init_levelspread(int *levelspread, const int *levelcnt)
64db4cff 4009{
64db4cff
PM
4010 int i;
4011
7fa27001 4012 if (rcu_fanout_exact) {
199977bf 4013 levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
66292405 4014 for (i = rcu_num_lvls - 2; i >= 0; i--)
199977bf 4015 levelspread[i] = RCU_FANOUT;
66292405
PM
4016 } else {
4017 int ccur;
4018 int cprv;
4019
4020 cprv = nr_cpu_ids;
4021 for (i = rcu_num_lvls - 1; i >= 0; i--) {
199977bf
AG
4022 ccur = levelcnt[i];
4023 levelspread[i] = (cprv + ccur - 1) / ccur;
66292405
PM
4024 cprv = ccur;
4025 }
64db4cff
PM
4026 }
4027}
64db4cff
PM
4028
4029/*
4030 * Helper function for rcu_init() that initializes one rcu_state structure.
4031 */
a87f203e 4032static void __init rcu_init_one(struct rcu_state *rsp)
64db4cff 4033{
cb007102
AG
4034 static const char * const buf[] = RCU_NODE_NAME_INIT;
4035 static const char * const fqs[] = RCU_FQS_NAME_INIT;
3dc5dbe9
PM
4036 static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
4037 static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
4a81e832 4038 static u8 fl_mask = 0x1;
199977bf
AG
4039
4040 int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */
4041 int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */
64db4cff
PM
4042 int cpustride = 1;
4043 int i;
4044 int j;
4045 struct rcu_node *rnp;
4046
05b84aec 4047 BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
b6407e86 4048
3eaaaf6c
PM
4049 /* Silence gcc 4.8 false positive about array index out of range. */
4050 if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS)
4051 panic("rcu_init_one: rcu_num_lvls out of range");
4930521a 4052
64db4cff
PM
4053 /* Initialize the level-tracking arrays. */
4054
f885b7f2 4055 for (i = 0; i < rcu_num_lvls; i++)
199977bf 4056 levelcnt[i] = num_rcu_lvl[i];
f885b7f2 4057 for (i = 1; i < rcu_num_lvls; i++)
199977bf
AG
4058 rsp->level[i] = rsp->level[i - 1] + levelcnt[i - 1];
4059 rcu_init_levelspread(levelspread, levelcnt);
4a81e832
PM
4060 rsp->flavor_mask = fl_mask;
4061 fl_mask <<= 1;
64db4cff
PM
4062
4063 /* Initialize the elements themselves, starting from the leaves. */
4064
f885b7f2 4065 for (i = rcu_num_lvls - 1; i >= 0; i--) {
199977bf 4066 cpustride *= levelspread[i];
64db4cff 4067 rnp = rsp->level[i];
199977bf 4068 for (j = 0; j < levelcnt[i]; j++, rnp++) {
67c583a7
BF
4069 raw_spin_lock_init(&ACCESS_PRIVATE(rnp, lock));
4070 lockdep_set_class_and_name(&ACCESS_PRIVATE(rnp, lock),
b6407e86 4071 &rcu_node_class[i], buf[i]);
394f2769
PM
4072 raw_spin_lock_init(&rnp->fqslock);
4073 lockdep_set_class_and_name(&rnp->fqslock,
4074 &rcu_fqs_class[i], fqs[i]);
25d30cf4
PM
4075 rnp->gpnum = rsp->gpnum;
4076 rnp->completed = rsp->completed;
64db4cff
PM
4077 rnp->qsmask = 0;
4078 rnp->qsmaskinit = 0;
4079 rnp->grplo = j * cpustride;
4080 rnp->grphi = (j + 1) * cpustride - 1;
595f3900
HS
4081 if (rnp->grphi >= nr_cpu_ids)
4082 rnp->grphi = nr_cpu_ids - 1;
64db4cff
PM
4083 if (i == 0) {
4084 rnp->grpnum = 0;
4085 rnp->grpmask = 0;
4086 rnp->parent = NULL;
4087 } else {
199977bf 4088 rnp->grpnum = j % levelspread[i - 1];
64db4cff
PM
4089 rnp->grpmask = 1UL << rnp->grpnum;
4090 rnp->parent = rsp->level[i - 1] +
199977bf 4091 j / levelspread[i - 1];
64db4cff
PM
4092 }
4093 rnp->level = i;
12f5f524 4094 INIT_LIST_HEAD(&rnp->blkd_tasks);
dae6e64d 4095 rcu_init_one_nocb(rnp);
f6a12f34
PM
4096 init_waitqueue_head(&rnp->exp_wq[0]);
4097 init_waitqueue_head(&rnp->exp_wq[1]);
3b5f668e
PM
4098 init_waitqueue_head(&rnp->exp_wq[2]);
4099 init_waitqueue_head(&rnp->exp_wq[3]);
f6a12f34 4100 spin_lock_init(&rnp->exp_lock);
64db4cff
PM
4101 }
4102 }
0c34029a 4103
abedf8e2
PG
4104 init_swait_queue_head(&rsp->gp_wq);
4105 init_swait_queue_head(&rsp->expedited_wq);
f885b7f2 4106 rnp = rsp->level[rcu_num_lvls - 1];
0c34029a 4107 for_each_possible_cpu(i) {
4a90a068 4108 while (i > rnp->grphi)
0c34029a 4109 rnp++;
394f99a9 4110 per_cpu_ptr(rsp->rda, i)->mynode = rnp;
0c34029a
LJ
4111 rcu_boot_init_percpu_data(i, rsp);
4112 }
6ce75a23 4113 list_add(&rsp->flavors, &rcu_struct_flavors);
64db4cff
PM
4114}
4115
f885b7f2
PM
4116/*
4117 * Compute the rcu_node tree geometry from kernel parameters. This cannot
4102adab 4118 * replace the definitions in tree.h because those are needed to size
f885b7f2
PM
4119 * the ->node array in the rcu_state structure.
4120 */
4121static void __init rcu_init_geometry(void)
4122{
026ad283 4123 ulong d;
f885b7f2 4124 int i;
05b84aec 4125 int rcu_capacity[RCU_NUM_LVLS];
f885b7f2 4126
026ad283
PM
4127 /*
4128 * Initialize any unspecified boot parameters.
4129 * The default values of jiffies_till_first_fqs and
4130 * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS
4131 * value, which is a function of HZ, then adding one for each
4132 * RCU_JIFFIES_FQS_DIV CPUs that might be on the system.
4133 */
4134 d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
4135 if (jiffies_till_first_fqs == ULONG_MAX)
4136 jiffies_till_first_fqs = d;
4137 if (jiffies_till_next_fqs == ULONG_MAX)
4138 jiffies_till_next_fqs = d;
4139
f885b7f2 4140 /* If the compile-time values are accurate, just leave. */
47d631af 4141 if (rcu_fanout_leaf == RCU_FANOUT_LEAF &&
b17c7035 4142 nr_cpu_ids == NR_CPUS)
f885b7f2 4143 return;
39479098
PM
4144 pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n",
4145 rcu_fanout_leaf, nr_cpu_ids);
f885b7f2 4146
f885b7f2 4147 /*
ee968ac6
PM
4148 * The boot-time rcu_fanout_leaf parameter must be at least two
4149 * and cannot exceed the number of bits in the rcu_node masks.
4150 * Complain and fall back to the compile-time values if this
4151 * limit is exceeded.
f885b7f2 4152 */
ee968ac6 4153 if (rcu_fanout_leaf < 2 ||
75cf15a4 4154 rcu_fanout_leaf > sizeof(unsigned long) * 8) {
13bd6494 4155 rcu_fanout_leaf = RCU_FANOUT_LEAF;
f885b7f2
PM
4156 WARN_ON(1);
4157 return;
4158 }
4159
f885b7f2
PM
4160 /*
4161 * Compute number of nodes that can be handled an rcu_node tree
9618138b 4162 * with the given number of levels.
f885b7f2 4163 */
9618138b 4164 rcu_capacity[0] = rcu_fanout_leaf;
05b84aec 4165 for (i = 1; i < RCU_NUM_LVLS; i++)
05c5df31 4166 rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
f885b7f2
PM
4167
4168 /*
75cf15a4 4169 * The tree must be able to accommodate the configured number of CPUs.
ee968ac6 4170 * If this limit is exceeded, fall back to the compile-time values.
f885b7f2 4171 */
ee968ac6
PM
4172 if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1]) {
4173 rcu_fanout_leaf = RCU_FANOUT_LEAF;
4174 WARN_ON(1);
4175 return;
4176 }
f885b7f2 4177
679f9858 4178 /* Calculate the number of levels in the tree. */
9618138b 4179 for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) {
679f9858 4180 }
9618138b 4181 rcu_num_lvls = i + 1;
679f9858 4182
f885b7f2 4183 /* Calculate the number of rcu_nodes at each level of the tree. */
679f9858 4184 for (i = 0; i < rcu_num_lvls; i++) {
9618138b 4185 int cap = rcu_capacity[(rcu_num_lvls - 1) - i];
679f9858
AG
4186 num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap);
4187 }
f885b7f2
PM
4188
4189 /* Calculate the total number of rcu_node structures. */
4190 rcu_num_nodes = 0;
679f9858 4191 for (i = 0; i < rcu_num_lvls; i++)
f885b7f2 4192 rcu_num_nodes += num_rcu_lvl[i];
f885b7f2
PM
4193}
4194
a3dc2948
PM
4195/*
4196 * Dump out the structure of the rcu_node combining tree associated
4197 * with the rcu_state structure referenced by rsp.
4198 */
4199static void __init rcu_dump_rcu_node_tree(struct rcu_state *rsp)
4200{
4201 int level = 0;
4202 struct rcu_node *rnp;
4203
4204 pr_info("rcu_node tree layout dump\n");
4205 pr_info(" ");
4206 rcu_for_each_node_breadth_first(rsp, rnp) {
4207 if (rnp->level != level) {
4208 pr_cont("\n");
4209 pr_info(" ");
4210 level = rnp->level;
4211 }
4212 pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum);
4213 }
4214 pr_cont("\n");
4215}
4216
9f680ab4 4217void __init rcu_init(void)
64db4cff 4218{
017c4261 4219 int cpu;
9f680ab4 4220
47627678
PM
4221 rcu_early_boot_tests();
4222
f41d911f 4223 rcu_bootup_announce();
f885b7f2 4224 rcu_init_geometry();
a87f203e
PM
4225 rcu_init_one(&rcu_bh_state);
4226 rcu_init_one(&rcu_sched_state);
a3dc2948
PM
4227 if (dump_tree)
4228 rcu_dump_rcu_node_tree(&rcu_sched_state);
f41d911f 4229 __rcu_init_preempt();
b5b39360 4230 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
9f680ab4
PM
4231
4232 /*
4233 * We don't need protection against CPU-hotplug here because
4234 * this is called early in boot, before either interrupts
4235 * or the scheduler are operational.
4236 */
d1d74d14 4237 pm_notifier(rcu_pm_notify, 0);
7ec99de3 4238 for_each_online_cpu(cpu) {
4df83742 4239 rcutree_prepare_cpu(cpu);
7ec99de3
PM
4240 rcu_cpu_starting(cpu);
4241 }
64db4cff
PM
4242}
4243
3549c2bc 4244#include "tree_exp.h"
4102adab 4245#include "tree_plugin.h"