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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
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright IBM Corporation, 2008
19 *
20 * Authors: Dipankar Sarma <dipankar@in.ibm.com>
21 * Manfred Spraul <manfred@colorfullife.com>
22 * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version
23 *
24 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
25 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
26 *
27 * For detailed explanation of Read-Copy Update mechanism see -
a71fca58 28 * Documentation/RCU
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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>
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39#include <asm/atomic.h>
40#include <linux/bitops.h>
41#include <linux/module.h>
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>
64db4cff 50
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51#include "rcutree.h"
52
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53/* Data structures. */
54
b668c9cf 55static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
88b91c7c 56
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57#define RCU_STATE_INITIALIZER(structname) { \
58 .level = { &structname.node[0] }, \
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59 .levelcnt = { \
60 NUM_RCU_LVL_0, /* root of hierarchy. */ \
61 NUM_RCU_LVL_1, \
62 NUM_RCU_LVL_2, \
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63 NUM_RCU_LVL_3, \
64 NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \
64db4cff 65 }, \
83f5b01f 66 .signaled = RCU_GP_IDLE, \
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67 .gpnum = -300, \
68 .completed = -300, \
4300aa64 69 .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \
e74f4c45 70 .orphan_cbs_list = NULL, \
4300aa64 71 .orphan_cbs_tail = &structname.orphan_cbs_list, \
e74f4c45 72 .orphan_qlen = 0, \
4300aa64 73 .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \
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74 .n_force_qs = 0, \
75 .n_force_qs_ngp = 0, \
4300aa64 76 .name = #structname, \
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77}
78
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79struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state);
80DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
64db4cff 81
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82struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
83DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
b1f77b05 84
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85int rcu_scheduler_active __read_mostly;
86EXPORT_SYMBOL_GPL(rcu_scheduler_active);
87
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88/*
89 * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
90 * permit this function to be invoked without holding the root rcu_node
91 * structure's ->lock, but of course results can be subject to change.
92 */
93static int rcu_gp_in_progress(struct rcu_state *rsp)
94{
95 return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
96}
97
b1f77b05 98/*
d6714c22 99 * Note a quiescent state. Because we do not need to know
b1f77b05 100 * how many quiescent states passed, just if there was at least
d6714c22 101 * one since the start of the grace period, this just sets a flag.
b1f77b05 102 */
d6714c22 103void rcu_sched_qs(int cpu)
b1f77b05 104{
25502a6c 105 struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
f41d911f 106
c64ac3ce 107 rdp->passed_quiesc_completed = rdp->gpnum - 1;
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108 barrier();
109 rdp->passed_quiesc = 1;
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110}
111
d6714c22 112void rcu_bh_qs(int cpu)
b1f77b05 113{
25502a6c 114 struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
f41d911f 115
c64ac3ce 116 rdp->passed_quiesc_completed = rdp->gpnum - 1;
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117 barrier();
118 rdp->passed_quiesc = 1;
b1f77b05 119}
64db4cff 120
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121/*
122 * Note a context switch. This is a quiescent state for RCU-sched,
123 * and requires special handling for preemptible RCU.
124 */
125void rcu_note_context_switch(int cpu)
126{
127 rcu_sched_qs(cpu);
128 rcu_preempt_note_context_switch(cpu);
129}
130
64db4cff 131#ifdef CONFIG_NO_HZ
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132DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
133 .dynticks_nesting = 1,
134 .dynticks = 1,
135};
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136#endif /* #ifdef CONFIG_NO_HZ */
137
138static int blimit = 10; /* Maximum callbacks per softirq. */
139static int qhimark = 10000; /* If this many pending, ignore blimit. */
140static int qlowmark = 100; /* Once only this many pending, use blimit. */
141
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142module_param(blimit, int, 0);
143module_param(qhimark, int, 0);
144module_param(qlowmark, int, 0);
145
742734ee 146#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
910b1b7e 147int rcu_cpu_stall_suppress __read_mostly = RCU_CPU_STALL_SUPPRESS_INIT;
f2e0dd70 148module_param(rcu_cpu_stall_suppress, int, 0644);
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149#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
150
64db4cff 151static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
a157229c 152static int rcu_pending(int cpu);
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153
154/*
d6714c22 155 * Return the number of RCU-sched batches processed thus far for debug & stats.
64db4cff 156 */
d6714c22 157long rcu_batches_completed_sched(void)
64db4cff 158{
d6714c22 159 return rcu_sched_state.completed;
64db4cff 160}
d6714c22 161EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
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162
163/*
164 * Return the number of RCU BH batches processed thus far for debug & stats.
165 */
166long rcu_batches_completed_bh(void)
167{
168 return rcu_bh_state.completed;
169}
170EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
171
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172/*
173 * Force a quiescent state for RCU BH.
174 */
175void rcu_bh_force_quiescent_state(void)
176{
177 force_quiescent_state(&rcu_bh_state, 0);
178}
179EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
180
181/*
182 * Force a quiescent state for RCU-sched.
183 */
184void rcu_sched_force_quiescent_state(void)
185{
186 force_quiescent_state(&rcu_sched_state, 0);
187}
188EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
189
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190/*
191 * Does the CPU have callbacks ready to be invoked?
192 */
193static int
194cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
195{
196 return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL];
197}
198
199/*
200 * Does the current CPU require a yet-as-unscheduled grace period?
201 */
202static int
203cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
204{
fc2219d4 205 return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp);
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206}
207
208/*
209 * Return the root node of the specified rcu_state structure.
210 */
211static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
212{
213 return &rsp->node[0];
214}
215
216#ifdef CONFIG_SMP
217
218/*
219 * If the specified CPU is offline, tell the caller that it is in
220 * a quiescent state. Otherwise, whack it with a reschedule IPI.
221 * Grace periods can end up waiting on an offline CPU when that
222 * CPU is in the process of coming online -- it will be added to the
223 * rcu_node bitmasks before it actually makes it online. The same thing
224 * can happen while a CPU is in the process of coming online. Because this
225 * race is quite rare, we check for it after detecting that the grace
226 * period has been delayed rather than checking each and every CPU
227 * each and every time we start a new grace period.
228 */
229static int rcu_implicit_offline_qs(struct rcu_data *rdp)
230{
231 /*
232 * If the CPU is offline, it is in a quiescent state. We can
233 * trust its state not to change because interrupts are disabled.
234 */
235 if (cpu_is_offline(rdp->cpu)) {
236 rdp->offline_fqs++;
237 return 1;
238 }
239
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240 /* If preemptable RCU, no point in sending reschedule IPI. */
241 if (rdp->preemptable)
242 return 0;
243
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244 /* The CPU is online, so send it a reschedule IPI. */
245 if (rdp->cpu != smp_processor_id())
246 smp_send_reschedule(rdp->cpu);
247 else
248 set_need_resched();
249 rdp->resched_ipi++;
250 return 0;
251}
252
253#endif /* #ifdef CONFIG_SMP */
254
255#ifdef CONFIG_NO_HZ
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256
257/**
258 * rcu_enter_nohz - inform RCU that current CPU is entering nohz
259 *
260 * Enter nohz mode, in other words, -leave- the mode in which RCU
261 * read-side critical sections can occur. (Though RCU read-side
262 * critical sections can occur in irq handlers in nohz mode, a possibility
263 * handled by rcu_irq_enter() and rcu_irq_exit()).
264 */
265void rcu_enter_nohz(void)
266{
267 unsigned long flags;
268 struct rcu_dynticks *rdtp;
269
270 smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
271 local_irq_save(flags);
272 rdtp = &__get_cpu_var(rcu_dynticks);
273 rdtp->dynticks++;
274 rdtp->dynticks_nesting--;
86848966 275 WARN_ON_ONCE(rdtp->dynticks & 0x1);
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276 local_irq_restore(flags);
277}
278
279/*
280 * rcu_exit_nohz - inform RCU that current CPU is leaving nohz
281 *
282 * Exit nohz mode, in other words, -enter- the mode in which RCU
283 * read-side critical sections normally occur.
284 */
285void rcu_exit_nohz(void)
286{
287 unsigned long flags;
288 struct rcu_dynticks *rdtp;
289
290 local_irq_save(flags);
291 rdtp = &__get_cpu_var(rcu_dynticks);
292 rdtp->dynticks++;
293 rdtp->dynticks_nesting++;
86848966 294 WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
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295 local_irq_restore(flags);
296 smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
297}
298
299/**
300 * rcu_nmi_enter - inform RCU of entry to NMI context
301 *
302 * If the CPU was idle with dynamic ticks active, and there is no
303 * irq handler running, this updates rdtp->dynticks_nmi to let the
304 * RCU grace-period handling know that the CPU is active.
305 */
306void rcu_nmi_enter(void)
307{
308 struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
309
310 if (rdtp->dynticks & 0x1)
311 return;
312 rdtp->dynticks_nmi++;
86848966 313 WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1));
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314 smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
315}
316
317/**
318 * rcu_nmi_exit - inform RCU of exit from NMI context
319 *
320 * If the CPU was idle with dynamic ticks active, and there is no
321 * irq handler running, this updates rdtp->dynticks_nmi to let the
322 * RCU grace-period handling know that the CPU is no longer active.
323 */
324void rcu_nmi_exit(void)
325{
326 struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
327
328 if (rdtp->dynticks & 0x1)
329 return;
330 smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
331 rdtp->dynticks_nmi++;
86848966 332 WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1);
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333}
334
335/**
336 * rcu_irq_enter - inform RCU of entry to hard irq context
337 *
338 * If the CPU was idle with dynamic ticks active, this updates the
339 * rdtp->dynticks to let the RCU handling know that the CPU is active.
340 */
341void rcu_irq_enter(void)
342{
343 struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
344
345 if (rdtp->dynticks_nesting++)
346 return;
347 rdtp->dynticks++;
86848966 348 WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
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349 smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
350}
351
352/**
353 * rcu_irq_exit - inform RCU of exit from hard irq context
354 *
355 * If the CPU was idle with dynamic ticks active, update the rdp->dynticks
356 * to put let the RCU handling be aware that the CPU is going back to idle
357 * with no ticks.
358 */
359void rcu_irq_exit(void)
360{
361 struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
362
363 if (--rdtp->dynticks_nesting)
364 return;
365 smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
366 rdtp->dynticks++;
86848966 367 WARN_ON_ONCE(rdtp->dynticks & 0x1);
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368
369 /* If the interrupt queued a callback, get out of dyntick mode. */
d6714c22 370 if (__get_cpu_var(rcu_sched_data).nxtlist ||
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371 __get_cpu_var(rcu_bh_data).nxtlist)
372 set_need_resched();
373}
374
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375#ifdef CONFIG_SMP
376
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377/*
378 * Snapshot the specified CPU's dynticks counter so that we can later
379 * credit them with an implicit quiescent state. Return 1 if this CPU
1eba8f84 380 * is in dynticks idle mode, which is an extended quiescent state.
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381 */
382static int dyntick_save_progress_counter(struct rcu_data *rdp)
383{
384 int ret;
385 int snap;
386 int snap_nmi;
387
388 snap = rdp->dynticks->dynticks;
389 snap_nmi = rdp->dynticks->dynticks_nmi;
390 smp_mb(); /* Order sampling of snap with end of grace period. */
391 rdp->dynticks_snap = snap;
392 rdp->dynticks_nmi_snap = snap_nmi;
393 ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0);
394 if (ret)
395 rdp->dynticks_fqs++;
396 return ret;
397}
398
399/*
400 * Return true if the specified CPU has passed through a quiescent
401 * state by virtue of being in or having passed through an dynticks
402 * idle state since the last call to dyntick_save_progress_counter()
403 * for this same CPU.
404 */
405static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
406{
407 long curr;
408 long curr_nmi;
409 long snap;
410 long snap_nmi;
411
412 curr = rdp->dynticks->dynticks;
413 snap = rdp->dynticks_snap;
414 curr_nmi = rdp->dynticks->dynticks_nmi;
415 snap_nmi = rdp->dynticks_nmi_snap;
416 smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
417
418 /*
419 * If the CPU passed through or entered a dynticks idle phase with
420 * no active irq/NMI handlers, then we can safely pretend that the CPU
421 * already acknowledged the request to pass through a quiescent
422 * state. Either way, that CPU cannot possibly be in an RCU
423 * read-side critical section that started before the beginning
424 * of the current RCU grace period.
425 */
426 if ((curr != snap || (curr & 0x1) == 0) &&
427 (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) {
428 rdp->dynticks_fqs++;
429 return 1;
430 }
431
432 /* Go check for the CPU being offline. */
433 return rcu_implicit_offline_qs(rdp);
434}
435
436#endif /* #ifdef CONFIG_SMP */
437
438#else /* #ifdef CONFIG_NO_HZ */
439
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440#ifdef CONFIG_SMP
441
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442static int dyntick_save_progress_counter(struct rcu_data *rdp)
443{
444 return 0;
445}
446
447static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
448{
449 return rcu_implicit_offline_qs(rdp);
450}
451
452#endif /* #ifdef CONFIG_SMP */
453
454#endif /* #else #ifdef CONFIG_NO_HZ */
455
456#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
457
742734ee 458int rcu_cpu_stall_suppress __read_mostly;
c68de209 459
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460static void record_gp_stall_check_time(struct rcu_state *rsp)
461{
462 rsp->gp_start = jiffies;
463 rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
464}
465
466static void print_other_cpu_stall(struct rcu_state *rsp)
467{
468 int cpu;
469 long delta;
470 unsigned long flags;
471 struct rcu_node *rnp = rcu_get_root(rsp);
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472
473 /* Only let one CPU complain about others per time interval. */
474
1304afb2 475 raw_spin_lock_irqsave(&rnp->lock, flags);
64db4cff 476 delta = jiffies - rsp->jiffies_stall;
fc2219d4 477 if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
1304afb2 478 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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479 return;
480 }
481 rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
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482
483 /*
484 * Now rat on any tasks that got kicked up to the root rcu_node
485 * due to CPU offlining.
486 */
487 rcu_print_task_stall(rnp);
1304afb2 488 raw_spin_unlock_irqrestore(&rnp->lock, flags);
64db4cff 489
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490 /*
491 * OK, time to rat on our buddy...
492 * See Documentation/RCU/stallwarn.txt for info on how to debug
493 * RCU CPU stall warnings.
494 */
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495 printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {",
496 rsp->name);
a0b6c9a7 497 rcu_for_each_leaf_node(rsp, rnp) {
3acd9eb3 498 raw_spin_lock_irqsave(&rnp->lock, flags);
f41d911f 499 rcu_print_task_stall(rnp);
3acd9eb3 500 raw_spin_unlock_irqrestore(&rnp->lock, flags);
a0b6c9a7 501 if (rnp->qsmask == 0)
64db4cff 502 continue;
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503 for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
504 if (rnp->qsmask & (1UL << cpu))
505 printk(" %d", rnp->grplo + cpu);
64db4cff 506 }
4300aa64 507 printk("} (detected by %d, t=%ld jiffies)\n",
64db4cff 508 smp_processor_id(), (long)(jiffies - rsp->gp_start));
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509 trigger_all_cpu_backtrace();
510
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511 /* If so configured, complain about tasks blocking the grace period. */
512
513 rcu_print_detail_task_stall(rsp);
514
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515 force_quiescent_state(rsp, 0); /* Kick them all. */
516}
517
518static void print_cpu_stall(struct rcu_state *rsp)
519{
520 unsigned long flags;
521 struct rcu_node *rnp = rcu_get_root(rsp);
522
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523 /*
524 * OK, time to rat on ourselves...
525 * See Documentation/RCU/stallwarn.txt for info on how to debug
526 * RCU CPU stall warnings.
527 */
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528 printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n",
529 rsp->name, smp_processor_id(), jiffies - rsp->gp_start);
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530 trigger_all_cpu_backtrace();
531
1304afb2 532 raw_spin_lock_irqsave(&rnp->lock, flags);
20133cfc 533 if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
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534 rsp->jiffies_stall =
535 jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
1304afb2 536 raw_spin_unlock_irqrestore(&rnp->lock, flags);
c1dc0b9c 537
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538 set_need_resched(); /* kick ourselves to get things going. */
539}
540
541static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
542{
543 long delta;
544 struct rcu_node *rnp;
545
742734ee 546 if (rcu_cpu_stall_suppress)
c68de209 547 return;
4ee0a603 548 delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall);
64db4cff 549 rnp = rdp->mynode;
4ee0a603 550 if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) {
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551
552 /* We haven't checked in, so go dump stack. */
553 print_cpu_stall(rsp);
554
fc2219d4 555 } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) {
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556
557 /* They had two time units to dump stack, so complain. */
558 print_other_cpu_stall(rsp);
559 }
560}
561
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562static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
563{
742734ee 564 rcu_cpu_stall_suppress = 1;
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565 return NOTIFY_DONE;
566}
567
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568/**
569 * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
570 *
571 * Set the stall-warning timeout way off into the future, thus preventing
572 * any RCU CPU stall-warning messages from appearing in the current set of
573 * RCU grace periods.
574 *
575 * The caller must disable hard irqs.
576 */
577void rcu_cpu_stall_reset(void)
578{
579 rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
580 rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
581 rcu_preempt_stall_reset();
582}
583
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584static struct notifier_block rcu_panic_block = {
585 .notifier_call = rcu_panic,
586};
587
588static void __init check_cpu_stall_init(void)
589{
590 atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
591}
592
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593#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
594
595static void record_gp_stall_check_time(struct rcu_state *rsp)
596{
597}
598
599static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
600{
601}
602
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603void rcu_cpu_stall_reset(void)
604{
605}
606
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607static void __init check_cpu_stall_init(void)
608{
609}
610
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611#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
612
613/*
614 * Update CPU-local rcu_data state to record the newly noticed grace period.
615 * This is used both when we started the grace period and when we notice
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616 * that someone else started the grace period. The caller must hold the
617 * ->lock of the leaf rcu_node structure corresponding to the current CPU,
618 * and must have irqs disabled.
64db4cff 619 */
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620static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
621{
622 if (rdp->gpnum != rnp->gpnum) {
623 rdp->qs_pending = 1;
624 rdp->passed_quiesc = 0;
625 rdp->gpnum = rnp->gpnum;
626 }
627}
628
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629static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
630{
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631 unsigned long flags;
632 struct rcu_node *rnp;
633
634 local_irq_save(flags);
635 rnp = rdp->mynode;
636 if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */
1304afb2 637 !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
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638 local_irq_restore(flags);
639 return;
640 }
641 __note_new_gpnum(rsp, rnp, rdp);
1304afb2 642 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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643}
644
645/*
646 * Did someone else start a new RCU grace period start since we last
647 * checked? Update local state appropriately if so. Must be called
648 * on the CPU corresponding to rdp.
649 */
650static int
651check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
652{
653 unsigned long flags;
654 int ret = 0;
655
656 local_irq_save(flags);
657 if (rdp->gpnum != rsp->gpnum) {
658 note_new_gpnum(rsp, rdp);
659 ret = 1;
660 }
661 local_irq_restore(flags);
662 return ret;
663}
664
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665/*
666 * Advance this CPU's callbacks, but only if the current grace period
667 * has ended. This may be called only from the CPU to whom the rdp
668 * belongs. In addition, the corresponding leaf rcu_node structure's
669 * ->lock must be held by the caller, with irqs disabled.
670 */
671static void
672__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
673{
674 /* Did another grace period end? */
675 if (rdp->completed != rnp->completed) {
676
677 /* Advance callbacks. No harm if list empty. */
678 rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
679 rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
680 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
681
682 /* Remember that we saw this grace-period completion. */
683 rdp->completed = rnp->completed;
684 }
685}
686
687/*
688 * Advance this CPU's callbacks, but only if the current grace period
689 * has ended. This may be called only from the CPU to whom the rdp
690 * belongs.
691 */
692static void
693rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
694{
695 unsigned long flags;
696 struct rcu_node *rnp;
697
698 local_irq_save(flags);
699 rnp = rdp->mynode;
700 if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */
1304afb2 701 !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
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702 local_irq_restore(flags);
703 return;
704 }
705 __rcu_process_gp_end(rsp, rnp, rdp);
1304afb2 706 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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707}
708
709/*
710 * Do per-CPU grace-period initialization for running CPU. The caller
711 * must hold the lock of the leaf rcu_node structure corresponding to
712 * this CPU.
713 */
714static void
715rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
716{
717 /* Prior grace period ended, so advance callbacks for current CPU. */
718 __rcu_process_gp_end(rsp, rnp, rdp);
719
720 /*
721 * Because this CPU just now started the new grace period, we know
722 * that all of its callbacks will be covered by this upcoming grace
723 * period, even the ones that were registered arbitrarily recently.
724 * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
725 *
726 * Other CPUs cannot be sure exactly when the grace period started.
727 * Therefore, their recently registered callbacks must pass through
728 * an additional RCU_NEXT_READY stage, so that they will be handled
729 * by the next RCU grace period.
730 */
731 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
732 rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
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733
734 /* Set state so that this CPU will detect the next quiescent state. */
735 __note_new_gpnum(rsp, rnp, rdp);
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736}
737
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738/*
739 * Start a new RCU grace period if warranted, re-initializing the hierarchy
740 * in preparation for detecting the next grace period. The caller must hold
741 * the root node's ->lock, which is released before return. Hard irqs must
742 * be disabled.
743 */
744static void
745rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
746 __releases(rcu_get_root(rsp)->lock)
747{
394f99a9 748 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
64db4cff 749 struct rcu_node *rnp = rcu_get_root(rsp);
64db4cff 750
07079d53 751 if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
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752 if (cpu_needs_another_gp(rsp, rdp))
753 rsp->fqs_need_gp = 1;
b32e9eb6 754 if (rnp->completed == rsp->completed) {
1304afb2 755 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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756 return;
757 }
1304afb2 758 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
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759
760 /*
761 * Propagate new ->completed value to rcu_node structures
762 * so that other CPUs don't have to wait until the start
763 * of the next grace period to process their callbacks.
764 */
765 rcu_for_each_node_breadth_first(rsp, rnp) {
1304afb2 766 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
b32e9eb6 767 rnp->completed = rsp->completed;
1304afb2 768 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
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769 }
770 local_irq_restore(flags);
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771 return;
772 }
773
774 /* Advance to a new grace period and initialize state. */
775 rsp->gpnum++;
c3422bea 776 WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT);
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777 rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
778 rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
64db4cff 779 record_gp_stall_check_time(rsp);
64db4cff 780
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781 /* Special-case the common single-level case. */
782 if (NUM_RCU_NODES == 1) {
b0e165c0 783 rcu_preempt_check_blocked_tasks(rnp);
28ecd580 784 rnp->qsmask = rnp->qsmaskinit;
de078d87 785 rnp->gpnum = rsp->gpnum;
d09b62df 786 rnp->completed = rsp->completed;
c12172c0 787 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
d09b62df 788 rcu_start_gp_per_cpu(rsp, rnp, rdp);
1304afb2 789 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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790 return;
791 }
792
1304afb2 793 raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */
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794
795
796 /* Exclude any concurrent CPU-hotplug operations. */
1304afb2 797 raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
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798
799 /*
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800 * Set the quiescent-state-needed bits in all the rcu_node
801 * structures for all currently online CPUs in breadth-first
802 * order, starting from the root rcu_node structure. This
803 * operation relies on the layout of the hierarchy within the
804 * rsp->node[] array. Note that other CPUs will access only
805 * the leaves of the hierarchy, which still indicate that no
806 * grace period is in progress, at least until the corresponding
807 * leaf node has been initialized. In addition, we have excluded
808 * CPU-hotplug operations.
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809 *
810 * Note that the grace period cannot complete until we finish
811 * the initialization process, as there will be at least one
812 * qsmask bit set in the root node until that time, namely the
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813 * one corresponding to this CPU, due to the fact that we have
814 * irqs disabled.
64db4cff 815 */
a0b6c9a7 816 rcu_for_each_node_breadth_first(rsp, rnp) {
1304afb2 817 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
b0e165c0 818 rcu_preempt_check_blocked_tasks(rnp);
49e29126 819 rnp->qsmask = rnp->qsmaskinit;
de078d87 820 rnp->gpnum = rsp->gpnum;
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821 rnp->completed = rsp->completed;
822 if (rnp == rdp->mynode)
823 rcu_start_gp_per_cpu(rsp, rnp, rdp);
1304afb2 824 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
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825 }
826
83f5b01f 827 rnp = rcu_get_root(rsp);
1304afb2 828 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
64db4cff 829 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
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830 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
831 raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
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832}
833
f41d911f 834/*
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835 * Report a full set of quiescent states to the specified rcu_state
836 * data structure. This involves cleaning up after the prior grace
837 * period and letting rcu_start_gp() start up the next grace period
838 * if one is needed. Note that the caller must hold rnp->lock, as
839 * required by rcu_start_gp(), which will release it.
f41d911f 840 */
d3f6bad3 841static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
fc2219d4 842 __releases(rcu_get_root(rsp)->lock)
f41d911f 843{
fc2219d4 844 WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
f41d911f 845 rsp->completed = rsp->gpnum;
83f5b01f 846 rsp->signaled = RCU_GP_IDLE;
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847 rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
848}
849
64db4cff 850/*
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851 * Similar to rcu_report_qs_rdp(), for which it is a helper function.
852 * Allows quiescent states for a group of CPUs to be reported at one go
853 * to the specified rcu_node structure, though all the CPUs in the group
854 * must be represented by the same rcu_node structure (which need not be
855 * a leaf rcu_node structure, though it often will be). That structure's
856 * lock must be held upon entry, and it is released before return.
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857 */
858static void
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859rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
860 struct rcu_node *rnp, unsigned long flags)
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861 __releases(rnp->lock)
862{
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863 struct rcu_node *rnp_c;
864
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865 /* Walk up the rcu_node hierarchy. */
866 for (;;) {
867 if (!(rnp->qsmask & mask)) {
868
869 /* Our bit has already been cleared, so done. */
1304afb2 870 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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871 return;
872 }
873 rnp->qsmask &= ~mask;
f41d911f 874 if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) {
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875
876 /* Other bits still set at this level, so done. */
1304afb2 877 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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878 return;
879 }
880 mask = rnp->grpmask;
881 if (rnp->parent == NULL) {
882
883 /* No more levels. Exit loop holding root lock. */
884
885 break;
886 }
1304afb2 887 raw_spin_unlock_irqrestore(&rnp->lock, flags);
28ecd580 888 rnp_c = rnp;
64db4cff 889 rnp = rnp->parent;
1304afb2 890 raw_spin_lock_irqsave(&rnp->lock, flags);
28ecd580 891 WARN_ON_ONCE(rnp_c->qsmask);
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892 }
893
894 /*
895 * Get here if we are the last CPU to pass through a quiescent
d3f6bad3 896 * state for this grace period. Invoke rcu_report_qs_rsp()
f41d911f 897 * to clean up and start the next grace period if one is needed.
64db4cff 898 */
d3f6bad3 899 rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
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900}
901
902/*
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903 * Record a quiescent state for the specified CPU to that CPU's rcu_data
904 * structure. This must be either called from the specified CPU, or
905 * called when the specified CPU is known to be offline (and when it is
906 * also known that no other CPU is concurrently trying to help the offline
907 * CPU). The lastcomp argument is used to make sure we are still in the
908 * grace period of interest. We don't want to end the current grace period
909 * based on quiescent states detected in an earlier grace period!
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910 */
911static void
d3f6bad3 912rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
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913{
914 unsigned long flags;
915 unsigned long mask;
916 struct rcu_node *rnp;
917
918 rnp = rdp->mynode;
1304afb2 919 raw_spin_lock_irqsave(&rnp->lock, flags);
560d4bc0 920 if (lastcomp != rnp->completed) {
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921
922 /*
923 * Someone beat us to it for this grace period, so leave.
924 * The race with GP start is resolved by the fact that we
925 * hold the leaf rcu_node lock, so that the per-CPU bits
926 * cannot yet be initialized -- so we would simply find our
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927 * CPU's bit already cleared in rcu_report_qs_rnp() if this
928 * race occurred.
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929 */
930 rdp->passed_quiesc = 0; /* try again later! */
1304afb2 931 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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932 return;
933 }
934 mask = rdp->grpmask;
935 if ((rnp->qsmask & mask) == 0) {
1304afb2 936 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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937 } else {
938 rdp->qs_pending = 0;
939
940 /*
941 * This GP can't end until cpu checks in, so all of our
942 * callbacks can be processed during the next GP.
943 */
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944 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
945
d3f6bad3 946 rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
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947 }
948}
949
950/*
951 * Check to see if there is a new grace period of which this CPU
952 * is not yet aware, and if so, set up local rcu_data state for it.
953 * Otherwise, see if this CPU has just passed through its first
954 * quiescent state for this grace period, and record that fact if so.
955 */
956static void
957rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
958{
959 /* If there is now a new grace period, record and return. */
960 if (check_for_new_grace_period(rsp, rdp))
961 return;
962
963 /*
964 * Does this CPU still need to do its part for current grace period?
965 * If no, return and let the other CPUs do their part as well.
966 */
967 if (!rdp->qs_pending)
968 return;
969
970 /*
971 * Was there a quiescent state since the beginning of the grace
972 * period? If no, then exit and wait for the next call.
973 */
974 if (!rdp->passed_quiesc)
975 return;
976
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977 /*
978 * Tell RCU we are done (but rcu_report_qs_rdp() will be the
979 * judge of that).
980 */
981 rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed);
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982}
983
984#ifdef CONFIG_HOTPLUG_CPU
985
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986/*
987 * Move a dying CPU's RCU callbacks to the ->orphan_cbs_list for the
988 * specified flavor of RCU. The callbacks will be adopted by the next
989 * _rcu_barrier() invocation or by the CPU_DEAD notifier, whichever
990 * comes first. Because this is invoked from the CPU_DYING notifier,
991 * irqs are already disabled.
992 */
993static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp)
994{
995 int i;
394f99a9 996 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
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997
998 if (rdp->nxtlist == NULL)
999 return; /* irqs disabled, so comparison is stable. */
1304afb2 1000 raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
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1001 *rsp->orphan_cbs_tail = rdp->nxtlist;
1002 rsp->orphan_cbs_tail = rdp->nxttail[RCU_NEXT_TAIL];
1003 rdp->nxtlist = NULL;
1004 for (i = 0; i < RCU_NEXT_SIZE; i++)
1005 rdp->nxttail[i] = &rdp->nxtlist;
1006 rsp->orphan_qlen += rdp->qlen;
269dcc1c 1007 rdp->n_cbs_orphaned += rdp->qlen;
e74f4c45 1008 rdp->qlen = 0;
1304afb2 1009 raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
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1010}
1011
1012/*
1013 * Adopt previously orphaned RCU callbacks.
1014 */
1015static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
1016{
1017 unsigned long flags;
1018 struct rcu_data *rdp;
1019
1304afb2 1020 raw_spin_lock_irqsave(&rsp->onofflock, flags);
394f99a9 1021 rdp = this_cpu_ptr(rsp->rda);
e74f4c45 1022 if (rsp->orphan_cbs_list == NULL) {
1304afb2 1023 raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
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1024 return;
1025 }
1026 *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_list;
1027 rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_tail;
1028 rdp->qlen += rsp->orphan_qlen;
269dcc1c 1029 rdp->n_cbs_adopted += rsp->orphan_qlen;
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1030 rsp->orphan_cbs_list = NULL;
1031 rsp->orphan_cbs_tail = &rsp->orphan_cbs_list;
1032 rsp->orphan_qlen = 0;
1304afb2 1033 raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
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1034}
1035
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1036/*
1037 * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
1038 * and move all callbacks from the outgoing CPU to the current one.
1039 */
1040static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
1041{
64db4cff 1042 unsigned long flags;
64db4cff 1043 unsigned long mask;
d9a3da06 1044 int need_report = 0;
394f99a9 1045 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
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1046 struct rcu_node *rnp;
1047
1048 /* Exclude any attempts to start a new grace period. */
1304afb2 1049 raw_spin_lock_irqsave(&rsp->onofflock, flags);
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1050
1051 /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
28ecd580 1052 rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */
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1053 mask = rdp->grpmask; /* rnp->grplo is constant. */
1054 do {
1304afb2 1055 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
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1056 rnp->qsmaskinit &= ~mask;
1057 if (rnp->qsmaskinit != 0) {
b668c9cf 1058 if (rnp != rdp->mynode)
1304afb2 1059 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
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1060 break;
1061 }
b668c9cf 1062 if (rnp == rdp->mynode)
d9a3da06 1063 need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
b668c9cf 1064 else
1304afb2 1065 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
64db4cff 1066 mask = rnp->grpmask;
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1067 rnp = rnp->parent;
1068 } while (rnp != NULL);
64db4cff 1069
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1070 /*
1071 * We still hold the leaf rcu_node structure lock here, and
1072 * irqs are still disabled. The reason for this subterfuge is
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1073 * because invoking rcu_report_unblock_qs_rnp() with ->onofflock
1074 * held leads to deadlock.
b668c9cf 1075 */
1304afb2 1076 raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
b668c9cf 1077 rnp = rdp->mynode;
d9a3da06 1078 if (need_report & RCU_OFL_TASKS_NORM_GP)
d3f6bad3 1079 rcu_report_unblock_qs_rnp(rnp, flags);
b668c9cf 1080 else
1304afb2 1081 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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1082 if (need_report & RCU_OFL_TASKS_EXP_GP)
1083 rcu_report_exp_rnp(rsp, rnp);
64db4cff 1084
e74f4c45 1085 rcu_adopt_orphan_cbs(rsp);
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1086}
1087
1088/*
1089 * Remove the specified CPU from the RCU hierarchy and move any pending
1090 * callbacks that it might have to the current CPU. This code assumes
1091 * that at least one CPU in the system will remain running at all times.
1092 * Any attempt to offline -all- CPUs is likely to strand RCU callbacks.
1093 */
1094static void rcu_offline_cpu(int cpu)
1095{
d6714c22 1096 __rcu_offline_cpu(cpu, &rcu_sched_state);
64db4cff 1097 __rcu_offline_cpu(cpu, &rcu_bh_state);
33f76148 1098 rcu_preempt_offline_cpu(cpu);
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1099}
1100
1101#else /* #ifdef CONFIG_HOTPLUG_CPU */
1102
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1103static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp)
1104{
1105}
1106
1107static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
1108{
1109}
1110
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1111static void rcu_offline_cpu(int cpu)
1112{
1113}
1114
1115#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
1116
1117/*
1118 * Invoke any RCU callbacks that have made it to the end of their grace
1119 * period. Thottle as specified by rdp->blimit.
1120 */
37c72e56 1121static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
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1122{
1123 unsigned long flags;
1124 struct rcu_head *next, *list, **tail;
1125 int count;
1126
1127 /* If no callbacks are ready, just return.*/
1128 if (!cpu_has_callbacks_ready_to_invoke(rdp))
1129 return;
1130
1131 /*
1132 * Extract the list of ready callbacks, disabling to prevent
1133 * races with call_rcu() from interrupt handlers.
1134 */
1135 local_irq_save(flags);
1136 list = rdp->nxtlist;
1137 rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
1138 *rdp->nxttail[RCU_DONE_TAIL] = NULL;
1139 tail = rdp->nxttail[RCU_DONE_TAIL];
1140 for (count = RCU_NEXT_SIZE - 1; count >= 0; count--)
1141 if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL])
1142 rdp->nxttail[count] = &rdp->nxtlist;
1143 local_irq_restore(flags);
1144
1145 /* Invoke callbacks. */
1146 count = 0;
1147 while (list) {
1148 next = list->next;
1149 prefetch(next);
551d55a9 1150 debug_rcu_head_unqueue(list);
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1151 list->func(list);
1152 list = next;
1153 if (++count >= rdp->blimit)
1154 break;
1155 }
1156
1157 local_irq_save(flags);
1158
1159 /* Update count, and requeue any remaining callbacks. */
1160 rdp->qlen -= count;
269dcc1c 1161 rdp->n_cbs_invoked += count;
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1162 if (list != NULL) {
1163 *tail = rdp->nxtlist;
1164 rdp->nxtlist = list;
1165 for (count = 0; count < RCU_NEXT_SIZE; count++)
1166 if (&rdp->nxtlist == rdp->nxttail[count])
1167 rdp->nxttail[count] = tail;
1168 else
1169 break;
1170 }
1171
1172 /* Reinstate batch limit if we have worked down the excess. */
1173 if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
1174 rdp->blimit = blimit;
1175
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1176 /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
1177 if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
1178 rdp->qlen_last_fqs_check = 0;
1179 rdp->n_force_qs_snap = rsp->n_force_qs;
1180 } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
1181 rdp->qlen_last_fqs_check = rdp->qlen;
1182
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1183 local_irq_restore(flags);
1184
1185 /* Re-raise the RCU softirq if there are callbacks remaining. */
1186 if (cpu_has_callbacks_ready_to_invoke(rdp))
1187 raise_softirq(RCU_SOFTIRQ);
1188}
1189
1190/*
1191 * Check to see if this CPU is in a non-context-switch quiescent state
1192 * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
1193 * Also schedule the RCU softirq handler.
1194 *
1195 * This function must be called with hardirqs disabled. It is normally
1196 * invoked from the scheduling-clock interrupt. If rcu_pending returns
1197 * false, there is no point in invoking rcu_check_callbacks().
1198 */
1199void rcu_check_callbacks(int cpu, int user)
1200{
1201 if (user ||
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1202 (idle_cpu(cpu) && rcu_scheduler_active &&
1203 !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
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1204
1205 /*
1206 * Get here if this CPU took its interrupt from user
1207 * mode or from the idle loop, and if this is not a
1208 * nested interrupt. In this case, the CPU is in
d6714c22 1209 * a quiescent state, so note it.
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1210 *
1211 * No memory barrier is required here because both
d6714c22
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1212 * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
1213 * variables that other CPUs neither access nor modify,
1214 * at least not while the corresponding CPU is online.
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1215 */
1216
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1217 rcu_sched_qs(cpu);
1218 rcu_bh_qs(cpu);
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1219
1220 } else if (!in_softirq()) {
1221
1222 /*
1223 * Get here if this CPU did not take its interrupt from
1224 * softirq, in other words, if it is not interrupting
1225 * a rcu_bh read-side critical section. This is an _bh
d6714c22 1226 * critical section, so note it.
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1227 */
1228
d6714c22 1229 rcu_bh_qs(cpu);
64db4cff 1230 }
f41d911f 1231 rcu_preempt_check_callbacks(cpu);
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1232 if (rcu_pending(cpu))
1233 raise_softirq(RCU_SOFTIRQ);
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1234}
1235
1236#ifdef CONFIG_SMP
1237
1238/*
1239 * Scan the leaf rcu_node structures, processing dyntick state for any that
1240 * have not yet encountered a quiescent state, using the function specified.
ee47eb9f 1241 * The caller must have suppressed start of new grace periods.
64db4cff 1242 */
45f014c5 1243static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
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1244{
1245 unsigned long bit;
1246 int cpu;
1247 unsigned long flags;
1248 unsigned long mask;
a0b6c9a7 1249 struct rcu_node *rnp;
64db4cff 1250
a0b6c9a7 1251 rcu_for_each_leaf_node(rsp, rnp) {
64db4cff 1252 mask = 0;
1304afb2 1253 raw_spin_lock_irqsave(&rnp->lock, flags);
ee47eb9f 1254 if (!rcu_gp_in_progress(rsp)) {
1304afb2 1255 raw_spin_unlock_irqrestore(&rnp->lock, flags);
0f10dc82 1256 return;
64db4cff 1257 }
a0b6c9a7 1258 if (rnp->qsmask == 0) {
1304afb2 1259 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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1260 continue;
1261 }
a0b6c9a7 1262 cpu = rnp->grplo;
64db4cff 1263 bit = 1;
a0b6c9a7 1264 for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
394f99a9
LJ
1265 if ((rnp->qsmask & bit) != 0 &&
1266 f(per_cpu_ptr(rsp->rda, cpu)))
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1267 mask |= bit;
1268 }
45f014c5 1269 if (mask != 0) {
64db4cff 1270
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1271 /* rcu_report_qs_rnp() releases rnp->lock. */
1272 rcu_report_qs_rnp(mask, rsp, rnp, flags);
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1273 continue;
1274 }
1304afb2 1275 raw_spin_unlock_irqrestore(&rnp->lock, flags);
64db4cff 1276 }
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1277}
1278
1279/*
1280 * Force quiescent states on reluctant CPUs, and also detect which
1281 * CPUs are in dyntick-idle mode.
1282 */
1283static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
1284{
1285 unsigned long flags;
64db4cff 1286 struct rcu_node *rnp = rcu_get_root(rsp);
64db4cff 1287
fc2219d4 1288 if (!rcu_gp_in_progress(rsp))
64db4cff 1289 return; /* No grace period in progress, nothing to force. */
1304afb2 1290 if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) {
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1291 rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
1292 return; /* Someone else is already on the job. */
1293 }
20133cfc 1294 if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
f96e9232 1295 goto unlock_fqs_ret; /* no emergency and done recently. */
64db4cff 1296 rsp->n_force_qs++;
1304afb2 1297 raw_spin_lock(&rnp->lock); /* irqs already disabled */
64db4cff 1298 rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
560d4bc0 1299 if(!rcu_gp_in_progress(rsp)) {
64db4cff 1300 rsp->n_force_qs_ngp++;
1304afb2 1301 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
f96e9232 1302 goto unlock_fqs_ret; /* no GP in progress, time updated. */
64db4cff 1303 }
07079d53 1304 rsp->fqs_active = 1;
f3a8b5c6 1305 switch (rsp->signaled) {
83f5b01f 1306 case RCU_GP_IDLE:
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1307 case RCU_GP_INIT:
1308
83f5b01f 1309 break; /* grace period idle or initializing, ignore. */
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1310
1311 case RCU_SAVE_DYNTICK:
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1312 if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
1313 break; /* So gcc recognizes the dead code. */
1314
f261414f
LJ
1315 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
1316
64db4cff 1317 /* Record dyntick-idle state. */
45f014c5 1318 force_qs_rnp(rsp, dyntick_save_progress_counter);
1304afb2 1319 raw_spin_lock(&rnp->lock); /* irqs already disabled */
ee47eb9f 1320 if (rcu_gp_in_progress(rsp))
64db4cff 1321 rsp->signaled = RCU_FORCE_QS;
ee47eb9f 1322 break;
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1323
1324 case RCU_FORCE_QS:
1325
1326 /* Check dyntick-idle state, send IPI to laggarts. */
1304afb2 1327 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
45f014c5 1328 force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
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1329
1330 /* Leave state in case more forcing is required. */
1331
1304afb2 1332 raw_spin_lock(&rnp->lock); /* irqs already disabled */
f96e9232 1333 break;
64db4cff 1334 }
07079d53 1335 rsp->fqs_active = 0;
46a1e34e 1336 if (rsp->fqs_need_gp) {
1304afb2 1337 raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */
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1338 rsp->fqs_need_gp = 0;
1339 rcu_start_gp(rsp, flags); /* releases rnp->lock */
1340 return;
1341 }
1304afb2 1342 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
f96e9232 1343unlock_fqs_ret:
1304afb2 1344 raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
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1345}
1346
1347#else /* #ifdef CONFIG_SMP */
1348
1349static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
1350{
1351 set_need_resched();
1352}
1353
1354#endif /* #else #ifdef CONFIG_SMP */
1355
1356/*
1357 * This does the RCU processing work from softirq context for the
1358 * specified rcu_state and rcu_data structures. This may be called
1359 * only from the CPU to whom the rdp belongs.
1360 */
1361static void
1362__rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
1363{
1364 unsigned long flags;
1365
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1366 WARN_ON_ONCE(rdp->beenonline == 0);
1367
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1368 /*
1369 * If an RCU GP has gone long enough, go check for dyntick
1370 * idle CPUs and, if needed, send resched IPIs.
1371 */
20133cfc 1372 if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
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1373 force_quiescent_state(rsp, 1);
1374
1375 /*
1376 * Advance callbacks in response to end of earlier grace
1377 * period that some other CPU ended.
1378 */
1379 rcu_process_gp_end(rsp, rdp);
1380
1381 /* Update RCU state based on any recent quiescent states. */
1382 rcu_check_quiescent_state(rsp, rdp);
1383
1384 /* Does this CPU require a not-yet-started grace period? */
1385 if (cpu_needs_another_gp(rsp, rdp)) {
1304afb2 1386 raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
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1387 rcu_start_gp(rsp, flags); /* releases above lock */
1388 }
1389
1390 /* If there are callbacks ready, invoke them. */
37c72e56 1391 rcu_do_batch(rsp, rdp);
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1392}
1393
1394/*
1395 * Do softirq processing for the current CPU.
1396 */
1397static void rcu_process_callbacks(struct softirq_action *unused)
1398{
1399 /*
1400 * Memory references from any prior RCU read-side critical sections
1401 * executed by the interrupted code must be seen before any RCU
1402 * grace-period manipulations below.
1403 */
1404 smp_mb(); /* See above block comment. */
1405
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1406 __rcu_process_callbacks(&rcu_sched_state,
1407 &__get_cpu_var(rcu_sched_data));
64db4cff 1408 __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
f41d911f 1409 rcu_preempt_process_callbacks();
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1410
1411 /*
1412 * Memory references from any later RCU read-side critical sections
1413 * executed by the interrupted code must be seen after any RCU
1414 * grace-period manipulations above.
1415 */
1416 smp_mb(); /* See above block comment. */
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1417
1418 /* If we are last CPU on way to dyntick-idle mode, accelerate it. */
1419 rcu_needs_cpu_flush();
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1420}
1421
1422static void
1423__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
1424 struct rcu_state *rsp)
1425{
1426 unsigned long flags;
1427 struct rcu_data *rdp;
1428
551d55a9 1429 debug_rcu_head_queue(head);
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1430 head->func = func;
1431 head->next = NULL;
1432
1433 smp_mb(); /* Ensure RCU update seen before callback registry. */
1434
1435 /*
1436 * Opportunistically note grace-period endings and beginnings.
1437 * Note that we might see a beginning right after we see an
1438 * end, but never vice versa, since this CPU has to pass through
1439 * a quiescent state betweentimes.
1440 */
1441 local_irq_save(flags);
394f99a9 1442 rdp = this_cpu_ptr(rsp->rda);
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1443 rcu_process_gp_end(rsp, rdp);
1444 check_for_new_grace_period(rsp, rdp);
1445
1446 /* Add the callback to our list. */
1447 *rdp->nxttail[RCU_NEXT_TAIL] = head;
1448 rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
1449
1450 /* Start a new grace period if one not already started. */
fc2219d4 1451 if (!rcu_gp_in_progress(rsp)) {
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1452 unsigned long nestflag;
1453 struct rcu_node *rnp_root = rcu_get_root(rsp);
1454
1304afb2 1455 raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
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1456 rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */
1457 }
1458
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1459 /*
1460 * Force the grace period if too many callbacks or too long waiting.
1461 * Enforce hysteresis, and don't invoke force_quiescent_state()
1462 * if some other CPU has recently done so. Also, don't bother
1463 * invoking force_quiescent_state() if the newly enqueued callback
1464 * is the only one waiting for a grace period to complete.
1465 */
1466 if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
64db4cff 1467 rdp->blimit = LONG_MAX;
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1468 if (rsp->n_force_qs == rdp->n_force_qs_snap &&
1469 *rdp->nxttail[RCU_DONE_TAIL] != head)
1470 force_quiescent_state(rsp, 0);
1471 rdp->n_force_qs_snap = rsp->n_force_qs;
1472 rdp->qlen_last_fqs_check = rdp->qlen;
20133cfc 1473 } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
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1474 force_quiescent_state(rsp, 1);
1475 local_irq_restore(flags);
1476}
1477
1478/*
d6714c22 1479 * Queue an RCU-sched callback for invocation after a grace period.
64db4cff 1480 */
d6714c22 1481void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
64db4cff 1482{
d6714c22 1483 __call_rcu(head, func, &rcu_sched_state);
64db4cff 1484}
d6714c22 1485EXPORT_SYMBOL_GPL(call_rcu_sched);
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1486
1487/*
1488 * Queue an RCU for invocation after a quicker grace period.
1489 */
1490void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
1491{
1492 __call_rcu(head, func, &rcu_bh_state);
1493}
1494EXPORT_SYMBOL_GPL(call_rcu_bh);
1495
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1496/**
1497 * synchronize_sched - wait until an rcu-sched grace period has elapsed.
1498 *
1499 * Control will return to the caller some time after a full rcu-sched
1500 * grace period has elapsed, in other words after all currently executing
1501 * rcu-sched read-side critical sections have completed. These read-side
1502 * critical sections are delimited by rcu_read_lock_sched() and
1503 * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
1504 * local_irq_disable(), and so on may be used in place of
1505 * rcu_read_lock_sched().
1506 *
1507 * This means that all preempt_disable code sequences, including NMI and
1508 * hardware-interrupt handlers, in progress on entry will have completed
1509 * before this primitive returns. However, this does not guarantee that
1510 * softirq handlers will have completed, since in some kernels, these
1511 * handlers can run in process context, and can block.
1512 *
1513 * This primitive provides the guarantees made by the (now removed)
1514 * synchronize_kernel() API. In contrast, synchronize_rcu() only
1515 * guarantees that rcu_read_lock() sections will have completed.
1516 * In "classic RCU", these two guarantees happen to be one and
1517 * the same, but can differ in realtime RCU implementations.
1518 */
1519void synchronize_sched(void)
1520{
1521 struct rcu_synchronize rcu;
1522
1523 if (rcu_blocking_is_gp())
1524 return;
1525
72d5a9f7 1526 init_rcu_head_on_stack(&rcu.head);
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1527 init_completion(&rcu.completion);
1528 /* Will wake me after RCU finished. */
1529 call_rcu_sched(&rcu.head, wakeme_after_rcu);
1530 /* Wait for it. */
1531 wait_for_completion(&rcu.completion);
72d5a9f7 1532 destroy_rcu_head_on_stack(&rcu.head);
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1533}
1534EXPORT_SYMBOL_GPL(synchronize_sched);
1535
1536/**
1537 * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
1538 *
1539 * Control will return to the caller some time after a full rcu_bh grace
1540 * period has elapsed, in other words after all currently executing rcu_bh
1541 * read-side critical sections have completed. RCU read-side critical
1542 * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
1543 * and may be nested.
1544 */
1545void synchronize_rcu_bh(void)
1546{
1547 struct rcu_synchronize rcu;
1548
1549 if (rcu_blocking_is_gp())
1550 return;
1551
72d5a9f7 1552 init_rcu_head_on_stack(&rcu.head);
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1553 init_completion(&rcu.completion);
1554 /* Will wake me after RCU finished. */
1555 call_rcu_bh(&rcu.head, wakeme_after_rcu);
1556 /* Wait for it. */
1557 wait_for_completion(&rcu.completion);
72d5a9f7 1558 destroy_rcu_head_on_stack(&rcu.head);
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1559}
1560EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
1561
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1562/*
1563 * Check to see if there is any immediate RCU-related work to be done
1564 * by the current CPU, for the specified type of RCU, returning 1 if so.
1565 * The checks are in order of increasing expense: checks that can be
1566 * carried out against CPU-local state are performed first. However,
1567 * we must check for CPU stalls first, else we might not get a chance.
1568 */
1569static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
1570{
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1571 struct rcu_node *rnp = rdp->mynode;
1572
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1573 rdp->n_rcu_pending++;
1574
1575 /* Check for CPU stalls, if enabled. */
1576 check_cpu_stall(rsp, rdp);
1577
1578 /* Is the RCU core waiting for a quiescent state from this CPU? */
d21670ac 1579 if (rdp->qs_pending && !rdp->passed_quiesc) {
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1580
1581 /*
1582 * If force_quiescent_state() coming soon and this CPU
1583 * needs a quiescent state, and this is either RCU-sched
1584 * or RCU-bh, force a local reschedule.
1585 */
d21670ac 1586 rdp->n_rp_qs_pending++;
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1587 if (!rdp->preemptable &&
1588 ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
1589 jiffies))
1590 set_need_resched();
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1591 } else if (rdp->qs_pending && rdp->passed_quiesc) {
1592 rdp->n_rp_report_qs++;
64db4cff 1593 return 1;
7ba5c840 1594 }
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1595
1596 /* Does this CPU have callbacks ready to invoke? */
7ba5c840
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1597 if (cpu_has_callbacks_ready_to_invoke(rdp)) {
1598 rdp->n_rp_cb_ready++;
64db4cff 1599 return 1;
7ba5c840 1600 }
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1601
1602 /* Has RCU gone idle with this CPU needing another grace period? */
7ba5c840
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1603 if (cpu_needs_another_gp(rsp, rdp)) {
1604 rdp->n_rp_cpu_needs_gp++;
64db4cff 1605 return 1;
7ba5c840 1606 }
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1607
1608 /* Has another RCU grace period completed? */
2f51f988 1609 if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
7ba5c840 1610 rdp->n_rp_gp_completed++;
64db4cff 1611 return 1;
7ba5c840 1612 }
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1613
1614 /* Has a new RCU grace period started? */
2f51f988 1615 if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
7ba5c840 1616 rdp->n_rp_gp_started++;
64db4cff 1617 return 1;
7ba5c840 1618 }
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1619
1620 /* Has an RCU GP gone long enough to send resched IPIs &c? */
fc2219d4 1621 if (rcu_gp_in_progress(rsp) &&
20133cfc 1622 ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) {
7ba5c840 1623 rdp->n_rp_need_fqs++;
64db4cff 1624 return 1;
7ba5c840 1625 }
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1626
1627 /* nothing to do */
7ba5c840 1628 rdp->n_rp_need_nothing++;
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1629 return 0;
1630}
1631
1632/*
1633 * Check to see if there is any immediate RCU-related work to be done
1634 * by the current CPU, returning 1 if so. This function is part of the
1635 * RCU implementation; it is -not- an exported member of the RCU API.
1636 */
a157229c 1637static int rcu_pending(int cpu)
64db4cff 1638{
d6714c22 1639 return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
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1640 __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) ||
1641 rcu_preempt_pending(cpu);
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1642}
1643
1644/*
1645 * Check to see if any future RCU-related work will need to be done
1646 * by the current CPU, even if none need be done immediately, returning
8bd93a2c 1647 * 1 if so.
64db4cff 1648 */
8bd93a2c 1649static int rcu_needs_cpu_quick_check(int cpu)
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1650{
1651 /* RCU callbacks either ready or pending? */
d6714c22 1652 return per_cpu(rcu_sched_data, cpu).nxtlist ||
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1653 per_cpu(rcu_bh_data, cpu).nxtlist ||
1654 rcu_preempt_needs_cpu(cpu);
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1655}
1656
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1657static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
1658static atomic_t rcu_barrier_cpu_count;
1659static DEFINE_MUTEX(rcu_barrier_mutex);
1660static struct completion rcu_barrier_completion;
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1661
1662static void rcu_barrier_callback(struct rcu_head *notused)
1663{
1664 if (atomic_dec_and_test(&rcu_barrier_cpu_count))
1665 complete(&rcu_barrier_completion);
1666}
1667
1668/*
1669 * Called with preemption disabled, and from cross-cpu IRQ context.
1670 */
1671static void rcu_barrier_func(void *type)
1672{
1673 int cpu = smp_processor_id();
1674 struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
1675 void (*call_rcu_func)(struct rcu_head *head,
1676 void (*func)(struct rcu_head *head));
1677
1678 atomic_inc(&rcu_barrier_cpu_count);
1679 call_rcu_func = type;
1680 call_rcu_func(head, rcu_barrier_callback);
1681}
1682
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1683/*
1684 * Orchestrate the specified type of RCU barrier, waiting for all
1685 * RCU callbacks of the specified type to complete.
1686 */
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1687static void _rcu_barrier(struct rcu_state *rsp,
1688 void (*call_rcu_func)(struct rcu_head *head,
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1689 void (*func)(struct rcu_head *head)))
1690{
1691 BUG_ON(in_interrupt());
e74f4c45 1692 /* Take mutex to serialize concurrent rcu_barrier() requests. */
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1693 mutex_lock(&rcu_barrier_mutex);
1694 init_completion(&rcu_barrier_completion);
1695 /*
1696 * Initialize rcu_barrier_cpu_count to 1, then invoke
1697 * rcu_barrier_func() on each CPU, so that each CPU also has
1698 * incremented rcu_barrier_cpu_count. Only then is it safe to
1699 * decrement rcu_barrier_cpu_count -- otherwise the first CPU
1700 * might complete its grace period before all of the other CPUs
1701 * did their increment, causing this function to return too
1702 * early.
1703 */
1704 atomic_set(&rcu_barrier_cpu_count, 1);
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1705 preempt_disable(); /* stop CPU_DYING from filling orphan_cbs_list */
1706 rcu_adopt_orphan_cbs(rsp);
d0ec774c 1707 on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
e74f4c45 1708 preempt_enable(); /* CPU_DYING can again fill orphan_cbs_list */
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1709 if (atomic_dec_and_test(&rcu_barrier_cpu_count))
1710 complete(&rcu_barrier_completion);
1711 wait_for_completion(&rcu_barrier_completion);
1712 mutex_unlock(&rcu_barrier_mutex);
d0ec774c 1713}
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1714
1715/**
1716 * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
1717 */
1718void rcu_barrier_bh(void)
1719{
e74f4c45 1720 _rcu_barrier(&rcu_bh_state, call_rcu_bh);
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1721}
1722EXPORT_SYMBOL_GPL(rcu_barrier_bh);
1723
1724/**
1725 * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
1726 */
1727void rcu_barrier_sched(void)
1728{
e74f4c45 1729 _rcu_barrier(&rcu_sched_state, call_rcu_sched);
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1730}
1731EXPORT_SYMBOL_GPL(rcu_barrier_sched);
1732
64db4cff 1733/*
27569620 1734 * Do boot-time initialization of a CPU's per-CPU RCU data.
64db4cff 1735 */
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1736static void __init
1737rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
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1738{
1739 unsigned long flags;
1740 int i;
394f99a9 1741 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
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1742 struct rcu_node *rnp = rcu_get_root(rsp);
1743
1744 /* Set up local state, ensuring consistent view of global state. */
1304afb2 1745 raw_spin_lock_irqsave(&rnp->lock, flags);
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1746 rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
1747 rdp->nxtlist = NULL;
1748 for (i = 0; i < RCU_NEXT_SIZE; i++)
1749 rdp->nxttail[i] = &rdp->nxtlist;
1750 rdp->qlen = 0;
1751#ifdef CONFIG_NO_HZ
1752 rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
1753#endif /* #ifdef CONFIG_NO_HZ */
1754 rdp->cpu = cpu;
1304afb2 1755 raw_spin_unlock_irqrestore(&rnp->lock, flags);
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1756}
1757
1758/*
1759 * Initialize a CPU's per-CPU RCU data. Note that only one online or
1760 * offline event can be happening at a given time. Note also that we
1761 * can accept some slop in the rsp->completed access due to the fact
1762 * that this CPU cannot possibly have any RCU callbacks in flight yet.
64db4cff 1763 */
e4fa4c97 1764static void __cpuinit
f41d911f 1765rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
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1766{
1767 unsigned long flags;
64db4cff 1768 unsigned long mask;
394f99a9 1769 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
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1770 struct rcu_node *rnp = rcu_get_root(rsp);
1771
1772 /* Set up local state, ensuring consistent view of global state. */
1304afb2 1773 raw_spin_lock_irqsave(&rnp->lock, flags);
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1774 rdp->passed_quiesc = 0; /* We could be racing with new GP, */
1775 rdp->qs_pending = 1; /* so set up to respond to current GP. */
1776 rdp->beenonline = 1; /* We have now been online. */
f41d911f 1777 rdp->preemptable = preemptable;
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1778 rdp->qlen_last_fqs_check = 0;
1779 rdp->n_force_qs_snap = rsp->n_force_qs;
64db4cff 1780 rdp->blimit = blimit;
1304afb2 1781 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
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1782
1783 /*
1784 * A new grace period might start here. If so, we won't be part
1785 * of it, but that is OK, as we are currently in a quiescent state.
1786 */
1787
1788 /* Exclude any attempts to start a new GP on large systems. */
1304afb2 1789 raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
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1790
1791 /* Add CPU to rcu_node bitmasks. */
1792 rnp = rdp->mynode;
1793 mask = rdp->grpmask;
1794 do {
1795 /* Exclude any attempts to start a new GP on small systems. */
1304afb2 1796 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
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1797 rnp->qsmaskinit |= mask;
1798 mask = rnp->grpmask;
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1799 if (rnp == rdp->mynode) {
1800 rdp->gpnum = rnp->completed; /* if GP in progress... */
1801 rdp->completed = rnp->completed;
1802 rdp->passed_quiesc_completed = rnp->completed - 1;
1803 }
1304afb2 1804 raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
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1805 rnp = rnp->parent;
1806 } while (rnp != NULL && !(rnp->qsmaskinit & mask));
1807
1304afb2 1808 raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
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1809}
1810
1811static void __cpuinit rcu_online_cpu(int cpu)
1812{
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1813 rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
1814 rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
1815 rcu_preempt_init_percpu_data(cpu);
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1816}
1817
1818/*
f41d911f 1819 * Handle CPU online/offline notification events.
64db4cff 1820 */
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1821static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
1822 unsigned long action, void *hcpu)
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1823{
1824 long cpu = (long)hcpu;
1825
1826 switch (action) {
1827 case CPU_UP_PREPARE:
1828 case CPU_UP_PREPARE_FROZEN:
1829 rcu_online_cpu(cpu);
1830 break;
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1831 case CPU_DYING:
1832 case CPU_DYING_FROZEN:
1833 /*
e74f4c45 1834 * preempt_disable() in _rcu_barrier() prevents stop_machine(),
d0ec774c 1835 * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);"
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1836 * returns, all online cpus have queued rcu_barrier_func().
1837 * The dying CPU clears its cpu_online_mask bit and
1838 * moves all of its RCU callbacks to ->orphan_cbs_list
1839 * in the context of stop_machine(), so subsequent calls
1840 * to _rcu_barrier() will adopt these callbacks and only
1841 * then queue rcu_barrier_func() on all remaining CPUs.
d0ec774c 1842 */
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1843 rcu_send_cbs_to_orphanage(&rcu_bh_state);
1844 rcu_send_cbs_to_orphanage(&rcu_sched_state);
1845 rcu_preempt_send_cbs_to_orphanage();
d0ec774c 1846 break;
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1847 case CPU_DEAD:
1848 case CPU_DEAD_FROZEN:
1849 case CPU_UP_CANCELED:
1850 case CPU_UP_CANCELED_FROZEN:
1851 rcu_offline_cpu(cpu);
1852 break;
1853 default:
1854 break;
1855 }
1856 return NOTIFY_OK;
1857}
1858
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1859/*
1860 * This function is invoked towards the end of the scheduler's initialization
1861 * process. Before this is called, the idle task might contain
1862 * RCU read-side critical sections (during which time, this idle
1863 * task is booting the system). After this function is called, the
1864 * idle tasks are prohibited from containing RCU read-side critical
1865 * sections. This function also enables RCU lockdep checking.
1866 */
1867void rcu_scheduler_starting(void)
1868{
1869 WARN_ON(num_online_cpus() != 1);
1870 WARN_ON(nr_context_switches() > 0);
1871 rcu_scheduler_active = 1;
1872}
1873
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1874/*
1875 * Compute the per-level fanout, either using the exact fanout specified
1876 * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
1877 */
1878#ifdef CONFIG_RCU_FANOUT_EXACT
1879static void __init rcu_init_levelspread(struct rcu_state *rsp)
1880{
1881 int i;
1882
1883 for (i = NUM_RCU_LVLS - 1; i >= 0; i--)
1884 rsp->levelspread[i] = CONFIG_RCU_FANOUT;
1885}
1886#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
1887static void __init rcu_init_levelspread(struct rcu_state *rsp)
1888{
1889 int ccur;
1890 int cprv;
1891 int i;
1892
1893 cprv = NR_CPUS;
1894 for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
1895 ccur = rsp->levelcnt[i];
1896 rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
1897 cprv = ccur;
1898 }
1899}
1900#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
1901
1902/*
1903 * Helper function for rcu_init() that initializes one rcu_state structure.
1904 */
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1905static void __init rcu_init_one(struct rcu_state *rsp,
1906 struct rcu_data __percpu *rda)
64db4cff 1907{
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1908 static char *buf[] = { "rcu_node_level_0",
1909 "rcu_node_level_1",
1910 "rcu_node_level_2",
1911 "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */
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1912 int cpustride = 1;
1913 int i;
1914 int j;
1915 struct rcu_node *rnp;
1916
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1917 BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
1918
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1919 /* Initialize the level-tracking arrays. */
1920
1921 for (i = 1; i < NUM_RCU_LVLS; i++)
1922 rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
1923 rcu_init_levelspread(rsp);
1924
1925 /* Initialize the elements themselves, starting from the leaves. */
1926
1927 for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
1928 cpustride *= rsp->levelspread[i];
1929 rnp = rsp->level[i];
1930 for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
1304afb2 1931 raw_spin_lock_init(&rnp->lock);
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1932 lockdep_set_class_and_name(&rnp->lock,
1933 &rcu_node_class[i], buf[i]);
f41d911f 1934 rnp->gpnum = 0;
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1935 rnp->qsmask = 0;
1936 rnp->qsmaskinit = 0;
1937 rnp->grplo = j * cpustride;
1938 rnp->grphi = (j + 1) * cpustride - 1;
1939 if (rnp->grphi >= NR_CPUS)
1940 rnp->grphi = NR_CPUS - 1;
1941 if (i == 0) {
1942 rnp->grpnum = 0;
1943 rnp->grpmask = 0;
1944 rnp->parent = NULL;
1945 } else {
1946 rnp->grpnum = j % rsp->levelspread[i - 1];
1947 rnp->grpmask = 1UL << rnp->grpnum;
1948 rnp->parent = rsp->level[i - 1] +
1949 j / rsp->levelspread[i - 1];
1950 }
1951 rnp->level = i;
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1952 INIT_LIST_HEAD(&rnp->blocked_tasks[0]);
1953 INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
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1954 INIT_LIST_HEAD(&rnp->blocked_tasks[2]);
1955 INIT_LIST_HEAD(&rnp->blocked_tasks[3]);
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1956 }
1957 }
0c34029a 1958
394f99a9 1959 rsp->rda = rda;
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1960 rnp = rsp->level[NUM_RCU_LVLS - 1];
1961 for_each_possible_cpu(i) {
4a90a068 1962 while (i > rnp->grphi)
0c34029a 1963 rnp++;
394f99a9 1964 per_cpu_ptr(rsp->rda, i)->mynode = rnp;
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1965 rcu_boot_init_percpu_data(i, rsp);
1966 }
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1967}
1968
9f680ab4 1969void __init rcu_init(void)
64db4cff 1970{
017c4261 1971 int cpu;
9f680ab4 1972
f41d911f 1973 rcu_bootup_announce();
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1974 rcu_init_one(&rcu_sched_state, &rcu_sched_data);
1975 rcu_init_one(&rcu_bh_state, &rcu_bh_data);
f41d911f 1976 __rcu_init_preempt();
2e597558 1977 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
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1978
1979 /*
1980 * We don't need protection against CPU-hotplug here because
1981 * this is called early in boot, before either interrupts
1982 * or the scheduler are operational.
1983 */
1984 cpu_notifier(rcu_cpu_notify, 0);
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1985 for_each_online_cpu(cpu)
1986 rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
c68de209 1987 check_cpu_stall_init();
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1988}
1989
1eba8f84 1990#include "rcutree_plugin.h"