2 * Read-Copy Update mechanism for mutual exclusion
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.
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.
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.
18 * Copyright IBM Corporation, 2008
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
24 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
25 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
27 * For detailed explanation of Read-Copy Update mechanism see -
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>
38 #include <linux/nmi.h>
39 #include <linux/atomic.h>
40 #include <linux/bitops.h>
41 #include <linux/export.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>
49 #include <linux/kernel_stat.h>
50 #include <linux/wait.h>
51 #include <linux/kthread.h>
52 #include <linux/prefetch.h>
53 #include <linux/delay.h>
54 #include <linux/stop_machine.h>
55 #include <linux/random.h>
58 #include <trace/events/rcu.h>
62 /* Data structures. */
64 static struct lock_class_key rcu_node_class
[RCU_NUM_LVLS
];
65 static struct lock_class_key rcu_fqs_class
[RCU_NUM_LVLS
];
67 #define RCU_STATE_INITIALIZER(sname, sabbr, cr) { \
68 .level = { &sname##_state.node[0] }, \
70 .fqs_state = RCU_GP_IDLE, \
71 .gpnum = 0UL - 300UL, \
72 .completed = 0UL - 300UL, \
73 .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \
74 .orphan_nxttail = &sname##_state.orphan_nxtlist, \
75 .orphan_donetail = &sname##_state.orphan_donelist, \
76 .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
77 .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
82 struct rcu_state rcu_sched_state
=
83 RCU_STATE_INITIALIZER(rcu_sched
, 's', call_rcu_sched
);
84 DEFINE_PER_CPU(struct rcu_data
, rcu_sched_data
);
86 struct rcu_state rcu_bh_state
= RCU_STATE_INITIALIZER(rcu_bh
, 'b', call_rcu_bh
);
87 DEFINE_PER_CPU(struct rcu_data
, rcu_bh_data
);
89 static struct rcu_state
*rcu_state
;
90 LIST_HEAD(rcu_struct_flavors
);
92 /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
93 static int rcu_fanout_leaf
= CONFIG_RCU_FANOUT_LEAF
;
94 module_param(rcu_fanout_leaf
, int, 0444);
95 int rcu_num_lvls __read_mostly
= RCU_NUM_LVLS
;
96 static int num_rcu_lvl
[] = { /* Number of rcu_nodes at specified level. */
103 int rcu_num_nodes __read_mostly
= NUM_RCU_NODES
; /* Total # rcu_nodes in use. */
106 * The rcu_scheduler_active variable transitions from zero to one just
107 * before the first task is spawned. So when this variable is zero, RCU
108 * can assume that there is but one task, allowing RCU to (for example)
109 * optimize synchronize_sched() to a simple barrier(). When this variable
110 * is one, RCU must actually do all the hard work required to detect real
111 * grace periods. This variable is also used to suppress boot-time false
112 * positives from lockdep-RCU error checking.
114 int rcu_scheduler_active __read_mostly
;
115 EXPORT_SYMBOL_GPL(rcu_scheduler_active
);
118 * The rcu_scheduler_fully_active variable transitions from zero to one
119 * during the early_initcall() processing, which is after the scheduler
120 * is capable of creating new tasks. So RCU processing (for example,
121 * creating tasks for RCU priority boosting) must be delayed until after
122 * rcu_scheduler_fully_active transitions from zero to one. We also
123 * currently delay invocation of any RCU callbacks until after this point.
125 * It might later prove better for people registering RCU callbacks during
126 * early boot to take responsibility for these callbacks, but one step at
129 static int rcu_scheduler_fully_active __read_mostly
;
131 #ifdef CONFIG_RCU_BOOST
134 * Control variables for per-CPU and per-rcu_node kthreads. These
135 * handle all flavors of RCU.
137 static DEFINE_PER_CPU(struct task_struct
*, rcu_cpu_kthread_task
);
138 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status
);
139 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops
);
140 DEFINE_PER_CPU(char, rcu_cpu_has_work
);
142 #endif /* #ifdef CONFIG_RCU_BOOST */
144 static void rcu_boost_kthread_setaffinity(struct rcu_node
*rnp
, int outgoingcpu
);
145 static void invoke_rcu_core(void);
146 static void invoke_rcu_callbacks(struct rcu_state
*rsp
, struct rcu_data
*rdp
);
149 * Track the rcutorture test sequence number and the update version
150 * number within a given test. The rcutorture_testseq is incremented
151 * on every rcutorture module load and unload, so has an odd value
152 * when a test is running. The rcutorture_vernum is set to zero
153 * when rcutorture starts and is incremented on each rcutorture update.
154 * These variables enable correlating rcutorture output with the
155 * RCU tracing information.
157 unsigned long rcutorture_testseq
;
158 unsigned long rcutorture_vernum
;
161 * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
162 * permit this function to be invoked without holding the root rcu_node
163 * structure's ->lock, but of course results can be subject to change.
165 static int rcu_gp_in_progress(struct rcu_state
*rsp
)
167 return ACCESS_ONCE(rsp
->completed
) != ACCESS_ONCE(rsp
->gpnum
);
171 * Note a quiescent state. Because we do not need to know
172 * how many quiescent states passed, just if there was at least
173 * one since the start of the grace period, this just sets a flag.
174 * The caller must have disabled preemption.
176 void rcu_sched_qs(int cpu
)
178 struct rcu_data
*rdp
= &per_cpu(rcu_sched_data
, cpu
);
180 if (rdp
->passed_quiesce
== 0)
181 trace_rcu_grace_period("rcu_sched", rdp
->gpnum
, "cpuqs");
182 rdp
->passed_quiesce
= 1;
185 void rcu_bh_qs(int cpu
)
187 struct rcu_data
*rdp
= &per_cpu(rcu_bh_data
, cpu
);
189 if (rdp
->passed_quiesce
== 0)
190 trace_rcu_grace_period("rcu_bh", rdp
->gpnum
, "cpuqs");
191 rdp
->passed_quiesce
= 1;
195 * Note a context switch. This is a quiescent state for RCU-sched,
196 * and requires special handling for preemptible RCU.
197 * The caller must have disabled preemption.
199 void rcu_note_context_switch(int cpu
)
201 trace_rcu_utilization("Start context switch");
203 rcu_preempt_note_context_switch(cpu
);
204 trace_rcu_utilization("End context switch");
206 EXPORT_SYMBOL_GPL(rcu_note_context_switch
);
208 DEFINE_PER_CPU(struct rcu_dynticks
, rcu_dynticks
) = {
209 .dynticks_nesting
= DYNTICK_TASK_EXIT_IDLE
,
210 .dynticks
= ATOMIC_INIT(1),
213 static long blimit
= 10; /* Maximum callbacks per rcu_do_batch. */
214 static long qhimark
= 10000; /* If this many pending, ignore blimit. */
215 static long qlowmark
= 100; /* Once only this many pending, use blimit. */
217 module_param(blimit
, long, 0444);
218 module_param(qhimark
, long, 0444);
219 module_param(qlowmark
, long, 0444);
221 static ulong jiffies_till_first_fqs
= RCU_JIFFIES_TILL_FORCE_QS
;
222 static ulong jiffies_till_next_fqs
= RCU_JIFFIES_TILL_FORCE_QS
;
224 module_param(jiffies_till_first_fqs
, ulong
, 0644);
225 module_param(jiffies_till_next_fqs
, ulong
, 0644);
227 static void force_qs_rnp(struct rcu_state
*rsp
, int (*f
)(struct rcu_data
*));
228 static void force_quiescent_state(struct rcu_state
*rsp
);
229 static int rcu_pending(int cpu
);
232 * Return the number of RCU-sched batches processed thus far for debug & stats.
234 long rcu_batches_completed_sched(void)
236 return rcu_sched_state
.completed
;
238 EXPORT_SYMBOL_GPL(rcu_batches_completed_sched
);
241 * Return the number of RCU BH batches processed thus far for debug & stats.
243 long rcu_batches_completed_bh(void)
245 return rcu_bh_state
.completed
;
247 EXPORT_SYMBOL_GPL(rcu_batches_completed_bh
);
250 * Force a quiescent state for RCU BH.
252 void rcu_bh_force_quiescent_state(void)
254 force_quiescent_state(&rcu_bh_state
);
256 EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state
);
259 * Record the number of times rcutorture tests have been initiated and
260 * terminated. This information allows the debugfs tracing stats to be
261 * correlated to the rcutorture messages, even when the rcutorture module
262 * is being repeatedly loaded and unloaded. In other words, we cannot
263 * store this state in rcutorture itself.
265 void rcutorture_record_test_transition(void)
267 rcutorture_testseq
++;
268 rcutorture_vernum
= 0;
270 EXPORT_SYMBOL_GPL(rcutorture_record_test_transition
);
273 * Record the number of writer passes through the current rcutorture test.
274 * This is also used to correlate debugfs tracing stats with the rcutorture
277 void rcutorture_record_progress(unsigned long vernum
)
281 EXPORT_SYMBOL_GPL(rcutorture_record_progress
);
284 * Force a quiescent state for RCU-sched.
286 void rcu_sched_force_quiescent_state(void)
288 force_quiescent_state(&rcu_sched_state
);
290 EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state
);
293 * Does the CPU have callbacks ready to be invoked?
296 cpu_has_callbacks_ready_to_invoke(struct rcu_data
*rdp
)
298 return &rdp
->nxtlist
!= rdp
->nxttail
[RCU_DONE_TAIL
] &&
299 rdp
->nxttail
[RCU_DONE_TAIL
] != NULL
;
303 * Does the current CPU require a not-yet-started grace period?
304 * The caller must have disabled interrupts to prevent races with
305 * normal callback registry.
308 cpu_needs_another_gp(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
312 if (rcu_gp_in_progress(rsp
))
313 return 0; /* No, a grace period is already in progress. */
314 if (rcu_nocb_needs_gp(rsp
))
315 return 1; /* Yes, a no-CBs CPU needs one. */
316 if (!rdp
->nxttail
[RCU_NEXT_TAIL
])
317 return 0; /* No, this is a no-CBs (or offline) CPU. */
318 if (*rdp
->nxttail
[RCU_NEXT_READY_TAIL
])
319 return 1; /* Yes, this CPU has newly registered callbacks. */
320 for (i
= RCU_WAIT_TAIL
; i
< RCU_NEXT_TAIL
; i
++)
321 if (rdp
->nxttail
[i
- 1] != rdp
->nxttail
[i
] &&
322 ULONG_CMP_LT(ACCESS_ONCE(rsp
->completed
),
323 rdp
->nxtcompleted
[i
]))
324 return 1; /* Yes, CBs for future grace period. */
325 return 0; /* No grace period needed. */
329 * Return the root node of the specified rcu_state structure.
331 static struct rcu_node
*rcu_get_root(struct rcu_state
*rsp
)
333 return &rsp
->node
[0];
337 * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state
339 * If the new value of the ->dynticks_nesting counter now is zero,
340 * we really have entered idle, and must do the appropriate accounting.
341 * The caller must have disabled interrupts.
343 static void rcu_eqs_enter_common(struct rcu_dynticks
*rdtp
, long long oldval
,
346 trace_rcu_dyntick("Start", oldval
, rdtp
->dynticks_nesting
);
347 if (!user
&& !is_idle_task(current
)) {
348 struct task_struct
*idle
= idle_task(smp_processor_id());
350 trace_rcu_dyntick("Error on entry: not idle task", oldval
, 0);
351 ftrace_dump(DUMP_ORIG
);
352 WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
353 current
->pid
, current
->comm
,
354 idle
->pid
, idle
->comm
); /* must be idle task! */
356 rcu_prepare_for_idle(smp_processor_id());
357 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
358 smp_mb__before_atomic_inc(); /* See above. */
359 atomic_inc(&rdtp
->dynticks
);
360 smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
361 WARN_ON_ONCE(atomic_read(&rdtp
->dynticks
) & 0x1);
364 * It is illegal to enter an extended quiescent state while
365 * in an RCU read-side critical section.
367 rcu_lockdep_assert(!lock_is_held(&rcu_lock_map
),
368 "Illegal idle entry in RCU read-side critical section.");
369 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map
),
370 "Illegal idle entry in RCU-bh read-side critical section.");
371 rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map
),
372 "Illegal idle entry in RCU-sched read-side critical section.");
376 * Enter an RCU extended quiescent state, which can be either the
377 * idle loop or adaptive-tickless usermode execution.
379 static void rcu_eqs_enter(bool user
)
382 struct rcu_dynticks
*rdtp
;
384 rdtp
= &__get_cpu_var(rcu_dynticks
);
385 oldval
= rdtp
->dynticks_nesting
;
386 WARN_ON_ONCE((oldval
& DYNTICK_TASK_NEST_MASK
) == 0);
387 if ((oldval
& DYNTICK_TASK_NEST_MASK
) == DYNTICK_TASK_NEST_VALUE
)
388 rdtp
->dynticks_nesting
= 0;
390 rdtp
->dynticks_nesting
-= DYNTICK_TASK_NEST_VALUE
;
391 rcu_eqs_enter_common(rdtp
, oldval
, user
);
395 * rcu_idle_enter - inform RCU that current CPU is entering idle
397 * Enter idle mode, in other words, -leave- the mode in which RCU
398 * read-side critical sections can occur. (Though RCU read-side
399 * critical sections can occur in irq handlers in idle, a possibility
400 * handled by irq_enter() and irq_exit().)
402 * We crowbar the ->dynticks_nesting field to zero to allow for
403 * the possibility of usermode upcalls having messed up our count
404 * of interrupt nesting level during the prior busy period.
406 void rcu_idle_enter(void)
410 local_irq_save(flags
);
411 rcu_eqs_enter(false);
412 local_irq_restore(flags
);
414 EXPORT_SYMBOL_GPL(rcu_idle_enter
);
416 #ifdef CONFIG_RCU_USER_QS
418 * rcu_user_enter - inform RCU that we are resuming userspace.
420 * Enter RCU idle mode right before resuming userspace. No use of RCU
421 * is permitted between this call and rcu_user_exit(). This way the
422 * CPU doesn't need to maintain the tick for RCU maintenance purposes
423 * when the CPU runs in userspace.
425 void rcu_user_enter(void)
431 * rcu_user_enter_after_irq - inform RCU that we are going to resume userspace
432 * after the current irq returns.
434 * This is similar to rcu_user_enter() but in the context of a non-nesting
435 * irq. After this call, RCU enters into idle mode when the interrupt
438 void rcu_user_enter_after_irq(void)
441 struct rcu_dynticks
*rdtp
;
443 local_irq_save(flags
);
444 rdtp
= &__get_cpu_var(rcu_dynticks
);
445 /* Ensure this irq is interrupting a non-idle RCU state. */
446 WARN_ON_ONCE(!(rdtp
->dynticks_nesting
& DYNTICK_TASK_MASK
));
447 rdtp
->dynticks_nesting
= 1;
448 local_irq_restore(flags
);
450 #endif /* CONFIG_RCU_USER_QS */
453 * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
455 * Exit from an interrupt handler, which might possibly result in entering
456 * idle mode, in other words, leaving the mode in which read-side critical
457 * sections can occur.
459 * This code assumes that the idle loop never does anything that might
460 * result in unbalanced calls to irq_enter() and irq_exit(). If your
461 * architecture violates this assumption, RCU will give you what you
462 * deserve, good and hard. But very infrequently and irreproducibly.
464 * Use things like work queues to work around this limitation.
466 * You have been warned.
468 void rcu_irq_exit(void)
472 struct rcu_dynticks
*rdtp
;
474 local_irq_save(flags
);
475 rdtp
= &__get_cpu_var(rcu_dynticks
);
476 oldval
= rdtp
->dynticks_nesting
;
477 rdtp
->dynticks_nesting
--;
478 WARN_ON_ONCE(rdtp
->dynticks_nesting
< 0);
479 if (rdtp
->dynticks_nesting
)
480 trace_rcu_dyntick("--=", oldval
, rdtp
->dynticks_nesting
);
482 rcu_eqs_enter_common(rdtp
, oldval
, true);
483 local_irq_restore(flags
);
487 * rcu_eqs_exit_common - current CPU moving away from extended quiescent state
489 * If the new value of the ->dynticks_nesting counter was previously zero,
490 * we really have exited idle, and must do the appropriate accounting.
491 * The caller must have disabled interrupts.
493 static void rcu_eqs_exit_common(struct rcu_dynticks
*rdtp
, long long oldval
,
496 smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
497 atomic_inc(&rdtp
->dynticks
);
498 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
499 smp_mb__after_atomic_inc(); /* See above. */
500 WARN_ON_ONCE(!(atomic_read(&rdtp
->dynticks
) & 0x1));
501 rcu_cleanup_after_idle(smp_processor_id());
502 trace_rcu_dyntick("End", oldval
, rdtp
->dynticks_nesting
);
503 if (!user
&& !is_idle_task(current
)) {
504 struct task_struct
*idle
= idle_task(smp_processor_id());
506 trace_rcu_dyntick("Error on exit: not idle task",
507 oldval
, rdtp
->dynticks_nesting
);
508 ftrace_dump(DUMP_ORIG
);
509 WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
510 current
->pid
, current
->comm
,
511 idle
->pid
, idle
->comm
); /* must be idle task! */
516 * Exit an RCU extended quiescent state, which can be either the
517 * idle loop or adaptive-tickless usermode execution.
519 static void rcu_eqs_exit(bool user
)
521 struct rcu_dynticks
*rdtp
;
524 rdtp
= &__get_cpu_var(rcu_dynticks
);
525 oldval
= rdtp
->dynticks_nesting
;
526 WARN_ON_ONCE(oldval
< 0);
527 if (oldval
& DYNTICK_TASK_NEST_MASK
)
528 rdtp
->dynticks_nesting
+= DYNTICK_TASK_NEST_VALUE
;
530 rdtp
->dynticks_nesting
= DYNTICK_TASK_EXIT_IDLE
;
531 rcu_eqs_exit_common(rdtp
, oldval
, user
);
535 * rcu_idle_exit - inform RCU that current CPU is leaving idle
537 * Exit idle mode, in other words, -enter- the mode in which RCU
538 * read-side critical sections can occur.
540 * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to
541 * allow for the possibility of usermode upcalls messing up our count
542 * of interrupt nesting level during the busy period that is just
545 void rcu_idle_exit(void)
549 local_irq_save(flags
);
551 local_irq_restore(flags
);
553 EXPORT_SYMBOL_GPL(rcu_idle_exit
);
555 #ifdef CONFIG_RCU_USER_QS
557 * rcu_user_exit - inform RCU that we are exiting userspace.
559 * Exit RCU idle mode while entering the kernel because it can
560 * run a RCU read side critical section anytime.
562 void rcu_user_exit(void)
568 * rcu_user_exit_after_irq - inform RCU that we won't resume to userspace
569 * idle mode after the current non-nesting irq returns.
571 * This is similar to rcu_user_exit() but in the context of an irq.
572 * This is called when the irq has interrupted a userspace RCU idle mode
573 * context. When the current non-nesting interrupt returns after this call,
574 * the CPU won't restore the RCU idle mode.
576 void rcu_user_exit_after_irq(void)
579 struct rcu_dynticks
*rdtp
;
581 local_irq_save(flags
);
582 rdtp
= &__get_cpu_var(rcu_dynticks
);
583 /* Ensure we are interrupting an RCU idle mode. */
584 WARN_ON_ONCE(rdtp
->dynticks_nesting
& DYNTICK_TASK_NEST_MASK
);
585 rdtp
->dynticks_nesting
+= DYNTICK_TASK_EXIT_IDLE
;
586 local_irq_restore(flags
);
588 #endif /* CONFIG_RCU_USER_QS */
591 * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
593 * Enter an interrupt handler, which might possibly result in exiting
594 * idle mode, in other words, entering the mode in which read-side critical
595 * sections can occur.
597 * Note that the Linux kernel is fully capable of entering an interrupt
598 * handler that it never exits, for example when doing upcalls to
599 * user mode! This code assumes that the idle loop never does upcalls to
600 * user mode. If your architecture does do upcalls from the idle loop (or
601 * does anything else that results in unbalanced calls to the irq_enter()
602 * and irq_exit() functions), RCU will give you what you deserve, good
603 * and hard. But very infrequently and irreproducibly.
605 * Use things like work queues to work around this limitation.
607 * You have been warned.
609 void rcu_irq_enter(void)
612 struct rcu_dynticks
*rdtp
;
615 local_irq_save(flags
);
616 rdtp
= &__get_cpu_var(rcu_dynticks
);
617 oldval
= rdtp
->dynticks_nesting
;
618 rdtp
->dynticks_nesting
++;
619 WARN_ON_ONCE(rdtp
->dynticks_nesting
== 0);
621 trace_rcu_dyntick("++=", oldval
, rdtp
->dynticks_nesting
);
623 rcu_eqs_exit_common(rdtp
, oldval
, true);
624 local_irq_restore(flags
);
628 * rcu_nmi_enter - inform RCU of entry to NMI context
630 * If the CPU was idle with dynamic ticks active, and there is no
631 * irq handler running, this updates rdtp->dynticks_nmi to let the
632 * RCU grace-period handling know that the CPU is active.
634 void rcu_nmi_enter(void)
636 struct rcu_dynticks
*rdtp
= &__get_cpu_var(rcu_dynticks
);
638 if (rdtp
->dynticks_nmi_nesting
== 0 &&
639 (atomic_read(&rdtp
->dynticks
) & 0x1))
641 rdtp
->dynticks_nmi_nesting
++;
642 smp_mb__before_atomic_inc(); /* Force delay from prior write. */
643 atomic_inc(&rdtp
->dynticks
);
644 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
645 smp_mb__after_atomic_inc(); /* See above. */
646 WARN_ON_ONCE(!(atomic_read(&rdtp
->dynticks
) & 0x1));
650 * rcu_nmi_exit - inform RCU of exit from NMI context
652 * If the CPU was idle with dynamic ticks active, and there is no
653 * irq handler running, this updates rdtp->dynticks_nmi to let the
654 * RCU grace-period handling know that the CPU is no longer active.
656 void rcu_nmi_exit(void)
658 struct rcu_dynticks
*rdtp
= &__get_cpu_var(rcu_dynticks
);
660 if (rdtp
->dynticks_nmi_nesting
== 0 ||
661 --rdtp
->dynticks_nmi_nesting
!= 0)
663 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
664 smp_mb__before_atomic_inc(); /* See above. */
665 atomic_inc(&rdtp
->dynticks
);
666 smp_mb__after_atomic_inc(); /* Force delay to next write. */
667 WARN_ON_ONCE(atomic_read(&rdtp
->dynticks
) & 0x1);
671 * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
673 * If the current CPU is in its idle loop and is neither in an interrupt
674 * or NMI handler, return true.
676 int rcu_is_cpu_idle(void)
681 ret
= (atomic_read(&__get_cpu_var(rcu_dynticks
).dynticks
) & 0x1) == 0;
685 EXPORT_SYMBOL(rcu_is_cpu_idle
);
687 #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
690 * Is the current CPU online? Disable preemption to avoid false positives
691 * that could otherwise happen due to the current CPU number being sampled,
692 * this task being preempted, its old CPU being taken offline, resuming
693 * on some other CPU, then determining that its old CPU is now offline.
694 * It is OK to use RCU on an offline processor during initial boot, hence
695 * the check for rcu_scheduler_fully_active. Note also that it is OK
696 * for a CPU coming online to use RCU for one jiffy prior to marking itself
697 * online in the cpu_online_mask. Similarly, it is OK for a CPU going
698 * offline to continue to use RCU for one jiffy after marking itself
699 * offline in the cpu_online_mask. This leniency is necessary given the
700 * non-atomic nature of the online and offline processing, for example,
701 * the fact that a CPU enters the scheduler after completing the CPU_DYING
704 * This is also why RCU internally marks CPUs online during the
705 * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase.
707 * Disable checking if in an NMI handler because we cannot safely report
708 * errors from NMI handlers anyway.
710 bool rcu_lockdep_current_cpu_online(void)
712 struct rcu_data
*rdp
;
713 struct rcu_node
*rnp
;
719 rdp
= &__get_cpu_var(rcu_sched_data
);
721 ret
= (rdp
->grpmask
& rnp
->qsmaskinit
) ||
722 !rcu_scheduler_fully_active
;
726 EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online
);
728 #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
731 * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
733 * If the current CPU is idle or running at a first-level (not nested)
734 * interrupt from idle, return true. The caller must have at least
735 * disabled preemption.
737 static int rcu_is_cpu_rrupt_from_idle(void)
739 return __get_cpu_var(rcu_dynticks
).dynticks_nesting
<= 1;
743 * Snapshot the specified CPU's dynticks counter so that we can later
744 * credit them with an implicit quiescent state. Return 1 if this CPU
745 * is in dynticks idle mode, which is an extended quiescent state.
747 static int dyntick_save_progress_counter(struct rcu_data
*rdp
)
749 rdp
->dynticks_snap
= atomic_add_return(0, &rdp
->dynticks
->dynticks
);
750 return (rdp
->dynticks_snap
& 0x1) == 0;
754 * Return true if the specified CPU has passed through a quiescent
755 * state by virtue of being in or having passed through an dynticks
756 * idle state since the last call to dyntick_save_progress_counter()
757 * for this same CPU, or by virtue of having been offline.
759 static int rcu_implicit_dynticks_qs(struct rcu_data
*rdp
)
764 curr
= (unsigned int)atomic_add_return(0, &rdp
->dynticks
->dynticks
);
765 snap
= (unsigned int)rdp
->dynticks_snap
;
768 * If the CPU passed through or entered a dynticks idle phase with
769 * no active irq/NMI handlers, then we can safely pretend that the CPU
770 * already acknowledged the request to pass through a quiescent
771 * state. Either way, that CPU cannot possibly be in an RCU
772 * read-side critical section that started before the beginning
773 * of the current RCU grace period.
775 if ((curr
& 0x1) == 0 || UINT_CMP_GE(curr
, snap
+ 2)) {
776 trace_rcu_fqs(rdp
->rsp
->name
, rdp
->gpnum
, rdp
->cpu
, "dti");
782 * Check for the CPU being offline, but only if the grace period
783 * is old enough. We don't need to worry about the CPU changing
784 * state: If we see it offline even once, it has been through a
787 * The reason for insisting that the grace period be at least
788 * one jiffy old is that CPUs that are not quite online and that
789 * have just gone offline can still execute RCU read-side critical
792 if (ULONG_CMP_GE(rdp
->rsp
->gp_start
+ 2, jiffies
))
793 return 0; /* Grace period is not old enough. */
795 if (cpu_is_offline(rdp
->cpu
)) {
796 trace_rcu_fqs(rdp
->rsp
->name
, rdp
->gpnum
, rdp
->cpu
, "ofl");
803 static void record_gp_stall_check_time(struct rcu_state
*rsp
)
805 rsp
->gp_start
= jiffies
;
806 rsp
->jiffies_stall
= jiffies
+ rcu_jiffies_till_stall_check();
810 * Dump stacks of all tasks running on stalled CPUs. This is a fallback
811 * for architectures that do not implement trigger_all_cpu_backtrace().
812 * The NMI-triggered stack traces are more accurate because they are
813 * printed by the target CPU.
815 static void rcu_dump_cpu_stacks(struct rcu_state
*rsp
)
819 struct rcu_node
*rnp
;
821 rcu_for_each_leaf_node(rsp
, rnp
) {
822 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
823 if (rnp
->qsmask
!= 0) {
824 for (cpu
= 0; cpu
<= rnp
->grphi
- rnp
->grplo
; cpu
++)
825 if (rnp
->qsmask
& (1UL << cpu
))
826 dump_cpu_task(rnp
->grplo
+ cpu
);
828 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
832 static void print_other_cpu_stall(struct rcu_state
*rsp
)
838 struct rcu_node
*rnp
= rcu_get_root(rsp
);
841 /* Only let one CPU complain about others per time interval. */
843 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
844 delta
= jiffies
- rsp
->jiffies_stall
;
845 if (delta
< RCU_STALL_RAT_DELAY
|| !rcu_gp_in_progress(rsp
)) {
846 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
849 rsp
->jiffies_stall
= jiffies
+ 3 * rcu_jiffies_till_stall_check() + 3;
850 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
853 * OK, time to rat on our buddy...
854 * See Documentation/RCU/stallwarn.txt for info on how to debug
855 * RCU CPU stall warnings.
857 printk(KERN_ERR
"INFO: %s detected stalls on CPUs/tasks:",
859 print_cpu_stall_info_begin();
860 rcu_for_each_leaf_node(rsp
, rnp
) {
861 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
862 ndetected
+= rcu_print_task_stall(rnp
);
863 if (rnp
->qsmask
!= 0) {
864 for (cpu
= 0; cpu
<= rnp
->grphi
- rnp
->grplo
; cpu
++)
865 if (rnp
->qsmask
& (1UL << cpu
)) {
866 print_cpu_stall_info(rsp
,
871 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
875 * Now rat on any tasks that got kicked up to the root rcu_node
876 * due to CPU offlining.
878 rnp
= rcu_get_root(rsp
);
879 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
880 ndetected
+= rcu_print_task_stall(rnp
);
881 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
883 print_cpu_stall_info_end();
884 for_each_possible_cpu(cpu
)
885 totqlen
+= per_cpu_ptr(rsp
->rda
, cpu
)->qlen
;
886 pr_cont("(detected by %d, t=%ld jiffies, g=%lu, c=%lu, q=%lu)\n",
887 smp_processor_id(), (long)(jiffies
- rsp
->gp_start
),
888 rsp
->gpnum
, rsp
->completed
, totqlen
);
890 printk(KERN_ERR
"INFO: Stall ended before state dump start\n");
891 else if (!trigger_all_cpu_backtrace())
892 rcu_dump_cpu_stacks(rsp
);
894 /* Complain about tasks blocking the grace period. */
896 rcu_print_detail_task_stall(rsp
);
898 force_quiescent_state(rsp
); /* Kick them all. */
901 static void print_cpu_stall(struct rcu_state
*rsp
)
905 struct rcu_node
*rnp
= rcu_get_root(rsp
);
909 * OK, time to rat on ourselves...
910 * See Documentation/RCU/stallwarn.txt for info on how to debug
911 * RCU CPU stall warnings.
913 printk(KERN_ERR
"INFO: %s self-detected stall on CPU", rsp
->name
);
914 print_cpu_stall_info_begin();
915 print_cpu_stall_info(rsp
, smp_processor_id());
916 print_cpu_stall_info_end();
917 for_each_possible_cpu(cpu
)
918 totqlen
+= per_cpu_ptr(rsp
->rda
, cpu
)->qlen
;
919 pr_cont(" (t=%lu jiffies g=%lu c=%lu q=%lu)\n",
920 jiffies
- rsp
->gp_start
, rsp
->gpnum
, rsp
->completed
, totqlen
);
921 if (!trigger_all_cpu_backtrace())
924 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
925 if (ULONG_CMP_GE(jiffies
, rsp
->jiffies_stall
))
926 rsp
->jiffies_stall
= jiffies
+
927 3 * rcu_jiffies_till_stall_check() + 3;
928 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
930 set_need_resched(); /* kick ourselves to get things going. */
933 static void check_cpu_stall(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
937 struct rcu_node
*rnp
;
939 if (rcu_cpu_stall_suppress
)
941 j
= ACCESS_ONCE(jiffies
);
942 js
= ACCESS_ONCE(rsp
->jiffies_stall
);
944 if (rcu_gp_in_progress(rsp
) &&
945 (ACCESS_ONCE(rnp
->qsmask
) & rdp
->grpmask
) && ULONG_CMP_GE(j
, js
)) {
947 /* We haven't checked in, so go dump stack. */
948 print_cpu_stall(rsp
);
950 } else if (rcu_gp_in_progress(rsp
) &&
951 ULONG_CMP_GE(j
, js
+ RCU_STALL_RAT_DELAY
)) {
953 /* They had a few time units to dump stack, so complain. */
954 print_other_cpu_stall(rsp
);
959 * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
961 * Set the stall-warning timeout way off into the future, thus preventing
962 * any RCU CPU stall-warning messages from appearing in the current set of
965 * The caller must disable hard irqs.
967 void rcu_cpu_stall_reset(void)
969 struct rcu_state
*rsp
;
971 for_each_rcu_flavor(rsp
)
972 rsp
->jiffies_stall
= jiffies
+ ULONG_MAX
/ 2;
976 * Update CPU-local rcu_data state to record the newly noticed grace period.
977 * This is used both when we started the grace period and when we notice
978 * that someone else started the grace period. The caller must hold the
979 * ->lock of the leaf rcu_node structure corresponding to the current CPU,
980 * and must have irqs disabled.
982 static void __note_new_gpnum(struct rcu_state
*rsp
, struct rcu_node
*rnp
, struct rcu_data
*rdp
)
984 if (rdp
->gpnum
!= rnp
->gpnum
) {
986 * If the current grace period is waiting for this CPU,
987 * set up to detect a quiescent state, otherwise don't
988 * go looking for one.
990 rdp
->gpnum
= rnp
->gpnum
;
991 trace_rcu_grace_period(rsp
->name
, rdp
->gpnum
, "cpustart");
992 rdp
->passed_quiesce
= 0;
993 rdp
->qs_pending
= !!(rnp
->qsmask
& rdp
->grpmask
);
994 zero_cpu_stall_ticks(rdp
);
998 static void note_new_gpnum(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
1000 unsigned long flags
;
1001 struct rcu_node
*rnp
;
1003 local_irq_save(flags
);
1005 if (rdp
->gpnum
== ACCESS_ONCE(rnp
->gpnum
) || /* outside lock. */
1006 !raw_spin_trylock(&rnp
->lock
)) { /* irqs already off, so later. */
1007 local_irq_restore(flags
);
1010 __note_new_gpnum(rsp
, rnp
, rdp
);
1011 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
1015 * Did someone else start a new RCU grace period start since we last
1016 * checked? Update local state appropriately if so. Must be called
1017 * on the CPU corresponding to rdp.
1020 check_for_new_grace_period(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
1022 unsigned long flags
;
1025 local_irq_save(flags
);
1026 if (rdp
->gpnum
!= rsp
->gpnum
) {
1027 note_new_gpnum(rsp
, rdp
);
1030 local_irq_restore(flags
);
1035 * Initialize the specified rcu_data structure's callback list to empty.
1037 static void init_callback_list(struct rcu_data
*rdp
)
1041 if (init_nocb_callback_list(rdp
))
1043 rdp
->nxtlist
= NULL
;
1044 for (i
= 0; i
< RCU_NEXT_SIZE
; i
++)
1045 rdp
->nxttail
[i
] = &rdp
->nxtlist
;
1049 * Determine the value that ->completed will have at the end of the
1050 * next subsequent grace period. This is used to tag callbacks so that
1051 * a CPU can invoke callbacks in a timely fashion even if that CPU has
1052 * been dyntick-idle for an extended period with callbacks under the
1053 * influence of RCU_FAST_NO_HZ.
1055 * The caller must hold rnp->lock with interrupts disabled.
1057 static unsigned long rcu_cbs_completed(struct rcu_state
*rsp
,
1058 struct rcu_node
*rnp
)
1061 * If RCU is idle, we just wait for the next grace period.
1062 * But we can only be sure that RCU is idle if we are looking
1063 * at the root rcu_node structure -- otherwise, a new grace
1064 * period might have started, but just not yet gotten around
1065 * to initializing the current non-root rcu_node structure.
1067 if (rcu_get_root(rsp
) == rnp
&& rnp
->gpnum
== rnp
->completed
)
1068 return rnp
->completed
+ 1;
1071 * Otherwise, wait for a possible partial grace period and
1072 * then the subsequent full grace period.
1074 return rnp
->completed
+ 2;
1078 * If there is room, assign a ->completed number to any callbacks on
1079 * this CPU that have not already been assigned. Also accelerate any
1080 * callbacks that were previously assigned a ->completed number that has
1081 * since proven to be too conservative, which can happen if callbacks get
1082 * assigned a ->completed number while RCU is idle, but with reference to
1083 * a non-root rcu_node structure. This function is idempotent, so it does
1084 * not hurt to call it repeatedly.
1086 * The caller must hold rnp->lock with interrupts disabled.
1088 static void rcu_accelerate_cbs(struct rcu_state
*rsp
, struct rcu_node
*rnp
,
1089 struct rcu_data
*rdp
)
1094 /* If the CPU has no callbacks, nothing to do. */
1095 if (!rdp
->nxttail
[RCU_NEXT_TAIL
] || !*rdp
->nxttail
[RCU_DONE_TAIL
])
1099 * Starting from the sublist containing the callbacks most
1100 * recently assigned a ->completed number and working down, find the
1101 * first sublist that is not assignable to an upcoming grace period.
1102 * Such a sublist has something in it (first two tests) and has
1103 * a ->completed number assigned that will complete sooner than
1104 * the ->completed number for newly arrived callbacks (last test).
1106 * The key point is that any later sublist can be assigned the
1107 * same ->completed number as the newly arrived callbacks, which
1108 * means that the callbacks in any of these later sublist can be
1109 * grouped into a single sublist, whether or not they have already
1110 * been assigned a ->completed number.
1112 c
= rcu_cbs_completed(rsp
, rnp
);
1113 for (i
= RCU_NEXT_TAIL
- 1; i
> RCU_DONE_TAIL
; i
--)
1114 if (rdp
->nxttail
[i
] != rdp
->nxttail
[i
- 1] &&
1115 !ULONG_CMP_GE(rdp
->nxtcompleted
[i
], c
))
1119 * If there are no sublist for unassigned callbacks, leave.
1120 * At the same time, advance "i" one sublist, so that "i" will
1121 * index into the sublist where all the remaining callbacks should
1124 if (++i
>= RCU_NEXT_TAIL
)
1128 * Assign all subsequent callbacks' ->completed number to the next
1129 * full grace period and group them all in the sublist initially
1132 for (; i
<= RCU_NEXT_TAIL
; i
++) {
1133 rdp
->nxttail
[i
] = rdp
->nxttail
[RCU_NEXT_TAIL
];
1134 rdp
->nxtcompleted
[i
] = c
;
1137 /* Trace depending on how much we were able to accelerate. */
1138 if (!*rdp
->nxttail
[RCU_WAIT_TAIL
])
1139 trace_rcu_grace_period(rsp
->name
, rdp
->gpnum
, "AccWaitCB");
1141 trace_rcu_grace_period(rsp
->name
, rdp
->gpnum
, "AccReadyCB");
1145 * Move any callbacks whose grace period has completed to the
1146 * RCU_DONE_TAIL sublist, then compact the remaining sublists and
1147 * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL
1148 * sublist. This function is idempotent, so it does not hurt to
1149 * invoke it repeatedly. As long as it is not invoked -too- often...
1151 * The caller must hold rnp->lock with interrupts disabled.
1153 static void rcu_advance_cbs(struct rcu_state
*rsp
, struct rcu_node
*rnp
,
1154 struct rcu_data
*rdp
)
1158 /* If the CPU has no callbacks, nothing to do. */
1159 if (!rdp
->nxttail
[RCU_NEXT_TAIL
] || !*rdp
->nxttail
[RCU_DONE_TAIL
])
1163 * Find all callbacks whose ->completed numbers indicate that they
1164 * are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
1166 for (i
= RCU_WAIT_TAIL
; i
< RCU_NEXT_TAIL
; i
++) {
1167 if (ULONG_CMP_LT(rnp
->completed
, rdp
->nxtcompleted
[i
]))
1169 rdp
->nxttail
[RCU_DONE_TAIL
] = rdp
->nxttail
[i
];
1171 /* Clean up any sublist tail pointers that were misordered above. */
1172 for (j
= RCU_WAIT_TAIL
; j
< i
; j
++)
1173 rdp
->nxttail
[j
] = rdp
->nxttail
[RCU_DONE_TAIL
];
1175 /* Copy down callbacks to fill in empty sublists. */
1176 for (j
= RCU_WAIT_TAIL
; i
< RCU_NEXT_TAIL
; i
++, j
++) {
1177 if (rdp
->nxttail
[j
] == rdp
->nxttail
[RCU_NEXT_TAIL
])
1179 rdp
->nxttail
[j
] = rdp
->nxttail
[i
];
1180 rdp
->nxtcompleted
[j
] = rdp
->nxtcompleted
[i
];
1183 /* Classify any remaining callbacks. */
1184 rcu_accelerate_cbs(rsp
, rnp
, rdp
);
1188 * Advance this CPU's callbacks, but only if the current grace period
1189 * has ended. This may be called only from the CPU to whom the rdp
1190 * belongs. In addition, the corresponding leaf rcu_node structure's
1191 * ->lock must be held by the caller, with irqs disabled.
1194 __rcu_process_gp_end(struct rcu_state
*rsp
, struct rcu_node
*rnp
, struct rcu_data
*rdp
)
1196 /* Did another grace period end? */
1197 if (rdp
->completed
== rnp
->completed
) {
1199 /* No, so just accelerate recent callbacks. */
1200 rcu_accelerate_cbs(rsp
, rnp
, rdp
);
1204 /* Advance callbacks. */
1205 rcu_advance_cbs(rsp
, rnp
, rdp
);
1207 /* Remember that we saw this grace-period completion. */
1208 rdp
->completed
= rnp
->completed
;
1209 trace_rcu_grace_period(rsp
->name
, rdp
->gpnum
, "cpuend");
1212 * If we were in an extended quiescent state, we may have
1213 * missed some grace periods that others CPUs handled on
1214 * our behalf. Catch up with this state to avoid noting
1215 * spurious new grace periods. If another grace period
1216 * has started, then rnp->gpnum will have advanced, so
1217 * we will detect this later on. Of course, any quiescent
1218 * states we found for the old GP are now invalid.
1220 if (ULONG_CMP_LT(rdp
->gpnum
, rdp
->completed
)) {
1221 rdp
->gpnum
= rdp
->completed
;
1222 rdp
->passed_quiesce
= 0;
1226 * If RCU does not need a quiescent state from this CPU,
1227 * then make sure that this CPU doesn't go looking for one.
1229 if ((rnp
->qsmask
& rdp
->grpmask
) == 0)
1230 rdp
->qs_pending
= 0;
1235 * Advance this CPU's callbacks, but only if the current grace period
1236 * has ended. This may be called only from the CPU to whom the rdp
1240 rcu_process_gp_end(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
1242 unsigned long flags
;
1243 struct rcu_node
*rnp
;
1245 local_irq_save(flags
);
1247 if (rdp
->completed
== ACCESS_ONCE(rnp
->completed
) || /* outside lock. */
1248 !raw_spin_trylock(&rnp
->lock
)) { /* irqs already off, so later. */
1249 local_irq_restore(flags
);
1252 __rcu_process_gp_end(rsp
, rnp
, rdp
);
1253 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
1257 * Do per-CPU grace-period initialization for running CPU. The caller
1258 * must hold the lock of the leaf rcu_node structure corresponding to
1262 rcu_start_gp_per_cpu(struct rcu_state
*rsp
, struct rcu_node
*rnp
, struct rcu_data
*rdp
)
1264 /* Prior grace period ended, so advance callbacks for current CPU. */
1265 __rcu_process_gp_end(rsp
, rnp
, rdp
);
1267 /* Set state so that this CPU will detect the next quiescent state. */
1268 __note_new_gpnum(rsp
, rnp
, rdp
);
1272 * Initialize a new grace period.
1274 static int rcu_gp_init(struct rcu_state
*rsp
)
1276 struct rcu_data
*rdp
;
1277 struct rcu_node
*rnp
= rcu_get_root(rsp
);
1279 raw_spin_lock_irq(&rnp
->lock
);
1280 rsp
->gp_flags
= 0; /* Clear all flags: New grace period. */
1282 if (rcu_gp_in_progress(rsp
)) {
1283 /* Grace period already in progress, don't start another. */
1284 raw_spin_unlock_irq(&rnp
->lock
);
1288 /* Advance to a new grace period and initialize state. */
1290 trace_rcu_grace_period(rsp
->name
, rsp
->gpnum
, "start");
1291 record_gp_stall_check_time(rsp
);
1292 raw_spin_unlock_irq(&rnp
->lock
);
1294 /* Exclude any concurrent CPU-hotplug operations. */
1295 mutex_lock(&rsp
->onoff_mutex
);
1298 * Set the quiescent-state-needed bits in all the rcu_node
1299 * structures for all currently online CPUs in breadth-first order,
1300 * starting from the root rcu_node structure, relying on the layout
1301 * of the tree within the rsp->node[] array. Note that other CPUs
1302 * will access only the leaves of the hierarchy, thus seeing that no
1303 * grace period is in progress, at least until the corresponding
1304 * leaf node has been initialized. In addition, we have excluded
1305 * CPU-hotplug operations.
1307 * The grace period cannot complete until the initialization
1308 * process finishes, because this kthread handles both.
1310 rcu_for_each_node_breadth_first(rsp
, rnp
) {
1311 raw_spin_lock_irq(&rnp
->lock
);
1312 rdp
= this_cpu_ptr(rsp
->rda
);
1313 rcu_preempt_check_blocked_tasks(rnp
);
1314 rnp
->qsmask
= rnp
->qsmaskinit
;
1315 rnp
->gpnum
= rsp
->gpnum
;
1316 WARN_ON_ONCE(rnp
->completed
!= rsp
->completed
);
1317 rnp
->completed
= rsp
->completed
;
1318 if (rnp
== rdp
->mynode
)
1319 rcu_start_gp_per_cpu(rsp
, rnp
, rdp
);
1320 rcu_preempt_boost_start_gp(rnp
);
1321 trace_rcu_grace_period_init(rsp
->name
, rnp
->gpnum
,
1322 rnp
->level
, rnp
->grplo
,
1323 rnp
->grphi
, rnp
->qsmask
);
1324 raw_spin_unlock_irq(&rnp
->lock
);
1325 #ifdef CONFIG_PROVE_RCU_DELAY
1326 if ((random32() % (rcu_num_nodes
* 8)) == 0)
1327 schedule_timeout_uninterruptible(2);
1328 #endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
1332 mutex_unlock(&rsp
->onoff_mutex
);
1337 * Do one round of quiescent-state forcing.
1339 int rcu_gp_fqs(struct rcu_state
*rsp
, int fqs_state_in
)
1341 int fqs_state
= fqs_state_in
;
1342 struct rcu_node
*rnp
= rcu_get_root(rsp
);
1345 if (fqs_state
== RCU_SAVE_DYNTICK
) {
1346 /* Collect dyntick-idle snapshots. */
1347 force_qs_rnp(rsp
, dyntick_save_progress_counter
);
1348 fqs_state
= RCU_FORCE_QS
;
1350 /* Handle dyntick-idle and offline CPUs. */
1351 force_qs_rnp(rsp
, rcu_implicit_dynticks_qs
);
1353 /* Clear flag to prevent immediate re-entry. */
1354 if (ACCESS_ONCE(rsp
->gp_flags
) & RCU_GP_FLAG_FQS
) {
1355 raw_spin_lock_irq(&rnp
->lock
);
1356 rsp
->gp_flags
&= ~RCU_GP_FLAG_FQS
;
1357 raw_spin_unlock_irq(&rnp
->lock
);
1363 * Clean up after the old grace period.
1365 static void rcu_gp_cleanup(struct rcu_state
*rsp
)
1367 unsigned long gp_duration
;
1369 struct rcu_data
*rdp
;
1370 struct rcu_node
*rnp
= rcu_get_root(rsp
);
1372 raw_spin_lock_irq(&rnp
->lock
);
1373 gp_duration
= jiffies
- rsp
->gp_start
;
1374 if (gp_duration
> rsp
->gp_max
)
1375 rsp
->gp_max
= gp_duration
;
1378 * We know the grace period is complete, but to everyone else
1379 * it appears to still be ongoing. But it is also the case
1380 * that to everyone else it looks like there is nothing that
1381 * they can do to advance the grace period. It is therefore
1382 * safe for us to drop the lock in order to mark the grace
1383 * period as completed in all of the rcu_node structures.
1385 raw_spin_unlock_irq(&rnp
->lock
);
1388 * Propagate new ->completed value to rcu_node structures so
1389 * that other CPUs don't have to wait until the start of the next
1390 * grace period to process their callbacks. This also avoids
1391 * some nasty RCU grace-period initialization races by forcing
1392 * the end of the current grace period to be completely recorded in
1393 * all of the rcu_node structures before the beginning of the next
1394 * grace period is recorded in any of the rcu_node structures.
1396 rcu_for_each_node_breadth_first(rsp
, rnp
) {
1397 raw_spin_lock_irq(&rnp
->lock
);
1398 rnp
->completed
= rsp
->gpnum
;
1399 rdp
= this_cpu_ptr(rsp
->rda
);
1400 if (rnp
== rdp
->mynode
)
1401 __rcu_process_gp_end(rsp
, rnp
, rdp
);
1402 nocb
+= rcu_nocb_gp_cleanup(rsp
, rnp
);
1403 raw_spin_unlock_irq(&rnp
->lock
);
1406 rnp
= rcu_get_root(rsp
);
1407 raw_spin_lock_irq(&rnp
->lock
);
1408 rcu_nocb_gp_set(rnp
, nocb
);
1410 rsp
->completed
= rsp
->gpnum
; /* Declare grace period done. */
1411 trace_rcu_grace_period(rsp
->name
, rsp
->completed
, "end");
1412 rsp
->fqs_state
= RCU_GP_IDLE
;
1413 rdp
= this_cpu_ptr(rsp
->rda
);
1414 rcu_advance_cbs(rsp
, rnp
, rdp
); /* Reduce false positives below. */
1415 if (cpu_needs_another_gp(rsp
, rdp
))
1417 raw_spin_unlock_irq(&rnp
->lock
);
1421 * Body of kthread that handles grace periods.
1423 static int __noreturn
rcu_gp_kthread(void *arg
)
1428 struct rcu_state
*rsp
= arg
;
1429 struct rcu_node
*rnp
= rcu_get_root(rsp
);
1433 /* Handle grace-period start. */
1435 wait_event_interruptible(rsp
->gp_wq
,
1438 if ((rsp
->gp_flags
& RCU_GP_FLAG_INIT
) &&
1442 flush_signals(current
);
1445 /* Handle quiescent-state forcing. */
1446 fqs_state
= RCU_SAVE_DYNTICK
;
1447 j
= jiffies_till_first_fqs
;
1450 jiffies_till_first_fqs
= HZ
;
1453 rsp
->jiffies_force_qs
= jiffies
+ j
;
1454 ret
= wait_event_interruptible_timeout(rsp
->gp_wq
,
1455 (rsp
->gp_flags
& RCU_GP_FLAG_FQS
) ||
1456 (!ACCESS_ONCE(rnp
->qsmask
) &&
1457 !rcu_preempt_blocked_readers_cgp(rnp
)),
1459 /* If grace period done, leave loop. */
1460 if (!ACCESS_ONCE(rnp
->qsmask
) &&
1461 !rcu_preempt_blocked_readers_cgp(rnp
))
1463 /* If time for quiescent-state forcing, do it. */
1464 if (ret
== 0 || (rsp
->gp_flags
& RCU_GP_FLAG_FQS
)) {
1465 fqs_state
= rcu_gp_fqs(rsp
, fqs_state
);
1468 /* Deal with stray signal. */
1470 flush_signals(current
);
1472 j
= jiffies_till_next_fqs
;
1475 jiffies_till_next_fqs
= HZ
;
1478 jiffies_till_next_fqs
= 1;
1482 /* Handle grace-period end. */
1483 rcu_gp_cleanup(rsp
);
1488 * Start a new RCU grace period if warranted, re-initializing the hierarchy
1489 * in preparation for detecting the next grace period. The caller must hold
1490 * the root node's ->lock and hard irqs must be disabled.
1492 * Note that it is legal for a dying CPU (which is marked as offline) to
1493 * invoke this function. This can happen when the dying CPU reports its
1497 rcu_start_gp(struct rcu_state
*rsp
)
1499 struct rcu_data
*rdp
= this_cpu_ptr(rsp
->rda
);
1500 struct rcu_node
*rnp
= rcu_get_root(rsp
);
1503 * If there is no grace period in progress right now, any
1504 * callbacks we have up to this point will be satisfied by the
1505 * next grace period. Also, advancing the callbacks reduces the
1506 * probability of false positives from cpu_needs_another_gp()
1507 * resulting in pointless grace periods. So, advance callbacks!
1509 rcu_advance_cbs(rsp
, rnp
, rdp
);
1511 if (!rsp
->gp_kthread
|| !cpu_needs_another_gp(rsp
, rdp
)) {
1513 * Either we have not yet spawned the grace-period
1514 * task, this CPU does not need another grace period,
1515 * or a grace period is already in progress.
1516 * Either way, don't start a new grace period.
1520 rsp
->gp_flags
= RCU_GP_FLAG_INIT
;
1522 /* Ensure that CPU is aware of completion of last grace period. */
1523 __rcu_process_gp_end(rsp
, rdp
->mynode
, rdp
);
1525 /* Wake up rcu_gp_kthread() to start the grace period. */
1526 wake_up(&rsp
->gp_wq
);
1530 * Report a full set of quiescent states to the specified rcu_state
1531 * data structure. This involves cleaning up after the prior grace
1532 * period and letting rcu_start_gp() start up the next grace period
1533 * if one is needed. Note that the caller must hold rnp->lock, which
1534 * is released before return.
1536 static void rcu_report_qs_rsp(struct rcu_state
*rsp
, unsigned long flags
)
1537 __releases(rcu_get_root(rsp
)->lock
)
1539 WARN_ON_ONCE(!rcu_gp_in_progress(rsp
));
1540 raw_spin_unlock_irqrestore(&rcu_get_root(rsp
)->lock
, flags
);
1541 wake_up(&rsp
->gp_wq
); /* Memory barrier implied by wake_up() path. */
1545 * Similar to rcu_report_qs_rdp(), for which it is a helper function.
1546 * Allows quiescent states for a group of CPUs to be reported at one go
1547 * to the specified rcu_node structure, though all the CPUs in the group
1548 * must be represented by the same rcu_node structure (which need not be
1549 * a leaf rcu_node structure, though it often will be). That structure's
1550 * lock must be held upon entry, and it is released before return.
1553 rcu_report_qs_rnp(unsigned long mask
, struct rcu_state
*rsp
,
1554 struct rcu_node
*rnp
, unsigned long flags
)
1555 __releases(rnp
->lock
)
1557 struct rcu_node
*rnp_c
;
1559 /* Walk up the rcu_node hierarchy. */
1561 if (!(rnp
->qsmask
& mask
)) {
1563 /* Our bit has already been cleared, so done. */
1564 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
1567 rnp
->qsmask
&= ~mask
;
1568 trace_rcu_quiescent_state_report(rsp
->name
, rnp
->gpnum
,
1569 mask
, rnp
->qsmask
, rnp
->level
,
1570 rnp
->grplo
, rnp
->grphi
,
1572 if (rnp
->qsmask
!= 0 || rcu_preempt_blocked_readers_cgp(rnp
)) {
1574 /* Other bits still set at this level, so done. */
1575 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
1578 mask
= rnp
->grpmask
;
1579 if (rnp
->parent
== NULL
) {
1581 /* No more levels. Exit loop holding root lock. */
1585 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
1588 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
1589 WARN_ON_ONCE(rnp_c
->qsmask
);
1593 * Get here if we are the last CPU to pass through a quiescent
1594 * state for this grace period. Invoke rcu_report_qs_rsp()
1595 * to clean up and start the next grace period if one is needed.
1597 rcu_report_qs_rsp(rsp
, flags
); /* releases rnp->lock. */
1601 * Record a quiescent state for the specified CPU to that CPU's rcu_data
1602 * structure. This must be either called from the specified CPU, or
1603 * called when the specified CPU is known to be offline (and when it is
1604 * also known that no other CPU is concurrently trying to help the offline
1605 * CPU). The lastcomp argument is used to make sure we are still in the
1606 * grace period of interest. We don't want to end the current grace period
1607 * based on quiescent states detected in an earlier grace period!
1610 rcu_report_qs_rdp(int cpu
, struct rcu_state
*rsp
, struct rcu_data
*rdp
)
1612 unsigned long flags
;
1614 struct rcu_node
*rnp
;
1617 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
1618 if (rdp
->passed_quiesce
== 0 || rdp
->gpnum
!= rnp
->gpnum
||
1619 rnp
->completed
== rnp
->gpnum
) {
1622 * The grace period in which this quiescent state was
1623 * recorded has ended, so don't report it upwards.
1624 * We will instead need a new quiescent state that lies
1625 * within the current grace period.
1627 rdp
->passed_quiesce
= 0; /* need qs for new gp. */
1628 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
1631 mask
= rdp
->grpmask
;
1632 if ((rnp
->qsmask
& mask
) == 0) {
1633 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
1635 rdp
->qs_pending
= 0;
1638 * This GP can't end until cpu checks in, so all of our
1639 * callbacks can be processed during the next GP.
1641 rcu_accelerate_cbs(rsp
, rnp
, rdp
);
1643 rcu_report_qs_rnp(mask
, rsp
, rnp
, flags
); /* rlses rnp->lock */
1648 * Check to see if there is a new grace period of which this CPU
1649 * is not yet aware, and if so, set up local rcu_data state for it.
1650 * Otherwise, see if this CPU has just passed through its first
1651 * quiescent state for this grace period, and record that fact if so.
1654 rcu_check_quiescent_state(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
1656 /* If there is now a new grace period, record and return. */
1657 if (check_for_new_grace_period(rsp
, rdp
))
1661 * Does this CPU still need to do its part for current grace period?
1662 * If no, return and let the other CPUs do their part as well.
1664 if (!rdp
->qs_pending
)
1668 * Was there a quiescent state since the beginning of the grace
1669 * period? If no, then exit and wait for the next call.
1671 if (!rdp
->passed_quiesce
)
1675 * Tell RCU we are done (but rcu_report_qs_rdp() will be the
1678 rcu_report_qs_rdp(rdp
->cpu
, rsp
, rdp
);
1681 #ifdef CONFIG_HOTPLUG_CPU
1684 * Send the specified CPU's RCU callbacks to the orphanage. The
1685 * specified CPU must be offline, and the caller must hold the
1689 rcu_send_cbs_to_orphanage(int cpu
, struct rcu_state
*rsp
,
1690 struct rcu_node
*rnp
, struct rcu_data
*rdp
)
1692 /* No-CBs CPUs do not have orphanable callbacks. */
1693 if (is_nocb_cpu(rdp
->cpu
))
1697 * Orphan the callbacks. First adjust the counts. This is safe
1698 * because _rcu_barrier() excludes CPU-hotplug operations, so it
1699 * cannot be running now. Thus no memory barrier is required.
1701 if (rdp
->nxtlist
!= NULL
) {
1702 rsp
->qlen_lazy
+= rdp
->qlen_lazy
;
1703 rsp
->qlen
+= rdp
->qlen
;
1704 rdp
->n_cbs_orphaned
+= rdp
->qlen
;
1706 ACCESS_ONCE(rdp
->qlen
) = 0;
1710 * Next, move those callbacks still needing a grace period to
1711 * the orphanage, where some other CPU will pick them up.
1712 * Some of the callbacks might have gone partway through a grace
1713 * period, but that is too bad. They get to start over because we
1714 * cannot assume that grace periods are synchronized across CPUs.
1715 * We don't bother updating the ->nxttail[] array yet, instead
1716 * we just reset the whole thing later on.
1718 if (*rdp
->nxttail
[RCU_DONE_TAIL
] != NULL
) {
1719 *rsp
->orphan_nxttail
= *rdp
->nxttail
[RCU_DONE_TAIL
];
1720 rsp
->orphan_nxttail
= rdp
->nxttail
[RCU_NEXT_TAIL
];
1721 *rdp
->nxttail
[RCU_DONE_TAIL
] = NULL
;
1725 * Then move the ready-to-invoke callbacks to the orphanage,
1726 * where some other CPU will pick them up. These will not be
1727 * required to pass though another grace period: They are done.
1729 if (rdp
->nxtlist
!= NULL
) {
1730 *rsp
->orphan_donetail
= rdp
->nxtlist
;
1731 rsp
->orphan_donetail
= rdp
->nxttail
[RCU_DONE_TAIL
];
1734 /* Finally, initialize the rcu_data structure's list to empty. */
1735 init_callback_list(rdp
);
1739 * Adopt the RCU callbacks from the specified rcu_state structure's
1740 * orphanage. The caller must hold the ->orphan_lock.
1742 static void rcu_adopt_orphan_cbs(struct rcu_state
*rsp
)
1745 struct rcu_data
*rdp
= __this_cpu_ptr(rsp
->rda
);
1747 /* No-CBs CPUs are handled specially. */
1748 if (rcu_nocb_adopt_orphan_cbs(rsp
, rdp
))
1751 /* Do the accounting first. */
1752 rdp
->qlen_lazy
+= rsp
->qlen_lazy
;
1753 rdp
->qlen
+= rsp
->qlen
;
1754 rdp
->n_cbs_adopted
+= rsp
->qlen
;
1755 if (rsp
->qlen_lazy
!= rsp
->qlen
)
1756 rcu_idle_count_callbacks_posted();
1761 * We do not need a memory barrier here because the only way we
1762 * can get here if there is an rcu_barrier() in flight is if
1763 * we are the task doing the rcu_barrier().
1766 /* First adopt the ready-to-invoke callbacks. */
1767 if (rsp
->orphan_donelist
!= NULL
) {
1768 *rsp
->orphan_donetail
= *rdp
->nxttail
[RCU_DONE_TAIL
];
1769 *rdp
->nxttail
[RCU_DONE_TAIL
] = rsp
->orphan_donelist
;
1770 for (i
= RCU_NEXT_SIZE
- 1; i
>= RCU_DONE_TAIL
; i
--)
1771 if (rdp
->nxttail
[i
] == rdp
->nxttail
[RCU_DONE_TAIL
])
1772 rdp
->nxttail
[i
] = rsp
->orphan_donetail
;
1773 rsp
->orphan_donelist
= NULL
;
1774 rsp
->orphan_donetail
= &rsp
->orphan_donelist
;
1777 /* And then adopt the callbacks that still need a grace period. */
1778 if (rsp
->orphan_nxtlist
!= NULL
) {
1779 *rdp
->nxttail
[RCU_NEXT_TAIL
] = rsp
->orphan_nxtlist
;
1780 rdp
->nxttail
[RCU_NEXT_TAIL
] = rsp
->orphan_nxttail
;
1781 rsp
->orphan_nxtlist
= NULL
;
1782 rsp
->orphan_nxttail
= &rsp
->orphan_nxtlist
;
1787 * Trace the fact that this CPU is going offline.
1789 static void rcu_cleanup_dying_cpu(struct rcu_state
*rsp
)
1791 RCU_TRACE(unsigned long mask
);
1792 RCU_TRACE(struct rcu_data
*rdp
= this_cpu_ptr(rsp
->rda
));
1793 RCU_TRACE(struct rcu_node
*rnp
= rdp
->mynode
);
1795 RCU_TRACE(mask
= rdp
->grpmask
);
1796 trace_rcu_grace_period(rsp
->name
,
1797 rnp
->gpnum
+ 1 - !!(rnp
->qsmask
& mask
),
1802 * The CPU has been completely removed, and some other CPU is reporting
1803 * this fact from process context. Do the remainder of the cleanup,
1804 * including orphaning the outgoing CPU's RCU callbacks, and also
1805 * adopting them. There can only be one CPU hotplug operation at a time,
1806 * so no other CPU can be attempting to update rcu_cpu_kthread_task.
1808 static void rcu_cleanup_dead_cpu(int cpu
, struct rcu_state
*rsp
)
1810 unsigned long flags
;
1812 int need_report
= 0;
1813 struct rcu_data
*rdp
= per_cpu_ptr(rsp
->rda
, cpu
);
1814 struct rcu_node
*rnp
= rdp
->mynode
; /* Outgoing CPU's rdp & rnp. */
1816 /* Adjust any no-longer-needed kthreads. */
1817 rcu_boost_kthread_setaffinity(rnp
, -1);
1819 /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */
1821 /* Exclude any attempts to start a new grace period. */
1822 mutex_lock(&rsp
->onoff_mutex
);
1823 raw_spin_lock_irqsave(&rsp
->orphan_lock
, flags
);
1825 /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
1826 rcu_send_cbs_to_orphanage(cpu
, rsp
, rnp
, rdp
);
1827 rcu_adopt_orphan_cbs(rsp
);
1829 /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
1830 mask
= rdp
->grpmask
; /* rnp->grplo is constant. */
1832 raw_spin_lock(&rnp
->lock
); /* irqs already disabled. */
1833 rnp
->qsmaskinit
&= ~mask
;
1834 if (rnp
->qsmaskinit
!= 0) {
1835 if (rnp
!= rdp
->mynode
)
1836 raw_spin_unlock(&rnp
->lock
); /* irqs remain disabled. */
1839 if (rnp
== rdp
->mynode
)
1840 need_report
= rcu_preempt_offline_tasks(rsp
, rnp
, rdp
);
1842 raw_spin_unlock(&rnp
->lock
); /* irqs remain disabled. */
1843 mask
= rnp
->grpmask
;
1845 } while (rnp
!= NULL
);
1848 * We still hold the leaf rcu_node structure lock here, and
1849 * irqs are still disabled. The reason for this subterfuge is
1850 * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock
1851 * held leads to deadlock.
1853 raw_spin_unlock(&rsp
->orphan_lock
); /* irqs remain disabled. */
1855 if (need_report
& RCU_OFL_TASKS_NORM_GP
)
1856 rcu_report_unblock_qs_rnp(rnp
, flags
);
1858 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
1859 if (need_report
& RCU_OFL_TASKS_EXP_GP
)
1860 rcu_report_exp_rnp(rsp
, rnp
, true);
1861 WARN_ONCE(rdp
->qlen
!= 0 || rdp
->nxtlist
!= NULL
,
1862 "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
1863 cpu
, rdp
->qlen
, rdp
->nxtlist
);
1864 init_callback_list(rdp
);
1865 /* Disallow further callbacks on this CPU. */
1866 rdp
->nxttail
[RCU_NEXT_TAIL
] = NULL
;
1867 mutex_unlock(&rsp
->onoff_mutex
);
1870 #else /* #ifdef CONFIG_HOTPLUG_CPU */
1872 static void rcu_cleanup_dying_cpu(struct rcu_state
*rsp
)
1876 static void rcu_cleanup_dead_cpu(int cpu
, struct rcu_state
*rsp
)
1880 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
1883 * Invoke any RCU callbacks that have made it to the end of their grace
1884 * period. Thottle as specified by rdp->blimit.
1886 static void rcu_do_batch(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
1888 unsigned long flags
;
1889 struct rcu_head
*next
, *list
, **tail
;
1890 long bl
, count
, count_lazy
;
1893 /* If no callbacks are ready, just return. */
1894 if (!cpu_has_callbacks_ready_to_invoke(rdp
)) {
1895 trace_rcu_batch_start(rsp
->name
, rdp
->qlen_lazy
, rdp
->qlen
, 0);
1896 trace_rcu_batch_end(rsp
->name
, 0, !!ACCESS_ONCE(rdp
->nxtlist
),
1897 need_resched(), is_idle_task(current
),
1898 rcu_is_callbacks_kthread());
1903 * Extract the list of ready callbacks, disabling to prevent
1904 * races with call_rcu() from interrupt handlers.
1906 local_irq_save(flags
);
1907 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
1909 trace_rcu_batch_start(rsp
->name
, rdp
->qlen_lazy
, rdp
->qlen
, bl
);
1910 list
= rdp
->nxtlist
;
1911 rdp
->nxtlist
= *rdp
->nxttail
[RCU_DONE_TAIL
];
1912 *rdp
->nxttail
[RCU_DONE_TAIL
] = NULL
;
1913 tail
= rdp
->nxttail
[RCU_DONE_TAIL
];
1914 for (i
= RCU_NEXT_SIZE
- 1; i
>= 0; i
--)
1915 if (rdp
->nxttail
[i
] == rdp
->nxttail
[RCU_DONE_TAIL
])
1916 rdp
->nxttail
[i
] = &rdp
->nxtlist
;
1917 local_irq_restore(flags
);
1919 /* Invoke callbacks. */
1920 count
= count_lazy
= 0;
1924 debug_rcu_head_unqueue(list
);
1925 if (__rcu_reclaim(rsp
->name
, list
))
1928 /* Stop only if limit reached and CPU has something to do. */
1929 if (++count
>= bl
&&
1931 (!is_idle_task(current
) && !rcu_is_callbacks_kthread())))
1935 local_irq_save(flags
);
1936 trace_rcu_batch_end(rsp
->name
, count
, !!list
, need_resched(),
1937 is_idle_task(current
),
1938 rcu_is_callbacks_kthread());
1940 /* Update count, and requeue any remaining callbacks. */
1942 *tail
= rdp
->nxtlist
;
1943 rdp
->nxtlist
= list
;
1944 for (i
= 0; i
< RCU_NEXT_SIZE
; i
++)
1945 if (&rdp
->nxtlist
== rdp
->nxttail
[i
])
1946 rdp
->nxttail
[i
] = tail
;
1950 smp_mb(); /* List handling before counting for rcu_barrier(). */
1951 rdp
->qlen_lazy
-= count_lazy
;
1952 ACCESS_ONCE(rdp
->qlen
) -= count
;
1953 rdp
->n_cbs_invoked
+= count
;
1955 /* Reinstate batch limit if we have worked down the excess. */
1956 if (rdp
->blimit
== LONG_MAX
&& rdp
->qlen
<= qlowmark
)
1957 rdp
->blimit
= blimit
;
1959 /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
1960 if (rdp
->qlen
== 0 && rdp
->qlen_last_fqs_check
!= 0) {
1961 rdp
->qlen_last_fqs_check
= 0;
1962 rdp
->n_force_qs_snap
= rsp
->n_force_qs
;
1963 } else if (rdp
->qlen
< rdp
->qlen_last_fqs_check
- qhimark
)
1964 rdp
->qlen_last_fqs_check
= rdp
->qlen
;
1965 WARN_ON_ONCE((rdp
->nxtlist
== NULL
) != (rdp
->qlen
== 0));
1967 local_irq_restore(flags
);
1969 /* Re-invoke RCU core processing if there are callbacks remaining. */
1970 if (cpu_has_callbacks_ready_to_invoke(rdp
))
1975 * Check to see if this CPU is in a non-context-switch quiescent state
1976 * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
1977 * Also schedule RCU core processing.
1979 * This function must be called from hardirq context. It is normally
1980 * invoked from the scheduling-clock interrupt. If rcu_pending returns
1981 * false, there is no point in invoking rcu_check_callbacks().
1983 void rcu_check_callbacks(int cpu
, int user
)
1985 trace_rcu_utilization("Start scheduler-tick");
1986 increment_cpu_stall_ticks();
1987 if (user
|| rcu_is_cpu_rrupt_from_idle()) {
1990 * Get here if this CPU took its interrupt from user
1991 * mode or from the idle loop, and if this is not a
1992 * nested interrupt. In this case, the CPU is in
1993 * a quiescent state, so note it.
1995 * No memory barrier is required here because both
1996 * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
1997 * variables that other CPUs neither access nor modify,
1998 * at least not while the corresponding CPU is online.
2004 } else if (!in_softirq()) {
2007 * Get here if this CPU did not take its interrupt from
2008 * softirq, in other words, if it is not interrupting
2009 * a rcu_bh read-side critical section. This is an _bh
2010 * critical section, so note it.
2015 rcu_preempt_check_callbacks(cpu
);
2016 if (rcu_pending(cpu
))
2018 trace_rcu_utilization("End scheduler-tick");
2022 * Scan the leaf rcu_node structures, processing dyntick state for any that
2023 * have not yet encountered a quiescent state, using the function specified.
2024 * Also initiate boosting for any threads blocked on the root rcu_node.
2026 * The caller must have suppressed start of new grace periods.
2028 static void force_qs_rnp(struct rcu_state
*rsp
, int (*f
)(struct rcu_data
*))
2032 unsigned long flags
;
2034 struct rcu_node
*rnp
;
2036 rcu_for_each_leaf_node(rsp
, rnp
) {
2039 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
2040 if (!rcu_gp_in_progress(rsp
)) {
2041 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
2044 if (rnp
->qsmask
== 0) {
2045 rcu_initiate_boost(rnp
, flags
); /* releases rnp->lock */
2050 for (; cpu
<= rnp
->grphi
; cpu
++, bit
<<= 1) {
2051 if ((rnp
->qsmask
& bit
) != 0 &&
2052 f(per_cpu_ptr(rsp
->rda
, cpu
)))
2057 /* rcu_report_qs_rnp() releases rnp->lock. */
2058 rcu_report_qs_rnp(mask
, rsp
, rnp
, flags
);
2061 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
2063 rnp
= rcu_get_root(rsp
);
2064 if (rnp
->qsmask
== 0) {
2065 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
2066 rcu_initiate_boost(rnp
, flags
); /* releases rnp->lock. */
2071 * Force quiescent states on reluctant CPUs, and also detect which
2072 * CPUs are in dyntick-idle mode.
2074 static void force_quiescent_state(struct rcu_state
*rsp
)
2076 unsigned long flags
;
2078 struct rcu_node
*rnp
;
2079 struct rcu_node
*rnp_old
= NULL
;
2081 /* Funnel through hierarchy to reduce memory contention. */
2082 rnp
= per_cpu_ptr(rsp
->rda
, raw_smp_processor_id())->mynode
;
2083 for (; rnp
!= NULL
; rnp
= rnp
->parent
) {
2084 ret
= (ACCESS_ONCE(rsp
->gp_flags
) & RCU_GP_FLAG_FQS
) ||
2085 !raw_spin_trylock(&rnp
->fqslock
);
2086 if (rnp_old
!= NULL
)
2087 raw_spin_unlock(&rnp_old
->fqslock
);
2089 rsp
->n_force_qs_lh
++;
2094 /* rnp_old == rcu_get_root(rsp), rnp == NULL. */
2096 /* Reached the root of the rcu_node tree, acquire lock. */
2097 raw_spin_lock_irqsave(&rnp_old
->lock
, flags
);
2098 raw_spin_unlock(&rnp_old
->fqslock
);
2099 if (ACCESS_ONCE(rsp
->gp_flags
) & RCU_GP_FLAG_FQS
) {
2100 rsp
->n_force_qs_lh
++;
2101 raw_spin_unlock_irqrestore(&rnp_old
->lock
, flags
);
2102 return; /* Someone beat us to it. */
2104 rsp
->gp_flags
|= RCU_GP_FLAG_FQS
;
2105 raw_spin_unlock_irqrestore(&rnp_old
->lock
, flags
);
2106 wake_up(&rsp
->gp_wq
); /* Memory barrier implied by wake_up() path. */
2110 * This does the RCU core processing work for the specified rcu_state
2111 * and rcu_data structures. This may be called only from the CPU to
2112 * whom the rdp belongs.
2115 __rcu_process_callbacks(struct rcu_state
*rsp
)
2117 unsigned long flags
;
2118 struct rcu_data
*rdp
= __this_cpu_ptr(rsp
->rda
);
2120 WARN_ON_ONCE(rdp
->beenonline
== 0);
2122 /* Handle the end of a grace period that some other CPU ended. */
2123 rcu_process_gp_end(rsp
, rdp
);
2125 /* Update RCU state based on any recent quiescent states. */
2126 rcu_check_quiescent_state(rsp
, rdp
);
2128 /* Does this CPU require a not-yet-started grace period? */
2129 local_irq_save(flags
);
2130 if (cpu_needs_another_gp(rsp
, rdp
)) {
2131 raw_spin_lock(&rcu_get_root(rsp
)->lock
); /* irqs disabled. */
2133 raw_spin_unlock_irqrestore(&rcu_get_root(rsp
)->lock
, flags
);
2135 local_irq_restore(flags
);
2138 /* If there are callbacks ready, invoke them. */
2139 if (cpu_has_callbacks_ready_to_invoke(rdp
))
2140 invoke_rcu_callbacks(rsp
, rdp
);
2144 * Do RCU core processing for the current CPU.
2146 static void rcu_process_callbacks(struct softirq_action
*unused
)
2148 struct rcu_state
*rsp
;
2150 if (cpu_is_offline(smp_processor_id()))
2152 trace_rcu_utilization("Start RCU core");
2153 for_each_rcu_flavor(rsp
)
2154 __rcu_process_callbacks(rsp
);
2155 trace_rcu_utilization("End RCU core");
2159 * Schedule RCU callback invocation. If the specified type of RCU
2160 * does not support RCU priority boosting, just do a direct call,
2161 * otherwise wake up the per-CPU kernel kthread. Note that because we
2162 * are running on the current CPU with interrupts disabled, the
2163 * rcu_cpu_kthread_task cannot disappear out from under us.
2165 static void invoke_rcu_callbacks(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
2167 if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active
)))
2169 if (likely(!rsp
->boost
)) {
2170 rcu_do_batch(rsp
, rdp
);
2173 invoke_rcu_callbacks_kthread();
2176 static void invoke_rcu_core(void)
2178 raise_softirq(RCU_SOFTIRQ
);
2182 * Handle any core-RCU processing required by a call_rcu() invocation.
2184 static void __call_rcu_core(struct rcu_state
*rsp
, struct rcu_data
*rdp
,
2185 struct rcu_head
*head
, unsigned long flags
)
2188 * If called from an extended quiescent state, invoke the RCU
2189 * core in order to force a re-evaluation of RCU's idleness.
2191 if (rcu_is_cpu_idle() && cpu_online(smp_processor_id()))
2194 /* If interrupts were disabled or CPU offline, don't invoke RCU core. */
2195 if (irqs_disabled_flags(flags
) || cpu_is_offline(smp_processor_id()))
2199 * Force the grace period if too many callbacks or too long waiting.
2200 * Enforce hysteresis, and don't invoke force_quiescent_state()
2201 * if some other CPU has recently done so. Also, don't bother
2202 * invoking force_quiescent_state() if the newly enqueued callback
2203 * is the only one waiting for a grace period to complete.
2205 if (unlikely(rdp
->qlen
> rdp
->qlen_last_fqs_check
+ qhimark
)) {
2207 /* Are we ignoring a completed grace period? */
2208 rcu_process_gp_end(rsp
, rdp
);
2209 check_for_new_grace_period(rsp
, rdp
);
2211 /* Start a new grace period if one not already started. */
2212 if (!rcu_gp_in_progress(rsp
)) {
2213 struct rcu_node
*rnp_root
= rcu_get_root(rsp
);
2215 raw_spin_lock(&rnp_root
->lock
);
2217 raw_spin_unlock(&rnp_root
->lock
);
2219 /* Give the grace period a kick. */
2220 rdp
->blimit
= LONG_MAX
;
2221 if (rsp
->n_force_qs
== rdp
->n_force_qs_snap
&&
2222 *rdp
->nxttail
[RCU_DONE_TAIL
] != head
)
2223 force_quiescent_state(rsp
);
2224 rdp
->n_force_qs_snap
= rsp
->n_force_qs
;
2225 rdp
->qlen_last_fqs_check
= rdp
->qlen
;
2231 * Helper function for call_rcu() and friends. The cpu argument will
2232 * normally be -1, indicating "currently running CPU". It may specify
2233 * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier()
2234 * is expected to specify a CPU.
2237 __call_rcu(struct rcu_head
*head
, void (*func
)(struct rcu_head
*rcu
),
2238 struct rcu_state
*rsp
, int cpu
, bool lazy
)
2240 unsigned long flags
;
2241 struct rcu_data
*rdp
;
2243 WARN_ON_ONCE((unsigned long)head
& 0x3); /* Misaligned rcu_head! */
2244 debug_rcu_head_queue(head
);
2249 * Opportunistically note grace-period endings and beginnings.
2250 * Note that we might see a beginning right after we see an
2251 * end, but never vice versa, since this CPU has to pass through
2252 * a quiescent state betweentimes.
2254 local_irq_save(flags
);
2255 rdp
= this_cpu_ptr(rsp
->rda
);
2257 /* Add the callback to our list. */
2258 if (unlikely(rdp
->nxttail
[RCU_NEXT_TAIL
] == NULL
) || cpu
!= -1) {
2262 rdp
= per_cpu_ptr(rsp
->rda
, cpu
);
2263 offline
= !__call_rcu_nocb(rdp
, head
, lazy
);
2264 WARN_ON_ONCE(offline
);
2265 /* _call_rcu() is illegal on offline CPU; leak the callback. */
2266 local_irq_restore(flags
);
2269 ACCESS_ONCE(rdp
->qlen
)++;
2273 rcu_idle_count_callbacks_posted();
2274 smp_mb(); /* Count before adding callback for rcu_barrier(). */
2275 *rdp
->nxttail
[RCU_NEXT_TAIL
] = head
;
2276 rdp
->nxttail
[RCU_NEXT_TAIL
] = &head
->next
;
2278 if (__is_kfree_rcu_offset((unsigned long)func
))
2279 trace_rcu_kfree_callback(rsp
->name
, head
, (unsigned long)func
,
2280 rdp
->qlen_lazy
, rdp
->qlen
);
2282 trace_rcu_callback(rsp
->name
, head
, rdp
->qlen_lazy
, rdp
->qlen
);
2284 /* Go handle any RCU core processing required. */
2285 __call_rcu_core(rsp
, rdp
, head
, flags
);
2286 local_irq_restore(flags
);
2290 * Queue an RCU-sched callback for invocation after a grace period.
2292 void call_rcu_sched(struct rcu_head
*head
, void (*func
)(struct rcu_head
*rcu
))
2294 __call_rcu(head
, func
, &rcu_sched_state
, -1, 0);
2296 EXPORT_SYMBOL_GPL(call_rcu_sched
);
2299 * Queue an RCU callback for invocation after a quicker grace period.
2301 void call_rcu_bh(struct rcu_head
*head
, void (*func
)(struct rcu_head
*rcu
))
2303 __call_rcu(head
, func
, &rcu_bh_state
, -1, 0);
2305 EXPORT_SYMBOL_GPL(call_rcu_bh
);
2308 * Because a context switch is a grace period for RCU-sched and RCU-bh,
2309 * any blocking grace-period wait automatically implies a grace period
2310 * if there is only one CPU online at any point time during execution
2311 * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
2312 * occasionally incorrectly indicate that there are multiple CPUs online
2313 * when there was in fact only one the whole time, as this just adds
2314 * some overhead: RCU still operates correctly.
2316 static inline int rcu_blocking_is_gp(void)
2320 might_sleep(); /* Check for RCU read-side critical section. */
2322 ret
= num_online_cpus() <= 1;
2328 * synchronize_sched - wait until an rcu-sched grace period has elapsed.
2330 * Control will return to the caller some time after a full rcu-sched
2331 * grace period has elapsed, in other words after all currently executing
2332 * rcu-sched read-side critical sections have completed. These read-side
2333 * critical sections are delimited by rcu_read_lock_sched() and
2334 * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
2335 * local_irq_disable(), and so on may be used in place of
2336 * rcu_read_lock_sched().
2338 * This means that all preempt_disable code sequences, including NMI and
2339 * non-threaded hardware-interrupt handlers, in progress on entry will
2340 * have completed before this primitive returns. However, this does not
2341 * guarantee that softirq handlers will have completed, since in some
2342 * kernels, these handlers can run in process context, and can block.
2344 * Note that this guarantee implies further memory-ordering guarantees.
2345 * On systems with more than one CPU, when synchronize_sched() returns,
2346 * each CPU is guaranteed to have executed a full memory barrier since the
2347 * end of its last RCU-sched read-side critical section whose beginning
2348 * preceded the call to synchronize_sched(). In addition, each CPU having
2349 * an RCU read-side critical section that extends beyond the return from
2350 * synchronize_sched() is guaranteed to have executed a full memory barrier
2351 * after the beginning of synchronize_sched() and before the beginning of
2352 * that RCU read-side critical section. Note that these guarantees include
2353 * CPUs that are offline, idle, or executing in user mode, as well as CPUs
2354 * that are executing in the kernel.
2356 * Furthermore, if CPU A invoked synchronize_sched(), which returned
2357 * to its caller on CPU B, then both CPU A and CPU B are guaranteed
2358 * to have executed a full memory barrier during the execution of
2359 * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but
2360 * again only if the system has more than one CPU).
2362 * This primitive provides the guarantees made by the (now removed)
2363 * synchronize_kernel() API. In contrast, synchronize_rcu() only
2364 * guarantees that rcu_read_lock() sections will have completed.
2365 * In "classic RCU", these two guarantees happen to be one and
2366 * the same, but can differ in realtime RCU implementations.
2368 void synchronize_sched(void)
2370 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map
) &&
2371 !lock_is_held(&rcu_lock_map
) &&
2372 !lock_is_held(&rcu_sched_lock_map
),
2373 "Illegal synchronize_sched() in RCU-sched read-side critical section");
2374 if (rcu_blocking_is_gp())
2377 synchronize_sched_expedited();
2379 wait_rcu_gp(call_rcu_sched
);
2381 EXPORT_SYMBOL_GPL(synchronize_sched
);
2384 * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
2386 * Control will return to the caller some time after a full rcu_bh grace
2387 * period has elapsed, in other words after all currently executing rcu_bh
2388 * read-side critical sections have completed. RCU read-side critical
2389 * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
2390 * and may be nested.
2392 * See the description of synchronize_sched() for more detailed information
2393 * on memory ordering guarantees.
2395 void synchronize_rcu_bh(void)
2397 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map
) &&
2398 !lock_is_held(&rcu_lock_map
) &&
2399 !lock_is_held(&rcu_sched_lock_map
),
2400 "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
2401 if (rcu_blocking_is_gp())
2404 synchronize_rcu_bh_expedited();
2406 wait_rcu_gp(call_rcu_bh
);
2408 EXPORT_SYMBOL_GPL(synchronize_rcu_bh
);
2410 static int synchronize_sched_expedited_cpu_stop(void *data
)
2413 * There must be a full memory barrier on each affected CPU
2414 * between the time that try_stop_cpus() is called and the
2415 * time that it returns.
2417 * In the current initial implementation of cpu_stop, the
2418 * above condition is already met when the control reaches
2419 * this point and the following smp_mb() is not strictly
2420 * necessary. Do smp_mb() anyway for documentation and
2421 * robustness against future implementation changes.
2423 smp_mb(); /* See above comment block. */
2428 * synchronize_sched_expedited - Brute-force RCU-sched grace period
2430 * Wait for an RCU-sched grace period to elapse, but use a "big hammer"
2431 * approach to force the grace period to end quickly. This consumes
2432 * significant time on all CPUs and is unfriendly to real-time workloads,
2433 * so is thus not recommended for any sort of common-case code. In fact,
2434 * if you are using synchronize_sched_expedited() in a loop, please
2435 * restructure your code to batch your updates, and then use a single
2436 * synchronize_sched() instead.
2438 * Note that it is illegal to call this function while holding any lock
2439 * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
2440 * to call this function from a CPU-hotplug notifier. Failing to observe
2441 * these restriction will result in deadlock.
2443 * This implementation can be thought of as an application of ticket
2444 * locking to RCU, with sync_sched_expedited_started and
2445 * sync_sched_expedited_done taking on the roles of the halves
2446 * of the ticket-lock word. Each task atomically increments
2447 * sync_sched_expedited_started upon entry, snapshotting the old value,
2448 * then attempts to stop all the CPUs. If this succeeds, then each
2449 * CPU will have executed a context switch, resulting in an RCU-sched
2450 * grace period. We are then done, so we use atomic_cmpxchg() to
2451 * update sync_sched_expedited_done to match our snapshot -- but
2452 * only if someone else has not already advanced past our snapshot.
2454 * On the other hand, if try_stop_cpus() fails, we check the value
2455 * of sync_sched_expedited_done. If it has advanced past our
2456 * initial snapshot, then someone else must have forced a grace period
2457 * some time after we took our snapshot. In this case, our work is
2458 * done for us, and we can simply return. Otherwise, we try again,
2459 * but keep our initial snapshot for purposes of checking for someone
2460 * doing our work for us.
2462 * If we fail too many times in a row, we fall back to synchronize_sched().
2464 void synchronize_sched_expedited(void)
2466 long firstsnap
, s
, snap
;
2468 struct rcu_state
*rsp
= &rcu_sched_state
;
2471 * If we are in danger of counter wrap, just do synchronize_sched().
2472 * By allowing sync_sched_expedited_started to advance no more than
2473 * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring
2474 * that more than 3.5 billion CPUs would be required to force a
2475 * counter wrap on a 32-bit system. Quite a few more CPUs would of
2476 * course be required on a 64-bit system.
2478 if (ULONG_CMP_GE((ulong
)atomic_long_read(&rsp
->expedited_start
),
2479 (ulong
)atomic_long_read(&rsp
->expedited_done
) +
2481 synchronize_sched();
2482 atomic_long_inc(&rsp
->expedited_wrap
);
2487 * Take a ticket. Note that atomic_inc_return() implies a
2488 * full memory barrier.
2490 snap
= atomic_long_inc_return(&rsp
->expedited_start
);
2493 WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
2496 * Each pass through the following loop attempts to force a
2497 * context switch on each CPU.
2499 while (try_stop_cpus(cpu_online_mask
,
2500 synchronize_sched_expedited_cpu_stop
,
2503 atomic_long_inc(&rsp
->expedited_tryfail
);
2505 /* Check to see if someone else did our work for us. */
2506 s
= atomic_long_read(&rsp
->expedited_done
);
2507 if (ULONG_CMP_GE((ulong
)s
, (ulong
)firstsnap
)) {
2508 /* ensure test happens before caller kfree */
2509 smp_mb__before_atomic_inc(); /* ^^^ */
2510 atomic_long_inc(&rsp
->expedited_workdone1
);
2514 /* No joy, try again later. Or just synchronize_sched(). */
2515 if (trycount
++ < 10) {
2516 udelay(trycount
* num_online_cpus());
2518 wait_rcu_gp(call_rcu_sched
);
2519 atomic_long_inc(&rsp
->expedited_normal
);
2523 /* Recheck to see if someone else did our work for us. */
2524 s
= atomic_long_read(&rsp
->expedited_done
);
2525 if (ULONG_CMP_GE((ulong
)s
, (ulong
)firstsnap
)) {
2526 /* ensure test happens before caller kfree */
2527 smp_mb__before_atomic_inc(); /* ^^^ */
2528 atomic_long_inc(&rsp
->expedited_workdone2
);
2533 * Refetching sync_sched_expedited_started allows later
2534 * callers to piggyback on our grace period. We retry
2535 * after they started, so our grace period works for them,
2536 * and they started after our first try, so their grace
2537 * period works for us.
2540 snap
= atomic_long_read(&rsp
->expedited_start
);
2541 smp_mb(); /* ensure read is before try_stop_cpus(). */
2543 atomic_long_inc(&rsp
->expedited_stoppedcpus
);
2546 * Everyone up to our most recent fetch is covered by our grace
2547 * period. Update the counter, but only if our work is still
2548 * relevant -- which it won't be if someone who started later
2549 * than we did already did their update.
2552 atomic_long_inc(&rsp
->expedited_done_tries
);
2553 s
= atomic_long_read(&rsp
->expedited_done
);
2554 if (ULONG_CMP_GE((ulong
)s
, (ulong
)snap
)) {
2555 /* ensure test happens before caller kfree */
2556 smp_mb__before_atomic_inc(); /* ^^^ */
2557 atomic_long_inc(&rsp
->expedited_done_lost
);
2560 } while (atomic_long_cmpxchg(&rsp
->expedited_done
, s
, snap
) != s
);
2561 atomic_long_inc(&rsp
->expedited_done_exit
);
2565 EXPORT_SYMBOL_GPL(synchronize_sched_expedited
);
2568 * Check to see if there is any immediate RCU-related work to be done
2569 * by the current CPU, for the specified type of RCU, returning 1 if so.
2570 * The checks are in order of increasing expense: checks that can be
2571 * carried out against CPU-local state are performed first. However,
2572 * we must check for CPU stalls first, else we might not get a chance.
2574 static int __rcu_pending(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
2576 struct rcu_node
*rnp
= rdp
->mynode
;
2578 rdp
->n_rcu_pending
++;
2580 /* Check for CPU stalls, if enabled. */
2581 check_cpu_stall(rsp
, rdp
);
2583 /* Is the RCU core waiting for a quiescent state from this CPU? */
2584 if (rcu_scheduler_fully_active
&&
2585 rdp
->qs_pending
&& !rdp
->passed_quiesce
) {
2586 rdp
->n_rp_qs_pending
++;
2587 } else if (rdp
->qs_pending
&& rdp
->passed_quiesce
) {
2588 rdp
->n_rp_report_qs
++;
2592 /* Does this CPU have callbacks ready to invoke? */
2593 if (cpu_has_callbacks_ready_to_invoke(rdp
)) {
2594 rdp
->n_rp_cb_ready
++;
2598 /* Has RCU gone idle with this CPU needing another grace period? */
2599 if (cpu_needs_another_gp(rsp
, rdp
)) {
2600 rdp
->n_rp_cpu_needs_gp
++;
2604 /* Has another RCU grace period completed? */
2605 if (ACCESS_ONCE(rnp
->completed
) != rdp
->completed
) { /* outside lock */
2606 rdp
->n_rp_gp_completed
++;
2610 /* Has a new RCU grace period started? */
2611 if (ACCESS_ONCE(rnp
->gpnum
) != rdp
->gpnum
) { /* outside lock */
2612 rdp
->n_rp_gp_started
++;
2617 rdp
->n_rp_need_nothing
++;
2622 * Check to see if there is any immediate RCU-related work to be done
2623 * by the current CPU, returning 1 if so. This function is part of the
2624 * RCU implementation; it is -not- an exported member of the RCU API.
2626 static int rcu_pending(int cpu
)
2628 struct rcu_state
*rsp
;
2630 for_each_rcu_flavor(rsp
)
2631 if (__rcu_pending(rsp
, per_cpu_ptr(rsp
->rda
, cpu
)))
2637 * Return true if the specified CPU has any callback. If all_lazy is
2638 * non-NULL, store an indication of whether all callbacks are lazy.
2639 * (If there are no callbacks, all of them are deemed to be lazy.)
2641 static int rcu_cpu_has_callbacks(int cpu
, bool *all_lazy
)
2645 struct rcu_data
*rdp
;
2646 struct rcu_state
*rsp
;
2648 for_each_rcu_flavor(rsp
) {
2649 rdp
= per_cpu_ptr(rsp
->rda
, cpu
);
2650 if (rdp
->qlen
!= rdp
->qlen_lazy
)
2661 * Helper function for _rcu_barrier() tracing. If tracing is disabled,
2662 * the compiler is expected to optimize this away.
2664 static void _rcu_barrier_trace(struct rcu_state
*rsp
, char *s
,
2665 int cpu
, unsigned long done
)
2667 trace_rcu_barrier(rsp
->name
, s
, cpu
,
2668 atomic_read(&rsp
->barrier_cpu_count
), done
);
2672 * RCU callback function for _rcu_barrier(). If we are last, wake
2673 * up the task executing _rcu_barrier().
2675 static void rcu_barrier_callback(struct rcu_head
*rhp
)
2677 struct rcu_data
*rdp
= container_of(rhp
, struct rcu_data
, barrier_head
);
2678 struct rcu_state
*rsp
= rdp
->rsp
;
2680 if (atomic_dec_and_test(&rsp
->barrier_cpu_count
)) {
2681 _rcu_barrier_trace(rsp
, "LastCB", -1, rsp
->n_barrier_done
);
2682 complete(&rsp
->barrier_completion
);
2684 _rcu_barrier_trace(rsp
, "CB", -1, rsp
->n_barrier_done
);
2689 * Called with preemption disabled, and from cross-cpu IRQ context.
2691 static void rcu_barrier_func(void *type
)
2693 struct rcu_state
*rsp
= type
;
2694 struct rcu_data
*rdp
= __this_cpu_ptr(rsp
->rda
);
2696 _rcu_barrier_trace(rsp
, "IRQ", -1, rsp
->n_barrier_done
);
2697 atomic_inc(&rsp
->barrier_cpu_count
);
2698 rsp
->call(&rdp
->barrier_head
, rcu_barrier_callback
);
2702 * Orchestrate the specified type of RCU barrier, waiting for all
2703 * RCU callbacks of the specified type to complete.
2705 static void _rcu_barrier(struct rcu_state
*rsp
)
2708 struct rcu_data
*rdp
;
2709 unsigned long snap
= ACCESS_ONCE(rsp
->n_barrier_done
);
2710 unsigned long snap_done
;
2712 _rcu_barrier_trace(rsp
, "Begin", -1, snap
);
2714 /* Take mutex to serialize concurrent rcu_barrier() requests. */
2715 mutex_lock(&rsp
->barrier_mutex
);
2718 * Ensure that all prior references, including to ->n_barrier_done,
2719 * are ordered before the _rcu_barrier() machinery.
2721 smp_mb(); /* See above block comment. */
2724 * Recheck ->n_barrier_done to see if others did our work for us.
2725 * This means checking ->n_barrier_done for an even-to-odd-to-even
2726 * transition. The "if" expression below therefore rounds the old
2727 * value up to the next even number and adds two before comparing.
2729 snap_done
= ACCESS_ONCE(rsp
->n_barrier_done
);
2730 _rcu_barrier_trace(rsp
, "Check", -1, snap_done
);
2731 if (ULONG_CMP_GE(snap_done
, ((snap
+ 1) & ~0x1) + 2)) {
2732 _rcu_barrier_trace(rsp
, "EarlyExit", -1, snap_done
);
2733 smp_mb(); /* caller's subsequent code after above check. */
2734 mutex_unlock(&rsp
->barrier_mutex
);
2739 * Increment ->n_barrier_done to avoid duplicate work. Use
2740 * ACCESS_ONCE() to prevent the compiler from speculating
2741 * the increment to precede the early-exit check.
2743 ACCESS_ONCE(rsp
->n_barrier_done
)++;
2744 WARN_ON_ONCE((rsp
->n_barrier_done
& 0x1) != 1);
2745 _rcu_barrier_trace(rsp
, "Inc1", -1, rsp
->n_barrier_done
);
2746 smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */
2749 * Initialize the count to one rather than to zero in order to
2750 * avoid a too-soon return to zero in case of a short grace period
2751 * (or preemption of this task). Exclude CPU-hotplug operations
2752 * to ensure that no offline CPU has callbacks queued.
2754 init_completion(&rsp
->barrier_completion
);
2755 atomic_set(&rsp
->barrier_cpu_count
, 1);
2759 * Force each CPU with callbacks to register a new callback.
2760 * When that callback is invoked, we will know that all of the
2761 * corresponding CPU's preceding callbacks have been invoked.
2763 for_each_possible_cpu(cpu
) {
2764 if (!cpu_online(cpu
) && !is_nocb_cpu(cpu
))
2766 rdp
= per_cpu_ptr(rsp
->rda
, cpu
);
2767 if (is_nocb_cpu(cpu
)) {
2768 _rcu_barrier_trace(rsp
, "OnlineNoCB", cpu
,
2769 rsp
->n_barrier_done
);
2770 atomic_inc(&rsp
->barrier_cpu_count
);
2771 __call_rcu(&rdp
->barrier_head
, rcu_barrier_callback
,
2773 } else if (ACCESS_ONCE(rdp
->qlen
)) {
2774 _rcu_barrier_trace(rsp
, "OnlineQ", cpu
,
2775 rsp
->n_barrier_done
);
2776 smp_call_function_single(cpu
, rcu_barrier_func
, rsp
, 1);
2778 _rcu_barrier_trace(rsp
, "OnlineNQ", cpu
,
2779 rsp
->n_barrier_done
);
2785 * Now that we have an rcu_barrier_callback() callback on each
2786 * CPU, and thus each counted, remove the initial count.
2788 if (atomic_dec_and_test(&rsp
->barrier_cpu_count
))
2789 complete(&rsp
->barrier_completion
);
2791 /* Increment ->n_barrier_done to prevent duplicate work. */
2792 smp_mb(); /* Keep increment after above mechanism. */
2793 ACCESS_ONCE(rsp
->n_barrier_done
)++;
2794 WARN_ON_ONCE((rsp
->n_barrier_done
& 0x1) != 0);
2795 _rcu_barrier_trace(rsp
, "Inc2", -1, rsp
->n_barrier_done
);
2796 smp_mb(); /* Keep increment before caller's subsequent code. */
2798 /* Wait for all rcu_barrier_callback() callbacks to be invoked. */
2799 wait_for_completion(&rsp
->barrier_completion
);
2801 /* Other rcu_barrier() invocations can now safely proceed. */
2802 mutex_unlock(&rsp
->barrier_mutex
);
2806 * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
2808 void rcu_barrier_bh(void)
2810 _rcu_barrier(&rcu_bh_state
);
2812 EXPORT_SYMBOL_GPL(rcu_barrier_bh
);
2815 * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
2817 void rcu_barrier_sched(void)
2819 _rcu_barrier(&rcu_sched_state
);
2821 EXPORT_SYMBOL_GPL(rcu_barrier_sched
);
2824 * Do boot-time initialization of a CPU's per-CPU RCU data.
2827 rcu_boot_init_percpu_data(int cpu
, struct rcu_state
*rsp
)
2829 unsigned long flags
;
2830 struct rcu_data
*rdp
= per_cpu_ptr(rsp
->rda
, cpu
);
2831 struct rcu_node
*rnp
= rcu_get_root(rsp
);
2833 /* Set up local state, ensuring consistent view of global state. */
2834 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
2835 rdp
->grpmask
= 1UL << (cpu
- rdp
->mynode
->grplo
);
2836 init_callback_list(rdp
);
2838 ACCESS_ONCE(rdp
->qlen
) = 0;
2839 rdp
->dynticks
= &per_cpu(rcu_dynticks
, cpu
);
2840 WARN_ON_ONCE(rdp
->dynticks
->dynticks_nesting
!= DYNTICK_TASK_EXIT_IDLE
);
2841 WARN_ON_ONCE(atomic_read(&rdp
->dynticks
->dynticks
) != 1);
2844 rcu_boot_init_nocb_percpu_data(rdp
);
2845 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
2849 * Initialize a CPU's per-CPU RCU data. Note that only one online or
2850 * offline event can be happening at a given time. Note also that we
2851 * can accept some slop in the rsp->completed access due to the fact
2852 * that this CPU cannot possibly have any RCU callbacks in flight yet.
2854 static void __cpuinit
2855 rcu_init_percpu_data(int cpu
, struct rcu_state
*rsp
, int preemptible
)
2857 unsigned long flags
;
2859 struct rcu_data
*rdp
= per_cpu_ptr(rsp
->rda
, cpu
);
2860 struct rcu_node
*rnp
= rcu_get_root(rsp
);
2862 /* Exclude new grace periods. */
2863 mutex_lock(&rsp
->onoff_mutex
);
2865 /* Set up local state, ensuring consistent view of global state. */
2866 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
2867 rdp
->beenonline
= 1; /* We have now been online. */
2868 rdp
->preemptible
= preemptible
;
2869 rdp
->qlen_last_fqs_check
= 0;
2870 rdp
->n_force_qs_snap
= rsp
->n_force_qs
;
2871 rdp
->blimit
= blimit
;
2872 init_callback_list(rdp
); /* Re-enable callbacks on this CPU. */
2873 rdp
->dynticks
->dynticks_nesting
= DYNTICK_TASK_EXIT_IDLE
;
2874 atomic_set(&rdp
->dynticks
->dynticks
,
2875 (atomic_read(&rdp
->dynticks
->dynticks
) & ~0x1) + 1);
2876 raw_spin_unlock(&rnp
->lock
); /* irqs remain disabled. */
2878 /* Add CPU to rcu_node bitmasks. */
2880 mask
= rdp
->grpmask
;
2882 /* Exclude any attempts to start a new GP on small systems. */
2883 raw_spin_lock(&rnp
->lock
); /* irqs already disabled. */
2884 rnp
->qsmaskinit
|= mask
;
2885 mask
= rnp
->grpmask
;
2886 if (rnp
== rdp
->mynode
) {
2888 * If there is a grace period in progress, we will
2889 * set up to wait for it next time we run the
2892 rdp
->gpnum
= rnp
->completed
;
2893 rdp
->completed
= rnp
->completed
;
2894 rdp
->passed_quiesce
= 0;
2895 rdp
->qs_pending
= 0;
2896 trace_rcu_grace_period(rsp
->name
, rdp
->gpnum
, "cpuonl");
2898 raw_spin_unlock(&rnp
->lock
); /* irqs already disabled. */
2900 } while (rnp
!= NULL
&& !(rnp
->qsmaskinit
& mask
));
2901 local_irq_restore(flags
);
2903 mutex_unlock(&rsp
->onoff_mutex
);
2906 static void __cpuinit
rcu_prepare_cpu(int cpu
)
2908 struct rcu_state
*rsp
;
2910 for_each_rcu_flavor(rsp
)
2911 rcu_init_percpu_data(cpu
, rsp
,
2912 strcmp(rsp
->name
, "rcu_preempt") == 0);
2916 * Handle CPU online/offline notification events.
2918 static int __cpuinit
rcu_cpu_notify(struct notifier_block
*self
,
2919 unsigned long action
, void *hcpu
)
2921 long cpu
= (long)hcpu
;
2922 struct rcu_data
*rdp
= per_cpu_ptr(rcu_state
->rda
, cpu
);
2923 struct rcu_node
*rnp
= rdp
->mynode
;
2924 struct rcu_state
*rsp
;
2926 trace_rcu_utilization("Start CPU hotplug");
2928 case CPU_UP_PREPARE
:
2929 case CPU_UP_PREPARE_FROZEN
:
2930 rcu_prepare_cpu(cpu
);
2931 rcu_prepare_kthreads(cpu
);
2934 case CPU_DOWN_FAILED
:
2935 rcu_boost_kthread_setaffinity(rnp
, -1);
2937 case CPU_DOWN_PREPARE
:
2938 rcu_boost_kthread_setaffinity(rnp
, cpu
);
2941 case CPU_DYING_FROZEN
:
2943 * The whole machine is "stopped" except this CPU, so we can
2944 * touch any data without introducing corruption. We send the
2945 * dying CPU's callbacks to an arbitrarily chosen online CPU.
2947 for_each_rcu_flavor(rsp
)
2948 rcu_cleanup_dying_cpu(rsp
);
2951 case CPU_DEAD_FROZEN
:
2952 case CPU_UP_CANCELED
:
2953 case CPU_UP_CANCELED_FROZEN
:
2954 for_each_rcu_flavor(rsp
)
2955 rcu_cleanup_dead_cpu(cpu
, rsp
);
2960 trace_rcu_utilization("End CPU hotplug");
2965 * Spawn the kthread that handles this RCU flavor's grace periods.
2967 static int __init
rcu_spawn_gp_kthread(void)
2969 unsigned long flags
;
2970 struct rcu_node
*rnp
;
2971 struct rcu_state
*rsp
;
2972 struct task_struct
*t
;
2974 for_each_rcu_flavor(rsp
) {
2975 t
= kthread_run(rcu_gp_kthread
, rsp
, rsp
->name
);
2977 rnp
= rcu_get_root(rsp
);
2978 raw_spin_lock_irqsave(&rnp
->lock
, flags
);
2979 rsp
->gp_kthread
= t
;
2980 raw_spin_unlock_irqrestore(&rnp
->lock
, flags
);
2981 rcu_spawn_nocb_kthreads(rsp
);
2985 early_initcall(rcu_spawn_gp_kthread
);
2988 * This function is invoked towards the end of the scheduler's initialization
2989 * process. Before this is called, the idle task might contain
2990 * RCU read-side critical sections (during which time, this idle
2991 * task is booting the system). After this function is called, the
2992 * idle tasks are prohibited from containing RCU read-side critical
2993 * sections. This function also enables RCU lockdep checking.
2995 void rcu_scheduler_starting(void)
2997 WARN_ON(num_online_cpus() != 1);
2998 WARN_ON(nr_context_switches() > 0);
2999 rcu_scheduler_active
= 1;
3003 * Compute the per-level fanout, either using the exact fanout specified
3004 * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
3006 #ifdef CONFIG_RCU_FANOUT_EXACT
3007 static void __init
rcu_init_levelspread(struct rcu_state
*rsp
)
3011 for (i
= rcu_num_lvls
- 1; i
> 0; i
--)
3012 rsp
->levelspread
[i
] = CONFIG_RCU_FANOUT
;
3013 rsp
->levelspread
[0] = rcu_fanout_leaf
;
3015 #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
3016 static void __init
rcu_init_levelspread(struct rcu_state
*rsp
)
3023 for (i
= rcu_num_lvls
- 1; i
>= 0; i
--) {
3024 ccur
= rsp
->levelcnt
[i
];
3025 rsp
->levelspread
[i
] = (cprv
+ ccur
- 1) / ccur
;
3029 #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
3032 * Helper function for rcu_init() that initializes one rcu_state structure.
3034 static void __init
rcu_init_one(struct rcu_state
*rsp
,
3035 struct rcu_data __percpu
*rda
)
3037 static char *buf
[] = { "rcu_node_0",
3040 "rcu_node_3" }; /* Match MAX_RCU_LVLS */
3041 static char *fqs
[] = { "rcu_node_fqs_0",
3044 "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */
3048 struct rcu_node
*rnp
;
3050 BUILD_BUG_ON(MAX_RCU_LVLS
> ARRAY_SIZE(buf
)); /* Fix buf[] init! */
3052 /* Silence gcc 4.8 warning about array index out of range. */
3053 if (rcu_num_lvls
> RCU_NUM_LVLS
)
3054 panic("rcu_init_one: rcu_num_lvls overflow");
3056 /* Initialize the level-tracking arrays. */
3058 for (i
= 0; i
< rcu_num_lvls
; i
++)
3059 rsp
->levelcnt
[i
] = num_rcu_lvl
[i
];
3060 for (i
= 1; i
< rcu_num_lvls
; i
++)
3061 rsp
->level
[i
] = rsp
->level
[i
- 1] + rsp
->levelcnt
[i
- 1];
3062 rcu_init_levelspread(rsp
);
3064 /* Initialize the elements themselves, starting from the leaves. */
3066 for (i
= rcu_num_lvls
- 1; i
>= 0; i
--) {
3067 cpustride
*= rsp
->levelspread
[i
];
3068 rnp
= rsp
->level
[i
];
3069 for (j
= 0; j
< rsp
->levelcnt
[i
]; j
++, rnp
++) {
3070 raw_spin_lock_init(&rnp
->lock
);
3071 lockdep_set_class_and_name(&rnp
->lock
,
3072 &rcu_node_class
[i
], buf
[i
]);
3073 raw_spin_lock_init(&rnp
->fqslock
);
3074 lockdep_set_class_and_name(&rnp
->fqslock
,
3075 &rcu_fqs_class
[i
], fqs
[i
]);
3076 rnp
->gpnum
= rsp
->gpnum
;
3077 rnp
->completed
= rsp
->completed
;
3079 rnp
->qsmaskinit
= 0;
3080 rnp
->grplo
= j
* cpustride
;
3081 rnp
->grphi
= (j
+ 1) * cpustride
- 1;
3082 if (rnp
->grphi
>= NR_CPUS
)
3083 rnp
->grphi
= NR_CPUS
- 1;
3089 rnp
->grpnum
= j
% rsp
->levelspread
[i
- 1];
3090 rnp
->grpmask
= 1UL << rnp
->grpnum
;
3091 rnp
->parent
= rsp
->level
[i
- 1] +
3092 j
/ rsp
->levelspread
[i
- 1];
3095 INIT_LIST_HEAD(&rnp
->blkd_tasks
);
3096 rcu_init_one_nocb(rnp
);
3101 init_waitqueue_head(&rsp
->gp_wq
);
3102 rnp
= rsp
->level
[rcu_num_lvls
- 1];
3103 for_each_possible_cpu(i
) {
3104 while (i
> rnp
->grphi
)
3106 per_cpu_ptr(rsp
->rda
, i
)->mynode
= rnp
;
3107 rcu_boot_init_percpu_data(i
, rsp
);
3109 list_add(&rsp
->flavors
, &rcu_struct_flavors
);
3113 * Compute the rcu_node tree geometry from kernel parameters. This cannot
3114 * replace the definitions in rcutree.h because those are needed to size
3115 * the ->node array in the rcu_state structure.
3117 static void __init
rcu_init_geometry(void)
3122 int rcu_capacity
[MAX_RCU_LVLS
+ 1];
3124 /* If the compile-time values are accurate, just leave. */
3125 if (rcu_fanout_leaf
== CONFIG_RCU_FANOUT_LEAF
&&
3126 nr_cpu_ids
== NR_CPUS
)
3130 * Compute number of nodes that can be handled an rcu_node tree
3131 * with the given number of levels. Setting rcu_capacity[0] makes
3132 * some of the arithmetic easier.
3134 rcu_capacity
[0] = 1;
3135 rcu_capacity
[1] = rcu_fanout_leaf
;
3136 for (i
= 2; i
<= MAX_RCU_LVLS
; i
++)
3137 rcu_capacity
[i
] = rcu_capacity
[i
- 1] * CONFIG_RCU_FANOUT
;
3140 * The boot-time rcu_fanout_leaf parameter is only permitted
3141 * to increase the leaf-level fanout, not decrease it. Of course,
3142 * the leaf-level fanout cannot exceed the number of bits in
3143 * the rcu_node masks. Finally, the tree must be able to accommodate
3144 * the configured number of CPUs. Complain and fall back to the
3145 * compile-time values if these limits are exceeded.
3147 if (rcu_fanout_leaf
< CONFIG_RCU_FANOUT_LEAF
||
3148 rcu_fanout_leaf
> sizeof(unsigned long) * 8 ||
3149 n
> rcu_capacity
[MAX_RCU_LVLS
]) {
3154 /* Calculate the number of rcu_nodes at each level of the tree. */
3155 for (i
= 1; i
<= MAX_RCU_LVLS
; i
++)
3156 if (n
<= rcu_capacity
[i
]) {
3157 for (j
= 0; j
<= i
; j
++)
3159 DIV_ROUND_UP(n
, rcu_capacity
[i
- j
]);
3161 for (j
= i
+ 1; j
<= MAX_RCU_LVLS
; j
++)
3166 /* Calculate the total number of rcu_node structures. */
3168 for (i
= 0; i
<= MAX_RCU_LVLS
; i
++)
3169 rcu_num_nodes
+= num_rcu_lvl
[i
];
3173 void __init
rcu_init(void)
3177 rcu_bootup_announce();
3178 rcu_init_geometry();
3179 rcu_init_one(&rcu_sched_state
, &rcu_sched_data
);
3180 rcu_init_one(&rcu_bh_state
, &rcu_bh_data
);
3181 __rcu_init_preempt();
3182 open_softirq(RCU_SOFTIRQ
, rcu_process_callbacks
);
3185 * We don't need protection against CPU-hotplug here because
3186 * this is called early in boot, before either interrupts
3187 * or the scheduler are operational.
3189 cpu_notifier(rcu_cpu_notify
, 0);
3190 for_each_online_cpu(cpu
)
3191 rcu_cpu_notify(NULL
, CPU_UP_PREPARE
, (void *)(long)cpu
);
3194 #include "rcutree_plugin.h"