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 | #include <linux/kernel_stat.h> |
50 | |
51 | #include "rcutree.h" |
52 | |
53 | /* Data structures. */ |
54 | |
55 | static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; |
56 | |
57 | #define RCU_STATE_INITIALIZER(structname) { \ |
58 | .level = { &structname.node[0] }, \ |
59 | .levelcnt = { \ |
60 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ |
61 | NUM_RCU_LVL_1, \ |
62 | NUM_RCU_LVL_2, \ |
63 | NUM_RCU_LVL_3, \ |
64 | NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ |
65 | }, \ |
66 | .signaled = RCU_GP_IDLE, \ |
67 | .gpnum = -300, \ |
68 | .completed = -300, \ |
69 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \ |
70 | .orphan_cbs_list = NULL, \ |
71 | .orphan_cbs_tail = &structname.orphan_cbs_list, \ |
72 | .orphan_qlen = 0, \ |
73 | .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \ |
74 | .n_force_qs = 0, \ |
75 | .n_force_qs_ngp = 0, \ |
76 | .name = #structname, \ |
77 | } |
78 | |
79 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
80 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
81 | |
82 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
83 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
84 | |
85 | int rcu_scheduler_active __read_mostly; |
86 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); |
87 | |
88 | /* |
89 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s |
90 | * permit this function to be invoked without holding the root rcu_node |
91 | * structure's ->lock, but of course results can be subject to change. |
92 | */ |
93 | static int rcu_gp_in_progress(struct rcu_state *rsp) |
94 | { |
95 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); |
96 | } |
97 | |
98 | /* |
99 | * Note a quiescent state. Because we do not need to know |
100 | * how many quiescent states passed, just if there was at least |
101 | * one since the start of the grace period, this just sets a flag. |
102 | */ |
103 | void rcu_sched_qs(int cpu) |
104 | { |
105 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
106 | |
107 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
108 | barrier(); |
109 | rdp->passed_quiesc = 1; |
110 | } |
111 | |
112 | void rcu_bh_qs(int cpu) |
113 | { |
114 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
115 | |
116 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
117 | barrier(); |
118 | rdp->passed_quiesc = 1; |
119 | } |
120 | |
121 | /* |
122 | * Note a context switch. This is a quiescent state for RCU-sched, |
123 | * and requires special handling for preemptible RCU. |
124 | */ |
125 | void rcu_note_context_switch(int cpu) |
126 | { |
127 | rcu_sched_qs(cpu); |
128 | rcu_preempt_note_context_switch(cpu); |
129 | } |
130 | |
131 | #ifdef CONFIG_NO_HZ |
132 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
133 | .dynticks_nesting = 1, |
134 | .dynticks = 1, |
135 | }; |
136 | #endif /* #ifdef CONFIG_NO_HZ */ |
137 | |
138 | static int blimit = 10; /* Maximum callbacks per softirq. */ |
139 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
140 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ |
141 | |
142 | module_param(blimit, int, 0); |
143 | module_param(qhimark, int, 0); |
144 | module_param(qlowmark, int, 0); |
145 | |
146 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
147 | int rcu_cpu_stall_suppress __read_mostly = RCU_CPU_STALL_SUPPRESS_INIT; |
148 | module_param(rcu_cpu_stall_suppress, int, 0644); |
149 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
150 | |
151 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
152 | static int rcu_pending(int cpu); |
153 | |
154 | /* |
155 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
156 | */ |
157 | long rcu_batches_completed_sched(void) |
158 | { |
159 | return rcu_sched_state.completed; |
160 | } |
161 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
162 | |
163 | /* |
164 | * Return the number of RCU BH batches processed thus far for debug & stats. |
165 | */ |
166 | long rcu_batches_completed_bh(void) |
167 | { |
168 | return rcu_bh_state.completed; |
169 | } |
170 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); |
171 | |
172 | /* |
173 | * Force a quiescent state for RCU BH. |
174 | */ |
175 | void rcu_bh_force_quiescent_state(void) |
176 | { |
177 | force_quiescent_state(&rcu_bh_state, 0); |
178 | } |
179 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); |
180 | |
181 | /* |
182 | * Force a quiescent state for RCU-sched. |
183 | */ |
184 | void rcu_sched_force_quiescent_state(void) |
185 | { |
186 | force_quiescent_state(&rcu_sched_state, 0); |
187 | } |
188 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); |
189 | |
190 | /* |
191 | * Does the CPU have callbacks ready to be invoked? |
192 | */ |
193 | static int |
194 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) |
195 | { |
196 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; |
197 | } |
198 | |
199 | /* |
200 | * Does the current CPU require a yet-as-unscheduled grace period? |
201 | */ |
202 | static int |
203 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) |
204 | { |
205 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
206 | } |
207 | |
208 | /* |
209 | * Return the root node of the specified rcu_state structure. |
210 | */ |
211 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) |
212 | { |
213 | return &rsp->node[0]; |
214 | } |
215 | |
216 | #ifdef CONFIG_SMP |
217 | |
218 | /* |
219 | * If the specified CPU is offline, tell the caller that it is in |
220 | * a quiescent state. Otherwise, whack it with a reschedule IPI. |
221 | * Grace periods can end up waiting on an offline CPU when that |
222 | * CPU is in the process of coming online -- it will be added to the |
223 | * rcu_node bitmasks before it actually makes it online. The same thing |
224 | * can happen while a CPU is in the process of coming online. Because this |
225 | * race is quite rare, we check for it after detecting that the grace |
226 | * period has been delayed rather than checking each and every CPU |
227 | * each and every time we start a new grace period. |
228 | */ |
229 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) |
230 | { |
231 | /* |
232 | * If the CPU is offline, it is in a quiescent state. We can |
233 | * trust its state not to change because interrupts are disabled. |
234 | */ |
235 | if (cpu_is_offline(rdp->cpu)) { |
236 | rdp->offline_fqs++; |
237 | return 1; |
238 | } |
239 | |
240 | /* If preemptable RCU, no point in sending reschedule IPI. */ |
241 | if (rdp->preemptable) |
242 | return 0; |
243 | |
244 | /* The CPU is online, so send it a reschedule IPI. */ |
245 | if (rdp->cpu != smp_processor_id()) |
246 | smp_send_reschedule(rdp->cpu); |
247 | else |
248 | set_need_resched(); |
249 | rdp->resched_ipi++; |
250 | return 0; |
251 | } |
252 | |
253 | #endif /* #ifdef CONFIG_SMP */ |
254 | |
255 | #ifdef CONFIG_NO_HZ |
256 | |
257 | /** |
258 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz |
259 | * |
260 | * Enter nohz mode, in other words, -leave- the mode in which RCU |
261 | * read-side critical sections can occur. (Though RCU read-side |
262 | * critical sections can occur in irq handlers in nohz mode, a possibility |
263 | * handled by rcu_irq_enter() and rcu_irq_exit()). |
264 | */ |
265 | void rcu_enter_nohz(void) |
266 | { |
267 | unsigned long flags; |
268 | struct rcu_dynticks *rdtp; |
269 | |
270 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
271 | local_irq_save(flags); |
272 | rdtp = &__get_cpu_var(rcu_dynticks); |
273 | rdtp->dynticks++; |
274 | rdtp->dynticks_nesting--; |
275 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
276 | local_irq_restore(flags); |
277 | } |
278 | |
279 | /* |
280 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz |
281 | * |
282 | * Exit nohz mode, in other words, -enter- the mode in which RCU |
283 | * read-side critical sections normally occur. |
284 | */ |
285 | void rcu_exit_nohz(void) |
286 | { |
287 | unsigned long flags; |
288 | struct rcu_dynticks *rdtp; |
289 | |
290 | local_irq_save(flags); |
291 | rdtp = &__get_cpu_var(rcu_dynticks); |
292 | rdtp->dynticks++; |
293 | rdtp->dynticks_nesting++; |
294 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
295 | local_irq_restore(flags); |
296 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
297 | } |
298 | |
299 | /** |
300 | * rcu_nmi_enter - inform RCU of entry to NMI context |
301 | * |
302 | * If the CPU was idle with dynamic ticks active, and there is no |
303 | * irq handler running, this updates rdtp->dynticks_nmi to let the |
304 | * RCU grace-period handling know that the CPU is active. |
305 | */ |
306 | void rcu_nmi_enter(void) |
307 | { |
308 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
309 | |
310 | if (rdtp->dynticks & 0x1) |
311 | return; |
312 | rdtp->dynticks_nmi++; |
313 | WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); |
314 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
315 | } |
316 | |
317 | /** |
318 | * rcu_nmi_exit - inform RCU of exit from NMI context |
319 | * |
320 | * If the CPU was idle with dynamic ticks active, and there is no |
321 | * irq handler running, this updates rdtp->dynticks_nmi to let the |
322 | * RCU grace-period handling know that the CPU is no longer active. |
323 | */ |
324 | void rcu_nmi_exit(void) |
325 | { |
326 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
327 | |
328 | if (rdtp->dynticks & 0x1) |
329 | return; |
330 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
331 | rdtp->dynticks_nmi++; |
332 | WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); |
333 | } |
334 | |
335 | /** |
336 | * rcu_irq_enter - inform RCU of entry to hard irq context |
337 | * |
338 | * If the CPU was idle with dynamic ticks active, this updates the |
339 | * rdtp->dynticks to let the RCU handling know that the CPU is active. |
340 | */ |
341 | void rcu_irq_enter(void) |
342 | { |
343 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
344 | |
345 | if (rdtp->dynticks_nesting++) |
346 | return; |
347 | rdtp->dynticks++; |
348 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
349 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
350 | } |
351 | |
352 | /** |
353 | * rcu_irq_exit - inform RCU of exit from hard irq context |
354 | * |
355 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks |
356 | * to put let the RCU handling be aware that the CPU is going back to idle |
357 | * with no ticks. |
358 | */ |
359 | void rcu_irq_exit(void) |
360 | { |
361 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
362 | |
363 | if (--rdtp->dynticks_nesting) |
364 | return; |
365 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
366 | rdtp->dynticks++; |
367 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
368 | |
369 | /* If the interrupt queued a callback, get out of dyntick mode. */ |
370 | if (__get_cpu_var(rcu_sched_data).nxtlist || |
371 | __get_cpu_var(rcu_bh_data).nxtlist) |
372 | set_need_resched(); |
373 | } |
374 | |
375 | #ifdef CONFIG_SMP |
376 | |
377 | /* |
378 | * Snapshot the specified CPU's dynticks counter so that we can later |
379 | * credit them with an implicit quiescent state. Return 1 if this CPU |
380 | * is in dynticks idle mode, which is an extended quiescent state. |
381 | */ |
382 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
383 | { |
384 | int ret; |
385 | int snap; |
386 | int snap_nmi; |
387 | |
388 | snap = rdp->dynticks->dynticks; |
389 | snap_nmi = rdp->dynticks->dynticks_nmi; |
390 | smp_mb(); /* Order sampling of snap with end of grace period. */ |
391 | rdp->dynticks_snap = snap; |
392 | rdp->dynticks_nmi_snap = snap_nmi; |
393 | ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); |
394 | if (ret) |
395 | rdp->dynticks_fqs++; |
396 | return ret; |
397 | } |
398 | |
399 | /* |
400 | * Return true if the specified CPU has passed through a quiescent |
401 | * state by virtue of being in or having passed through an dynticks |
402 | * idle state since the last call to dyntick_save_progress_counter() |
403 | * for this same CPU. |
404 | */ |
405 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
406 | { |
407 | long curr; |
408 | long curr_nmi; |
409 | long snap; |
410 | long snap_nmi; |
411 | |
412 | curr = rdp->dynticks->dynticks; |
413 | snap = rdp->dynticks_snap; |
414 | curr_nmi = rdp->dynticks->dynticks_nmi; |
415 | snap_nmi = rdp->dynticks_nmi_snap; |
416 | smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ |
417 | |
418 | /* |
419 | * If the CPU passed through or entered a dynticks idle phase with |
420 | * no active irq/NMI handlers, then we can safely pretend that the CPU |
421 | * already acknowledged the request to pass through a quiescent |
422 | * state. Either way, that CPU cannot possibly be in an RCU |
423 | * read-side critical section that started before the beginning |
424 | * of the current RCU grace period. |
425 | */ |
426 | if ((curr != snap || (curr & 0x1) == 0) && |
427 | (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { |
428 | rdp->dynticks_fqs++; |
429 | return 1; |
430 | } |
431 | |
432 | /* Go check for the CPU being offline. */ |
433 | return rcu_implicit_offline_qs(rdp); |
434 | } |
435 | |
436 | #endif /* #ifdef CONFIG_SMP */ |
437 | |
438 | #else /* #ifdef CONFIG_NO_HZ */ |
439 | |
440 | #ifdef CONFIG_SMP |
441 | |
442 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
443 | { |
444 | return 0; |
445 | } |
446 | |
447 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
448 | { |
449 | return rcu_implicit_offline_qs(rdp); |
450 | } |
451 | |
452 | #endif /* #ifdef CONFIG_SMP */ |
453 | |
454 | #endif /* #else #ifdef CONFIG_NO_HZ */ |
455 | |
456 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
457 | |
458 | int rcu_cpu_stall_suppress __read_mostly; |
459 | |
460 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
461 | { |
462 | rsp->gp_start = jiffies; |
463 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; |
464 | } |
465 | |
466 | static void print_other_cpu_stall(struct rcu_state *rsp) |
467 | { |
468 | int cpu; |
469 | long delta; |
470 | unsigned long flags; |
471 | struct rcu_node *rnp = rcu_get_root(rsp); |
472 | |
473 | /* Only let one CPU complain about others per time interval. */ |
474 | |
475 | raw_spin_lock_irqsave(&rnp->lock, flags); |
476 | delta = jiffies - rsp->jiffies_stall; |
477 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
478 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
479 | return; |
480 | } |
481 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
482 | |
483 | /* |
484 | * Now rat on any tasks that got kicked up to the root rcu_node |
485 | * due to CPU offlining. |
486 | */ |
487 | rcu_print_task_stall(rnp); |
488 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
489 | |
490 | /* |
491 | * OK, time to rat on our buddy... |
492 | * See Documentation/RCU/stallwarn.txt for info on how to debug |
493 | * RCU CPU stall warnings. |
494 | */ |
495 | printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {", |
496 | rsp->name); |
497 | rcu_for_each_leaf_node(rsp, rnp) { |
498 | raw_spin_lock_irqsave(&rnp->lock, flags); |
499 | rcu_print_task_stall(rnp); |
500 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
501 | if (rnp->qsmask == 0) |
502 | continue; |
503 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
504 | if (rnp->qsmask & (1UL << cpu)) |
505 | printk(" %d", rnp->grplo + cpu); |
506 | } |
507 | printk("} (detected by %d, t=%ld jiffies)\n", |
508 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
509 | trigger_all_cpu_backtrace(); |
510 | |
511 | /* If so configured, complain about tasks blocking the grace period. */ |
512 | |
513 | rcu_print_detail_task_stall(rsp); |
514 | |
515 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
516 | } |
517 | |
518 | static void print_cpu_stall(struct rcu_state *rsp) |
519 | { |
520 | unsigned long flags; |
521 | struct rcu_node *rnp = rcu_get_root(rsp); |
522 | |
523 | /* |
524 | * OK, time to rat on ourselves... |
525 | * See Documentation/RCU/stallwarn.txt for info on how to debug |
526 | * RCU CPU stall warnings. |
527 | */ |
528 | printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n", |
529 | rsp->name, smp_processor_id(), jiffies - rsp->gp_start); |
530 | trigger_all_cpu_backtrace(); |
531 | |
532 | raw_spin_lock_irqsave(&rnp->lock, flags); |
533 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
534 | rsp->jiffies_stall = |
535 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
536 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
537 | |
538 | set_need_resched(); /* kick ourselves to get things going. */ |
539 | } |
540 | |
541 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
542 | { |
543 | long delta; |
544 | struct rcu_node *rnp; |
545 | |
546 | if (rcu_cpu_stall_suppress) |
547 | return; |
548 | delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall); |
549 | rnp = rdp->mynode; |
550 | if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) { |
551 | |
552 | /* We haven't checked in, so go dump stack. */ |
553 | print_cpu_stall(rsp); |
554 | |
555 | } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) { |
556 | |
557 | /* They had two time units to dump stack, so complain. */ |
558 | print_other_cpu_stall(rsp); |
559 | } |
560 | } |
561 | |
562 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
563 | { |
564 | rcu_cpu_stall_suppress = 1; |
565 | return NOTIFY_DONE; |
566 | } |
567 | |
568 | /** |
569 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period |
570 | * |
571 | * Set the stall-warning timeout way off into the future, thus preventing |
572 | * any RCU CPU stall-warning messages from appearing in the current set of |
573 | * RCU grace periods. |
574 | * |
575 | * The caller must disable hard irqs. |
576 | */ |
577 | void rcu_cpu_stall_reset(void) |
578 | { |
579 | rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2; |
580 | rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2; |
581 | rcu_preempt_stall_reset(); |
582 | } |
583 | |
584 | static struct notifier_block rcu_panic_block = { |
585 | .notifier_call = rcu_panic, |
586 | }; |
587 | |
588 | static void __init check_cpu_stall_init(void) |
589 | { |
590 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); |
591 | } |
592 | |
593 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
594 | |
595 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
596 | { |
597 | } |
598 | |
599 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
600 | { |
601 | } |
602 | |
603 | void rcu_cpu_stall_reset(void) |
604 | { |
605 | } |
606 | |
607 | static void __init check_cpu_stall_init(void) |
608 | { |
609 | } |
610 | |
611 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
612 | |
613 | /* |
614 | * Update CPU-local rcu_data state to record the newly noticed grace period. |
615 | * This is used both when we started the grace period and when we notice |
616 | * that someone else started the grace period. The caller must hold the |
617 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, |
618 | * and must have irqs disabled. |
619 | */ |
620 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
621 | { |
622 | if (rdp->gpnum != rnp->gpnum) { |
623 | rdp->qs_pending = 1; |
624 | rdp->passed_quiesc = 0; |
625 | rdp->gpnum = rnp->gpnum; |
626 | } |
627 | } |
628 | |
629 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
630 | { |
631 | unsigned long flags; |
632 | struct rcu_node *rnp; |
633 | |
634 | local_irq_save(flags); |
635 | rnp = rdp->mynode; |
636 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ |
637 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
638 | local_irq_restore(flags); |
639 | return; |
640 | } |
641 | __note_new_gpnum(rsp, rnp, rdp); |
642 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
643 | } |
644 | |
645 | /* |
646 | * Did someone else start a new RCU grace period start since we last |
647 | * checked? Update local state appropriately if so. Must be called |
648 | * on the CPU corresponding to rdp. |
649 | */ |
650 | static int |
651 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) |
652 | { |
653 | unsigned long flags; |
654 | int ret = 0; |
655 | |
656 | local_irq_save(flags); |
657 | if (rdp->gpnum != rsp->gpnum) { |
658 | note_new_gpnum(rsp, rdp); |
659 | ret = 1; |
660 | } |
661 | local_irq_restore(flags); |
662 | return ret; |
663 | } |
664 | |
665 | /* |
666 | * Advance this CPU's callbacks, but only if the current grace period |
667 | * has ended. This may be called only from the CPU to whom the rdp |
668 | * belongs. In addition, the corresponding leaf rcu_node structure's |
669 | * ->lock must be held by the caller, with irqs disabled. |
670 | */ |
671 | static void |
672 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
673 | { |
674 | /* Did another grace period end? */ |
675 | if (rdp->completed != rnp->completed) { |
676 | |
677 | /* Advance callbacks. No harm if list empty. */ |
678 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; |
679 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; |
680 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
681 | |
682 | /* Remember that we saw this grace-period completion. */ |
683 | rdp->completed = rnp->completed; |
684 | } |
685 | } |
686 | |
687 | /* |
688 | * Advance this CPU's callbacks, but only if the current grace period |
689 | * has ended. This may be called only from the CPU to whom the rdp |
690 | * belongs. |
691 | */ |
692 | static void |
693 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) |
694 | { |
695 | unsigned long flags; |
696 | struct rcu_node *rnp; |
697 | |
698 | local_irq_save(flags); |
699 | rnp = rdp->mynode; |
700 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ |
701 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
702 | local_irq_restore(flags); |
703 | return; |
704 | } |
705 | __rcu_process_gp_end(rsp, rnp, rdp); |
706 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
707 | } |
708 | |
709 | /* |
710 | * Do per-CPU grace-period initialization for running CPU. The caller |
711 | * must hold the lock of the leaf rcu_node structure corresponding to |
712 | * this CPU. |
713 | */ |
714 | static void |
715 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
716 | { |
717 | /* Prior grace period ended, so advance callbacks for current CPU. */ |
718 | __rcu_process_gp_end(rsp, rnp, rdp); |
719 | |
720 | /* |
721 | * Because this CPU just now started the new grace period, we know |
722 | * that all of its callbacks will be covered by this upcoming grace |
723 | * period, even the ones that were registered arbitrarily recently. |
724 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. |
725 | * |
726 | * Other CPUs cannot be sure exactly when the grace period started. |
727 | * Therefore, their recently registered callbacks must pass through |
728 | * an additional RCU_NEXT_READY stage, so that they will be handled |
729 | * by the next RCU grace period. |
730 | */ |
731 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
732 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
733 | |
734 | /* Set state so that this CPU will detect the next quiescent state. */ |
735 | __note_new_gpnum(rsp, rnp, rdp); |
736 | } |
737 | |
738 | /* |
739 | * Start a new RCU grace period if warranted, re-initializing the hierarchy |
740 | * in preparation for detecting the next grace period. The caller must hold |
741 | * the root node's ->lock, which is released before return. Hard irqs must |
742 | * be disabled. |
743 | */ |
744 | static void |
745 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) |
746 | __releases(rcu_get_root(rsp)->lock) |
747 | { |
748 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
749 | struct rcu_node *rnp = rcu_get_root(rsp); |
750 | |
751 | if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { |
752 | if (cpu_needs_another_gp(rsp, rdp)) |
753 | rsp->fqs_need_gp = 1; |
754 | if (rnp->completed == rsp->completed) { |
755 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
756 | return; |
757 | } |
758 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
759 | |
760 | /* |
761 | * Propagate new ->completed value to rcu_node structures |
762 | * so that other CPUs don't have to wait until the start |
763 | * of the next grace period to process their callbacks. |
764 | */ |
765 | rcu_for_each_node_breadth_first(rsp, rnp) { |
766 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
767 | rnp->completed = rsp->completed; |
768 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
769 | } |
770 | local_irq_restore(flags); |
771 | return; |
772 | } |
773 | |
774 | /* Advance to a new grace period and initialize state. */ |
775 | rsp->gpnum++; |
776 | WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
777 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
778 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
779 | record_gp_stall_check_time(rsp); |
780 | |
781 | /* Special-case the common single-level case. */ |
782 | if (NUM_RCU_NODES == 1) { |
783 | rcu_preempt_check_blocked_tasks(rnp); |
784 | rnp->qsmask = rnp->qsmaskinit; |
785 | rnp->gpnum = rsp->gpnum; |
786 | rnp->completed = rsp->completed; |
787 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
788 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
789 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
790 | return; |
791 | } |
792 | |
793 | raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
794 | |
795 | |
796 | /* Exclude any concurrent CPU-hotplug operations. */ |
797 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
798 | |
799 | /* |
800 | * Set the quiescent-state-needed bits in all the rcu_node |
801 | * structures for all currently online CPUs in breadth-first |
802 | * order, starting from the root rcu_node structure. This |
803 | * operation relies on the layout of the hierarchy within the |
804 | * rsp->node[] array. Note that other CPUs will access only |
805 | * the leaves of the hierarchy, which still indicate that no |
806 | * grace period is in progress, at least until the corresponding |
807 | * leaf node has been initialized. In addition, we have excluded |
808 | * CPU-hotplug operations. |
809 | * |
810 | * Note that the grace period cannot complete until we finish |
811 | * the initialization process, as there will be at least one |
812 | * qsmask bit set in the root node until that time, namely the |
813 | * one corresponding to this CPU, due to the fact that we have |
814 | * irqs disabled. |
815 | */ |
816 | rcu_for_each_node_breadth_first(rsp, rnp) { |
817 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
818 | rcu_preempt_check_blocked_tasks(rnp); |
819 | rnp->qsmask = rnp->qsmaskinit; |
820 | rnp->gpnum = rsp->gpnum; |
821 | rnp->completed = rsp->completed; |
822 | if (rnp == rdp->mynode) |
823 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
824 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
825 | } |
826 | |
827 | rnp = rcu_get_root(rsp); |
828 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
829 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
830 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
831 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
832 | } |
833 | |
834 | /* |
835 | * Report a full set of quiescent states to the specified rcu_state |
836 | * data structure. This involves cleaning up after the prior grace |
837 | * period and letting rcu_start_gp() start up the next grace period |
838 | * if one is needed. Note that the caller must hold rnp->lock, as |
839 | * required by rcu_start_gp(), which will release it. |
840 | */ |
841 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
842 | __releases(rcu_get_root(rsp)->lock) |
843 | { |
844 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
845 | rsp->completed = rsp->gpnum; |
846 | rsp->signaled = RCU_GP_IDLE; |
847 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
848 | } |
849 | |
850 | /* |
851 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
852 | * Allows quiescent states for a group of CPUs to be reported at one go |
853 | * to the specified rcu_node structure, though all the CPUs in the group |
854 | * must be represented by the same rcu_node structure (which need not be |
855 | * a leaf rcu_node structure, though it often will be). That structure's |
856 | * lock must be held upon entry, and it is released before return. |
857 | */ |
858 | static void |
859 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
860 | struct rcu_node *rnp, unsigned long flags) |
861 | __releases(rnp->lock) |
862 | { |
863 | struct rcu_node *rnp_c; |
864 | |
865 | /* Walk up the rcu_node hierarchy. */ |
866 | for (;;) { |
867 | if (!(rnp->qsmask & mask)) { |
868 | |
869 | /* Our bit has already been cleared, so done. */ |
870 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
871 | return; |
872 | } |
873 | rnp->qsmask &= ~mask; |
874 | if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { |
875 | |
876 | /* Other bits still set at this level, so done. */ |
877 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
878 | return; |
879 | } |
880 | mask = rnp->grpmask; |
881 | if (rnp->parent == NULL) { |
882 | |
883 | /* No more levels. Exit loop holding root lock. */ |
884 | |
885 | break; |
886 | } |
887 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
888 | rnp_c = rnp; |
889 | rnp = rnp->parent; |
890 | raw_spin_lock_irqsave(&rnp->lock, flags); |
891 | WARN_ON_ONCE(rnp_c->qsmask); |
892 | } |
893 | |
894 | /* |
895 | * Get here if we are the last CPU to pass through a quiescent |
896 | * state for this grace period. Invoke rcu_report_qs_rsp() |
897 | * to clean up and start the next grace period if one is needed. |
898 | */ |
899 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
900 | } |
901 | |
902 | /* |
903 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
904 | * structure. This must be either called from the specified CPU, or |
905 | * called when the specified CPU is known to be offline (and when it is |
906 | * also known that no other CPU is concurrently trying to help the offline |
907 | * CPU). The lastcomp argument is used to make sure we are still in the |
908 | * grace period of interest. We don't want to end the current grace period |
909 | * based on quiescent states detected in an earlier grace period! |
910 | */ |
911 | static void |
912 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
913 | { |
914 | unsigned long flags; |
915 | unsigned long mask; |
916 | struct rcu_node *rnp; |
917 | |
918 | rnp = rdp->mynode; |
919 | raw_spin_lock_irqsave(&rnp->lock, flags); |
920 | if (lastcomp != rnp->completed) { |
921 | |
922 | /* |
923 | * Someone beat us to it for this grace period, so leave. |
924 | * The race with GP start is resolved by the fact that we |
925 | * hold the leaf rcu_node lock, so that the per-CPU bits |
926 | * cannot yet be initialized -- so we would simply find our |
927 | * CPU's bit already cleared in rcu_report_qs_rnp() if this |
928 | * race occurred. |
929 | */ |
930 | rdp->passed_quiesc = 0; /* try again later! */ |
931 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
932 | return; |
933 | } |
934 | mask = rdp->grpmask; |
935 | if ((rnp->qsmask & mask) == 0) { |
936 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
937 | } else { |
938 | rdp->qs_pending = 0; |
939 | |
940 | /* |
941 | * This GP can't end until cpu checks in, so all of our |
942 | * callbacks can be processed during the next GP. |
943 | */ |
944 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
945 | |
946 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
947 | } |
948 | } |
949 | |
950 | /* |
951 | * Check to see if there is a new grace period of which this CPU |
952 | * is not yet aware, and if so, set up local rcu_data state for it. |
953 | * Otherwise, see if this CPU has just passed through its first |
954 | * quiescent state for this grace period, and record that fact if so. |
955 | */ |
956 | static void |
957 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) |
958 | { |
959 | /* If there is now a new grace period, record and return. */ |
960 | if (check_for_new_grace_period(rsp, rdp)) |
961 | return; |
962 | |
963 | /* |
964 | * Does this CPU still need to do its part for current grace period? |
965 | * If no, return and let the other CPUs do their part as well. |
966 | */ |
967 | if (!rdp->qs_pending) |
968 | return; |
969 | |
970 | /* |
971 | * Was there a quiescent state since the beginning of the grace |
972 | * period? If no, then exit and wait for the next call. |
973 | */ |
974 | if (!rdp->passed_quiesc) |
975 | return; |
976 | |
977 | /* |
978 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the |
979 | * judge of that). |
980 | */ |
981 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); |
982 | } |
983 | |
984 | #ifdef CONFIG_HOTPLUG_CPU |
985 | |
986 | /* |
987 | * Move a dying CPU's RCU callbacks to the ->orphan_cbs_list for the |
988 | * specified flavor of RCU. The callbacks will be adopted by the next |
989 | * _rcu_barrier() invocation or by the CPU_DEAD notifier, whichever |
990 | * comes first. Because this is invoked from the CPU_DYING notifier, |
991 | * irqs are already disabled. |
992 | */ |
993 | static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
994 | { |
995 | int i; |
996 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
997 | |
998 | if (rdp->nxtlist == NULL) |
999 | return; /* irqs disabled, so comparison is stable. */ |
1000 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
1001 | *rsp->orphan_cbs_tail = rdp->nxtlist; |
1002 | rsp->orphan_cbs_tail = rdp->nxttail[RCU_NEXT_TAIL]; |
1003 | rdp->nxtlist = NULL; |
1004 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
1005 | rdp->nxttail[i] = &rdp->nxtlist; |
1006 | rsp->orphan_qlen += rdp->qlen; |
1007 | rdp->n_cbs_orphaned += rdp->qlen; |
1008 | rdp->qlen = 0; |
1009 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
1010 | } |
1011 | |
1012 | /* |
1013 | * Adopt previously orphaned RCU callbacks. |
1014 | */ |
1015 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
1016 | { |
1017 | unsigned long flags; |
1018 | struct rcu_data *rdp; |
1019 | |
1020 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
1021 | rdp = this_cpu_ptr(rsp->rda); |
1022 | if (rsp->orphan_cbs_list == NULL) { |
1023 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
1024 | return; |
1025 | } |
1026 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_list; |
1027 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_tail; |
1028 | rdp->qlen += rsp->orphan_qlen; |
1029 | rdp->n_cbs_adopted += rsp->orphan_qlen; |
1030 | rsp->orphan_cbs_list = NULL; |
1031 | rsp->orphan_cbs_tail = &rsp->orphan_cbs_list; |
1032 | rsp->orphan_qlen = 0; |
1033 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
1034 | } |
1035 | |
1036 | /* |
1037 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy |
1038 | * and move all callbacks from the outgoing CPU to the current one. |
1039 | */ |
1040 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) |
1041 | { |
1042 | unsigned long flags; |
1043 | unsigned long mask; |
1044 | int need_report = 0; |
1045 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
1046 | struct rcu_node *rnp; |
1047 | |
1048 | /* Exclude any attempts to start a new grace period. */ |
1049 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
1050 | |
1051 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
1052 | rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
1053 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
1054 | do { |
1055 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
1056 | rnp->qsmaskinit &= ~mask; |
1057 | if (rnp->qsmaskinit != 0) { |
1058 | if (rnp != rdp->mynode) |
1059 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
1060 | break; |
1061 | } |
1062 | if (rnp == rdp->mynode) |
1063 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); |
1064 | else |
1065 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
1066 | mask = rnp->grpmask; |
1067 | rnp = rnp->parent; |
1068 | } while (rnp != NULL); |
1069 | |
1070 | /* |
1071 | * We still hold the leaf rcu_node structure lock here, and |
1072 | * irqs are still disabled. The reason for this subterfuge is |
1073 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock |
1074 | * held leads to deadlock. |
1075 | */ |
1076 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
1077 | rnp = rdp->mynode; |
1078 | if (need_report & RCU_OFL_TASKS_NORM_GP) |
1079 | rcu_report_unblock_qs_rnp(rnp, flags); |
1080 | else |
1081 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1082 | if (need_report & RCU_OFL_TASKS_EXP_GP) |
1083 | rcu_report_exp_rnp(rsp, rnp); |
1084 | |
1085 | rcu_adopt_orphan_cbs(rsp); |
1086 | } |
1087 | |
1088 | /* |
1089 | * Remove the specified CPU from the RCU hierarchy and move any pending |
1090 | * callbacks that it might have to the current CPU. This code assumes |
1091 | * that at least one CPU in the system will remain running at all times. |
1092 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. |
1093 | */ |
1094 | static void rcu_offline_cpu(int cpu) |
1095 | { |
1096 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
1097 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
1098 | rcu_preempt_offline_cpu(cpu); |
1099 | } |
1100 | |
1101 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ |
1102 | |
1103 | static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
1104 | { |
1105 | } |
1106 | |
1107 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
1108 | { |
1109 | } |
1110 | |
1111 | static void rcu_offline_cpu(int cpu) |
1112 | { |
1113 | } |
1114 | |
1115 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ |
1116 | |
1117 | /* |
1118 | * Invoke any RCU callbacks that have made it to the end of their grace |
1119 | * period. Thottle as specified by rdp->blimit. |
1120 | */ |
1121 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
1122 | { |
1123 | unsigned long flags; |
1124 | struct rcu_head *next, *list, **tail; |
1125 | int count; |
1126 | |
1127 | /* If no callbacks are ready, just return.*/ |
1128 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) |
1129 | return; |
1130 | |
1131 | /* |
1132 | * Extract the list of ready callbacks, disabling to prevent |
1133 | * races with call_rcu() from interrupt handlers. |
1134 | */ |
1135 | local_irq_save(flags); |
1136 | list = rdp->nxtlist; |
1137 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; |
1138 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; |
1139 | tail = rdp->nxttail[RCU_DONE_TAIL]; |
1140 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) |
1141 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) |
1142 | rdp->nxttail[count] = &rdp->nxtlist; |
1143 | local_irq_restore(flags); |
1144 | |
1145 | /* Invoke callbacks. */ |
1146 | count = 0; |
1147 | while (list) { |
1148 | next = list->next; |
1149 | prefetch(next); |
1150 | debug_rcu_head_unqueue(list); |
1151 | list->func(list); |
1152 | list = next; |
1153 | if (++count >= rdp->blimit) |
1154 | break; |
1155 | } |
1156 | |
1157 | local_irq_save(flags); |
1158 | |
1159 | /* Update count, and requeue any remaining callbacks. */ |
1160 | rdp->qlen -= count; |
1161 | rdp->n_cbs_invoked += count; |
1162 | if (list != NULL) { |
1163 | *tail = rdp->nxtlist; |
1164 | rdp->nxtlist = list; |
1165 | for (count = 0; count < RCU_NEXT_SIZE; count++) |
1166 | if (&rdp->nxtlist == rdp->nxttail[count]) |
1167 | rdp->nxttail[count] = tail; |
1168 | else |
1169 | break; |
1170 | } |
1171 | |
1172 | /* Reinstate batch limit if we have worked down the excess. */ |
1173 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) |
1174 | rdp->blimit = blimit; |
1175 | |
1176 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1177 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { |
1178 | rdp->qlen_last_fqs_check = 0; |
1179 | rdp->n_force_qs_snap = rsp->n_force_qs; |
1180 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) |
1181 | rdp->qlen_last_fqs_check = rdp->qlen; |
1182 | |
1183 | local_irq_restore(flags); |
1184 | |
1185 | /* Re-raise the RCU softirq if there are callbacks remaining. */ |
1186 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
1187 | raise_softirq(RCU_SOFTIRQ); |
1188 | } |
1189 | |
1190 | /* |
1191 | * Check to see if this CPU is in a non-context-switch quiescent state |
1192 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). |
1193 | * Also schedule the RCU softirq handler. |
1194 | * |
1195 | * This function must be called with hardirqs disabled. It is normally |
1196 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
1197 | * false, there is no point in invoking rcu_check_callbacks(). |
1198 | */ |
1199 | void rcu_check_callbacks(int cpu, int user) |
1200 | { |
1201 | if (user || |
1202 | (idle_cpu(cpu) && rcu_scheduler_active && |
1203 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { |
1204 | |
1205 | /* |
1206 | * Get here if this CPU took its interrupt from user |
1207 | * mode or from the idle loop, and if this is not a |
1208 | * nested interrupt. In this case, the CPU is in |
1209 | * a quiescent state, so note it. |
1210 | * |
1211 | * No memory barrier is required here because both |
1212 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1213 | * variables that other CPUs neither access nor modify, |
1214 | * at least not while the corresponding CPU is online. |
1215 | */ |
1216 | |
1217 | rcu_sched_qs(cpu); |
1218 | rcu_bh_qs(cpu); |
1219 | |
1220 | } else if (!in_softirq()) { |
1221 | |
1222 | /* |
1223 | * Get here if this CPU did not take its interrupt from |
1224 | * softirq, in other words, if it is not interrupting |
1225 | * a rcu_bh read-side critical section. This is an _bh |
1226 | * critical section, so note it. |
1227 | */ |
1228 | |
1229 | rcu_bh_qs(cpu); |
1230 | } |
1231 | rcu_preempt_check_callbacks(cpu); |
1232 | if (rcu_pending(cpu)) |
1233 | raise_softirq(RCU_SOFTIRQ); |
1234 | } |
1235 | |
1236 | #ifdef CONFIG_SMP |
1237 | |
1238 | /* |
1239 | * Scan the leaf rcu_node structures, processing dyntick state for any that |
1240 | * have not yet encountered a quiescent state, using the function specified. |
1241 | * The caller must have suppressed start of new grace periods. |
1242 | */ |
1243 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
1244 | { |
1245 | unsigned long bit; |
1246 | int cpu; |
1247 | unsigned long flags; |
1248 | unsigned long mask; |
1249 | struct rcu_node *rnp; |
1250 | |
1251 | rcu_for_each_leaf_node(rsp, rnp) { |
1252 | mask = 0; |
1253 | raw_spin_lock_irqsave(&rnp->lock, flags); |
1254 | if (!rcu_gp_in_progress(rsp)) { |
1255 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1256 | return; |
1257 | } |
1258 | if (rnp->qsmask == 0) { |
1259 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1260 | continue; |
1261 | } |
1262 | cpu = rnp->grplo; |
1263 | bit = 1; |
1264 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
1265 | if ((rnp->qsmask & bit) != 0 && |
1266 | f(per_cpu_ptr(rsp->rda, cpu))) |
1267 | mask |= bit; |
1268 | } |
1269 | if (mask != 0) { |
1270 | |
1271 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
1272 | rcu_report_qs_rnp(mask, rsp, rnp, flags); |
1273 | continue; |
1274 | } |
1275 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1276 | } |
1277 | } |
1278 | |
1279 | /* |
1280 | * Force quiescent states on reluctant CPUs, and also detect which |
1281 | * CPUs are in dyntick-idle mode. |
1282 | */ |
1283 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
1284 | { |
1285 | unsigned long flags; |
1286 | struct rcu_node *rnp = rcu_get_root(rsp); |
1287 | |
1288 | if (!rcu_gp_in_progress(rsp)) |
1289 | return; /* No grace period in progress, nothing to force. */ |
1290 | if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { |
1291 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
1292 | return; /* Someone else is already on the job. */ |
1293 | } |
1294 | if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) |
1295 | goto unlock_fqs_ret; /* no emergency and done recently. */ |
1296 | rsp->n_force_qs++; |
1297 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
1298 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
1299 | if(!rcu_gp_in_progress(rsp)) { |
1300 | rsp->n_force_qs_ngp++; |
1301 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1302 | goto unlock_fqs_ret; /* no GP in progress, time updated. */ |
1303 | } |
1304 | rsp->fqs_active = 1; |
1305 | switch (rsp->signaled) { |
1306 | case RCU_GP_IDLE: |
1307 | case RCU_GP_INIT: |
1308 | |
1309 | break; /* grace period idle or initializing, ignore. */ |
1310 | |
1311 | case RCU_SAVE_DYNTICK: |
1312 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
1313 | break; /* So gcc recognizes the dead code. */ |
1314 | |
1315 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1316 | |
1317 | /* Record dyntick-idle state. */ |
1318 | force_qs_rnp(rsp, dyntick_save_progress_counter); |
1319 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
1320 | if (rcu_gp_in_progress(rsp)) |
1321 | rsp->signaled = RCU_FORCE_QS; |
1322 | break; |
1323 | |
1324 | case RCU_FORCE_QS: |
1325 | |
1326 | /* Check dyntick-idle state, send IPI to laggarts. */ |
1327 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1328 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
1329 | |
1330 | /* Leave state in case more forcing is required. */ |
1331 | |
1332 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
1333 | break; |
1334 | } |
1335 | rsp->fqs_active = 0; |
1336 | if (rsp->fqs_need_gp) { |
1337 | raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ |
1338 | rsp->fqs_need_gp = 0; |
1339 | rcu_start_gp(rsp, flags); /* releases rnp->lock */ |
1340 | return; |
1341 | } |
1342 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1343 | unlock_fqs_ret: |
1344 | raw_spin_unlock_irqrestore(&rsp->fqslock, flags); |
1345 | } |
1346 | |
1347 | #else /* #ifdef CONFIG_SMP */ |
1348 | |
1349 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
1350 | { |
1351 | set_need_resched(); |
1352 | } |
1353 | |
1354 | #endif /* #else #ifdef CONFIG_SMP */ |
1355 | |
1356 | /* |
1357 | * This does the RCU processing work from softirq context for the |
1358 | * specified rcu_state and rcu_data structures. This may be called |
1359 | * only from the CPU to whom the rdp belongs. |
1360 | */ |
1361 | static void |
1362 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
1363 | { |
1364 | unsigned long flags; |
1365 | |
1366 | WARN_ON_ONCE(rdp->beenonline == 0); |
1367 | |
1368 | /* |
1369 | * If an RCU GP has gone long enough, go check for dyntick |
1370 | * idle CPUs and, if needed, send resched IPIs. |
1371 | */ |
1372 | if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
1373 | force_quiescent_state(rsp, 1); |
1374 | |
1375 | /* |
1376 | * Advance callbacks in response to end of earlier grace |
1377 | * period that some other CPU ended. |
1378 | */ |
1379 | rcu_process_gp_end(rsp, rdp); |
1380 | |
1381 | /* Update RCU state based on any recent quiescent states. */ |
1382 | rcu_check_quiescent_state(rsp, rdp); |
1383 | |
1384 | /* Does this CPU require a not-yet-started grace period? */ |
1385 | if (cpu_needs_another_gp(rsp, rdp)) { |
1386 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
1387 | rcu_start_gp(rsp, flags); /* releases above lock */ |
1388 | } |
1389 | |
1390 | /* If there are callbacks ready, invoke them. */ |
1391 | rcu_do_batch(rsp, rdp); |
1392 | } |
1393 | |
1394 | /* |
1395 | * Do softirq processing for the current CPU. |
1396 | */ |
1397 | static void rcu_process_callbacks(struct softirq_action *unused) |
1398 | { |
1399 | /* |
1400 | * Memory references from any prior RCU read-side critical sections |
1401 | * executed by the interrupted code must be seen before any RCU |
1402 | * grace-period manipulations below. |
1403 | */ |
1404 | smp_mb(); /* See above block comment. */ |
1405 | |
1406 | __rcu_process_callbacks(&rcu_sched_state, |
1407 | &__get_cpu_var(rcu_sched_data)); |
1408 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
1409 | rcu_preempt_process_callbacks(); |
1410 | |
1411 | /* |
1412 | * Memory references from any later RCU read-side critical sections |
1413 | * executed by the interrupted code must be seen after any RCU |
1414 | * grace-period manipulations above. |
1415 | */ |
1416 | smp_mb(); /* See above block comment. */ |
1417 | |
1418 | /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ |
1419 | rcu_needs_cpu_flush(); |
1420 | } |
1421 | |
1422 | static void |
1423 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), |
1424 | struct rcu_state *rsp) |
1425 | { |
1426 | unsigned long flags; |
1427 | struct rcu_data *rdp; |
1428 | |
1429 | debug_rcu_head_queue(head); |
1430 | head->func = func; |
1431 | head->next = NULL; |
1432 | |
1433 | smp_mb(); /* Ensure RCU update seen before callback registry. */ |
1434 | |
1435 | /* |
1436 | * Opportunistically note grace-period endings and beginnings. |
1437 | * Note that we might see a beginning right after we see an |
1438 | * end, but never vice versa, since this CPU has to pass through |
1439 | * a quiescent state betweentimes. |
1440 | */ |
1441 | local_irq_save(flags); |
1442 | rdp = this_cpu_ptr(rsp->rda); |
1443 | rcu_process_gp_end(rsp, rdp); |
1444 | check_for_new_grace_period(rsp, rdp); |
1445 | |
1446 | /* Add the callback to our list. */ |
1447 | *rdp->nxttail[RCU_NEXT_TAIL] = head; |
1448 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; |
1449 | |
1450 | /* Start a new grace period if one not already started. */ |
1451 | if (!rcu_gp_in_progress(rsp)) { |
1452 | unsigned long nestflag; |
1453 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
1454 | |
1455 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); |
1456 | rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */ |
1457 | } |
1458 | |
1459 | /* |
1460 | * Force the grace period if too many callbacks or too long waiting. |
1461 | * Enforce hysteresis, and don't invoke force_quiescent_state() |
1462 | * if some other CPU has recently done so. Also, don't bother |
1463 | * invoking force_quiescent_state() if the newly enqueued callback |
1464 | * is the only one waiting for a grace period to complete. |
1465 | */ |
1466 | if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
1467 | rdp->blimit = LONG_MAX; |
1468 | if (rsp->n_force_qs == rdp->n_force_qs_snap && |
1469 | *rdp->nxttail[RCU_DONE_TAIL] != head) |
1470 | force_quiescent_state(rsp, 0); |
1471 | rdp->n_force_qs_snap = rsp->n_force_qs; |
1472 | rdp->qlen_last_fqs_check = rdp->qlen; |
1473 | } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
1474 | force_quiescent_state(rsp, 1); |
1475 | local_irq_restore(flags); |
1476 | } |
1477 | |
1478 | /* |
1479 | * Queue an RCU-sched callback for invocation after a grace period. |
1480 | */ |
1481 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
1482 | { |
1483 | __call_rcu(head, func, &rcu_sched_state); |
1484 | } |
1485 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
1486 | |
1487 | /* |
1488 | * Queue an RCU for invocation after a quicker grace period. |
1489 | */ |
1490 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
1491 | { |
1492 | __call_rcu(head, func, &rcu_bh_state); |
1493 | } |
1494 | EXPORT_SYMBOL_GPL(call_rcu_bh); |
1495 | |
1496 | /** |
1497 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. |
1498 | * |
1499 | * Control will return to the caller some time after a full rcu-sched |
1500 | * grace period has elapsed, in other words after all currently executing |
1501 | * rcu-sched read-side critical sections have completed. These read-side |
1502 | * critical sections are delimited by rcu_read_lock_sched() and |
1503 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), |
1504 | * local_irq_disable(), and so on may be used in place of |
1505 | * rcu_read_lock_sched(). |
1506 | * |
1507 | * This means that all preempt_disable code sequences, including NMI and |
1508 | * hardware-interrupt handlers, in progress on entry will have completed |
1509 | * before this primitive returns. However, this does not guarantee that |
1510 | * softirq handlers will have completed, since in some kernels, these |
1511 | * handlers can run in process context, and can block. |
1512 | * |
1513 | * This primitive provides the guarantees made by the (now removed) |
1514 | * synchronize_kernel() API. In contrast, synchronize_rcu() only |
1515 | * guarantees that rcu_read_lock() sections will have completed. |
1516 | * In "classic RCU", these two guarantees happen to be one and |
1517 | * the same, but can differ in realtime RCU implementations. |
1518 | */ |
1519 | void synchronize_sched(void) |
1520 | { |
1521 | struct rcu_synchronize rcu; |
1522 | |
1523 | if (rcu_blocking_is_gp()) |
1524 | return; |
1525 | |
1526 | init_rcu_head_on_stack(&rcu.head); |
1527 | init_completion(&rcu.completion); |
1528 | /* Will wake me after RCU finished. */ |
1529 | call_rcu_sched(&rcu.head, wakeme_after_rcu); |
1530 | /* Wait for it. */ |
1531 | wait_for_completion(&rcu.completion); |
1532 | destroy_rcu_head_on_stack(&rcu.head); |
1533 | } |
1534 | EXPORT_SYMBOL_GPL(synchronize_sched); |
1535 | |
1536 | /** |
1537 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. |
1538 | * |
1539 | * Control will return to the caller some time after a full rcu_bh grace |
1540 | * period has elapsed, in other words after all currently executing rcu_bh |
1541 | * read-side critical sections have completed. RCU read-side critical |
1542 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), |
1543 | * and may be nested. |
1544 | */ |
1545 | void synchronize_rcu_bh(void) |
1546 | { |
1547 | struct rcu_synchronize rcu; |
1548 | |
1549 | if (rcu_blocking_is_gp()) |
1550 | return; |
1551 | |
1552 | init_rcu_head_on_stack(&rcu.head); |
1553 | init_completion(&rcu.completion); |
1554 | /* Will wake me after RCU finished. */ |
1555 | call_rcu_bh(&rcu.head, wakeme_after_rcu); |
1556 | /* Wait for it. */ |
1557 | wait_for_completion(&rcu.completion); |
1558 | destroy_rcu_head_on_stack(&rcu.head); |
1559 | } |
1560 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); |
1561 | |
1562 | /* |
1563 | * Check to see if there is any immediate RCU-related work to be done |
1564 | * by the current CPU, for the specified type of RCU, returning 1 if so. |
1565 | * The checks are in order of increasing expense: checks that can be |
1566 | * carried out against CPU-local state are performed first. However, |
1567 | * we must check for CPU stalls first, else we might not get a chance. |
1568 | */ |
1569 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) |
1570 | { |
1571 | struct rcu_node *rnp = rdp->mynode; |
1572 | |
1573 | rdp->n_rcu_pending++; |
1574 | |
1575 | /* Check for CPU stalls, if enabled. */ |
1576 | check_cpu_stall(rsp, rdp); |
1577 | |
1578 | /* Is the RCU core waiting for a quiescent state from this CPU? */ |
1579 | if (rdp->qs_pending && !rdp->passed_quiesc) { |
1580 | |
1581 | /* |
1582 | * If force_quiescent_state() coming soon and this CPU |
1583 | * needs a quiescent state, and this is either RCU-sched |
1584 | * or RCU-bh, force a local reschedule. |
1585 | */ |
1586 | rdp->n_rp_qs_pending++; |
1587 | if (!rdp->preemptable && |
1588 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, |
1589 | jiffies)) |
1590 | set_need_resched(); |
1591 | } else if (rdp->qs_pending && rdp->passed_quiesc) { |
1592 | rdp->n_rp_report_qs++; |
1593 | return 1; |
1594 | } |
1595 | |
1596 | /* Does this CPU have callbacks ready to invoke? */ |
1597 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
1598 | rdp->n_rp_cb_ready++; |
1599 | return 1; |
1600 | } |
1601 | |
1602 | /* Has RCU gone idle with this CPU needing another grace period? */ |
1603 | if (cpu_needs_another_gp(rsp, rdp)) { |
1604 | rdp->n_rp_cpu_needs_gp++; |
1605 | return 1; |
1606 | } |
1607 | |
1608 | /* Has another RCU grace period completed? */ |
1609 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
1610 | rdp->n_rp_gp_completed++; |
1611 | return 1; |
1612 | } |
1613 | |
1614 | /* Has a new RCU grace period started? */ |
1615 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
1616 | rdp->n_rp_gp_started++; |
1617 | return 1; |
1618 | } |
1619 | |
1620 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ |
1621 | if (rcu_gp_in_progress(rsp) && |
1622 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { |
1623 | rdp->n_rp_need_fqs++; |
1624 | return 1; |
1625 | } |
1626 | |
1627 | /* nothing to do */ |
1628 | rdp->n_rp_need_nothing++; |
1629 | return 0; |
1630 | } |
1631 | |
1632 | /* |
1633 | * Check to see if there is any immediate RCU-related work to be done |
1634 | * by the current CPU, returning 1 if so. This function is part of the |
1635 | * RCU implementation; it is -not- an exported member of the RCU API. |
1636 | */ |
1637 | static int rcu_pending(int cpu) |
1638 | { |
1639 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
1640 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
1641 | rcu_preempt_pending(cpu); |
1642 | } |
1643 | |
1644 | /* |
1645 | * Check to see if any future RCU-related work will need to be done |
1646 | * by the current CPU, even if none need be done immediately, returning |
1647 | * 1 if so. |
1648 | */ |
1649 | static int rcu_needs_cpu_quick_check(int cpu) |
1650 | { |
1651 | /* RCU callbacks either ready or pending? */ |
1652 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
1653 | per_cpu(rcu_bh_data, cpu).nxtlist || |
1654 | rcu_preempt_needs_cpu(cpu); |
1655 | } |
1656 | |
1657 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
1658 | static atomic_t rcu_barrier_cpu_count; |
1659 | static DEFINE_MUTEX(rcu_barrier_mutex); |
1660 | static struct completion rcu_barrier_completion; |
1661 | |
1662 | static void rcu_barrier_callback(struct rcu_head *notused) |
1663 | { |
1664 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
1665 | complete(&rcu_barrier_completion); |
1666 | } |
1667 | |
1668 | /* |
1669 | * Called with preemption disabled, and from cross-cpu IRQ context. |
1670 | */ |
1671 | static void rcu_barrier_func(void *type) |
1672 | { |
1673 | int cpu = smp_processor_id(); |
1674 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); |
1675 | void (*call_rcu_func)(struct rcu_head *head, |
1676 | void (*func)(struct rcu_head *head)); |
1677 | |
1678 | atomic_inc(&rcu_barrier_cpu_count); |
1679 | call_rcu_func = type; |
1680 | call_rcu_func(head, rcu_barrier_callback); |
1681 | } |
1682 | |
1683 | /* |
1684 | * Orchestrate the specified type of RCU barrier, waiting for all |
1685 | * RCU callbacks of the specified type to complete. |
1686 | */ |
1687 | static void _rcu_barrier(struct rcu_state *rsp, |
1688 | void (*call_rcu_func)(struct rcu_head *head, |
1689 | void (*func)(struct rcu_head *head))) |
1690 | { |
1691 | BUG_ON(in_interrupt()); |
1692 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
1693 | mutex_lock(&rcu_barrier_mutex); |
1694 | init_completion(&rcu_barrier_completion); |
1695 | /* |
1696 | * Initialize rcu_barrier_cpu_count to 1, then invoke |
1697 | * rcu_barrier_func() on each CPU, so that each CPU also has |
1698 | * incremented rcu_barrier_cpu_count. Only then is it safe to |
1699 | * decrement rcu_barrier_cpu_count -- otherwise the first CPU |
1700 | * might complete its grace period before all of the other CPUs |
1701 | * did their increment, causing this function to return too |
1702 | * early. |
1703 | */ |
1704 | atomic_set(&rcu_barrier_cpu_count, 1); |
1705 | preempt_disable(); /* stop CPU_DYING from filling orphan_cbs_list */ |
1706 | rcu_adopt_orphan_cbs(rsp); |
1707 | on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); |
1708 | preempt_enable(); /* CPU_DYING can again fill orphan_cbs_list */ |
1709 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
1710 | complete(&rcu_barrier_completion); |
1711 | wait_for_completion(&rcu_barrier_completion); |
1712 | mutex_unlock(&rcu_barrier_mutex); |
1713 | } |
1714 | |
1715 | /** |
1716 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. |
1717 | */ |
1718 | void rcu_barrier_bh(void) |
1719 | { |
1720 | _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
1721 | } |
1722 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); |
1723 | |
1724 | /** |
1725 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. |
1726 | */ |
1727 | void rcu_barrier_sched(void) |
1728 | { |
1729 | _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
1730 | } |
1731 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); |
1732 | |
1733 | /* |
1734 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
1735 | */ |
1736 | static void __init |
1737 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) |
1738 | { |
1739 | unsigned long flags; |
1740 | int i; |
1741 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
1742 | struct rcu_node *rnp = rcu_get_root(rsp); |
1743 | |
1744 | /* Set up local state, ensuring consistent view of global state. */ |
1745 | raw_spin_lock_irqsave(&rnp->lock, flags); |
1746 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
1747 | rdp->nxtlist = NULL; |
1748 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
1749 | rdp->nxttail[i] = &rdp->nxtlist; |
1750 | rdp->qlen = 0; |
1751 | #ifdef CONFIG_NO_HZ |
1752 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
1753 | #endif /* #ifdef CONFIG_NO_HZ */ |
1754 | rdp->cpu = cpu; |
1755 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1756 | } |
1757 | |
1758 | /* |
1759 | * Initialize a CPU's per-CPU RCU data. Note that only one online or |
1760 | * offline event can be happening at a given time. Note also that we |
1761 | * can accept some slop in the rsp->completed access due to the fact |
1762 | * that this CPU cannot possibly have any RCU callbacks in flight yet. |
1763 | */ |
1764 | static void __cpuinit |
1765 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
1766 | { |
1767 | unsigned long flags; |
1768 | unsigned long mask; |
1769 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
1770 | struct rcu_node *rnp = rcu_get_root(rsp); |
1771 | |
1772 | /* Set up local state, ensuring consistent view of global state. */ |
1773 | raw_spin_lock_irqsave(&rnp->lock, flags); |
1774 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
1775 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ |
1776 | rdp->beenonline = 1; /* We have now been online. */ |
1777 | rdp->preemptable = preemptable; |
1778 | rdp->qlen_last_fqs_check = 0; |
1779 | rdp->n_force_qs_snap = rsp->n_force_qs; |
1780 | rdp->blimit = blimit; |
1781 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
1782 | |
1783 | /* |
1784 | * A new grace period might start here. If so, we won't be part |
1785 | * of it, but that is OK, as we are currently in a quiescent state. |
1786 | */ |
1787 | |
1788 | /* Exclude any attempts to start a new GP on large systems. */ |
1789 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
1790 | |
1791 | /* Add CPU to rcu_node bitmasks. */ |
1792 | rnp = rdp->mynode; |
1793 | mask = rdp->grpmask; |
1794 | do { |
1795 | /* Exclude any attempts to start a new GP on small systems. */ |
1796 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
1797 | rnp->qsmaskinit |= mask; |
1798 | mask = rnp->grpmask; |
1799 | if (rnp == rdp->mynode) { |
1800 | rdp->gpnum = rnp->completed; /* if GP in progress... */ |
1801 | rdp->completed = rnp->completed; |
1802 | rdp->passed_quiesc_completed = rnp->completed - 1; |
1803 | } |
1804 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
1805 | rnp = rnp->parent; |
1806 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); |
1807 | |
1808 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
1809 | } |
1810 | |
1811 | static void __cpuinit rcu_online_cpu(int cpu) |
1812 | { |
1813 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
1814 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); |
1815 | rcu_preempt_init_percpu_data(cpu); |
1816 | } |
1817 | |
1818 | /* |
1819 | * Handle CPU online/offline notification events. |
1820 | */ |
1821 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
1822 | unsigned long action, void *hcpu) |
1823 | { |
1824 | long cpu = (long)hcpu; |
1825 | |
1826 | switch (action) { |
1827 | case CPU_UP_PREPARE: |
1828 | case CPU_UP_PREPARE_FROZEN: |
1829 | rcu_online_cpu(cpu); |
1830 | break; |
1831 | case CPU_DYING: |
1832 | case CPU_DYING_FROZEN: |
1833 | /* |
1834 | * preempt_disable() in _rcu_barrier() prevents stop_machine(), |
1835 | * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);" |
1836 | * returns, all online cpus have queued rcu_barrier_func(). |
1837 | * The dying CPU clears its cpu_online_mask bit and |
1838 | * moves all of its RCU callbacks to ->orphan_cbs_list |
1839 | * in the context of stop_machine(), so subsequent calls |
1840 | * to _rcu_barrier() will adopt these callbacks and only |
1841 | * then queue rcu_barrier_func() on all remaining CPUs. |
1842 | */ |
1843 | rcu_send_cbs_to_orphanage(&rcu_bh_state); |
1844 | rcu_send_cbs_to_orphanage(&rcu_sched_state); |
1845 | rcu_preempt_send_cbs_to_orphanage(); |
1846 | break; |
1847 | case CPU_DEAD: |
1848 | case CPU_DEAD_FROZEN: |
1849 | case CPU_UP_CANCELED: |
1850 | case CPU_UP_CANCELED_FROZEN: |
1851 | rcu_offline_cpu(cpu); |
1852 | break; |
1853 | default: |
1854 | break; |
1855 | } |
1856 | return NOTIFY_OK; |
1857 | } |
1858 | |
1859 | /* |
1860 | * This function is invoked towards the end of the scheduler's initialization |
1861 | * process. Before this is called, the idle task might contain |
1862 | * RCU read-side critical sections (during which time, this idle |
1863 | * task is booting the system). After this function is called, the |
1864 | * idle tasks are prohibited from containing RCU read-side critical |
1865 | * sections. This function also enables RCU lockdep checking. |
1866 | */ |
1867 | void rcu_scheduler_starting(void) |
1868 | { |
1869 | WARN_ON(num_online_cpus() != 1); |
1870 | WARN_ON(nr_context_switches() > 0); |
1871 | rcu_scheduler_active = 1; |
1872 | } |
1873 | |
1874 | /* |
1875 | * Compute the per-level fanout, either using the exact fanout specified |
1876 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. |
1877 | */ |
1878 | #ifdef CONFIG_RCU_FANOUT_EXACT |
1879 | static void __init rcu_init_levelspread(struct rcu_state *rsp) |
1880 | { |
1881 | int i; |
1882 | |
1883 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) |
1884 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
1885 | } |
1886 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ |
1887 | static void __init rcu_init_levelspread(struct rcu_state *rsp) |
1888 | { |
1889 | int ccur; |
1890 | int cprv; |
1891 | int i; |
1892 | |
1893 | cprv = NR_CPUS; |
1894 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
1895 | ccur = rsp->levelcnt[i]; |
1896 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; |
1897 | cprv = ccur; |
1898 | } |
1899 | } |
1900 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ |
1901 | |
1902 | /* |
1903 | * Helper function for rcu_init() that initializes one rcu_state structure. |
1904 | */ |
1905 | static void __init rcu_init_one(struct rcu_state *rsp, |
1906 | struct rcu_data __percpu *rda) |
1907 | { |
1908 | static char *buf[] = { "rcu_node_level_0", |
1909 | "rcu_node_level_1", |
1910 | "rcu_node_level_2", |
1911 | "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ |
1912 | int cpustride = 1; |
1913 | int i; |
1914 | int j; |
1915 | struct rcu_node *rnp; |
1916 | |
1917 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
1918 | |
1919 | /* Initialize the level-tracking arrays. */ |
1920 | |
1921 | for (i = 1; i < NUM_RCU_LVLS; i++) |
1922 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
1923 | rcu_init_levelspread(rsp); |
1924 | |
1925 | /* Initialize the elements themselves, starting from the leaves. */ |
1926 | |
1927 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
1928 | cpustride *= rsp->levelspread[i]; |
1929 | rnp = rsp->level[i]; |
1930 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { |
1931 | raw_spin_lock_init(&rnp->lock); |
1932 | lockdep_set_class_and_name(&rnp->lock, |
1933 | &rcu_node_class[i], buf[i]); |
1934 | rnp->gpnum = 0; |
1935 | rnp->qsmask = 0; |
1936 | rnp->qsmaskinit = 0; |
1937 | rnp->grplo = j * cpustride; |
1938 | rnp->grphi = (j + 1) * cpustride - 1; |
1939 | if (rnp->grphi >= NR_CPUS) |
1940 | rnp->grphi = NR_CPUS - 1; |
1941 | if (i == 0) { |
1942 | rnp->grpnum = 0; |
1943 | rnp->grpmask = 0; |
1944 | rnp->parent = NULL; |
1945 | } else { |
1946 | rnp->grpnum = j % rsp->levelspread[i - 1]; |
1947 | rnp->grpmask = 1UL << rnp->grpnum; |
1948 | rnp->parent = rsp->level[i - 1] + |
1949 | j / rsp->levelspread[i - 1]; |
1950 | } |
1951 | rnp->level = i; |
1952 | INIT_LIST_HEAD(&rnp->blocked_tasks[0]); |
1953 | INIT_LIST_HEAD(&rnp->blocked_tasks[1]); |
1954 | INIT_LIST_HEAD(&rnp->blocked_tasks[2]); |
1955 | INIT_LIST_HEAD(&rnp->blocked_tasks[3]); |
1956 | } |
1957 | } |
1958 | |
1959 | rsp->rda = rda; |
1960 | rnp = rsp->level[NUM_RCU_LVLS - 1]; |
1961 | for_each_possible_cpu(i) { |
1962 | while (i > rnp->grphi) |
1963 | rnp++; |
1964 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
1965 | rcu_boot_init_percpu_data(i, rsp); |
1966 | } |
1967 | } |
1968 | |
1969 | void __init rcu_init(void) |
1970 | { |
1971 | int cpu; |
1972 | |
1973 | rcu_bootup_announce(); |
1974 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
1975 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); |
1976 | __rcu_init_preempt(); |
1977 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
1978 | |
1979 | /* |
1980 | * We don't need protection against CPU-hotplug here because |
1981 | * this is called early in boot, before either interrupts |
1982 | * or the scheduler are operational. |
1983 | */ |
1984 | cpu_notifier(rcu_cpu_notify, 0); |
1985 | for_each_online_cpu(cpu) |
1986 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); |
1987 | check_cpu_stall_init(); |
1988 | } |
1989 | |
1990 | #include "rcutree_plugin.h" |
1991 |
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