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 <asm/atomic.h>
40 #include <linux/bitops.h>
41 #include <linux/module.h>
42 #include <linux/completion.h>
43 #include <linux/moduleparam.h>
44 #include <linux/percpu.h>
45 #include <linux/notifier.h>
46 #include <linux/cpu.h>
47 #include <linux/mutex.h>
48 #include <linux/time.h>
52 /* Data structures. */
54 #define RCU_STATE_INITIALIZER(name) { \
55 .level = { &name.node[0] }, \
57 NUM_RCU_LVL_0, /* root of hierarchy. */ \
60 NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \
62 .signaled = RCU_SIGNAL_INIT, \
65 .onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \
66 .fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \
68 .n_force_qs_ngp = 0, \
71 struct rcu_state rcu_sched_state
= RCU_STATE_INITIALIZER(rcu_sched_state
);
72 DEFINE_PER_CPU(struct rcu_data
, rcu_sched_data
);
74 struct rcu_state rcu_bh_state
= RCU_STATE_INITIALIZER(rcu_bh_state
);
75 DEFINE_PER_CPU(struct rcu_data
, rcu_bh_data
);
79 * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
80 * permit this function to be invoked without holding the root rcu_node
81 * structure's ->lock, but of course results can be subject to change.
83 static int rcu_gp_in_progress(struct rcu_state
*rsp
)
85 return ACCESS_ONCE(rsp
->completed
) != ACCESS_ONCE(rsp
->gpnum
);
89 * Note a quiescent state. Because we do not need to know
90 * how many quiescent states passed, just if there was at least
91 * one since the start of the grace period, this just sets a flag.
93 void rcu_sched_qs(int cpu
)
97 rdp
= &per_cpu(rcu_sched_data
, cpu
);
98 rdp
->passed_quiesc_completed
= rdp
->completed
;
100 rdp
->passed_quiesc
= 1;
101 rcu_preempt_note_context_switch(cpu
);
104 void rcu_bh_qs(int cpu
)
106 struct rcu_data
*rdp
;
108 rdp
= &per_cpu(rcu_bh_data
, cpu
);
109 rdp
->passed_quiesc_completed
= rdp
->completed
;
111 rdp
->passed_quiesc
= 1;
115 DEFINE_PER_CPU(struct rcu_dynticks
, rcu_dynticks
) = {
116 .dynticks_nesting
= 1,
119 #endif /* #ifdef CONFIG_NO_HZ */
121 static int blimit
= 10; /* Maximum callbacks per softirq. */
122 static int qhimark
= 10000; /* If this many pending, ignore blimit. */
123 static int qlowmark
= 100; /* Once only this many pending, use blimit. */
125 module_param(blimit
, int, 0);
126 module_param(qhimark
, int, 0);
127 module_param(qlowmark
, int, 0);
129 static void force_quiescent_state(struct rcu_state
*rsp
, int relaxed
);
130 static int rcu_pending(int cpu
);
133 * Return the number of RCU-sched batches processed thus far for debug & stats.
135 long rcu_batches_completed_sched(void)
137 return rcu_sched_state
.completed
;
139 EXPORT_SYMBOL_GPL(rcu_batches_completed_sched
);
142 * Return the number of RCU BH batches processed thus far for debug & stats.
144 long rcu_batches_completed_bh(void)
146 return rcu_bh_state
.completed
;
148 EXPORT_SYMBOL_GPL(rcu_batches_completed_bh
);
151 * Does the CPU have callbacks ready to be invoked?
154 cpu_has_callbacks_ready_to_invoke(struct rcu_data
*rdp
)
156 return &rdp
->nxtlist
!= rdp
->nxttail
[RCU_DONE_TAIL
];
160 * Does the current CPU require a yet-as-unscheduled grace period?
163 cpu_needs_another_gp(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
165 return *rdp
->nxttail
[RCU_DONE_TAIL
] && !rcu_gp_in_progress(rsp
);
169 * Return the root node of the specified rcu_state structure.
171 static struct rcu_node
*rcu_get_root(struct rcu_state
*rsp
)
173 return &rsp
->node
[0];
179 * If the specified CPU is offline, tell the caller that it is in
180 * a quiescent state. Otherwise, whack it with a reschedule IPI.
181 * Grace periods can end up waiting on an offline CPU when that
182 * CPU is in the process of coming online -- it will be added to the
183 * rcu_node bitmasks before it actually makes it online. The same thing
184 * can happen while a CPU is in the process of coming online. Because this
185 * race is quite rare, we check for it after detecting that the grace
186 * period has been delayed rather than checking each and every CPU
187 * each and every time we start a new grace period.
189 static int rcu_implicit_offline_qs(struct rcu_data
*rdp
)
192 * If the CPU is offline, it is in a quiescent state. We can
193 * trust its state not to change because interrupts are disabled.
195 if (cpu_is_offline(rdp
->cpu
)) {
200 /* If preemptable RCU, no point in sending reschedule IPI. */
201 if (rdp
->preemptable
)
204 /* The CPU is online, so send it a reschedule IPI. */
205 if (rdp
->cpu
!= smp_processor_id())
206 smp_send_reschedule(rdp
->cpu
);
213 #endif /* #ifdef CONFIG_SMP */
218 * rcu_enter_nohz - inform RCU that current CPU is entering nohz
220 * Enter nohz mode, in other words, -leave- the mode in which RCU
221 * read-side critical sections can occur. (Though RCU read-side
222 * critical sections can occur in irq handlers in nohz mode, a possibility
223 * handled by rcu_irq_enter() and rcu_irq_exit()).
225 void rcu_enter_nohz(void)
228 struct rcu_dynticks
*rdtp
;
230 smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
231 local_irq_save(flags
);
232 rdtp
= &__get_cpu_var(rcu_dynticks
);
234 rdtp
->dynticks_nesting
--;
235 WARN_ON_ONCE(rdtp
->dynticks
& 0x1);
236 local_irq_restore(flags
);
240 * rcu_exit_nohz - inform RCU that current CPU is leaving nohz
242 * Exit nohz mode, in other words, -enter- the mode in which RCU
243 * read-side critical sections normally occur.
245 void rcu_exit_nohz(void)
248 struct rcu_dynticks
*rdtp
;
250 local_irq_save(flags
);
251 rdtp
= &__get_cpu_var(rcu_dynticks
);
253 rdtp
->dynticks_nesting
++;
254 WARN_ON_ONCE(!(rdtp
->dynticks
& 0x1));
255 local_irq_restore(flags
);
256 smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
260 * rcu_nmi_enter - inform RCU of entry to NMI context
262 * If the CPU was idle with dynamic ticks active, and there is no
263 * irq handler running, this updates rdtp->dynticks_nmi to let the
264 * RCU grace-period handling know that the CPU is active.
266 void rcu_nmi_enter(void)
268 struct rcu_dynticks
*rdtp
= &__get_cpu_var(rcu_dynticks
);
270 if (rdtp
->dynticks
& 0x1)
272 rdtp
->dynticks_nmi
++;
273 WARN_ON_ONCE(!(rdtp
->dynticks_nmi
& 0x1));
274 smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
278 * rcu_nmi_exit - inform RCU of exit from NMI context
280 * If the CPU was idle with dynamic ticks active, and there is no
281 * irq handler running, this updates rdtp->dynticks_nmi to let the
282 * RCU grace-period handling know that the CPU is no longer active.
284 void rcu_nmi_exit(void)
286 struct rcu_dynticks
*rdtp
= &__get_cpu_var(rcu_dynticks
);
288 if (rdtp
->dynticks
& 0x1)
290 smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
291 rdtp
->dynticks_nmi
++;
292 WARN_ON_ONCE(rdtp
->dynticks_nmi
& 0x1);
296 * rcu_irq_enter - inform RCU of entry to hard irq context
298 * If the CPU was idle with dynamic ticks active, this updates the
299 * rdtp->dynticks to let the RCU handling know that the CPU is active.
301 void rcu_irq_enter(void)
303 struct rcu_dynticks
*rdtp
= &__get_cpu_var(rcu_dynticks
);
305 if (rdtp
->dynticks_nesting
++)
308 WARN_ON_ONCE(!(rdtp
->dynticks
& 0x1));
309 smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
313 * rcu_irq_exit - inform RCU of exit from hard irq context
315 * If the CPU was idle with dynamic ticks active, update the rdp->dynticks
316 * to put let the RCU handling be aware that the CPU is going back to idle
319 void rcu_irq_exit(void)
321 struct rcu_dynticks
*rdtp
= &__get_cpu_var(rcu_dynticks
);
323 if (--rdtp
->dynticks_nesting
)
325 smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
327 WARN_ON_ONCE(rdtp
->dynticks
& 0x1);
329 /* If the interrupt queued a callback, get out of dyntick mode. */
330 if (__get_cpu_var(rcu_sched_data
).nxtlist
||
331 __get_cpu_var(rcu_bh_data
).nxtlist
)
336 * Record the specified "completed" value, which is later used to validate
337 * dynticks counter manipulations. Specify "rsp->completed - 1" to
338 * unconditionally invalidate any future dynticks manipulations (which is
339 * useful at the beginning of a grace period).
341 static void dyntick_record_completed(struct rcu_state
*rsp
, long comp
)
343 rsp
->dynticks_completed
= comp
;
349 * Recall the previously recorded value of the completion for dynticks.
351 static long dyntick_recall_completed(struct rcu_state
*rsp
)
353 return rsp
->dynticks_completed
;
357 * Snapshot the specified CPU's dynticks counter so that we can later
358 * credit them with an implicit quiescent state. Return 1 if this CPU
359 * is in dynticks idle mode, which is an extended quiescent state.
361 static int dyntick_save_progress_counter(struct rcu_data
*rdp
)
367 snap
= rdp
->dynticks
->dynticks
;
368 snap_nmi
= rdp
->dynticks
->dynticks_nmi
;
369 smp_mb(); /* Order sampling of snap with end of grace period. */
370 rdp
->dynticks_snap
= snap
;
371 rdp
->dynticks_nmi_snap
= snap_nmi
;
372 ret
= ((snap
& 0x1) == 0) && ((snap_nmi
& 0x1) == 0);
379 * Return true if the specified CPU has passed through a quiescent
380 * state by virtue of being in or having passed through an dynticks
381 * idle state since the last call to dyntick_save_progress_counter()
384 static int rcu_implicit_dynticks_qs(struct rcu_data
*rdp
)
391 curr
= rdp
->dynticks
->dynticks
;
392 snap
= rdp
->dynticks_snap
;
393 curr_nmi
= rdp
->dynticks
->dynticks_nmi
;
394 snap_nmi
= rdp
->dynticks_nmi_snap
;
395 smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
398 * If the CPU passed through or entered a dynticks idle phase with
399 * no active irq/NMI handlers, then we can safely pretend that the CPU
400 * already acknowledged the request to pass through a quiescent
401 * state. Either way, that CPU cannot possibly be in an RCU
402 * read-side critical section that started before the beginning
403 * of the current RCU grace period.
405 if ((curr
!= snap
|| (curr
& 0x1) == 0) &&
406 (curr_nmi
!= snap_nmi
|| (curr_nmi
& 0x1) == 0)) {
411 /* Go check for the CPU being offline. */
412 return rcu_implicit_offline_qs(rdp
);
415 #endif /* #ifdef CONFIG_SMP */
417 #else /* #ifdef CONFIG_NO_HZ */
419 static void dyntick_record_completed(struct rcu_state
*rsp
, long comp
)
426 * If there are no dynticks, then the only way that a CPU can passively
427 * be in a quiescent state is to be offline. Unlike dynticks idle, which
428 * is a point in time during the prior (already finished) grace period,
429 * an offline CPU is always in a quiescent state, and thus can be
430 * unconditionally applied. So just return the current value of completed.
432 static long dyntick_recall_completed(struct rcu_state
*rsp
)
434 return rsp
->completed
;
437 static int dyntick_save_progress_counter(struct rcu_data
*rdp
)
442 static int rcu_implicit_dynticks_qs(struct rcu_data
*rdp
)
444 return rcu_implicit_offline_qs(rdp
);
447 #endif /* #ifdef CONFIG_SMP */
449 #endif /* #else #ifdef CONFIG_NO_HZ */
451 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
453 static void record_gp_stall_check_time(struct rcu_state
*rsp
)
455 rsp
->gp_start
= jiffies
;
456 rsp
->jiffies_stall
= jiffies
+ RCU_SECONDS_TILL_STALL_CHECK
;
459 static void print_other_cpu_stall(struct rcu_state
*rsp
)
464 struct rcu_node
*rnp
= rcu_get_root(rsp
);
466 /* Only let one CPU complain about others per time interval. */
468 spin_lock_irqsave(&rnp
->lock
, flags
);
469 delta
= jiffies
- rsp
->jiffies_stall
;
470 if (delta
< RCU_STALL_RAT_DELAY
|| !rcu_gp_in_progress(rsp
)) {
471 spin_unlock_irqrestore(&rnp
->lock
, flags
);
474 rsp
->jiffies_stall
= jiffies
+ RCU_SECONDS_TILL_STALL_RECHECK
;
477 * Now rat on any tasks that got kicked up to the root rcu_node
478 * due to CPU offlining.
480 rcu_print_task_stall(rnp
);
481 spin_unlock_irqrestore(&rnp
->lock
, flags
);
483 /* OK, time to rat on our buddy... */
485 printk(KERN_ERR
"INFO: RCU detected CPU stalls:");
486 rcu_for_each_leaf_node(rsp
, rnp
) {
487 rcu_print_task_stall(rnp
);
488 if (rnp
->qsmask
== 0)
490 for (cpu
= 0; cpu
<= rnp
->grphi
- rnp
->grplo
; cpu
++)
491 if (rnp
->qsmask
& (1UL << cpu
))
492 printk(" %d", rnp
->grplo
+ cpu
);
494 printk(" (detected by %d, t=%ld jiffies)\n",
495 smp_processor_id(), (long)(jiffies
- rsp
->gp_start
));
496 trigger_all_cpu_backtrace();
498 force_quiescent_state(rsp
, 0); /* Kick them all. */
501 static void print_cpu_stall(struct rcu_state
*rsp
)
504 struct rcu_node
*rnp
= rcu_get_root(rsp
);
506 printk(KERN_ERR
"INFO: RCU detected CPU %d stall (t=%lu jiffies)\n",
507 smp_processor_id(), jiffies
- rsp
->gp_start
);
508 trigger_all_cpu_backtrace();
510 spin_lock_irqsave(&rnp
->lock
, flags
);
511 if ((long)(jiffies
- rsp
->jiffies_stall
) >= 0)
513 jiffies
+ RCU_SECONDS_TILL_STALL_RECHECK
;
514 spin_unlock_irqrestore(&rnp
->lock
, flags
);
516 set_need_resched(); /* kick ourselves to get things going. */
519 static void check_cpu_stall(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
522 struct rcu_node
*rnp
;
524 delta
= jiffies
- rsp
->jiffies_stall
;
526 if ((rnp
->qsmask
& rdp
->grpmask
) && delta
>= 0) {
528 /* We haven't checked in, so go dump stack. */
529 print_cpu_stall(rsp
);
531 } else if (rcu_gp_in_progress(rsp
) && delta
>= RCU_STALL_RAT_DELAY
) {
533 /* They had two time units to dump stack, so complain. */
534 print_other_cpu_stall(rsp
);
538 #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
540 static void record_gp_stall_check_time(struct rcu_state
*rsp
)
544 static void check_cpu_stall(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
548 #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
551 * Update CPU-local rcu_data state to record the newly noticed grace period.
552 * This is used both when we started the grace period and when we notice
553 * that someone else started the grace period.
555 static void note_new_gpnum(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
558 rdp
->passed_quiesc
= 0;
559 rdp
->gpnum
= rsp
->gpnum
;
563 * Did someone else start a new RCU grace period start since we last
564 * checked? Update local state appropriately if so. Must be called
565 * on the CPU corresponding to rdp.
568 check_for_new_grace_period(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
573 local_irq_save(flags
);
574 if (rdp
->gpnum
!= rsp
->gpnum
) {
575 note_new_gpnum(rsp
, rdp
);
578 local_irq_restore(flags
);
583 * Start a new RCU grace period if warranted, re-initializing the hierarchy
584 * in preparation for detecting the next grace period. The caller must hold
585 * the root node's ->lock, which is released before return. Hard irqs must
589 rcu_start_gp(struct rcu_state
*rsp
, unsigned long flags
)
590 __releases(rcu_get_root(rsp
)->lock
)
592 struct rcu_data
*rdp
= rsp
->rda
[smp_processor_id()];
593 struct rcu_node
*rnp
= rcu_get_root(rsp
);
595 if (!cpu_needs_another_gp(rsp
, rdp
)) {
596 spin_unlock_irqrestore(&rnp
->lock
, flags
);
600 /* Advance to a new grace period and initialize state. */
602 WARN_ON_ONCE(rsp
->signaled
== RCU_GP_INIT
);
603 rsp
->signaled
= RCU_GP_INIT
; /* Hold off force_quiescent_state. */
604 rsp
->jiffies_force_qs
= jiffies
+ RCU_JIFFIES_TILL_FORCE_QS
;
605 record_gp_stall_check_time(rsp
);
606 dyntick_record_completed(rsp
, rsp
->completed
- 1);
607 note_new_gpnum(rsp
, rdp
);
610 * Because this CPU just now started the new grace period, we know
611 * that all of its callbacks will be covered by this upcoming grace
612 * period, even the ones that were registered arbitrarily recently.
613 * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
615 * Other CPUs cannot be sure exactly when the grace period started.
616 * Therefore, their recently registered callbacks must pass through
617 * an additional RCU_NEXT_READY stage, so that they will be handled
618 * by the next RCU grace period.
620 rdp
->nxttail
[RCU_NEXT_READY_TAIL
] = rdp
->nxttail
[RCU_NEXT_TAIL
];
621 rdp
->nxttail
[RCU_WAIT_TAIL
] = rdp
->nxttail
[RCU_NEXT_TAIL
];
623 /* Special-case the common single-level case. */
624 if (NUM_RCU_NODES
== 1) {
625 rcu_preempt_check_blocked_tasks(rnp
);
626 rnp
->qsmask
= rnp
->qsmaskinit
;
627 rnp
->gpnum
= rsp
->gpnum
;
628 rsp
->signaled
= RCU_SIGNAL_INIT
; /* force_quiescent_state OK. */
629 spin_unlock_irqrestore(&rnp
->lock
, flags
);
633 spin_unlock(&rnp
->lock
); /* leave irqs disabled. */
636 /* Exclude any concurrent CPU-hotplug operations. */
637 spin_lock(&rsp
->onofflock
); /* irqs already disabled. */
640 * Set the quiescent-state-needed bits in all the rcu_node
641 * structures for all currently online CPUs in breadth-first
642 * order, starting from the root rcu_node structure. This
643 * operation relies on the layout of the hierarchy within the
644 * rsp->node[] array. Note that other CPUs will access only
645 * the leaves of the hierarchy, which still indicate that no
646 * grace period is in progress, at least until the corresponding
647 * leaf node has been initialized. In addition, we have excluded
648 * CPU-hotplug operations.
650 * Note that the grace period cannot complete until we finish
651 * the initialization process, as there will be at least one
652 * qsmask bit set in the root node until that time, namely the
653 * one corresponding to this CPU, due to the fact that we have
656 rcu_for_each_node_breadth_first(rsp
, rnp
) {
657 spin_lock(&rnp
->lock
); /* irqs already disabled. */
658 rcu_preempt_check_blocked_tasks(rnp
);
659 rnp
->qsmask
= rnp
->qsmaskinit
;
660 rnp
->gpnum
= rsp
->gpnum
;
661 spin_unlock(&rnp
->lock
); /* irqs already disabled. */
664 rsp
->signaled
= RCU_SIGNAL_INIT
; /* force_quiescent_state now OK. */
665 spin_unlock_irqrestore(&rsp
->onofflock
, flags
);
669 * Advance this CPU's callbacks, but only if the current grace period
670 * has ended. This may be called only from the CPU to whom the rdp
674 rcu_process_gp_end(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
679 local_irq_save(flags
);
680 completed_snap
= ACCESS_ONCE(rsp
->completed
); /* outside of lock. */
682 /* Did another grace period end? */
683 if (rdp
->completed
!= completed_snap
) {
685 /* Advance callbacks. No harm if list empty. */
686 rdp
->nxttail
[RCU_DONE_TAIL
] = rdp
->nxttail
[RCU_WAIT_TAIL
];
687 rdp
->nxttail
[RCU_WAIT_TAIL
] = rdp
->nxttail
[RCU_NEXT_READY_TAIL
];
688 rdp
->nxttail
[RCU_NEXT_READY_TAIL
] = rdp
->nxttail
[RCU_NEXT_TAIL
];
690 /* Remember that we saw this grace-period completion. */
691 rdp
->completed
= completed_snap
;
693 local_irq_restore(flags
);
697 * Clean up after the prior grace period and let rcu_start_gp() start up
698 * the next grace period if one is needed. Note that the caller must
699 * hold rnp->lock, as required by rcu_start_gp(), which will release it.
701 static void cpu_quiet_msk_finish(struct rcu_state
*rsp
, unsigned long flags
)
702 __releases(rcu_get_root(rsp
)->lock
)
704 WARN_ON_ONCE(!rcu_gp_in_progress(rsp
));
705 rsp
->completed
= rsp
->gpnum
;
706 rcu_process_gp_end(rsp
, rsp
->rda
[smp_processor_id()]);
707 rcu_start_gp(rsp
, flags
); /* releases root node's rnp->lock. */
711 * Similar to cpu_quiet(), for which it is a helper function. Allows
712 * a group of CPUs to be quieted at one go, though all the CPUs in the
713 * group must be represented by the same leaf rcu_node structure.
714 * That structure's lock must be held upon entry, and it is released
718 cpu_quiet_msk(unsigned long mask
, struct rcu_state
*rsp
, struct rcu_node
*rnp
,
720 __releases(rnp
->lock
)
722 struct rcu_node
*rnp_c
;
724 /* Walk up the rcu_node hierarchy. */
726 if (!(rnp
->qsmask
& mask
)) {
728 /* Our bit has already been cleared, so done. */
729 spin_unlock_irqrestore(&rnp
->lock
, flags
);
732 rnp
->qsmask
&= ~mask
;
733 if (rnp
->qsmask
!= 0 || rcu_preempted_readers(rnp
)) {
735 /* Other bits still set at this level, so done. */
736 spin_unlock_irqrestore(&rnp
->lock
, flags
);
740 if (rnp
->parent
== NULL
) {
742 /* No more levels. Exit loop holding root lock. */
746 spin_unlock_irqrestore(&rnp
->lock
, flags
);
749 spin_lock_irqsave(&rnp
->lock
, flags
);
750 WARN_ON_ONCE(rnp_c
->qsmask
);
754 * Get here if we are the last CPU to pass through a quiescent
755 * state for this grace period. Invoke cpu_quiet_msk_finish()
756 * to clean up and start the next grace period if one is needed.
758 cpu_quiet_msk_finish(rsp
, flags
); /* releases rnp->lock. */
762 * Record a quiescent state for the specified CPU, which must either be
763 * the current CPU. The lastcomp argument is used to make sure we are
764 * still in the grace period of interest. We don't want to end the current
765 * grace period based on quiescent states detected in an earlier grace
769 cpu_quiet(int cpu
, struct rcu_state
*rsp
, struct rcu_data
*rdp
, long lastcomp
)
773 struct rcu_node
*rnp
;
776 spin_lock_irqsave(&rnp
->lock
, flags
);
777 if (lastcomp
!= ACCESS_ONCE(rsp
->completed
)) {
780 * Someone beat us to it for this grace period, so leave.
781 * The race with GP start is resolved by the fact that we
782 * hold the leaf rcu_node lock, so that the per-CPU bits
783 * cannot yet be initialized -- so we would simply find our
784 * CPU's bit already cleared in cpu_quiet_msk() if this race
787 rdp
->passed_quiesc
= 0; /* try again later! */
788 spin_unlock_irqrestore(&rnp
->lock
, flags
);
792 if ((rnp
->qsmask
& mask
) == 0) {
793 spin_unlock_irqrestore(&rnp
->lock
, flags
);
798 * This GP can't end until cpu checks in, so all of our
799 * callbacks can be processed during the next GP.
801 rdp
->nxttail
[RCU_NEXT_READY_TAIL
] = rdp
->nxttail
[RCU_NEXT_TAIL
];
803 cpu_quiet_msk(mask
, rsp
, rnp
, flags
); /* releases rnp->lock */
808 * Check to see if there is a new grace period of which this CPU
809 * is not yet aware, and if so, set up local rcu_data state for it.
810 * Otherwise, see if this CPU has just passed through its first
811 * quiescent state for this grace period, and record that fact if so.
814 rcu_check_quiescent_state(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
816 /* If there is now a new grace period, record and return. */
817 if (check_for_new_grace_period(rsp
, rdp
))
821 * Does this CPU still need to do its part for current grace period?
822 * If no, return and let the other CPUs do their part as well.
824 if (!rdp
->qs_pending
)
828 * Was there a quiescent state since the beginning of the grace
829 * period? If no, then exit and wait for the next call.
831 if (!rdp
->passed_quiesc
)
834 /* Tell RCU we are done (but cpu_quiet() will be the judge of that). */
835 cpu_quiet(rdp
->cpu
, rsp
, rdp
, rdp
->passed_quiesc_completed
);
838 #ifdef CONFIG_HOTPLUG_CPU
841 * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
842 * and move all callbacks from the outgoing CPU to the current one.
844 static void __rcu_offline_cpu(int cpu
, struct rcu_state
*rsp
)
850 struct rcu_data
*rdp
= rsp
->rda
[cpu
];
851 struct rcu_data
*rdp_me
;
852 struct rcu_node
*rnp
;
854 /* Exclude any attempts to start a new grace period. */
855 spin_lock_irqsave(&rsp
->onofflock
, flags
);
857 /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
858 rnp
= rdp
->mynode
; /* this is the outgoing CPU's rnp. */
859 mask
= rdp
->grpmask
; /* rnp->grplo is constant. */
861 spin_lock(&rnp
->lock
); /* irqs already disabled. */
862 rnp
->qsmaskinit
&= ~mask
;
863 if (rnp
->qsmaskinit
!= 0) {
864 spin_unlock(&rnp
->lock
); /* irqs remain disabled. */
867 rcu_preempt_offline_tasks(rsp
, rnp
, rdp
);
869 spin_unlock(&rnp
->lock
); /* irqs remain disabled. */
871 } while (rnp
!= NULL
);
872 lastcomp
= rsp
->completed
;
874 spin_unlock(&rsp
->onofflock
); /* irqs remain disabled. */
877 * Move callbacks from the outgoing CPU to the running CPU.
878 * Note that the outgoing CPU is now quiescent, so it is now
879 * (uncharacteristically) safe to access its rcu_data structure.
880 * Note also that we must carefully retain the order of the
881 * outgoing CPU's callbacks in order for rcu_barrier() to work
882 * correctly. Finally, note that we start all the callbacks
883 * afresh, even those that have passed through a grace period
884 * and are therefore ready to invoke. The theory is that hotplug
885 * events are rare, and that if they are frequent enough to
886 * indefinitely delay callbacks, you have far worse things to
889 if (rdp
->nxtlist
!= NULL
) {
890 rdp_me
= rsp
->rda
[smp_processor_id()];
891 *rdp_me
->nxttail
[RCU_NEXT_TAIL
] = rdp
->nxtlist
;
892 rdp_me
->nxttail
[RCU_NEXT_TAIL
] = rdp
->nxttail
[RCU_NEXT_TAIL
];
894 for (i
= 0; i
< RCU_NEXT_SIZE
; i
++)
895 rdp
->nxttail
[i
] = &rdp
->nxtlist
;
896 rdp_me
->qlen
+= rdp
->qlen
;
899 local_irq_restore(flags
);
903 * Remove the specified CPU from the RCU hierarchy and move any pending
904 * callbacks that it might have to the current CPU. This code assumes
905 * that at least one CPU in the system will remain running at all times.
906 * Any attempt to offline -all- CPUs is likely to strand RCU callbacks.
908 static void rcu_offline_cpu(int cpu
)
910 __rcu_offline_cpu(cpu
, &rcu_sched_state
);
911 __rcu_offline_cpu(cpu
, &rcu_bh_state
);
912 rcu_preempt_offline_cpu(cpu
);
915 #else /* #ifdef CONFIG_HOTPLUG_CPU */
917 static void rcu_offline_cpu(int cpu
)
921 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
924 * Invoke any RCU callbacks that have made it to the end of their grace
925 * period. Thottle as specified by rdp->blimit.
927 static void rcu_do_batch(struct rcu_data
*rdp
)
930 struct rcu_head
*next
, *list
, **tail
;
933 /* If no callbacks are ready, just return.*/
934 if (!cpu_has_callbacks_ready_to_invoke(rdp
))
938 * Extract the list of ready callbacks, disabling to prevent
939 * races with call_rcu() from interrupt handlers.
941 local_irq_save(flags
);
943 rdp
->nxtlist
= *rdp
->nxttail
[RCU_DONE_TAIL
];
944 *rdp
->nxttail
[RCU_DONE_TAIL
] = NULL
;
945 tail
= rdp
->nxttail
[RCU_DONE_TAIL
];
946 for (count
= RCU_NEXT_SIZE
- 1; count
>= 0; count
--)
947 if (rdp
->nxttail
[count
] == rdp
->nxttail
[RCU_DONE_TAIL
])
948 rdp
->nxttail
[count
] = &rdp
->nxtlist
;
949 local_irq_restore(flags
);
951 /* Invoke callbacks. */
958 if (++count
>= rdp
->blimit
)
962 local_irq_save(flags
);
964 /* Update count, and requeue any remaining callbacks. */
967 *tail
= rdp
->nxtlist
;
969 for (count
= 0; count
< RCU_NEXT_SIZE
; count
++)
970 if (&rdp
->nxtlist
== rdp
->nxttail
[count
])
971 rdp
->nxttail
[count
] = tail
;
976 /* Reinstate batch limit if we have worked down the excess. */
977 if (rdp
->blimit
== LONG_MAX
&& rdp
->qlen
<= qlowmark
)
978 rdp
->blimit
= blimit
;
980 local_irq_restore(flags
);
982 /* Re-raise the RCU softirq if there are callbacks remaining. */
983 if (cpu_has_callbacks_ready_to_invoke(rdp
))
984 raise_softirq(RCU_SOFTIRQ
);
988 * Check to see if this CPU is in a non-context-switch quiescent state
989 * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
990 * Also schedule the RCU softirq handler.
992 * This function must be called with hardirqs disabled. It is normally
993 * invoked from the scheduling-clock interrupt. If rcu_pending returns
994 * false, there is no point in invoking rcu_check_callbacks().
996 void rcu_check_callbacks(int cpu
, int user
)
998 if (!rcu_pending(cpu
))
999 return; /* if nothing for RCU to do. */
1001 (idle_cpu(cpu
) && rcu_scheduler_active
&&
1002 !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT
))) {
1005 * Get here if this CPU took its interrupt from user
1006 * mode or from the idle loop, and if this is not a
1007 * nested interrupt. In this case, the CPU is in
1008 * a quiescent state, so note it.
1010 * No memory barrier is required here because both
1011 * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
1012 * variables that other CPUs neither access nor modify,
1013 * at least not while the corresponding CPU is online.
1019 } else if (!in_softirq()) {
1022 * Get here if this CPU did not take its interrupt from
1023 * softirq, in other words, if it is not interrupting
1024 * a rcu_bh read-side critical section. This is an _bh
1025 * critical section, so note it.
1030 rcu_preempt_check_callbacks(cpu
);
1031 raise_softirq(RCU_SOFTIRQ
);
1037 * Scan the leaf rcu_node structures, processing dyntick state for any that
1038 * have not yet encountered a quiescent state, using the function specified.
1039 * Returns 1 if the current grace period ends while scanning (possibly
1040 * because we made it end).
1042 static int rcu_process_dyntick(struct rcu_state
*rsp
, long lastcomp
,
1043 int (*f
)(struct rcu_data
*))
1047 unsigned long flags
;
1049 struct rcu_node
*rnp
;
1051 rcu_for_each_leaf_node(rsp
, rnp
) {
1053 spin_lock_irqsave(&rnp
->lock
, flags
);
1054 if (rsp
->completed
!= lastcomp
) {
1055 spin_unlock_irqrestore(&rnp
->lock
, flags
);
1058 if (rnp
->qsmask
== 0) {
1059 spin_unlock_irqrestore(&rnp
->lock
, flags
);
1064 for (; cpu
<= rnp
->grphi
; cpu
++, bit
<<= 1) {
1065 if ((rnp
->qsmask
& bit
) != 0 && f(rsp
->rda
[cpu
]))
1068 if (mask
!= 0 && rsp
->completed
== lastcomp
) {
1070 /* cpu_quiet_msk() releases rnp->lock. */
1071 cpu_quiet_msk(mask
, rsp
, rnp
, flags
);
1074 spin_unlock_irqrestore(&rnp
->lock
, flags
);
1080 * Force quiescent states on reluctant CPUs, and also detect which
1081 * CPUs are in dyntick-idle mode.
1083 static void force_quiescent_state(struct rcu_state
*rsp
, int relaxed
)
1085 unsigned long flags
;
1087 struct rcu_node
*rnp
= rcu_get_root(rsp
);
1090 if (!rcu_gp_in_progress(rsp
))
1091 return; /* No grace period in progress, nothing to force. */
1092 if (!spin_trylock_irqsave(&rsp
->fqslock
, flags
)) {
1093 rsp
->n_force_qs_lh
++; /* Inexact, can lose counts. Tough! */
1094 return; /* Someone else is already on the job. */
1097 (long)(rsp
->jiffies_force_qs
- jiffies
) >= 0)
1098 goto unlock_ret
; /* no emergency and done recently. */
1100 spin_lock(&rnp
->lock
);
1101 lastcomp
= rsp
->completed
;
1102 signaled
= rsp
->signaled
;
1103 rsp
->jiffies_force_qs
= jiffies
+ RCU_JIFFIES_TILL_FORCE_QS
;
1104 if (lastcomp
== rsp
->gpnum
) {
1105 rsp
->n_force_qs_ngp
++;
1106 spin_unlock(&rnp
->lock
);
1107 goto unlock_ret
; /* no GP in progress, time updated. */
1109 spin_unlock(&rnp
->lock
);
1113 break; /* grace period still initializing, ignore. */
1115 case RCU_SAVE_DYNTICK
:
1117 if (RCU_SIGNAL_INIT
!= RCU_SAVE_DYNTICK
)
1118 break; /* So gcc recognizes the dead code. */
1120 /* Record dyntick-idle state. */
1121 if (rcu_process_dyntick(rsp
, lastcomp
,
1122 dyntick_save_progress_counter
))
1125 /* Update state, record completion counter. */
1126 spin_lock(&rnp
->lock
);
1127 if (lastcomp
== rsp
->completed
) {
1128 rsp
->signaled
= RCU_FORCE_QS
;
1129 dyntick_record_completed(rsp
, lastcomp
);
1131 spin_unlock(&rnp
->lock
);
1136 /* Check dyntick-idle state, send IPI to laggarts. */
1137 if (rcu_process_dyntick(rsp
, dyntick_recall_completed(rsp
),
1138 rcu_implicit_dynticks_qs
))
1141 /* Leave state in case more forcing is required. */
1146 spin_unlock_irqrestore(&rsp
->fqslock
, flags
);
1149 #else /* #ifdef CONFIG_SMP */
1151 static void force_quiescent_state(struct rcu_state
*rsp
, int relaxed
)
1156 #endif /* #else #ifdef CONFIG_SMP */
1159 * This does the RCU processing work from softirq context for the
1160 * specified rcu_state and rcu_data structures. This may be called
1161 * only from the CPU to whom the rdp belongs.
1164 __rcu_process_callbacks(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
1166 unsigned long flags
;
1168 WARN_ON_ONCE(rdp
->beenonline
== 0);
1171 * If an RCU GP has gone long enough, go check for dyntick
1172 * idle CPUs and, if needed, send resched IPIs.
1174 if ((long)(ACCESS_ONCE(rsp
->jiffies_force_qs
) - jiffies
) < 0)
1175 force_quiescent_state(rsp
, 1);
1178 * Advance callbacks in response to end of earlier grace
1179 * period that some other CPU ended.
1181 rcu_process_gp_end(rsp
, rdp
);
1183 /* Update RCU state based on any recent quiescent states. */
1184 rcu_check_quiescent_state(rsp
, rdp
);
1186 /* Does this CPU require a not-yet-started grace period? */
1187 if (cpu_needs_another_gp(rsp
, rdp
)) {
1188 spin_lock_irqsave(&rcu_get_root(rsp
)->lock
, flags
);
1189 rcu_start_gp(rsp
, flags
); /* releases above lock */
1192 /* If there are callbacks ready, invoke them. */
1197 * Do softirq processing for the current CPU.
1199 static void rcu_process_callbacks(struct softirq_action
*unused
)
1202 * Memory references from any prior RCU read-side critical sections
1203 * executed by the interrupted code must be seen before any RCU
1204 * grace-period manipulations below.
1206 smp_mb(); /* See above block comment. */
1208 __rcu_process_callbacks(&rcu_sched_state
,
1209 &__get_cpu_var(rcu_sched_data
));
1210 __rcu_process_callbacks(&rcu_bh_state
, &__get_cpu_var(rcu_bh_data
));
1211 rcu_preempt_process_callbacks();
1214 * Memory references from any later RCU read-side critical sections
1215 * executed by the interrupted code must be seen after any RCU
1216 * grace-period manipulations above.
1218 smp_mb(); /* See above block comment. */
1222 __call_rcu(struct rcu_head
*head
, void (*func
)(struct rcu_head
*rcu
),
1223 struct rcu_state
*rsp
)
1225 unsigned long flags
;
1226 struct rcu_data
*rdp
;
1231 smp_mb(); /* Ensure RCU update seen before callback registry. */
1234 * Opportunistically note grace-period endings and beginnings.
1235 * Note that we might see a beginning right after we see an
1236 * end, but never vice versa, since this CPU has to pass through
1237 * a quiescent state betweentimes.
1239 local_irq_save(flags
);
1240 rdp
= rsp
->rda
[smp_processor_id()];
1241 rcu_process_gp_end(rsp
, rdp
);
1242 check_for_new_grace_period(rsp
, rdp
);
1244 /* Add the callback to our list. */
1245 *rdp
->nxttail
[RCU_NEXT_TAIL
] = head
;
1246 rdp
->nxttail
[RCU_NEXT_TAIL
] = &head
->next
;
1248 /* Start a new grace period if one not already started. */
1249 if (!rcu_gp_in_progress(rsp
)) {
1250 unsigned long nestflag
;
1251 struct rcu_node
*rnp_root
= rcu_get_root(rsp
);
1253 spin_lock_irqsave(&rnp_root
->lock
, nestflag
);
1254 rcu_start_gp(rsp
, nestflag
); /* releases rnp_root->lock. */
1257 /* Force the grace period if too many callbacks or too long waiting. */
1258 if (unlikely(++rdp
->qlen
> qhimark
)) {
1259 rdp
->blimit
= LONG_MAX
;
1260 force_quiescent_state(rsp
, 0);
1261 } else if ((long)(ACCESS_ONCE(rsp
->jiffies_force_qs
) - jiffies
) < 0)
1262 force_quiescent_state(rsp
, 1);
1263 local_irq_restore(flags
);
1267 * Queue an RCU-sched callback for invocation after a grace period.
1269 void call_rcu_sched(struct rcu_head
*head
, void (*func
)(struct rcu_head
*rcu
))
1271 __call_rcu(head
, func
, &rcu_sched_state
);
1273 EXPORT_SYMBOL_GPL(call_rcu_sched
);
1276 * Queue an RCU for invocation after a quicker grace period.
1278 void call_rcu_bh(struct rcu_head
*head
, void (*func
)(struct rcu_head
*rcu
))
1280 __call_rcu(head
, func
, &rcu_bh_state
);
1282 EXPORT_SYMBOL_GPL(call_rcu_bh
);
1285 * Check to see if there is any immediate RCU-related work to be done
1286 * by the current CPU, for the specified type of RCU, returning 1 if so.
1287 * The checks are in order of increasing expense: checks that can be
1288 * carried out against CPU-local state are performed first. However,
1289 * we must check for CPU stalls first, else we might not get a chance.
1291 static int __rcu_pending(struct rcu_state
*rsp
, struct rcu_data
*rdp
)
1293 rdp
->n_rcu_pending
++;
1295 /* Check for CPU stalls, if enabled. */
1296 check_cpu_stall(rsp
, rdp
);
1298 /* Is the RCU core waiting for a quiescent state from this CPU? */
1299 if (rdp
->qs_pending
) {
1300 rdp
->n_rp_qs_pending
++;
1304 /* Does this CPU have callbacks ready to invoke? */
1305 if (cpu_has_callbacks_ready_to_invoke(rdp
)) {
1306 rdp
->n_rp_cb_ready
++;
1310 /* Has RCU gone idle with this CPU needing another grace period? */
1311 if (cpu_needs_another_gp(rsp
, rdp
)) {
1312 rdp
->n_rp_cpu_needs_gp
++;
1316 /* Has another RCU grace period completed? */
1317 if (ACCESS_ONCE(rsp
->completed
) != rdp
->completed
) { /* outside lock */
1318 rdp
->n_rp_gp_completed
++;
1322 /* Has a new RCU grace period started? */
1323 if (ACCESS_ONCE(rsp
->gpnum
) != rdp
->gpnum
) { /* outside lock */
1324 rdp
->n_rp_gp_started
++;
1328 /* Has an RCU GP gone long enough to send resched IPIs &c? */
1329 if (rcu_gp_in_progress(rsp
) &&
1330 ((long)(ACCESS_ONCE(rsp
->jiffies_force_qs
) - jiffies
) < 0)) {
1331 rdp
->n_rp_need_fqs
++;
1336 rdp
->n_rp_need_nothing
++;
1341 * Check to see if there is any immediate RCU-related work to be done
1342 * by the current CPU, returning 1 if so. This function is part of the
1343 * RCU implementation; it is -not- an exported member of the RCU API.
1345 static int rcu_pending(int cpu
)
1347 return __rcu_pending(&rcu_sched_state
, &per_cpu(rcu_sched_data
, cpu
)) ||
1348 __rcu_pending(&rcu_bh_state
, &per_cpu(rcu_bh_data
, cpu
)) ||
1349 rcu_preempt_pending(cpu
);
1353 * Check to see if any future RCU-related work will need to be done
1354 * by the current CPU, even if none need be done immediately, returning
1355 * 1 if so. This function is part of the RCU implementation; it is -not-
1356 * an exported member of the RCU API.
1358 int rcu_needs_cpu(int cpu
)
1360 /* RCU callbacks either ready or pending? */
1361 return per_cpu(rcu_sched_data
, cpu
).nxtlist
||
1362 per_cpu(rcu_bh_data
, cpu
).nxtlist
||
1363 rcu_preempt_needs_cpu(cpu
);
1367 * Do boot-time initialization of a CPU's per-CPU RCU data.
1370 rcu_boot_init_percpu_data(int cpu
, struct rcu_state
*rsp
)
1372 unsigned long flags
;
1374 struct rcu_data
*rdp
= rsp
->rda
[cpu
];
1375 struct rcu_node
*rnp
= rcu_get_root(rsp
);
1377 /* Set up local state, ensuring consistent view of global state. */
1378 spin_lock_irqsave(&rnp
->lock
, flags
);
1379 rdp
->grpmask
= 1UL << (cpu
- rdp
->mynode
->grplo
);
1380 rdp
->nxtlist
= NULL
;
1381 for (i
= 0; i
< RCU_NEXT_SIZE
; i
++)
1382 rdp
->nxttail
[i
] = &rdp
->nxtlist
;
1385 rdp
->dynticks
= &per_cpu(rcu_dynticks
, cpu
);
1386 #endif /* #ifdef CONFIG_NO_HZ */
1388 spin_unlock_irqrestore(&rnp
->lock
, flags
);
1392 * Initialize a CPU's per-CPU RCU data. Note that only one online or
1393 * offline event can be happening at a given time. Note also that we
1394 * can accept some slop in the rsp->completed access due to the fact
1395 * that this CPU cannot possibly have any RCU callbacks in flight yet.
1397 static void __cpuinit
1398 rcu_init_percpu_data(int cpu
, struct rcu_state
*rsp
, int preemptable
)
1400 unsigned long flags
;
1403 struct rcu_data
*rdp
= rsp
->rda
[cpu
];
1404 struct rcu_node
*rnp
= rcu_get_root(rsp
);
1406 /* Set up local state, ensuring consistent view of global state. */
1407 spin_lock_irqsave(&rnp
->lock
, flags
);
1408 lastcomp
= rsp
->completed
;
1409 rdp
->completed
= lastcomp
;
1410 rdp
->gpnum
= lastcomp
;
1411 rdp
->passed_quiesc
= 0; /* We could be racing with new GP, */
1412 rdp
->qs_pending
= 1; /* so set up to respond to current GP. */
1413 rdp
->beenonline
= 1; /* We have now been online. */
1414 rdp
->preemptable
= preemptable
;
1415 rdp
->passed_quiesc_completed
= lastcomp
- 1;
1416 rdp
->blimit
= blimit
;
1417 spin_unlock(&rnp
->lock
); /* irqs remain disabled. */
1420 * A new grace period might start here. If so, we won't be part
1421 * of it, but that is OK, as we are currently in a quiescent state.
1424 /* Exclude any attempts to start a new GP on large systems. */
1425 spin_lock(&rsp
->onofflock
); /* irqs already disabled. */
1427 /* Add CPU to rcu_node bitmasks. */
1429 mask
= rdp
->grpmask
;
1431 /* Exclude any attempts to start a new GP on small systems. */
1432 spin_lock(&rnp
->lock
); /* irqs already disabled. */
1433 rnp
->qsmaskinit
|= mask
;
1434 mask
= rnp
->grpmask
;
1435 spin_unlock(&rnp
->lock
); /* irqs already disabled. */
1437 } while (rnp
!= NULL
&& !(rnp
->qsmaskinit
& mask
));
1439 spin_unlock_irqrestore(&rsp
->onofflock
, flags
);
1442 static void __cpuinit
rcu_online_cpu(int cpu
)
1444 rcu_init_percpu_data(cpu
, &rcu_sched_state
, 0);
1445 rcu_init_percpu_data(cpu
, &rcu_bh_state
, 0);
1446 rcu_preempt_init_percpu_data(cpu
);
1450 * Handle CPU online/offline notification events.
1452 int __cpuinit
rcu_cpu_notify(struct notifier_block
*self
,
1453 unsigned long action
, void *hcpu
)
1455 long cpu
= (long)hcpu
;
1458 case CPU_UP_PREPARE
:
1459 case CPU_UP_PREPARE_FROZEN
:
1460 rcu_online_cpu(cpu
);
1463 case CPU_DEAD_FROZEN
:
1464 case CPU_UP_CANCELED
:
1465 case CPU_UP_CANCELED_FROZEN
:
1466 rcu_offline_cpu(cpu
);
1475 * Compute the per-level fanout, either using the exact fanout specified
1476 * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
1478 #ifdef CONFIG_RCU_FANOUT_EXACT
1479 static void __init
rcu_init_levelspread(struct rcu_state
*rsp
)
1483 for (i
= NUM_RCU_LVLS
- 1; i
>= 0; i
--)
1484 rsp
->levelspread
[i
] = CONFIG_RCU_FANOUT
;
1486 #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
1487 static void __init
rcu_init_levelspread(struct rcu_state
*rsp
)
1494 for (i
= NUM_RCU_LVLS
- 1; i
>= 0; i
--) {
1495 ccur
= rsp
->levelcnt
[i
];
1496 rsp
->levelspread
[i
] = (cprv
+ ccur
- 1) / ccur
;
1500 #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
1503 * Helper function for rcu_init() that initializes one rcu_state structure.
1505 static void __init
rcu_init_one(struct rcu_state
*rsp
)
1510 struct rcu_node
*rnp
;
1512 /* Initialize the level-tracking arrays. */
1514 for (i
= 1; i
< NUM_RCU_LVLS
; i
++)
1515 rsp
->level
[i
] = rsp
->level
[i
- 1] + rsp
->levelcnt
[i
- 1];
1516 rcu_init_levelspread(rsp
);
1518 /* Initialize the elements themselves, starting from the leaves. */
1520 for (i
= NUM_RCU_LVLS
- 1; i
>= 0; i
--) {
1521 cpustride
*= rsp
->levelspread
[i
];
1522 rnp
= rsp
->level
[i
];
1523 for (j
= 0; j
< rsp
->levelcnt
[i
]; j
++, rnp
++) {
1524 spin_lock_init(&rnp
->lock
);
1527 rnp
->qsmaskinit
= 0;
1528 rnp
->grplo
= j
* cpustride
;
1529 rnp
->grphi
= (j
+ 1) * cpustride
- 1;
1530 if (rnp
->grphi
>= NR_CPUS
)
1531 rnp
->grphi
= NR_CPUS
- 1;
1537 rnp
->grpnum
= j
% rsp
->levelspread
[i
- 1];
1538 rnp
->grpmask
= 1UL << rnp
->grpnum
;
1539 rnp
->parent
= rsp
->level
[i
- 1] +
1540 j
/ rsp
->levelspread
[i
- 1];
1543 INIT_LIST_HEAD(&rnp
->blocked_tasks
[0]);
1544 INIT_LIST_HEAD(&rnp
->blocked_tasks
[1]);
1550 * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used
1551 * nowhere else! Assigns leaf node pointers into each CPU's rcu_data
1554 #define RCU_INIT_FLAVOR(rsp, rcu_data) \
1558 struct rcu_node *rnp; \
1560 rcu_init_one(rsp); \
1561 rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \
1563 for_each_possible_cpu(i) { \
1564 if (i > rnp[j].grphi) \
1566 per_cpu(rcu_data, i).mynode = &rnp[j]; \
1567 (rsp)->rda[i] = &per_cpu(rcu_data, i); \
1568 rcu_boot_init_percpu_data(i, rsp); \
1572 void __init
__rcu_init(void)
1574 rcu_bootup_announce();
1575 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
1576 printk(KERN_INFO
"RCU-based detection of stalled CPUs is enabled.\n");
1577 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
1578 RCU_INIT_FLAVOR(&rcu_sched_state
, rcu_sched_data
);
1579 RCU_INIT_FLAVOR(&rcu_bh_state
, rcu_bh_data
);
1580 __rcu_init_preempt();
1581 open_softirq(RCU_SOFTIRQ
, rcu_process_callbacks
);
1584 #include "rcutree_plugin.h"