Root/
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion |
3 | * |
4 | * This program is free software; you can redistribute it and/or modify |
5 | * it under the terms of the GNU General Public License as published by |
6 | * the Free Software Foundation; either version 2 of the License, or |
7 | * (at your option) any later version. |
8 | * |
9 | * This program is distributed in the hope that it will be useful, |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
12 | * GNU General Public License for more details. |
13 | * |
14 | * You should have received a copy of the GNU General Public License |
15 | * along with this program; if not, write to the Free Software |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
17 | * |
18 | * Copyright IBM Corporation, 2008 |
19 | * |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
21 | * Manfred Spraul <manfred@colorfullife.com> |
22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version |
23 | * |
24 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
25 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
26 | * |
27 | * For detailed explanation of Read-Copy Update mechanism see - |
28 | * Documentation/RCU |
29 | */ |
30 | #include <linux/types.h> |
31 | #include <linux/kernel.h> |
32 | #include <linux/init.h> |
33 | #include <linux/spinlock.h> |
34 | #include <linux/smp.h> |
35 | #include <linux/rcupdate.h> |
36 | #include <linux/interrupt.h> |
37 | #include <linux/sched.h> |
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> |
49 | |
50 | #include "rcutree.h" |
51 | |
52 | /* Data structures. */ |
53 | |
54 | static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; |
55 | |
56 | #define RCU_STATE_INITIALIZER(name) { \ |
57 | .level = { &name.node[0] }, \ |
58 | .levelcnt = { \ |
59 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ |
60 | NUM_RCU_LVL_1, \ |
61 | NUM_RCU_LVL_2, \ |
62 | NUM_RCU_LVL_3, \ |
63 | NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ |
64 | }, \ |
65 | .signaled = RCU_GP_IDLE, \ |
66 | .gpnum = -300, \ |
67 | .completed = -300, \ |
68 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&name.onofflock), \ |
69 | .orphan_cbs_list = NULL, \ |
70 | .orphan_cbs_tail = &name.orphan_cbs_list, \ |
71 | .orphan_qlen = 0, \ |
72 | .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&name.fqslock), \ |
73 | .n_force_qs = 0, \ |
74 | .n_force_qs_ngp = 0, \ |
75 | } |
76 | |
77 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
78 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
79 | |
80 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
81 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
82 | |
83 | /* |
84 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s |
85 | * permit this function to be invoked without holding the root rcu_node |
86 | * structure's ->lock, but of course results can be subject to change. |
87 | */ |
88 | static int rcu_gp_in_progress(struct rcu_state *rsp) |
89 | { |
90 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); |
91 | } |
92 | |
93 | /* |
94 | * Note a quiescent state. Because we do not need to know |
95 | * how many quiescent states passed, just if there was at least |
96 | * one since the start of the grace period, this just sets a flag. |
97 | */ |
98 | void rcu_sched_qs(int cpu) |
99 | { |
100 | struct rcu_data *rdp; |
101 | |
102 | rdp = &per_cpu(rcu_sched_data, cpu); |
103 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
104 | barrier(); |
105 | rdp->passed_quiesc = 1; |
106 | rcu_preempt_note_context_switch(cpu); |
107 | } |
108 | |
109 | void rcu_bh_qs(int cpu) |
110 | { |
111 | struct rcu_data *rdp; |
112 | |
113 | rdp = &per_cpu(rcu_bh_data, cpu); |
114 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
115 | barrier(); |
116 | rdp->passed_quiesc = 1; |
117 | } |
118 | |
119 | #ifdef CONFIG_NO_HZ |
120 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
121 | .dynticks_nesting = 1, |
122 | .dynticks = 1, |
123 | }; |
124 | #endif /* #ifdef CONFIG_NO_HZ */ |
125 | |
126 | static int blimit = 10; /* Maximum callbacks per softirq. */ |
127 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
128 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ |
129 | |
130 | module_param(blimit, int, 0); |
131 | module_param(qhimark, int, 0); |
132 | module_param(qlowmark, int, 0); |
133 | |
134 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
135 | static int rcu_pending(int cpu); |
136 | |
137 | /* |
138 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
139 | */ |
140 | long rcu_batches_completed_sched(void) |
141 | { |
142 | return rcu_sched_state.completed; |
143 | } |
144 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
145 | |
146 | /* |
147 | * Return the number of RCU BH batches processed thus far for debug & stats. |
148 | */ |
149 | long rcu_batches_completed_bh(void) |
150 | { |
151 | return rcu_bh_state.completed; |
152 | } |
153 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); |
154 | |
155 | /* |
156 | * Force a quiescent state for RCU BH. |
157 | */ |
158 | void rcu_bh_force_quiescent_state(void) |
159 | { |
160 | force_quiescent_state(&rcu_bh_state, 0); |
161 | } |
162 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); |
163 | |
164 | /* |
165 | * Force a quiescent state for RCU-sched. |
166 | */ |
167 | void rcu_sched_force_quiescent_state(void) |
168 | { |
169 | force_quiescent_state(&rcu_sched_state, 0); |
170 | } |
171 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); |
172 | |
173 | /* |
174 | * Does the CPU have callbacks ready to be invoked? |
175 | */ |
176 | static int |
177 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) |
178 | { |
179 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; |
180 | } |
181 | |
182 | /* |
183 | * Does the current CPU require a yet-as-unscheduled grace period? |
184 | */ |
185 | static int |
186 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) |
187 | { |
188 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
189 | } |
190 | |
191 | /* |
192 | * Return the root node of the specified rcu_state structure. |
193 | */ |
194 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) |
195 | { |
196 | return &rsp->node[0]; |
197 | } |
198 | |
199 | #ifdef CONFIG_SMP |
200 | |
201 | /* |
202 | * If the specified CPU is offline, tell the caller that it is in |
203 | * a quiescent state. Otherwise, whack it with a reschedule IPI. |
204 | * Grace periods can end up waiting on an offline CPU when that |
205 | * CPU is in the process of coming online -- it will be added to the |
206 | * rcu_node bitmasks before it actually makes it online. The same thing |
207 | * can happen while a CPU is in the process of coming online. Because this |
208 | * race is quite rare, we check for it after detecting that the grace |
209 | * period has been delayed rather than checking each and every CPU |
210 | * each and every time we start a new grace period. |
211 | */ |
212 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) |
213 | { |
214 | /* |
215 | * If the CPU is offline, it is in a quiescent state. We can |
216 | * trust its state not to change because interrupts are disabled. |
217 | */ |
218 | if (cpu_is_offline(rdp->cpu)) { |
219 | rdp->offline_fqs++; |
220 | return 1; |
221 | } |
222 | |
223 | /* If preemptable RCU, no point in sending reschedule IPI. */ |
224 | if (rdp->preemptable) |
225 | return 0; |
226 | |
227 | /* The CPU is online, so send it a reschedule IPI. */ |
228 | if (rdp->cpu != smp_processor_id()) |
229 | smp_send_reschedule(rdp->cpu); |
230 | else |
231 | set_need_resched(); |
232 | rdp->resched_ipi++; |
233 | return 0; |
234 | } |
235 | |
236 | #endif /* #ifdef CONFIG_SMP */ |
237 | |
238 | #ifdef CONFIG_NO_HZ |
239 | |
240 | /** |
241 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz |
242 | * |
243 | * Enter nohz mode, in other words, -leave- the mode in which RCU |
244 | * read-side critical sections can occur. (Though RCU read-side |
245 | * critical sections can occur in irq handlers in nohz mode, a possibility |
246 | * handled by rcu_irq_enter() and rcu_irq_exit()). |
247 | */ |
248 | void rcu_enter_nohz(void) |
249 | { |
250 | unsigned long flags; |
251 | struct rcu_dynticks *rdtp; |
252 | |
253 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
254 | local_irq_save(flags); |
255 | rdtp = &__get_cpu_var(rcu_dynticks); |
256 | rdtp->dynticks++; |
257 | rdtp->dynticks_nesting--; |
258 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
259 | local_irq_restore(flags); |
260 | } |
261 | |
262 | /* |
263 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz |
264 | * |
265 | * Exit nohz mode, in other words, -enter- the mode in which RCU |
266 | * read-side critical sections normally occur. |
267 | */ |
268 | void rcu_exit_nohz(void) |
269 | { |
270 | unsigned long flags; |
271 | struct rcu_dynticks *rdtp; |
272 | |
273 | local_irq_save(flags); |
274 | rdtp = &__get_cpu_var(rcu_dynticks); |
275 | rdtp->dynticks++; |
276 | rdtp->dynticks_nesting++; |
277 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
278 | local_irq_restore(flags); |
279 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
280 | } |
281 | |
282 | /** |
283 | * rcu_nmi_enter - inform RCU of entry to NMI context |
284 | * |
285 | * If the CPU was idle with dynamic ticks active, and there is no |
286 | * irq handler running, this updates rdtp->dynticks_nmi to let the |
287 | * RCU grace-period handling know that the CPU is active. |
288 | */ |
289 | void rcu_nmi_enter(void) |
290 | { |
291 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
292 | |
293 | if (rdtp->dynticks & 0x1) |
294 | return; |
295 | rdtp->dynticks_nmi++; |
296 | WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); |
297 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
298 | } |
299 | |
300 | /** |
301 | * rcu_nmi_exit - inform RCU of exit from NMI context |
302 | * |
303 | * If the CPU was idle with dynamic ticks active, and there is no |
304 | * irq handler running, this updates rdtp->dynticks_nmi to let the |
305 | * RCU grace-period handling know that the CPU is no longer active. |
306 | */ |
307 | void rcu_nmi_exit(void) |
308 | { |
309 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
310 | |
311 | if (rdtp->dynticks & 0x1) |
312 | return; |
313 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
314 | rdtp->dynticks_nmi++; |
315 | WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); |
316 | } |
317 | |
318 | /** |
319 | * rcu_irq_enter - inform RCU of entry to hard irq context |
320 | * |
321 | * If the CPU was idle with dynamic ticks active, this updates the |
322 | * rdtp->dynticks to let the RCU handling know that the CPU is active. |
323 | */ |
324 | void rcu_irq_enter(void) |
325 | { |
326 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
327 | |
328 | if (rdtp->dynticks_nesting++) |
329 | return; |
330 | rdtp->dynticks++; |
331 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
332 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
333 | } |
334 | |
335 | /** |
336 | * rcu_irq_exit - inform RCU of exit from hard irq context |
337 | * |
338 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks |
339 | * to put let the RCU handling be aware that the CPU is going back to idle |
340 | * with no ticks. |
341 | */ |
342 | void rcu_irq_exit(void) |
343 | { |
344 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
345 | |
346 | if (--rdtp->dynticks_nesting) |
347 | return; |
348 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
349 | rdtp->dynticks++; |
350 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
351 | |
352 | /* If the interrupt queued a callback, get out of dyntick mode. */ |
353 | if (__get_cpu_var(rcu_sched_data).nxtlist || |
354 | __get_cpu_var(rcu_bh_data).nxtlist) |
355 | set_need_resched(); |
356 | } |
357 | |
358 | #ifdef CONFIG_SMP |
359 | |
360 | /* |
361 | * Snapshot the specified CPU's dynticks counter so that we can later |
362 | * credit them with an implicit quiescent state. Return 1 if this CPU |
363 | * is in dynticks idle mode, which is an extended quiescent state. |
364 | */ |
365 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
366 | { |
367 | int ret; |
368 | int snap; |
369 | int snap_nmi; |
370 | |
371 | snap = rdp->dynticks->dynticks; |
372 | snap_nmi = rdp->dynticks->dynticks_nmi; |
373 | smp_mb(); /* Order sampling of snap with end of grace period. */ |
374 | rdp->dynticks_snap = snap; |
375 | rdp->dynticks_nmi_snap = snap_nmi; |
376 | ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); |
377 | if (ret) |
378 | rdp->dynticks_fqs++; |
379 | return ret; |
380 | } |
381 | |
382 | /* |
383 | * Return true if the specified CPU has passed through a quiescent |
384 | * state by virtue of being in or having passed through an dynticks |
385 | * idle state since the last call to dyntick_save_progress_counter() |
386 | * for this same CPU. |
387 | */ |
388 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
389 | { |
390 | long curr; |
391 | long curr_nmi; |
392 | long snap; |
393 | long snap_nmi; |
394 | |
395 | curr = rdp->dynticks->dynticks; |
396 | snap = rdp->dynticks_snap; |
397 | curr_nmi = rdp->dynticks->dynticks_nmi; |
398 | snap_nmi = rdp->dynticks_nmi_snap; |
399 | smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ |
400 | |
401 | /* |
402 | * If the CPU passed through or entered a dynticks idle phase with |
403 | * no active irq/NMI handlers, then we can safely pretend that the CPU |
404 | * already acknowledged the request to pass through a quiescent |
405 | * state. Either way, that CPU cannot possibly be in an RCU |
406 | * read-side critical section that started before the beginning |
407 | * of the current RCU grace period. |
408 | */ |
409 | if ((curr != snap || (curr & 0x1) == 0) && |
410 | (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { |
411 | rdp->dynticks_fqs++; |
412 | return 1; |
413 | } |
414 | |
415 | /* Go check for the CPU being offline. */ |
416 | return rcu_implicit_offline_qs(rdp); |
417 | } |
418 | |
419 | #endif /* #ifdef CONFIG_SMP */ |
420 | |
421 | #else /* #ifdef CONFIG_NO_HZ */ |
422 | |
423 | #ifdef CONFIG_SMP |
424 | |
425 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
426 | { |
427 | return 0; |
428 | } |
429 | |
430 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
431 | { |
432 | return rcu_implicit_offline_qs(rdp); |
433 | } |
434 | |
435 | #endif /* #ifdef CONFIG_SMP */ |
436 | |
437 | #endif /* #else #ifdef CONFIG_NO_HZ */ |
438 | |
439 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
440 | |
441 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
442 | { |
443 | rsp->gp_start = jiffies; |
444 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; |
445 | } |
446 | |
447 | static void print_other_cpu_stall(struct rcu_state *rsp) |
448 | { |
449 | int cpu; |
450 | long delta; |
451 | unsigned long flags; |
452 | struct rcu_node *rnp = rcu_get_root(rsp); |
453 | |
454 | /* Only let one CPU complain about others per time interval. */ |
455 | |
456 | raw_spin_lock_irqsave(&rnp->lock, flags); |
457 | delta = jiffies - rsp->jiffies_stall; |
458 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
459 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
460 | return; |
461 | } |
462 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
463 | |
464 | /* |
465 | * Now rat on any tasks that got kicked up to the root rcu_node |
466 | * due to CPU offlining. |
467 | */ |
468 | rcu_print_task_stall(rnp); |
469 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
470 | |
471 | /* OK, time to rat on our buddy... */ |
472 | |
473 | printk(KERN_ERR "INFO: RCU detected CPU stalls:"); |
474 | rcu_for_each_leaf_node(rsp, rnp) { |
475 | raw_spin_lock_irqsave(&rnp->lock, flags); |
476 | rcu_print_task_stall(rnp); |
477 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
478 | if (rnp->qsmask == 0) |
479 | continue; |
480 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
481 | if (rnp->qsmask & (1UL << cpu)) |
482 | printk(" %d", rnp->grplo + cpu); |
483 | } |
484 | printk(" (detected by %d, t=%ld jiffies)\n", |
485 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
486 | trigger_all_cpu_backtrace(); |
487 | |
488 | /* If so configured, complain about tasks blocking the grace period. */ |
489 | |
490 | rcu_print_detail_task_stall(rsp); |
491 | |
492 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
493 | } |
494 | |
495 | static void print_cpu_stall(struct rcu_state *rsp) |
496 | { |
497 | unsigned long flags; |
498 | struct rcu_node *rnp = rcu_get_root(rsp); |
499 | |
500 | printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n", |
501 | smp_processor_id(), jiffies - rsp->gp_start); |
502 | trigger_all_cpu_backtrace(); |
503 | |
504 | raw_spin_lock_irqsave(&rnp->lock, flags); |
505 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
506 | rsp->jiffies_stall = |
507 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
508 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
509 | |
510 | set_need_resched(); /* kick ourselves to get things going. */ |
511 | } |
512 | |
513 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
514 | { |
515 | long delta; |
516 | struct rcu_node *rnp; |
517 | |
518 | delta = jiffies - rsp->jiffies_stall; |
519 | rnp = rdp->mynode; |
520 | if ((rnp->qsmask & rdp->grpmask) && delta >= 0) { |
521 | |
522 | /* We haven't checked in, so go dump stack. */ |
523 | print_cpu_stall(rsp); |
524 | |
525 | } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) { |
526 | |
527 | /* They had two time units to dump stack, so complain. */ |
528 | print_other_cpu_stall(rsp); |
529 | } |
530 | } |
531 | |
532 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
533 | |
534 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
535 | { |
536 | } |
537 | |
538 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
539 | { |
540 | } |
541 | |
542 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
543 | |
544 | /* |
545 | * Update CPU-local rcu_data state to record the newly noticed grace period. |
546 | * This is used both when we started the grace period and when we notice |
547 | * that someone else started the grace period. The caller must hold the |
548 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, |
549 | * and must have irqs disabled. |
550 | */ |
551 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
552 | { |
553 | if (rdp->gpnum != rnp->gpnum) { |
554 | rdp->qs_pending = 1; |
555 | rdp->passed_quiesc = 0; |
556 | rdp->gpnum = rnp->gpnum; |
557 | } |
558 | } |
559 | |
560 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
561 | { |
562 | unsigned long flags; |
563 | struct rcu_node *rnp; |
564 | |
565 | local_irq_save(flags); |
566 | rnp = rdp->mynode; |
567 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ |
568 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
569 | local_irq_restore(flags); |
570 | return; |
571 | } |
572 | __note_new_gpnum(rsp, rnp, rdp); |
573 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
574 | } |
575 | |
576 | /* |
577 | * Did someone else start a new RCU grace period start since we last |
578 | * checked? Update local state appropriately if so. Must be called |
579 | * on the CPU corresponding to rdp. |
580 | */ |
581 | static int |
582 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) |
583 | { |
584 | unsigned long flags; |
585 | int ret = 0; |
586 | |
587 | local_irq_save(flags); |
588 | if (rdp->gpnum != rsp->gpnum) { |
589 | note_new_gpnum(rsp, rdp); |
590 | ret = 1; |
591 | } |
592 | local_irq_restore(flags); |
593 | return ret; |
594 | } |
595 | |
596 | /* |
597 | * Advance this CPU's callbacks, but only if the current grace period |
598 | * has ended. This may be called only from the CPU to whom the rdp |
599 | * belongs. In addition, the corresponding leaf rcu_node structure's |
600 | * ->lock must be held by the caller, with irqs disabled. |
601 | */ |
602 | static void |
603 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
604 | { |
605 | /* Did another grace period end? */ |
606 | if (rdp->completed != rnp->completed) { |
607 | |
608 | /* Advance callbacks. No harm if list empty. */ |
609 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; |
610 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; |
611 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
612 | |
613 | /* Remember that we saw this grace-period completion. */ |
614 | rdp->completed = rnp->completed; |
615 | } |
616 | } |
617 | |
618 | /* |
619 | * Advance this CPU's callbacks, but only if the current grace period |
620 | * has ended. This may be called only from the CPU to whom the rdp |
621 | * belongs. |
622 | */ |
623 | static void |
624 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) |
625 | { |
626 | unsigned long flags; |
627 | struct rcu_node *rnp; |
628 | |
629 | local_irq_save(flags); |
630 | rnp = rdp->mynode; |
631 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ |
632 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
633 | local_irq_restore(flags); |
634 | return; |
635 | } |
636 | __rcu_process_gp_end(rsp, rnp, rdp); |
637 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
638 | } |
639 | |
640 | /* |
641 | * Do per-CPU grace-period initialization for running CPU. The caller |
642 | * must hold the lock of the leaf rcu_node structure corresponding to |
643 | * this CPU. |
644 | */ |
645 | static void |
646 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
647 | { |
648 | /* Prior grace period ended, so advance callbacks for current CPU. */ |
649 | __rcu_process_gp_end(rsp, rnp, rdp); |
650 | |
651 | /* |
652 | * Because this CPU just now started the new grace period, we know |
653 | * that all of its callbacks will be covered by this upcoming grace |
654 | * period, even the ones that were registered arbitrarily recently. |
655 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. |
656 | * |
657 | * Other CPUs cannot be sure exactly when the grace period started. |
658 | * Therefore, their recently registered callbacks must pass through |
659 | * an additional RCU_NEXT_READY stage, so that they will be handled |
660 | * by the next RCU grace period. |
661 | */ |
662 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
663 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
664 | |
665 | /* Set state so that this CPU will detect the next quiescent state. */ |
666 | __note_new_gpnum(rsp, rnp, rdp); |
667 | } |
668 | |
669 | /* |
670 | * Start a new RCU grace period if warranted, re-initializing the hierarchy |
671 | * in preparation for detecting the next grace period. The caller must hold |
672 | * the root node's ->lock, which is released before return. Hard irqs must |
673 | * be disabled. |
674 | */ |
675 | static void |
676 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) |
677 | __releases(rcu_get_root(rsp)->lock) |
678 | { |
679 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; |
680 | struct rcu_node *rnp = rcu_get_root(rsp); |
681 | |
682 | if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { |
683 | if (cpu_needs_another_gp(rsp, rdp)) |
684 | rsp->fqs_need_gp = 1; |
685 | if (rnp->completed == rsp->completed) { |
686 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
687 | return; |
688 | } |
689 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
690 | |
691 | /* |
692 | * Propagate new ->completed value to rcu_node structures |
693 | * so that other CPUs don't have to wait until the start |
694 | * of the next grace period to process their callbacks. |
695 | */ |
696 | rcu_for_each_node_breadth_first(rsp, rnp) { |
697 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
698 | rnp->completed = rsp->completed; |
699 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
700 | } |
701 | local_irq_restore(flags); |
702 | return; |
703 | } |
704 | |
705 | /* Advance to a new grace period and initialize state. */ |
706 | rsp->gpnum++; |
707 | WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
708 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
709 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
710 | record_gp_stall_check_time(rsp); |
711 | |
712 | /* Special-case the common single-level case. */ |
713 | if (NUM_RCU_NODES == 1) { |
714 | rcu_preempt_check_blocked_tasks(rnp); |
715 | rnp->qsmask = rnp->qsmaskinit; |
716 | rnp->gpnum = rsp->gpnum; |
717 | rnp->completed = rsp->completed; |
718 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
719 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
720 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
721 | return; |
722 | } |
723 | |
724 | raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
725 | |
726 | |
727 | /* Exclude any concurrent CPU-hotplug operations. */ |
728 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
729 | |
730 | /* |
731 | * Set the quiescent-state-needed bits in all the rcu_node |
732 | * structures for all currently online CPUs in breadth-first |
733 | * order, starting from the root rcu_node structure. This |
734 | * operation relies on the layout of the hierarchy within the |
735 | * rsp->node[] array. Note that other CPUs will access only |
736 | * the leaves of the hierarchy, which still indicate that no |
737 | * grace period is in progress, at least until the corresponding |
738 | * leaf node has been initialized. In addition, we have excluded |
739 | * CPU-hotplug operations. |
740 | * |
741 | * Note that the grace period cannot complete until we finish |
742 | * the initialization process, as there will be at least one |
743 | * qsmask bit set in the root node until that time, namely the |
744 | * one corresponding to this CPU, due to the fact that we have |
745 | * irqs disabled. |
746 | */ |
747 | rcu_for_each_node_breadth_first(rsp, rnp) { |
748 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
749 | rcu_preempt_check_blocked_tasks(rnp); |
750 | rnp->qsmask = rnp->qsmaskinit; |
751 | rnp->gpnum = rsp->gpnum; |
752 | rnp->completed = rsp->completed; |
753 | if (rnp == rdp->mynode) |
754 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
755 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
756 | } |
757 | |
758 | rnp = rcu_get_root(rsp); |
759 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
760 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
761 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
762 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
763 | } |
764 | |
765 | /* |
766 | * Report a full set of quiescent states to the specified rcu_state |
767 | * data structure. This involves cleaning up after the prior grace |
768 | * period and letting rcu_start_gp() start up the next grace period |
769 | * if one is needed. Note that the caller must hold rnp->lock, as |
770 | * required by rcu_start_gp(), which will release it. |
771 | */ |
772 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
773 | __releases(rcu_get_root(rsp)->lock) |
774 | { |
775 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
776 | rsp->completed = rsp->gpnum; |
777 | rsp->signaled = RCU_GP_IDLE; |
778 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
779 | } |
780 | |
781 | /* |
782 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
783 | * Allows quiescent states for a group of CPUs to be reported at one go |
784 | * to the specified rcu_node structure, though all the CPUs in the group |
785 | * must be represented by the same rcu_node structure (which need not be |
786 | * a leaf rcu_node structure, though it often will be). That structure's |
787 | * lock must be held upon entry, and it is released before return. |
788 | */ |
789 | static void |
790 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
791 | struct rcu_node *rnp, unsigned long flags) |
792 | __releases(rnp->lock) |
793 | { |
794 | struct rcu_node *rnp_c; |
795 | |
796 | /* Walk up the rcu_node hierarchy. */ |
797 | for (;;) { |
798 | if (!(rnp->qsmask & mask)) { |
799 | |
800 | /* Our bit has already been cleared, so done. */ |
801 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
802 | return; |
803 | } |
804 | rnp->qsmask &= ~mask; |
805 | if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { |
806 | |
807 | /* Other bits still set at this level, so done. */ |
808 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
809 | return; |
810 | } |
811 | mask = rnp->grpmask; |
812 | if (rnp->parent == NULL) { |
813 | |
814 | /* No more levels. Exit loop holding root lock. */ |
815 | |
816 | break; |
817 | } |
818 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
819 | rnp_c = rnp; |
820 | rnp = rnp->parent; |
821 | raw_spin_lock_irqsave(&rnp->lock, flags); |
822 | WARN_ON_ONCE(rnp_c->qsmask); |
823 | } |
824 | |
825 | /* |
826 | * Get here if we are the last CPU to pass through a quiescent |
827 | * state for this grace period. Invoke rcu_report_qs_rsp() |
828 | * to clean up and start the next grace period if one is needed. |
829 | */ |
830 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
831 | } |
832 | |
833 | /* |
834 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
835 | * structure. This must be either called from the specified CPU, or |
836 | * called when the specified CPU is known to be offline (and when it is |
837 | * also known that no other CPU is concurrently trying to help the offline |
838 | * CPU). The lastcomp argument is used to make sure we are still in the |
839 | * grace period of interest. We don't want to end the current grace period |
840 | * based on quiescent states detected in an earlier grace period! |
841 | */ |
842 | static void |
843 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
844 | { |
845 | unsigned long flags; |
846 | unsigned long mask; |
847 | struct rcu_node *rnp; |
848 | |
849 | rnp = rdp->mynode; |
850 | raw_spin_lock_irqsave(&rnp->lock, flags); |
851 | if (lastcomp != rnp->completed) { |
852 | |
853 | /* |
854 | * Someone beat us to it for this grace period, so leave. |
855 | * The race with GP start is resolved by the fact that we |
856 | * hold the leaf rcu_node lock, so that the per-CPU bits |
857 | * cannot yet be initialized -- so we would simply find our |
858 | * CPU's bit already cleared in rcu_report_qs_rnp() if this |
859 | * race occurred. |
860 | */ |
861 | rdp->passed_quiesc = 0; /* try again later! */ |
862 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
863 | return; |
864 | } |
865 | mask = rdp->grpmask; |
866 | if ((rnp->qsmask & mask) == 0) { |
867 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
868 | } else { |
869 | rdp->qs_pending = 0; |
870 | |
871 | /* |
872 | * This GP can't end until cpu checks in, so all of our |
873 | * callbacks can be processed during the next GP. |
874 | */ |
875 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
876 | |
877 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
878 | } |
879 | } |
880 | |
881 | /* |
882 | * Check to see if there is a new grace period of which this CPU |
883 | * is not yet aware, and if so, set up local rcu_data state for it. |
884 | * Otherwise, see if this CPU has just passed through its first |
885 | * quiescent state for this grace period, and record that fact if so. |
886 | */ |
887 | static void |
888 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) |
889 | { |
890 | /* If there is now a new grace period, record and return. */ |
891 | if (check_for_new_grace_period(rsp, rdp)) |
892 | return; |
893 | |
894 | /* |
895 | * Does this CPU still need to do its part for current grace period? |
896 | * If no, return and let the other CPUs do their part as well. |
897 | */ |
898 | if (!rdp->qs_pending) |
899 | return; |
900 | |
901 | /* |
902 | * Was there a quiescent state since the beginning of the grace |
903 | * period? If no, then exit and wait for the next call. |
904 | */ |
905 | if (!rdp->passed_quiesc) |
906 | return; |
907 | |
908 | /* |
909 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the |
910 | * judge of that). |
911 | */ |
912 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); |
913 | } |
914 | |
915 | #ifdef CONFIG_HOTPLUG_CPU |
916 | |
917 | /* |
918 | * Move a dying CPU's RCU callbacks to the ->orphan_cbs_list for the |
919 | * specified flavor of RCU. The callbacks will be adopted by the next |
920 | * _rcu_barrier() invocation or by the CPU_DEAD notifier, whichever |
921 | * comes first. Because this is invoked from the CPU_DYING notifier, |
922 | * irqs are already disabled. |
923 | */ |
924 | static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
925 | { |
926 | int i; |
927 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; |
928 | |
929 | if (rdp->nxtlist == NULL) |
930 | return; /* irqs disabled, so comparison is stable. */ |
931 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
932 | *rsp->orphan_cbs_tail = rdp->nxtlist; |
933 | rsp->orphan_cbs_tail = rdp->nxttail[RCU_NEXT_TAIL]; |
934 | rdp->nxtlist = NULL; |
935 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
936 | rdp->nxttail[i] = &rdp->nxtlist; |
937 | rsp->orphan_qlen += rdp->qlen; |
938 | rdp->qlen = 0; |
939 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
940 | } |
941 | |
942 | /* |
943 | * Adopt previously orphaned RCU callbacks. |
944 | */ |
945 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
946 | { |
947 | unsigned long flags; |
948 | struct rcu_data *rdp; |
949 | |
950 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
951 | rdp = rsp->rda[smp_processor_id()]; |
952 | if (rsp->orphan_cbs_list == NULL) { |
953 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
954 | return; |
955 | } |
956 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_list; |
957 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_tail; |
958 | rdp->qlen += rsp->orphan_qlen; |
959 | rsp->orphan_cbs_list = NULL; |
960 | rsp->orphan_cbs_tail = &rsp->orphan_cbs_list; |
961 | rsp->orphan_qlen = 0; |
962 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
963 | } |
964 | |
965 | /* |
966 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy |
967 | * and move all callbacks from the outgoing CPU to the current one. |
968 | */ |
969 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) |
970 | { |
971 | unsigned long flags; |
972 | unsigned long mask; |
973 | int need_report = 0; |
974 | struct rcu_data *rdp = rsp->rda[cpu]; |
975 | struct rcu_node *rnp; |
976 | |
977 | /* Exclude any attempts to start a new grace period. */ |
978 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
979 | |
980 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
981 | rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
982 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
983 | do { |
984 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
985 | rnp->qsmaskinit &= ~mask; |
986 | if (rnp->qsmaskinit != 0) { |
987 | if (rnp != rdp->mynode) |
988 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
989 | break; |
990 | } |
991 | if (rnp == rdp->mynode) |
992 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); |
993 | else |
994 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
995 | mask = rnp->grpmask; |
996 | rnp = rnp->parent; |
997 | } while (rnp != NULL); |
998 | |
999 | /* |
1000 | * We still hold the leaf rcu_node structure lock here, and |
1001 | * irqs are still disabled. The reason for this subterfuge is |
1002 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock |
1003 | * held leads to deadlock. |
1004 | */ |
1005 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
1006 | rnp = rdp->mynode; |
1007 | if (need_report & RCU_OFL_TASKS_NORM_GP) |
1008 | rcu_report_unblock_qs_rnp(rnp, flags); |
1009 | else |
1010 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1011 | if (need_report & RCU_OFL_TASKS_EXP_GP) |
1012 | rcu_report_exp_rnp(rsp, rnp); |
1013 | |
1014 | rcu_adopt_orphan_cbs(rsp); |
1015 | } |
1016 | |
1017 | /* |
1018 | * Remove the specified CPU from the RCU hierarchy and move any pending |
1019 | * callbacks that it might have to the current CPU. This code assumes |
1020 | * that at least one CPU in the system will remain running at all times. |
1021 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. |
1022 | */ |
1023 | static void rcu_offline_cpu(int cpu) |
1024 | { |
1025 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
1026 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
1027 | rcu_preempt_offline_cpu(cpu); |
1028 | } |
1029 | |
1030 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ |
1031 | |
1032 | static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
1033 | { |
1034 | } |
1035 | |
1036 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
1037 | { |
1038 | } |
1039 | |
1040 | static void rcu_offline_cpu(int cpu) |
1041 | { |
1042 | } |
1043 | |
1044 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ |
1045 | |
1046 | /* |
1047 | * Invoke any RCU callbacks that have made it to the end of their grace |
1048 | * period. Thottle as specified by rdp->blimit. |
1049 | */ |
1050 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
1051 | { |
1052 | unsigned long flags; |
1053 | struct rcu_head *next, *list, **tail; |
1054 | int count; |
1055 | |
1056 | /* If no callbacks are ready, just return.*/ |
1057 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) |
1058 | return; |
1059 | |
1060 | /* |
1061 | * Extract the list of ready callbacks, disabling to prevent |
1062 | * races with call_rcu() from interrupt handlers. |
1063 | */ |
1064 | local_irq_save(flags); |
1065 | list = rdp->nxtlist; |
1066 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; |
1067 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; |
1068 | tail = rdp->nxttail[RCU_DONE_TAIL]; |
1069 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) |
1070 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) |
1071 | rdp->nxttail[count] = &rdp->nxtlist; |
1072 | local_irq_restore(flags); |
1073 | |
1074 | /* Invoke callbacks. */ |
1075 | count = 0; |
1076 | while (list) { |
1077 | next = list->next; |
1078 | prefetch(next); |
1079 | list->func(list); |
1080 | list = next; |
1081 | if (++count >= rdp->blimit) |
1082 | break; |
1083 | } |
1084 | |
1085 | local_irq_save(flags); |
1086 | |
1087 | /* Update count, and requeue any remaining callbacks. */ |
1088 | rdp->qlen -= count; |
1089 | if (list != NULL) { |
1090 | *tail = rdp->nxtlist; |
1091 | rdp->nxtlist = list; |
1092 | for (count = 0; count < RCU_NEXT_SIZE; count++) |
1093 | if (&rdp->nxtlist == rdp->nxttail[count]) |
1094 | rdp->nxttail[count] = tail; |
1095 | else |
1096 | break; |
1097 | } |
1098 | |
1099 | /* Reinstate batch limit if we have worked down the excess. */ |
1100 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) |
1101 | rdp->blimit = blimit; |
1102 | |
1103 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1104 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { |
1105 | rdp->qlen_last_fqs_check = 0; |
1106 | rdp->n_force_qs_snap = rsp->n_force_qs; |
1107 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) |
1108 | rdp->qlen_last_fqs_check = rdp->qlen; |
1109 | |
1110 | local_irq_restore(flags); |
1111 | |
1112 | /* Re-raise the RCU softirq if there are callbacks remaining. */ |
1113 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
1114 | raise_softirq(RCU_SOFTIRQ); |
1115 | } |
1116 | |
1117 | /* |
1118 | * Check to see if this CPU is in a non-context-switch quiescent state |
1119 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). |
1120 | * Also schedule the RCU softirq handler. |
1121 | * |
1122 | * This function must be called with hardirqs disabled. It is normally |
1123 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
1124 | * false, there is no point in invoking rcu_check_callbacks(). |
1125 | */ |
1126 | void rcu_check_callbacks(int cpu, int user) |
1127 | { |
1128 | if (!rcu_pending(cpu)) |
1129 | return; /* if nothing for RCU to do. */ |
1130 | if (user || |
1131 | (idle_cpu(cpu) && rcu_scheduler_active && |
1132 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { |
1133 | |
1134 | /* |
1135 | * Get here if this CPU took its interrupt from user |
1136 | * mode or from the idle loop, and if this is not a |
1137 | * nested interrupt. In this case, the CPU is in |
1138 | * a quiescent state, so note it. |
1139 | * |
1140 | * No memory barrier is required here because both |
1141 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1142 | * variables that other CPUs neither access nor modify, |
1143 | * at least not while the corresponding CPU is online. |
1144 | */ |
1145 | |
1146 | rcu_sched_qs(cpu); |
1147 | rcu_bh_qs(cpu); |
1148 | |
1149 | } else if (!in_softirq()) { |
1150 | |
1151 | /* |
1152 | * Get here if this CPU did not take its interrupt from |
1153 | * softirq, in other words, if it is not interrupting |
1154 | * a rcu_bh read-side critical section. This is an _bh |
1155 | * critical section, so note it. |
1156 | */ |
1157 | |
1158 | rcu_bh_qs(cpu); |
1159 | } |
1160 | rcu_preempt_check_callbacks(cpu); |
1161 | raise_softirq(RCU_SOFTIRQ); |
1162 | } |
1163 | |
1164 | #ifdef CONFIG_SMP |
1165 | |
1166 | /* |
1167 | * Scan the leaf rcu_node structures, processing dyntick state for any that |
1168 | * have not yet encountered a quiescent state, using the function specified. |
1169 | * The caller must have suppressed start of new grace periods. |
1170 | */ |
1171 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
1172 | { |
1173 | unsigned long bit; |
1174 | int cpu; |
1175 | unsigned long flags; |
1176 | unsigned long mask; |
1177 | struct rcu_node *rnp; |
1178 | |
1179 | rcu_for_each_leaf_node(rsp, rnp) { |
1180 | mask = 0; |
1181 | raw_spin_lock_irqsave(&rnp->lock, flags); |
1182 | if (!rcu_gp_in_progress(rsp)) { |
1183 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1184 | return; |
1185 | } |
1186 | if (rnp->qsmask == 0) { |
1187 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1188 | continue; |
1189 | } |
1190 | cpu = rnp->grplo; |
1191 | bit = 1; |
1192 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
1193 | if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu])) |
1194 | mask |= bit; |
1195 | } |
1196 | if (mask != 0) { |
1197 | |
1198 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
1199 | rcu_report_qs_rnp(mask, rsp, rnp, flags); |
1200 | continue; |
1201 | } |
1202 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1203 | } |
1204 | } |
1205 | |
1206 | /* |
1207 | * Force quiescent states on reluctant CPUs, and also detect which |
1208 | * CPUs are in dyntick-idle mode. |
1209 | */ |
1210 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
1211 | { |
1212 | unsigned long flags; |
1213 | struct rcu_node *rnp = rcu_get_root(rsp); |
1214 | |
1215 | if (!rcu_gp_in_progress(rsp)) |
1216 | return; /* No grace period in progress, nothing to force. */ |
1217 | if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { |
1218 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
1219 | return; /* Someone else is already on the job. */ |
1220 | } |
1221 | if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) |
1222 | goto unlock_fqs_ret; /* no emergency and done recently. */ |
1223 | rsp->n_force_qs++; |
1224 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
1225 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
1226 | if(!rcu_gp_in_progress(rsp)) { |
1227 | rsp->n_force_qs_ngp++; |
1228 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1229 | goto unlock_fqs_ret; /* no GP in progress, time updated. */ |
1230 | } |
1231 | rsp->fqs_active = 1; |
1232 | switch (rsp->signaled) { |
1233 | case RCU_GP_IDLE: |
1234 | case RCU_GP_INIT: |
1235 | |
1236 | break; /* grace period idle or initializing, ignore. */ |
1237 | |
1238 | case RCU_SAVE_DYNTICK: |
1239 | |
1240 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1241 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
1242 | break; /* So gcc recognizes the dead code. */ |
1243 | |
1244 | /* Record dyntick-idle state. */ |
1245 | force_qs_rnp(rsp, dyntick_save_progress_counter); |
1246 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
1247 | if (rcu_gp_in_progress(rsp)) |
1248 | rsp->signaled = RCU_FORCE_QS; |
1249 | break; |
1250 | |
1251 | case RCU_FORCE_QS: |
1252 | |
1253 | /* Check dyntick-idle state, send IPI to laggarts. */ |
1254 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1255 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
1256 | |
1257 | /* Leave state in case more forcing is required. */ |
1258 | |
1259 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
1260 | break; |
1261 | } |
1262 | rsp->fqs_active = 0; |
1263 | if (rsp->fqs_need_gp) { |
1264 | raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ |
1265 | rsp->fqs_need_gp = 0; |
1266 | rcu_start_gp(rsp, flags); /* releases rnp->lock */ |
1267 | return; |
1268 | } |
1269 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1270 | unlock_fqs_ret: |
1271 | raw_spin_unlock_irqrestore(&rsp->fqslock, flags); |
1272 | } |
1273 | |
1274 | #else /* #ifdef CONFIG_SMP */ |
1275 | |
1276 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
1277 | { |
1278 | set_need_resched(); |
1279 | } |
1280 | |
1281 | #endif /* #else #ifdef CONFIG_SMP */ |
1282 | |
1283 | /* |
1284 | * This does the RCU processing work from softirq context for the |
1285 | * specified rcu_state and rcu_data structures. This may be called |
1286 | * only from the CPU to whom the rdp belongs. |
1287 | */ |
1288 | static void |
1289 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
1290 | { |
1291 | unsigned long flags; |
1292 | |
1293 | WARN_ON_ONCE(rdp->beenonline == 0); |
1294 | |
1295 | /* |
1296 | * If an RCU GP has gone long enough, go check for dyntick |
1297 | * idle CPUs and, if needed, send resched IPIs. |
1298 | */ |
1299 | if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
1300 | force_quiescent_state(rsp, 1); |
1301 | |
1302 | /* |
1303 | * Advance callbacks in response to end of earlier grace |
1304 | * period that some other CPU ended. |
1305 | */ |
1306 | rcu_process_gp_end(rsp, rdp); |
1307 | |
1308 | /* Update RCU state based on any recent quiescent states. */ |
1309 | rcu_check_quiescent_state(rsp, rdp); |
1310 | |
1311 | /* Does this CPU require a not-yet-started grace period? */ |
1312 | if (cpu_needs_another_gp(rsp, rdp)) { |
1313 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
1314 | rcu_start_gp(rsp, flags); /* releases above lock */ |
1315 | } |
1316 | |
1317 | /* If there are callbacks ready, invoke them. */ |
1318 | rcu_do_batch(rsp, rdp); |
1319 | } |
1320 | |
1321 | /* |
1322 | * Do softirq processing for the current CPU. |
1323 | */ |
1324 | static void rcu_process_callbacks(struct softirq_action *unused) |
1325 | { |
1326 | /* |
1327 | * Memory references from any prior RCU read-side critical sections |
1328 | * executed by the interrupted code must be seen before any RCU |
1329 | * grace-period manipulations below. |
1330 | */ |
1331 | smp_mb(); /* See above block comment. */ |
1332 | |
1333 | __rcu_process_callbacks(&rcu_sched_state, |
1334 | &__get_cpu_var(rcu_sched_data)); |
1335 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
1336 | rcu_preempt_process_callbacks(); |
1337 | |
1338 | /* |
1339 | * Memory references from any later RCU read-side critical sections |
1340 | * executed by the interrupted code must be seen after any RCU |
1341 | * grace-period manipulations above. |
1342 | */ |
1343 | smp_mb(); /* See above block comment. */ |
1344 | |
1345 | /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ |
1346 | rcu_needs_cpu_flush(); |
1347 | } |
1348 | |
1349 | static void |
1350 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), |
1351 | struct rcu_state *rsp) |
1352 | { |
1353 | unsigned long flags; |
1354 | struct rcu_data *rdp; |
1355 | |
1356 | head->func = func; |
1357 | head->next = NULL; |
1358 | |
1359 | smp_mb(); /* Ensure RCU update seen before callback registry. */ |
1360 | |
1361 | /* |
1362 | * Opportunistically note grace-period endings and beginnings. |
1363 | * Note that we might see a beginning right after we see an |
1364 | * end, but never vice versa, since this CPU has to pass through |
1365 | * a quiescent state betweentimes. |
1366 | */ |
1367 | local_irq_save(flags); |
1368 | rdp = rsp->rda[smp_processor_id()]; |
1369 | rcu_process_gp_end(rsp, rdp); |
1370 | check_for_new_grace_period(rsp, rdp); |
1371 | |
1372 | /* Add the callback to our list. */ |
1373 | *rdp->nxttail[RCU_NEXT_TAIL] = head; |
1374 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; |
1375 | |
1376 | /* Start a new grace period if one not already started. */ |
1377 | if (!rcu_gp_in_progress(rsp)) { |
1378 | unsigned long nestflag; |
1379 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
1380 | |
1381 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); |
1382 | rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */ |
1383 | } |
1384 | |
1385 | /* |
1386 | * Force the grace period if too many callbacks or too long waiting. |
1387 | * Enforce hysteresis, and don't invoke force_quiescent_state() |
1388 | * if some other CPU has recently done so. Also, don't bother |
1389 | * invoking force_quiescent_state() if the newly enqueued callback |
1390 | * is the only one waiting for a grace period to complete. |
1391 | */ |
1392 | if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
1393 | rdp->blimit = LONG_MAX; |
1394 | if (rsp->n_force_qs == rdp->n_force_qs_snap && |
1395 | *rdp->nxttail[RCU_DONE_TAIL] != head) |
1396 | force_quiescent_state(rsp, 0); |
1397 | rdp->n_force_qs_snap = rsp->n_force_qs; |
1398 | rdp->qlen_last_fqs_check = rdp->qlen; |
1399 | } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
1400 | force_quiescent_state(rsp, 1); |
1401 | local_irq_restore(flags); |
1402 | } |
1403 | |
1404 | /* |
1405 | * Queue an RCU-sched callback for invocation after a grace period. |
1406 | */ |
1407 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
1408 | { |
1409 | __call_rcu(head, func, &rcu_sched_state); |
1410 | } |
1411 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
1412 | |
1413 | /* |
1414 | * Queue an RCU for invocation after a quicker grace period. |
1415 | */ |
1416 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
1417 | { |
1418 | __call_rcu(head, func, &rcu_bh_state); |
1419 | } |
1420 | EXPORT_SYMBOL_GPL(call_rcu_bh); |
1421 | |
1422 | /** |
1423 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. |
1424 | * |
1425 | * Control will return to the caller some time after a full rcu-sched |
1426 | * grace period has elapsed, in other words after all currently executing |
1427 | * rcu-sched read-side critical sections have completed. These read-side |
1428 | * critical sections are delimited by rcu_read_lock_sched() and |
1429 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), |
1430 | * local_irq_disable(), and so on may be used in place of |
1431 | * rcu_read_lock_sched(). |
1432 | * |
1433 | * This means that all preempt_disable code sequences, including NMI and |
1434 | * hardware-interrupt handlers, in progress on entry will have completed |
1435 | * before this primitive returns. However, this does not guarantee that |
1436 | * softirq handlers will have completed, since in some kernels, these |
1437 | * handlers can run in process context, and can block. |
1438 | * |
1439 | * This primitive provides the guarantees made by the (now removed) |
1440 | * synchronize_kernel() API. In contrast, synchronize_rcu() only |
1441 | * guarantees that rcu_read_lock() sections will have completed. |
1442 | * In "classic RCU", these two guarantees happen to be one and |
1443 | * the same, but can differ in realtime RCU implementations. |
1444 | */ |
1445 | void synchronize_sched(void) |
1446 | { |
1447 | struct rcu_synchronize rcu; |
1448 | |
1449 | if (rcu_blocking_is_gp()) |
1450 | return; |
1451 | |
1452 | init_completion(&rcu.completion); |
1453 | /* Will wake me after RCU finished. */ |
1454 | call_rcu_sched(&rcu.head, wakeme_after_rcu); |
1455 | /* Wait for it. */ |
1456 | wait_for_completion(&rcu.completion); |
1457 | } |
1458 | EXPORT_SYMBOL_GPL(synchronize_sched); |
1459 | |
1460 | /** |
1461 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. |
1462 | * |
1463 | * Control will return to the caller some time after a full rcu_bh grace |
1464 | * period has elapsed, in other words after all currently executing rcu_bh |
1465 | * read-side critical sections have completed. RCU read-side critical |
1466 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), |
1467 | * and may be nested. |
1468 | */ |
1469 | void synchronize_rcu_bh(void) |
1470 | { |
1471 | struct rcu_synchronize rcu; |
1472 | |
1473 | if (rcu_blocking_is_gp()) |
1474 | return; |
1475 | |
1476 | init_completion(&rcu.completion); |
1477 | /* Will wake me after RCU finished. */ |
1478 | call_rcu_bh(&rcu.head, wakeme_after_rcu); |
1479 | /* Wait for it. */ |
1480 | wait_for_completion(&rcu.completion); |
1481 | } |
1482 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); |
1483 | |
1484 | /* |
1485 | * Check to see if there is any immediate RCU-related work to be done |
1486 | * by the current CPU, for the specified type of RCU, returning 1 if so. |
1487 | * The checks are in order of increasing expense: checks that can be |
1488 | * carried out against CPU-local state are performed first. However, |
1489 | * we must check for CPU stalls first, else we might not get a chance. |
1490 | */ |
1491 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) |
1492 | { |
1493 | struct rcu_node *rnp = rdp->mynode; |
1494 | |
1495 | rdp->n_rcu_pending++; |
1496 | |
1497 | /* Check for CPU stalls, if enabled. */ |
1498 | check_cpu_stall(rsp, rdp); |
1499 | |
1500 | /* Is the RCU core waiting for a quiescent state from this CPU? */ |
1501 | if (rdp->qs_pending) { |
1502 | rdp->n_rp_qs_pending++; |
1503 | return 1; |
1504 | } |
1505 | |
1506 | /* Does this CPU have callbacks ready to invoke? */ |
1507 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
1508 | rdp->n_rp_cb_ready++; |
1509 | return 1; |
1510 | } |
1511 | |
1512 | /* Has RCU gone idle with this CPU needing another grace period? */ |
1513 | if (cpu_needs_another_gp(rsp, rdp)) { |
1514 | rdp->n_rp_cpu_needs_gp++; |
1515 | return 1; |
1516 | } |
1517 | |
1518 | /* Has another RCU grace period completed? */ |
1519 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
1520 | rdp->n_rp_gp_completed++; |
1521 | return 1; |
1522 | } |
1523 | |
1524 | /* Has a new RCU grace period started? */ |
1525 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
1526 | rdp->n_rp_gp_started++; |
1527 | return 1; |
1528 | } |
1529 | |
1530 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ |
1531 | if (rcu_gp_in_progress(rsp) && |
1532 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { |
1533 | rdp->n_rp_need_fqs++; |
1534 | return 1; |
1535 | } |
1536 | |
1537 | /* nothing to do */ |
1538 | rdp->n_rp_need_nothing++; |
1539 | return 0; |
1540 | } |
1541 | |
1542 | /* |
1543 | * Check to see if there is any immediate RCU-related work to be done |
1544 | * by the current CPU, returning 1 if so. This function is part of the |
1545 | * RCU implementation; it is -not- an exported member of the RCU API. |
1546 | */ |
1547 | static int rcu_pending(int cpu) |
1548 | { |
1549 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
1550 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
1551 | rcu_preempt_pending(cpu); |
1552 | } |
1553 | |
1554 | /* |
1555 | * Check to see if any future RCU-related work will need to be done |
1556 | * by the current CPU, even if none need be done immediately, returning |
1557 | * 1 if so. |
1558 | */ |
1559 | static int rcu_needs_cpu_quick_check(int cpu) |
1560 | { |
1561 | /* RCU callbacks either ready or pending? */ |
1562 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
1563 | per_cpu(rcu_bh_data, cpu).nxtlist || |
1564 | rcu_preempt_needs_cpu(cpu); |
1565 | } |
1566 | |
1567 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
1568 | static atomic_t rcu_barrier_cpu_count; |
1569 | static DEFINE_MUTEX(rcu_barrier_mutex); |
1570 | static struct completion rcu_barrier_completion; |
1571 | |
1572 | static void rcu_barrier_callback(struct rcu_head *notused) |
1573 | { |
1574 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
1575 | complete(&rcu_barrier_completion); |
1576 | } |
1577 | |
1578 | /* |
1579 | * Called with preemption disabled, and from cross-cpu IRQ context. |
1580 | */ |
1581 | static void rcu_barrier_func(void *type) |
1582 | { |
1583 | int cpu = smp_processor_id(); |
1584 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); |
1585 | void (*call_rcu_func)(struct rcu_head *head, |
1586 | void (*func)(struct rcu_head *head)); |
1587 | |
1588 | atomic_inc(&rcu_barrier_cpu_count); |
1589 | call_rcu_func = type; |
1590 | call_rcu_func(head, rcu_barrier_callback); |
1591 | } |
1592 | |
1593 | /* |
1594 | * Orchestrate the specified type of RCU barrier, waiting for all |
1595 | * RCU callbacks of the specified type to complete. |
1596 | */ |
1597 | static void _rcu_barrier(struct rcu_state *rsp, |
1598 | void (*call_rcu_func)(struct rcu_head *head, |
1599 | void (*func)(struct rcu_head *head))) |
1600 | { |
1601 | BUG_ON(in_interrupt()); |
1602 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
1603 | mutex_lock(&rcu_barrier_mutex); |
1604 | init_completion(&rcu_barrier_completion); |
1605 | /* |
1606 | * Initialize rcu_barrier_cpu_count to 1, then invoke |
1607 | * rcu_barrier_func() on each CPU, so that each CPU also has |
1608 | * incremented rcu_barrier_cpu_count. Only then is it safe to |
1609 | * decrement rcu_barrier_cpu_count -- otherwise the first CPU |
1610 | * might complete its grace period before all of the other CPUs |
1611 | * did their increment, causing this function to return too |
1612 | * early. |
1613 | */ |
1614 | atomic_set(&rcu_barrier_cpu_count, 1); |
1615 | preempt_disable(); /* stop CPU_DYING from filling orphan_cbs_list */ |
1616 | rcu_adopt_orphan_cbs(rsp); |
1617 | on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); |
1618 | preempt_enable(); /* CPU_DYING can again fill orphan_cbs_list */ |
1619 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
1620 | complete(&rcu_barrier_completion); |
1621 | wait_for_completion(&rcu_barrier_completion); |
1622 | mutex_unlock(&rcu_barrier_mutex); |
1623 | } |
1624 | |
1625 | /** |
1626 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. |
1627 | */ |
1628 | void rcu_barrier_bh(void) |
1629 | { |
1630 | _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
1631 | } |
1632 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); |
1633 | |
1634 | /** |
1635 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. |
1636 | */ |
1637 | void rcu_barrier_sched(void) |
1638 | { |
1639 | _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
1640 | } |
1641 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); |
1642 | |
1643 | /* |
1644 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
1645 | */ |
1646 | static void __init |
1647 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) |
1648 | { |
1649 | unsigned long flags; |
1650 | int i; |
1651 | struct rcu_data *rdp = rsp->rda[cpu]; |
1652 | struct rcu_node *rnp = rcu_get_root(rsp); |
1653 | |
1654 | /* Set up local state, ensuring consistent view of global state. */ |
1655 | raw_spin_lock_irqsave(&rnp->lock, flags); |
1656 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
1657 | rdp->nxtlist = NULL; |
1658 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
1659 | rdp->nxttail[i] = &rdp->nxtlist; |
1660 | rdp->qlen = 0; |
1661 | #ifdef CONFIG_NO_HZ |
1662 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
1663 | #endif /* #ifdef CONFIG_NO_HZ */ |
1664 | rdp->cpu = cpu; |
1665 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1666 | } |
1667 | |
1668 | /* |
1669 | * Initialize a CPU's per-CPU RCU data. Note that only one online or |
1670 | * offline event can be happening at a given time. Note also that we |
1671 | * can accept some slop in the rsp->completed access due to the fact |
1672 | * that this CPU cannot possibly have any RCU callbacks in flight yet. |
1673 | */ |
1674 | static void __cpuinit |
1675 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
1676 | { |
1677 | unsigned long flags; |
1678 | unsigned long mask; |
1679 | struct rcu_data *rdp = rsp->rda[cpu]; |
1680 | struct rcu_node *rnp = rcu_get_root(rsp); |
1681 | |
1682 | /* Set up local state, ensuring consistent view of global state. */ |
1683 | raw_spin_lock_irqsave(&rnp->lock, flags); |
1684 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
1685 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ |
1686 | rdp->beenonline = 1; /* We have now been online. */ |
1687 | rdp->preemptable = preemptable; |
1688 | rdp->qlen_last_fqs_check = 0; |
1689 | rdp->n_force_qs_snap = rsp->n_force_qs; |
1690 | rdp->blimit = blimit; |
1691 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
1692 | |
1693 | /* |
1694 | * A new grace period might start here. If so, we won't be part |
1695 | * of it, but that is OK, as we are currently in a quiescent state. |
1696 | */ |
1697 | |
1698 | /* Exclude any attempts to start a new GP on large systems. */ |
1699 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
1700 | |
1701 | /* Add CPU to rcu_node bitmasks. */ |
1702 | rnp = rdp->mynode; |
1703 | mask = rdp->grpmask; |
1704 | do { |
1705 | /* Exclude any attempts to start a new GP on small systems. */ |
1706 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
1707 | rnp->qsmaskinit |= mask; |
1708 | mask = rnp->grpmask; |
1709 | if (rnp == rdp->mynode) { |
1710 | rdp->gpnum = rnp->completed; /* if GP in progress... */ |
1711 | rdp->completed = rnp->completed; |
1712 | rdp->passed_quiesc_completed = rnp->completed - 1; |
1713 | } |
1714 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
1715 | rnp = rnp->parent; |
1716 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); |
1717 | |
1718 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
1719 | } |
1720 | |
1721 | static void __cpuinit rcu_online_cpu(int cpu) |
1722 | { |
1723 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
1724 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); |
1725 | rcu_preempt_init_percpu_data(cpu); |
1726 | } |
1727 | |
1728 | /* |
1729 | * Handle CPU online/offline notification events. |
1730 | */ |
1731 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
1732 | unsigned long action, void *hcpu) |
1733 | { |
1734 | long cpu = (long)hcpu; |
1735 | |
1736 | switch (action) { |
1737 | case CPU_UP_PREPARE: |
1738 | case CPU_UP_PREPARE_FROZEN: |
1739 | rcu_online_cpu(cpu); |
1740 | break; |
1741 | case CPU_DYING: |
1742 | case CPU_DYING_FROZEN: |
1743 | /* |
1744 | * preempt_disable() in _rcu_barrier() prevents stop_machine(), |
1745 | * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);" |
1746 | * returns, all online cpus have queued rcu_barrier_func(). |
1747 | * The dying CPU clears its cpu_online_mask bit and |
1748 | * moves all of its RCU callbacks to ->orphan_cbs_list |
1749 | * in the context of stop_machine(), so subsequent calls |
1750 | * to _rcu_barrier() will adopt these callbacks and only |
1751 | * then queue rcu_barrier_func() on all remaining CPUs. |
1752 | */ |
1753 | rcu_send_cbs_to_orphanage(&rcu_bh_state); |
1754 | rcu_send_cbs_to_orphanage(&rcu_sched_state); |
1755 | rcu_preempt_send_cbs_to_orphanage(); |
1756 | break; |
1757 | case CPU_DEAD: |
1758 | case CPU_DEAD_FROZEN: |
1759 | case CPU_UP_CANCELED: |
1760 | case CPU_UP_CANCELED_FROZEN: |
1761 | rcu_offline_cpu(cpu); |
1762 | break; |
1763 | default: |
1764 | break; |
1765 | } |
1766 | return NOTIFY_OK; |
1767 | } |
1768 | |
1769 | /* |
1770 | * Compute the per-level fanout, either using the exact fanout specified |
1771 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. |
1772 | */ |
1773 | #ifdef CONFIG_RCU_FANOUT_EXACT |
1774 | static void __init rcu_init_levelspread(struct rcu_state *rsp) |
1775 | { |
1776 | int i; |
1777 | |
1778 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) |
1779 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
1780 | } |
1781 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ |
1782 | static void __init rcu_init_levelspread(struct rcu_state *rsp) |
1783 | { |
1784 | int ccur; |
1785 | int cprv; |
1786 | int i; |
1787 | |
1788 | cprv = NR_CPUS; |
1789 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
1790 | ccur = rsp->levelcnt[i]; |
1791 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; |
1792 | cprv = ccur; |
1793 | } |
1794 | } |
1795 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ |
1796 | |
1797 | /* |
1798 | * Helper function for rcu_init() that initializes one rcu_state structure. |
1799 | */ |
1800 | static void __init rcu_init_one(struct rcu_state *rsp) |
1801 | { |
1802 | static char *buf[] = { "rcu_node_level_0", |
1803 | "rcu_node_level_1", |
1804 | "rcu_node_level_2", |
1805 | "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ |
1806 | int cpustride = 1; |
1807 | int i; |
1808 | int j; |
1809 | struct rcu_node *rnp; |
1810 | |
1811 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
1812 | |
1813 | /* Initialize the level-tracking arrays. */ |
1814 | |
1815 | for (i = 1; i < NUM_RCU_LVLS; i++) |
1816 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
1817 | rcu_init_levelspread(rsp); |
1818 | |
1819 | /* Initialize the elements themselves, starting from the leaves. */ |
1820 | |
1821 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
1822 | cpustride *= rsp->levelspread[i]; |
1823 | rnp = rsp->level[i]; |
1824 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { |
1825 | raw_spin_lock_init(&rnp->lock); |
1826 | lockdep_set_class_and_name(&rnp->lock, |
1827 | &rcu_node_class[i], buf[i]); |
1828 | rnp->gpnum = 0; |
1829 | rnp->qsmask = 0; |
1830 | rnp->qsmaskinit = 0; |
1831 | rnp->grplo = j * cpustride; |
1832 | rnp->grphi = (j + 1) * cpustride - 1; |
1833 | if (rnp->grphi >= NR_CPUS) |
1834 | rnp->grphi = NR_CPUS - 1; |
1835 | if (i == 0) { |
1836 | rnp->grpnum = 0; |
1837 | rnp->grpmask = 0; |
1838 | rnp->parent = NULL; |
1839 | } else { |
1840 | rnp->grpnum = j % rsp->levelspread[i - 1]; |
1841 | rnp->grpmask = 1UL << rnp->grpnum; |
1842 | rnp->parent = rsp->level[i - 1] + |
1843 | j / rsp->levelspread[i - 1]; |
1844 | } |
1845 | rnp->level = i; |
1846 | INIT_LIST_HEAD(&rnp->blocked_tasks[0]); |
1847 | INIT_LIST_HEAD(&rnp->blocked_tasks[1]); |
1848 | INIT_LIST_HEAD(&rnp->blocked_tasks[2]); |
1849 | INIT_LIST_HEAD(&rnp->blocked_tasks[3]); |
1850 | } |
1851 | } |
1852 | } |
1853 | |
1854 | /* |
1855 | * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used |
1856 | * nowhere else! Assigns leaf node pointers into each CPU's rcu_data |
1857 | * structure. |
1858 | */ |
1859 | #define RCU_INIT_FLAVOR(rsp, rcu_data) \ |
1860 | do { \ |
1861 | int i; \ |
1862 | int j; \ |
1863 | struct rcu_node *rnp; \ |
1864 | \ |
1865 | rcu_init_one(rsp); \ |
1866 | rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \ |
1867 | j = 0; \ |
1868 | for_each_possible_cpu(i) { \ |
1869 | if (i > rnp[j].grphi) \ |
1870 | j++; \ |
1871 | per_cpu(rcu_data, i).mynode = &rnp[j]; \ |
1872 | (rsp)->rda[i] = &per_cpu(rcu_data, i); \ |
1873 | rcu_boot_init_percpu_data(i, rsp); \ |
1874 | } \ |
1875 | } while (0) |
1876 | |
1877 | void __init rcu_init(void) |
1878 | { |
1879 | int cpu; |
1880 | |
1881 | rcu_bootup_announce(); |
1882 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
1883 | printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); |
1884 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
1885 | #if NUM_RCU_LVL_4 != 0 |
1886 | printk(KERN_INFO "Experimental four-level hierarchy is enabled.\n"); |
1887 | #endif /* #if NUM_RCU_LVL_4 != 0 */ |
1888 | RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); |
1889 | RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); |
1890 | __rcu_init_preempt(); |
1891 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
1892 | |
1893 | /* |
1894 | * We don't need protection against CPU-hotplug here because |
1895 | * this is called early in boot, before either interrupts |
1896 | * or the scheduler are operational. |
1897 | */ |
1898 | cpu_notifier(rcu_cpu_notify, 0); |
1899 | for_each_online_cpu(cpu) |
1900 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); |
1901 | } |
1902 | |
1903 | #include "rcutree_plugin.h" |
1904 |
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