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64db4cff PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | * | |
18 | * Copyright IBM Corporation, 2008 | |
19 | * | |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version | |
23 | * | |
24 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> | |
25 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
26 | * | |
27 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 28 | * Documentation/RCU |
64db4cff PM |
29 | */ |
30 | #include <linux/types.h> | |
31 | #include <linux/kernel.h> | |
32 | #include <linux/init.h> | |
33 | #include <linux/spinlock.h> | |
34 | #include <linux/smp.h> | |
35 | #include <linux/rcupdate.h> | |
36 | #include <linux/interrupt.h> | |
37 | #include <linux/sched.h> | |
c1dc0b9c | 38 | #include <linux/nmi.h> |
64db4cff PM |
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> | |
6ebb237b | 49 | #include <linux/kernel_stat.h> |
64db4cff | 50 | |
9f77da9f PM |
51 | #include "rcutree.h" |
52 | ||
64db4cff PM |
53 | /* Data structures. */ |
54 | ||
b668c9cf | 55 | static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; |
88b91c7c | 56 | |
64db4cff PM |
57 | #define RCU_STATE_INITIALIZER(name) { \ |
58 | .level = { &name.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, /* == MAX_RCU_LVLS */ \ | |
64 | }, \ | |
83f5b01f | 65 | .signaled = RCU_GP_IDLE, \ |
64db4cff PM |
66 | .gpnum = -300, \ |
67 | .completed = -300, \ | |
68 | .onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \ | |
e74f4c45 PM |
69 | .orphan_cbs_list = NULL, \ |
70 | .orphan_cbs_tail = &name.orphan_cbs_list, \ | |
71 | .orphan_qlen = 0, \ | |
64db4cff PM |
72 | .fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \ |
73 | .n_force_qs = 0, \ | |
74 | .n_force_qs_ngp = 0, \ | |
75 | } | |
76 | ||
d6714c22 PM |
77 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
78 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); | |
64db4cff | 79 | |
6258c4fb IM |
80 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
81 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); | |
b1f77b05 | 82 | |
6ebb237b PM |
83 | static int rcu_scheduler_active __read_mostly; |
84 | ||
f41d911f | 85 | |
fc2219d4 PM |
86 | /* |
87 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
88 | * permit this function to be invoked without holding the root rcu_node | |
89 | * structure's ->lock, but of course results can be subject to change. | |
90 | */ | |
91 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
92 | { | |
93 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
94 | } | |
95 | ||
b1f77b05 | 96 | /* |
d6714c22 | 97 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 98 | * how many quiescent states passed, just if there was at least |
d6714c22 | 99 | * one since the start of the grace period, this just sets a flag. |
b1f77b05 | 100 | */ |
d6714c22 | 101 | void rcu_sched_qs(int cpu) |
b1f77b05 | 102 | { |
f41d911f PM |
103 | struct rcu_data *rdp; |
104 | ||
f41d911f | 105 | rdp = &per_cpu(rcu_sched_data, cpu); |
c64ac3ce | 106 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
c3422bea PM |
107 | barrier(); |
108 | rdp->passed_quiesc = 1; | |
109 | rcu_preempt_note_context_switch(cpu); | |
b1f77b05 IM |
110 | } |
111 | ||
d6714c22 | 112 | void rcu_bh_qs(int cpu) |
b1f77b05 | 113 | { |
f41d911f PM |
114 | struct rcu_data *rdp; |
115 | ||
f41d911f | 116 | rdp = &per_cpu(rcu_bh_data, cpu); |
c64ac3ce | 117 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
c3422bea PM |
118 | barrier(); |
119 | rdp->passed_quiesc = 1; | |
b1f77b05 | 120 | } |
64db4cff PM |
121 | |
122 | #ifdef CONFIG_NO_HZ | |
90a4d2c0 PM |
123 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
124 | .dynticks_nesting = 1, | |
125 | .dynticks = 1, | |
126 | }; | |
64db4cff PM |
127 | #endif /* #ifdef CONFIG_NO_HZ */ |
128 | ||
129 | static int blimit = 10; /* Maximum callbacks per softirq. */ | |
130 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ | |
131 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
132 | ||
3d76c082 PM |
133 | module_param(blimit, int, 0); |
134 | module_param(qhimark, int, 0); | |
135 | module_param(qlowmark, int, 0); | |
136 | ||
64db4cff | 137 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
a157229c | 138 | static int rcu_pending(int cpu); |
64db4cff PM |
139 | |
140 | /* | |
d6714c22 | 141 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 142 | */ |
d6714c22 | 143 | long rcu_batches_completed_sched(void) |
64db4cff | 144 | { |
d6714c22 | 145 | return rcu_sched_state.completed; |
64db4cff | 146 | } |
d6714c22 | 147 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
148 | |
149 | /* | |
150 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
151 | */ | |
152 | long rcu_batches_completed_bh(void) | |
153 | { | |
154 | return rcu_bh_state.completed; | |
155 | } | |
156 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
157 | ||
158 | /* | |
159 | * Does the CPU have callbacks ready to be invoked? | |
160 | */ | |
161 | static int | |
162 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
163 | { | |
164 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
165 | } | |
166 | ||
167 | /* | |
168 | * Does the current CPU require a yet-as-unscheduled grace period? | |
169 | */ | |
170 | static int | |
171 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
172 | { | |
fc2219d4 | 173 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
64db4cff PM |
174 | } |
175 | ||
176 | /* | |
177 | * Return the root node of the specified rcu_state structure. | |
178 | */ | |
179 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
180 | { | |
181 | return &rsp->node[0]; | |
182 | } | |
183 | ||
184 | #ifdef CONFIG_SMP | |
185 | ||
186 | /* | |
187 | * If the specified CPU is offline, tell the caller that it is in | |
188 | * a quiescent state. Otherwise, whack it with a reschedule IPI. | |
189 | * Grace periods can end up waiting on an offline CPU when that | |
190 | * CPU is in the process of coming online -- it will be added to the | |
191 | * rcu_node bitmasks before it actually makes it online. The same thing | |
192 | * can happen while a CPU is in the process of coming online. Because this | |
193 | * race is quite rare, we check for it after detecting that the grace | |
194 | * period has been delayed rather than checking each and every CPU | |
195 | * each and every time we start a new grace period. | |
196 | */ | |
197 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) | |
198 | { | |
199 | /* | |
200 | * If the CPU is offline, it is in a quiescent state. We can | |
201 | * trust its state not to change because interrupts are disabled. | |
202 | */ | |
203 | if (cpu_is_offline(rdp->cpu)) { | |
204 | rdp->offline_fqs++; | |
205 | return 1; | |
206 | } | |
207 | ||
f41d911f PM |
208 | /* If preemptable RCU, no point in sending reschedule IPI. */ |
209 | if (rdp->preemptable) | |
210 | return 0; | |
211 | ||
64db4cff PM |
212 | /* The CPU is online, so send it a reschedule IPI. */ |
213 | if (rdp->cpu != smp_processor_id()) | |
214 | smp_send_reschedule(rdp->cpu); | |
215 | else | |
216 | set_need_resched(); | |
217 | rdp->resched_ipi++; | |
218 | return 0; | |
219 | } | |
220 | ||
221 | #endif /* #ifdef CONFIG_SMP */ | |
222 | ||
223 | #ifdef CONFIG_NO_HZ | |
64db4cff PM |
224 | |
225 | /** | |
226 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz | |
227 | * | |
228 | * Enter nohz mode, in other words, -leave- the mode in which RCU | |
229 | * read-side critical sections can occur. (Though RCU read-side | |
230 | * critical sections can occur in irq handlers in nohz mode, a possibility | |
231 | * handled by rcu_irq_enter() and rcu_irq_exit()). | |
232 | */ | |
233 | void rcu_enter_nohz(void) | |
234 | { | |
235 | unsigned long flags; | |
236 | struct rcu_dynticks *rdtp; | |
237 | ||
238 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
239 | local_irq_save(flags); | |
240 | rdtp = &__get_cpu_var(rcu_dynticks); | |
241 | rdtp->dynticks++; | |
242 | rdtp->dynticks_nesting--; | |
86848966 | 243 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
64db4cff PM |
244 | local_irq_restore(flags); |
245 | } | |
246 | ||
247 | /* | |
248 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz | |
249 | * | |
250 | * Exit nohz mode, in other words, -enter- the mode in which RCU | |
251 | * read-side critical sections normally occur. | |
252 | */ | |
253 | void rcu_exit_nohz(void) | |
254 | { | |
255 | unsigned long flags; | |
256 | struct rcu_dynticks *rdtp; | |
257 | ||
258 | local_irq_save(flags); | |
259 | rdtp = &__get_cpu_var(rcu_dynticks); | |
260 | rdtp->dynticks++; | |
261 | rdtp->dynticks_nesting++; | |
86848966 | 262 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
64db4cff PM |
263 | local_irq_restore(flags); |
264 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ | |
265 | } | |
266 | ||
267 | /** | |
268 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
269 | * | |
270 | * If the CPU was idle with dynamic ticks active, and there is no | |
271 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
272 | * RCU grace-period handling know that the CPU is active. | |
273 | */ | |
274 | void rcu_nmi_enter(void) | |
275 | { | |
276 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
277 | ||
278 | if (rdtp->dynticks & 0x1) | |
279 | return; | |
280 | rdtp->dynticks_nmi++; | |
86848966 | 281 | WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); |
64db4cff PM |
282 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
283 | } | |
284 | ||
285 | /** | |
286 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
287 | * | |
288 | * If the CPU was idle with dynamic ticks active, and there is no | |
289 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
290 | * RCU grace-period handling know that the CPU is no longer active. | |
291 | */ | |
292 | void rcu_nmi_exit(void) | |
293 | { | |
294 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
295 | ||
296 | if (rdtp->dynticks & 0x1) | |
297 | return; | |
298 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
299 | rdtp->dynticks_nmi++; | |
86848966 | 300 | WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); |
64db4cff PM |
301 | } |
302 | ||
303 | /** | |
304 | * rcu_irq_enter - inform RCU of entry to hard irq context | |
305 | * | |
306 | * If the CPU was idle with dynamic ticks active, this updates the | |
307 | * rdtp->dynticks to let the RCU handling know that the CPU is active. | |
308 | */ | |
309 | void rcu_irq_enter(void) | |
310 | { | |
311 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
312 | ||
313 | if (rdtp->dynticks_nesting++) | |
314 | return; | |
315 | rdtp->dynticks++; | |
86848966 | 316 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
64db4cff PM |
317 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
318 | } | |
319 | ||
320 | /** | |
321 | * rcu_irq_exit - inform RCU of exit from hard irq context | |
322 | * | |
323 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks | |
324 | * to put let the RCU handling be aware that the CPU is going back to idle | |
325 | * with no ticks. | |
326 | */ | |
327 | void rcu_irq_exit(void) | |
328 | { | |
329 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
330 | ||
331 | if (--rdtp->dynticks_nesting) | |
332 | return; | |
333 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
334 | rdtp->dynticks++; | |
86848966 | 335 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
64db4cff PM |
336 | |
337 | /* If the interrupt queued a callback, get out of dyntick mode. */ | |
d6714c22 | 338 | if (__get_cpu_var(rcu_sched_data).nxtlist || |
64db4cff PM |
339 | __get_cpu_var(rcu_bh_data).nxtlist) |
340 | set_need_resched(); | |
341 | } | |
342 | ||
64db4cff PM |
343 | #ifdef CONFIG_SMP |
344 | ||
64db4cff PM |
345 | /* |
346 | * Snapshot the specified CPU's dynticks counter so that we can later | |
347 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 348 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
349 | */ |
350 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
351 | { | |
352 | int ret; | |
353 | int snap; | |
354 | int snap_nmi; | |
355 | ||
356 | snap = rdp->dynticks->dynticks; | |
357 | snap_nmi = rdp->dynticks->dynticks_nmi; | |
358 | smp_mb(); /* Order sampling of snap with end of grace period. */ | |
359 | rdp->dynticks_snap = snap; | |
360 | rdp->dynticks_nmi_snap = snap_nmi; | |
361 | ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); | |
362 | if (ret) | |
363 | rdp->dynticks_fqs++; | |
364 | return ret; | |
365 | } | |
366 | ||
367 | /* | |
368 | * Return true if the specified CPU has passed through a quiescent | |
369 | * state by virtue of being in or having passed through an dynticks | |
370 | * idle state since the last call to dyntick_save_progress_counter() | |
371 | * for this same CPU. | |
372 | */ | |
373 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
374 | { | |
375 | long curr; | |
376 | long curr_nmi; | |
377 | long snap; | |
378 | long snap_nmi; | |
379 | ||
380 | curr = rdp->dynticks->dynticks; | |
381 | snap = rdp->dynticks_snap; | |
382 | curr_nmi = rdp->dynticks->dynticks_nmi; | |
383 | snap_nmi = rdp->dynticks_nmi_snap; | |
384 | smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ | |
385 | ||
386 | /* | |
387 | * If the CPU passed through or entered a dynticks idle phase with | |
388 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
389 | * already acknowledged the request to pass through a quiescent | |
390 | * state. Either way, that CPU cannot possibly be in an RCU | |
391 | * read-side critical section that started before the beginning | |
392 | * of the current RCU grace period. | |
393 | */ | |
394 | if ((curr != snap || (curr & 0x1) == 0) && | |
395 | (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { | |
396 | rdp->dynticks_fqs++; | |
397 | return 1; | |
398 | } | |
399 | ||
400 | /* Go check for the CPU being offline. */ | |
401 | return rcu_implicit_offline_qs(rdp); | |
402 | } | |
403 | ||
404 | #endif /* #ifdef CONFIG_SMP */ | |
405 | ||
406 | #else /* #ifdef CONFIG_NO_HZ */ | |
407 | ||
64db4cff PM |
408 | #ifdef CONFIG_SMP |
409 | ||
64db4cff PM |
410 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
411 | { | |
412 | return 0; | |
413 | } | |
414 | ||
415 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
416 | { | |
417 | return rcu_implicit_offline_qs(rdp); | |
418 | } | |
419 | ||
420 | #endif /* #ifdef CONFIG_SMP */ | |
421 | ||
422 | #endif /* #else #ifdef CONFIG_NO_HZ */ | |
423 | ||
424 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
425 | ||
426 | static void record_gp_stall_check_time(struct rcu_state *rsp) | |
427 | { | |
428 | rsp->gp_start = jiffies; | |
429 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; | |
430 | } | |
431 | ||
432 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
433 | { | |
434 | int cpu; | |
435 | long delta; | |
436 | unsigned long flags; | |
437 | struct rcu_node *rnp = rcu_get_root(rsp); | |
64db4cff PM |
438 | |
439 | /* Only let one CPU complain about others per time interval. */ | |
440 | ||
441 | spin_lock_irqsave(&rnp->lock, flags); | |
442 | delta = jiffies - rsp->jiffies_stall; | |
fc2219d4 | 443 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
64db4cff PM |
444 | spin_unlock_irqrestore(&rnp->lock, flags); |
445 | return; | |
446 | } | |
447 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
a0b6c9a7 PM |
448 | |
449 | /* | |
450 | * Now rat on any tasks that got kicked up to the root rcu_node | |
451 | * due to CPU offlining. | |
452 | */ | |
453 | rcu_print_task_stall(rnp); | |
64db4cff PM |
454 | spin_unlock_irqrestore(&rnp->lock, flags); |
455 | ||
456 | /* OK, time to rat on our buddy... */ | |
457 | ||
458 | printk(KERN_ERR "INFO: RCU detected CPU stalls:"); | |
a0b6c9a7 | 459 | rcu_for_each_leaf_node(rsp, rnp) { |
f41d911f | 460 | rcu_print_task_stall(rnp); |
a0b6c9a7 | 461 | if (rnp->qsmask == 0) |
64db4cff | 462 | continue; |
a0b6c9a7 PM |
463 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
464 | if (rnp->qsmask & (1UL << cpu)) | |
465 | printk(" %d", rnp->grplo + cpu); | |
64db4cff PM |
466 | } |
467 | printk(" (detected by %d, t=%ld jiffies)\n", | |
468 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); | |
c1dc0b9c IM |
469 | trigger_all_cpu_backtrace(); |
470 | ||
64db4cff PM |
471 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
472 | } | |
473 | ||
474 | static void print_cpu_stall(struct rcu_state *rsp) | |
475 | { | |
476 | unsigned long flags; | |
477 | struct rcu_node *rnp = rcu_get_root(rsp); | |
478 | ||
479 | printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n", | |
480 | smp_processor_id(), jiffies - rsp->gp_start); | |
c1dc0b9c IM |
481 | trigger_all_cpu_backtrace(); |
482 | ||
64db4cff PM |
483 | spin_lock_irqsave(&rnp->lock, flags); |
484 | if ((long)(jiffies - rsp->jiffies_stall) >= 0) | |
485 | rsp->jiffies_stall = | |
486 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
487 | spin_unlock_irqrestore(&rnp->lock, flags); | |
c1dc0b9c | 488 | |
64db4cff PM |
489 | set_need_resched(); /* kick ourselves to get things going. */ |
490 | } | |
491 | ||
492 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
493 | { | |
494 | long delta; | |
495 | struct rcu_node *rnp; | |
496 | ||
497 | delta = jiffies - rsp->jiffies_stall; | |
498 | rnp = rdp->mynode; | |
499 | if ((rnp->qsmask & rdp->grpmask) && delta >= 0) { | |
500 | ||
501 | /* We haven't checked in, so go dump stack. */ | |
502 | print_cpu_stall(rsp); | |
503 | ||
fc2219d4 | 504 | } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) { |
64db4cff PM |
505 | |
506 | /* They had two time units to dump stack, so complain. */ | |
507 | print_other_cpu_stall(rsp); | |
508 | } | |
509 | } | |
510 | ||
511 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
512 | ||
513 | static void record_gp_stall_check_time(struct rcu_state *rsp) | |
514 | { | |
515 | } | |
516 | ||
517 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
518 | { | |
519 | } | |
520 | ||
521 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
522 | ||
523 | /* | |
524 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
525 | * This is used both when we started the grace period and when we notice | |
9160306e PM |
526 | * that someone else started the grace period. The caller must hold the |
527 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, | |
528 | * and must have irqs disabled. | |
64db4cff | 529 | */ |
9160306e PM |
530 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
531 | { | |
532 | if (rdp->gpnum != rnp->gpnum) { | |
533 | rdp->qs_pending = 1; | |
534 | rdp->passed_quiesc = 0; | |
535 | rdp->gpnum = rnp->gpnum; | |
536 | } | |
537 | } | |
538 | ||
64db4cff PM |
539 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
540 | { | |
9160306e PM |
541 | unsigned long flags; |
542 | struct rcu_node *rnp; | |
543 | ||
544 | local_irq_save(flags); | |
545 | rnp = rdp->mynode; | |
546 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ | |
547 | !spin_trylock(&rnp->lock)) { /* irqs already off, retry later. */ | |
548 | local_irq_restore(flags); | |
549 | return; | |
550 | } | |
551 | __note_new_gpnum(rsp, rnp, rdp); | |
552 | spin_unlock_irqrestore(&rnp->lock, flags); | |
64db4cff PM |
553 | } |
554 | ||
555 | /* | |
556 | * Did someone else start a new RCU grace period start since we last | |
557 | * checked? Update local state appropriately if so. Must be called | |
558 | * on the CPU corresponding to rdp. | |
559 | */ | |
560 | static int | |
561 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
562 | { | |
563 | unsigned long flags; | |
564 | int ret = 0; | |
565 | ||
566 | local_irq_save(flags); | |
567 | if (rdp->gpnum != rsp->gpnum) { | |
568 | note_new_gpnum(rsp, rdp); | |
569 | ret = 1; | |
570 | } | |
571 | local_irq_restore(flags); | |
572 | return ret; | |
573 | } | |
574 | ||
d09b62df PM |
575 | /* |
576 | * Advance this CPU's callbacks, but only if the current grace period | |
577 | * has ended. This may be called only from the CPU to whom the rdp | |
578 | * belongs. In addition, the corresponding leaf rcu_node structure's | |
579 | * ->lock must be held by the caller, with irqs disabled. | |
580 | */ | |
581 | static void | |
582 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
583 | { | |
584 | /* Did another grace period end? */ | |
585 | if (rdp->completed != rnp->completed) { | |
586 | ||
587 | /* Advance callbacks. No harm if list empty. */ | |
588 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
589 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
590 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
591 | ||
592 | /* Remember that we saw this grace-period completion. */ | |
593 | rdp->completed = rnp->completed; | |
594 | } | |
595 | } | |
596 | ||
597 | /* | |
598 | * Advance this CPU's callbacks, but only if the current grace period | |
599 | * has ended. This may be called only from the CPU to whom the rdp | |
600 | * belongs. | |
601 | */ | |
602 | static void | |
603 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
604 | { | |
605 | unsigned long flags; | |
606 | struct rcu_node *rnp; | |
607 | ||
608 | local_irq_save(flags); | |
609 | rnp = rdp->mynode; | |
610 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ | |
611 | !spin_trylock(&rnp->lock)) { /* irqs already off, retry later. */ | |
612 | local_irq_restore(flags); | |
613 | return; | |
614 | } | |
615 | __rcu_process_gp_end(rsp, rnp, rdp); | |
616 | spin_unlock_irqrestore(&rnp->lock, flags); | |
617 | } | |
618 | ||
619 | /* | |
620 | * Do per-CPU grace-period initialization for running CPU. The caller | |
621 | * must hold the lock of the leaf rcu_node structure corresponding to | |
622 | * this CPU. | |
623 | */ | |
624 | static void | |
625 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
626 | { | |
627 | /* Prior grace period ended, so advance callbacks for current CPU. */ | |
628 | __rcu_process_gp_end(rsp, rnp, rdp); | |
629 | ||
630 | /* | |
631 | * Because this CPU just now started the new grace period, we know | |
632 | * that all of its callbacks will be covered by this upcoming grace | |
633 | * period, even the ones that were registered arbitrarily recently. | |
634 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. | |
635 | * | |
636 | * Other CPUs cannot be sure exactly when the grace period started. | |
637 | * Therefore, their recently registered callbacks must pass through | |
638 | * an additional RCU_NEXT_READY stage, so that they will be handled | |
639 | * by the next RCU grace period. | |
640 | */ | |
641 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
642 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
9160306e PM |
643 | |
644 | /* Set state so that this CPU will detect the next quiescent state. */ | |
645 | __note_new_gpnum(rsp, rnp, rdp); | |
d09b62df PM |
646 | } |
647 | ||
64db4cff PM |
648 | /* |
649 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
650 | * in preparation for detecting the next grace period. The caller must hold | |
651 | * the root node's ->lock, which is released before return. Hard irqs must | |
652 | * be disabled. | |
653 | */ | |
654 | static void | |
655 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
656 | __releases(rcu_get_root(rsp)->lock) | |
657 | { | |
658 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; | |
659 | struct rcu_node *rnp = rcu_get_root(rsp); | |
64db4cff PM |
660 | |
661 | if (!cpu_needs_another_gp(rsp, rdp)) { | |
b32e9eb6 PM |
662 | if (rnp->completed == rsp->completed) { |
663 | spin_unlock_irqrestore(&rnp->lock, flags); | |
664 | return; | |
665 | } | |
666 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
667 | ||
668 | /* | |
669 | * Propagate new ->completed value to rcu_node structures | |
670 | * so that other CPUs don't have to wait until the start | |
671 | * of the next grace period to process their callbacks. | |
672 | */ | |
673 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
674 | spin_lock(&rnp->lock); /* irqs already disabled. */ | |
675 | rnp->completed = rsp->completed; | |
676 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
677 | } | |
678 | local_irq_restore(flags); | |
64db4cff PM |
679 | return; |
680 | } | |
681 | ||
682 | /* Advance to a new grace period and initialize state. */ | |
683 | rsp->gpnum++; | |
c3422bea | 684 | WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
64db4cff PM |
685 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
686 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
64db4cff | 687 | record_gp_stall_check_time(rsp); |
64db4cff | 688 | |
64db4cff PM |
689 | /* Special-case the common single-level case. */ |
690 | if (NUM_RCU_NODES == 1) { | |
b0e165c0 | 691 | rcu_preempt_check_blocked_tasks(rnp); |
28ecd580 | 692 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 693 | rnp->gpnum = rsp->gpnum; |
d09b62df | 694 | rnp->completed = rsp->completed; |
c12172c0 | 695 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
d09b62df | 696 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
64db4cff PM |
697 | spin_unlock_irqrestore(&rnp->lock, flags); |
698 | return; | |
699 | } | |
700 | ||
701 | spin_unlock(&rnp->lock); /* leave irqs disabled. */ | |
702 | ||
703 | ||
704 | /* Exclude any concurrent CPU-hotplug operations. */ | |
705 | spin_lock(&rsp->onofflock); /* irqs already disabled. */ | |
706 | ||
707 | /* | |
b835db1f PM |
708 | * Set the quiescent-state-needed bits in all the rcu_node |
709 | * structures for all currently online CPUs in breadth-first | |
710 | * order, starting from the root rcu_node structure. This | |
711 | * operation relies on the layout of the hierarchy within the | |
712 | * rsp->node[] array. Note that other CPUs will access only | |
713 | * the leaves of the hierarchy, which still indicate that no | |
714 | * grace period is in progress, at least until the corresponding | |
715 | * leaf node has been initialized. In addition, we have excluded | |
716 | * CPU-hotplug operations. | |
64db4cff PM |
717 | * |
718 | * Note that the grace period cannot complete until we finish | |
719 | * the initialization process, as there will be at least one | |
720 | * qsmask bit set in the root node until that time, namely the | |
b835db1f PM |
721 | * one corresponding to this CPU, due to the fact that we have |
722 | * irqs disabled. | |
64db4cff | 723 | */ |
a0b6c9a7 | 724 | rcu_for_each_node_breadth_first(rsp, rnp) { |
83f5b01f | 725 | spin_lock(&rnp->lock); /* irqs already disabled. */ |
b0e165c0 | 726 | rcu_preempt_check_blocked_tasks(rnp); |
49e29126 | 727 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 728 | rnp->gpnum = rsp->gpnum; |
d09b62df PM |
729 | rnp->completed = rsp->completed; |
730 | if (rnp == rdp->mynode) | |
731 | rcu_start_gp_per_cpu(rsp, rnp, rdp); | |
83f5b01f | 732 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
733 | } |
734 | ||
83f5b01f PM |
735 | rnp = rcu_get_root(rsp); |
736 | spin_lock(&rnp->lock); /* irqs already disabled. */ | |
64db4cff | 737 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
83f5b01f | 738 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
739 | spin_unlock_irqrestore(&rsp->onofflock, flags); |
740 | } | |
741 | ||
f41d911f PM |
742 | /* |
743 | * Clean up after the prior grace period and let rcu_start_gp() start up | |
744 | * the next grace period if one is needed. Note that the caller must | |
745 | * hold rnp->lock, as required by rcu_start_gp(), which will release it. | |
746 | */ | |
747 | static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags) | |
fc2219d4 | 748 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 749 | { |
fc2219d4 | 750 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
f41d911f | 751 | rsp->completed = rsp->gpnum; |
83f5b01f | 752 | rsp->signaled = RCU_GP_IDLE; |
f41d911f PM |
753 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
754 | } | |
755 | ||
64db4cff PM |
756 | /* |
757 | * Similar to cpu_quiet(), for which it is a helper function. Allows | |
758 | * a group of CPUs to be quieted at one go, though all the CPUs in the | |
759 | * group must be represented by the same leaf rcu_node structure. | |
760 | * That structure's lock must be held upon entry, and it is released | |
761 | * before return. | |
762 | */ | |
763 | static void | |
764 | cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, | |
765 | unsigned long flags) | |
766 | __releases(rnp->lock) | |
767 | { | |
28ecd580 PM |
768 | struct rcu_node *rnp_c; |
769 | ||
64db4cff PM |
770 | /* Walk up the rcu_node hierarchy. */ |
771 | for (;;) { | |
772 | if (!(rnp->qsmask & mask)) { | |
773 | ||
774 | /* Our bit has already been cleared, so done. */ | |
775 | spin_unlock_irqrestore(&rnp->lock, flags); | |
776 | return; | |
777 | } | |
778 | rnp->qsmask &= ~mask; | |
f41d911f | 779 | if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { |
64db4cff PM |
780 | |
781 | /* Other bits still set at this level, so done. */ | |
782 | spin_unlock_irqrestore(&rnp->lock, flags); | |
783 | return; | |
784 | } | |
785 | mask = rnp->grpmask; | |
786 | if (rnp->parent == NULL) { | |
787 | ||
788 | /* No more levels. Exit loop holding root lock. */ | |
789 | ||
790 | break; | |
791 | } | |
792 | spin_unlock_irqrestore(&rnp->lock, flags); | |
28ecd580 | 793 | rnp_c = rnp; |
64db4cff PM |
794 | rnp = rnp->parent; |
795 | spin_lock_irqsave(&rnp->lock, flags); | |
28ecd580 | 796 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
797 | } |
798 | ||
799 | /* | |
800 | * Get here if we are the last CPU to pass through a quiescent | |
f41d911f PM |
801 | * state for this grace period. Invoke cpu_quiet_msk_finish() |
802 | * to clean up and start the next grace period if one is needed. | |
64db4cff | 803 | */ |
f41d911f | 804 | cpu_quiet_msk_finish(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
805 | } |
806 | ||
807 | /* | |
808 | * Record a quiescent state for the specified CPU, which must either be | |
e7d8842e PM |
809 | * the current CPU. The lastcomp argument is used to make sure we are |
810 | * still in the grace period of interest. We don't want to end the current | |
811 | * grace period based on quiescent states detected in an earlier grace | |
812 | * period! | |
64db4cff PM |
813 | */ |
814 | static void | |
815 | cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) | |
816 | { | |
817 | unsigned long flags; | |
818 | unsigned long mask; | |
819 | struct rcu_node *rnp; | |
820 | ||
821 | rnp = rdp->mynode; | |
822 | spin_lock_irqsave(&rnp->lock, flags); | |
560d4bc0 | 823 | if (lastcomp != rnp->completed) { |
64db4cff PM |
824 | |
825 | /* | |
826 | * Someone beat us to it for this grace period, so leave. | |
827 | * The race with GP start is resolved by the fact that we | |
828 | * hold the leaf rcu_node lock, so that the per-CPU bits | |
829 | * cannot yet be initialized -- so we would simply find our | |
830 | * CPU's bit already cleared in cpu_quiet_msk() if this race | |
831 | * occurred. | |
832 | */ | |
833 | rdp->passed_quiesc = 0; /* try again later! */ | |
834 | spin_unlock_irqrestore(&rnp->lock, flags); | |
835 | return; | |
836 | } | |
837 | mask = rdp->grpmask; | |
838 | if ((rnp->qsmask & mask) == 0) { | |
839 | spin_unlock_irqrestore(&rnp->lock, flags); | |
840 | } else { | |
841 | rdp->qs_pending = 0; | |
842 | ||
843 | /* | |
844 | * This GP can't end until cpu checks in, so all of our | |
845 | * callbacks can be processed during the next GP. | |
846 | */ | |
64db4cff PM |
847 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
848 | ||
849 | cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */ | |
850 | } | |
851 | } | |
852 | ||
853 | /* | |
854 | * Check to see if there is a new grace period of which this CPU | |
855 | * is not yet aware, and if so, set up local rcu_data state for it. | |
856 | * Otherwise, see if this CPU has just passed through its first | |
857 | * quiescent state for this grace period, and record that fact if so. | |
858 | */ | |
859 | static void | |
860 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
861 | { | |
862 | /* If there is now a new grace period, record and return. */ | |
863 | if (check_for_new_grace_period(rsp, rdp)) | |
864 | return; | |
865 | ||
866 | /* | |
867 | * Does this CPU still need to do its part for current grace period? | |
868 | * If no, return and let the other CPUs do their part as well. | |
869 | */ | |
870 | if (!rdp->qs_pending) | |
871 | return; | |
872 | ||
873 | /* | |
874 | * Was there a quiescent state since the beginning of the grace | |
875 | * period? If no, then exit and wait for the next call. | |
876 | */ | |
877 | if (!rdp->passed_quiesc) | |
878 | return; | |
879 | ||
880 | /* Tell RCU we are done (but cpu_quiet() will be the judge of that). */ | |
881 | cpu_quiet(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); | |
882 | } | |
883 | ||
884 | #ifdef CONFIG_HOTPLUG_CPU | |
885 | ||
e74f4c45 PM |
886 | /* |
887 | * Move a dying CPU's RCU callbacks to the ->orphan_cbs_list for the | |
888 | * specified flavor of RCU. The callbacks will be adopted by the next | |
889 | * _rcu_barrier() invocation or by the CPU_DEAD notifier, whichever | |
890 | * comes first. Because this is invoked from the CPU_DYING notifier, | |
891 | * irqs are already disabled. | |
892 | */ | |
893 | static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) | |
894 | { | |
895 | int i; | |
896 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; | |
897 | ||
898 | if (rdp->nxtlist == NULL) | |
899 | return; /* irqs disabled, so comparison is stable. */ | |
900 | spin_lock(&rsp->onofflock); /* irqs already disabled. */ | |
901 | *rsp->orphan_cbs_tail = rdp->nxtlist; | |
902 | rsp->orphan_cbs_tail = rdp->nxttail[RCU_NEXT_TAIL]; | |
903 | rdp->nxtlist = NULL; | |
904 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
905 | rdp->nxttail[i] = &rdp->nxtlist; | |
906 | rsp->orphan_qlen += rdp->qlen; | |
907 | rdp->qlen = 0; | |
908 | spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ | |
909 | } | |
910 | ||
911 | /* | |
912 | * Adopt previously orphaned RCU callbacks. | |
913 | */ | |
914 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) | |
915 | { | |
916 | unsigned long flags; | |
917 | struct rcu_data *rdp; | |
918 | ||
919 | spin_lock_irqsave(&rsp->onofflock, flags); | |
920 | rdp = rsp->rda[smp_processor_id()]; | |
921 | if (rsp->orphan_cbs_list == NULL) { | |
922 | spin_unlock_irqrestore(&rsp->onofflock, flags); | |
923 | return; | |
924 | } | |
925 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_list; | |
926 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_tail; | |
927 | rdp->qlen += rsp->orphan_qlen; | |
928 | rsp->orphan_cbs_list = NULL; | |
929 | rsp->orphan_cbs_tail = &rsp->orphan_cbs_list; | |
930 | rsp->orphan_qlen = 0; | |
931 | spin_unlock_irqrestore(&rsp->onofflock, flags); | |
932 | } | |
933 | ||
64db4cff PM |
934 | /* |
935 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy | |
936 | * and move all callbacks from the outgoing CPU to the current one. | |
937 | */ | |
938 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) | |
939 | { | |
64db4cff | 940 | unsigned long flags; |
64db4cff | 941 | unsigned long mask; |
b668c9cf | 942 | int need_quiet = 0; |
64db4cff | 943 | struct rcu_data *rdp = rsp->rda[cpu]; |
64db4cff PM |
944 | struct rcu_node *rnp; |
945 | ||
946 | /* Exclude any attempts to start a new grace period. */ | |
947 | spin_lock_irqsave(&rsp->onofflock, flags); | |
948 | ||
949 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ | |
28ecd580 | 950 | rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
64db4cff PM |
951 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
952 | do { | |
953 | spin_lock(&rnp->lock); /* irqs already disabled. */ | |
954 | rnp->qsmaskinit &= ~mask; | |
955 | if (rnp->qsmaskinit != 0) { | |
b668c9cf PM |
956 | if (rnp != rdp->mynode) |
957 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
64db4cff PM |
958 | break; |
959 | } | |
b668c9cf PM |
960 | if (rnp == rdp->mynode) |
961 | need_quiet = rcu_preempt_offline_tasks(rsp, rnp, rdp); | |
962 | else | |
963 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
64db4cff | 964 | mask = rnp->grpmask; |
64db4cff PM |
965 | rnp = rnp->parent; |
966 | } while (rnp != NULL); | |
64db4cff | 967 | |
b668c9cf PM |
968 | /* |
969 | * We still hold the leaf rcu_node structure lock here, and | |
970 | * irqs are still disabled. The reason for this subterfuge is | |
971 | * because invoking task_quiet() with ->onofflock held leads | |
972 | * to deadlock. | |
973 | */ | |
974 | spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ | |
975 | rnp = rdp->mynode; | |
976 | if (need_quiet) | |
977 | task_quiet(rnp, flags); | |
978 | else | |
979 | spin_unlock_irqrestore(&rnp->lock, flags); | |
64db4cff | 980 | |
e74f4c45 | 981 | rcu_adopt_orphan_cbs(rsp); |
64db4cff PM |
982 | } |
983 | ||
984 | /* | |
985 | * Remove the specified CPU from the RCU hierarchy and move any pending | |
986 | * callbacks that it might have to the current CPU. This code assumes | |
987 | * that at least one CPU in the system will remain running at all times. | |
988 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. | |
989 | */ | |
990 | static void rcu_offline_cpu(int cpu) | |
991 | { | |
d6714c22 | 992 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
64db4cff | 993 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
33f76148 | 994 | rcu_preempt_offline_cpu(cpu); |
64db4cff PM |
995 | } |
996 | ||
997 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
998 | ||
e74f4c45 PM |
999 | static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
1000 | { | |
1001 | } | |
1002 | ||
1003 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) | |
1004 | { | |
1005 | } | |
1006 | ||
64db4cff PM |
1007 | static void rcu_offline_cpu(int cpu) |
1008 | { | |
1009 | } | |
1010 | ||
1011 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
1012 | ||
1013 | /* | |
1014 | * Invoke any RCU callbacks that have made it to the end of their grace | |
1015 | * period. Thottle as specified by rdp->blimit. | |
1016 | */ | |
37c72e56 | 1017 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1018 | { |
1019 | unsigned long flags; | |
1020 | struct rcu_head *next, *list, **tail; | |
1021 | int count; | |
1022 | ||
1023 | /* If no callbacks are ready, just return.*/ | |
1024 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) | |
1025 | return; | |
1026 | ||
1027 | /* | |
1028 | * Extract the list of ready callbacks, disabling to prevent | |
1029 | * races with call_rcu() from interrupt handlers. | |
1030 | */ | |
1031 | local_irq_save(flags); | |
1032 | list = rdp->nxtlist; | |
1033 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
1034 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
1035 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
1036 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) | |
1037 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) | |
1038 | rdp->nxttail[count] = &rdp->nxtlist; | |
1039 | local_irq_restore(flags); | |
1040 | ||
1041 | /* Invoke callbacks. */ | |
1042 | count = 0; | |
1043 | while (list) { | |
1044 | next = list->next; | |
1045 | prefetch(next); | |
1046 | list->func(list); | |
1047 | list = next; | |
1048 | if (++count >= rdp->blimit) | |
1049 | break; | |
1050 | } | |
1051 | ||
1052 | local_irq_save(flags); | |
1053 | ||
1054 | /* Update count, and requeue any remaining callbacks. */ | |
1055 | rdp->qlen -= count; | |
1056 | if (list != NULL) { | |
1057 | *tail = rdp->nxtlist; | |
1058 | rdp->nxtlist = list; | |
1059 | for (count = 0; count < RCU_NEXT_SIZE; count++) | |
1060 | if (&rdp->nxtlist == rdp->nxttail[count]) | |
1061 | rdp->nxttail[count] = tail; | |
1062 | else | |
1063 | break; | |
1064 | } | |
1065 | ||
1066 | /* Reinstate batch limit if we have worked down the excess. */ | |
1067 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
1068 | rdp->blimit = blimit; | |
1069 | ||
37c72e56 PM |
1070 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1071 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
1072 | rdp->qlen_last_fqs_check = 0; | |
1073 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1074 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
1075 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1076 | ||
64db4cff PM |
1077 | local_irq_restore(flags); |
1078 | ||
1079 | /* Re-raise the RCU softirq if there are callbacks remaining. */ | |
1080 | if (cpu_has_callbacks_ready_to_invoke(rdp)) | |
1081 | raise_softirq(RCU_SOFTIRQ); | |
1082 | } | |
1083 | ||
1084 | /* | |
1085 | * Check to see if this CPU is in a non-context-switch quiescent state | |
1086 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
1087 | * Also schedule the RCU softirq handler. | |
1088 | * | |
1089 | * This function must be called with hardirqs disabled. It is normally | |
1090 | * invoked from the scheduling-clock interrupt. If rcu_pending returns | |
1091 | * false, there is no point in invoking rcu_check_callbacks(). | |
1092 | */ | |
1093 | void rcu_check_callbacks(int cpu, int user) | |
1094 | { | |
a157229c PM |
1095 | if (!rcu_pending(cpu)) |
1096 | return; /* if nothing for RCU to do. */ | |
64db4cff | 1097 | if (user || |
a6826048 PM |
1098 | (idle_cpu(cpu) && rcu_scheduler_active && |
1099 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
64db4cff PM |
1100 | |
1101 | /* | |
1102 | * Get here if this CPU took its interrupt from user | |
1103 | * mode or from the idle loop, and if this is not a | |
1104 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1105 | * a quiescent state, so note it. |
64db4cff PM |
1106 | * |
1107 | * No memory barrier is required here because both | |
d6714c22 PM |
1108 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1109 | * variables that other CPUs neither access nor modify, | |
1110 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1111 | */ |
1112 | ||
d6714c22 PM |
1113 | rcu_sched_qs(cpu); |
1114 | rcu_bh_qs(cpu); | |
64db4cff PM |
1115 | |
1116 | } else if (!in_softirq()) { | |
1117 | ||
1118 | /* | |
1119 | * Get here if this CPU did not take its interrupt from | |
1120 | * softirq, in other words, if it is not interrupting | |
1121 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1122 | * critical section, so note it. |
64db4cff PM |
1123 | */ |
1124 | ||
d6714c22 | 1125 | rcu_bh_qs(cpu); |
64db4cff | 1126 | } |
f41d911f | 1127 | rcu_preempt_check_callbacks(cpu); |
64db4cff PM |
1128 | raise_softirq(RCU_SOFTIRQ); |
1129 | } | |
1130 | ||
1131 | #ifdef CONFIG_SMP | |
1132 | ||
1133 | /* | |
1134 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1135 | * have not yet encountered a quiescent state, using the function specified. | |
1136 | * Returns 1 if the current grace period ends while scanning (possibly | |
1137 | * because we made it end). | |
1138 | */ | |
1139 | static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp, | |
1140 | int (*f)(struct rcu_data *)) | |
1141 | { | |
1142 | unsigned long bit; | |
1143 | int cpu; | |
1144 | unsigned long flags; | |
1145 | unsigned long mask; | |
a0b6c9a7 | 1146 | struct rcu_node *rnp; |
64db4cff | 1147 | |
a0b6c9a7 | 1148 | rcu_for_each_leaf_node(rsp, rnp) { |
64db4cff | 1149 | mask = 0; |
a0b6c9a7 | 1150 | spin_lock_irqsave(&rnp->lock, flags); |
560d4bc0 | 1151 | if (rnp->completed != lastcomp) { |
a0b6c9a7 | 1152 | spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1153 | return 1; |
1154 | } | |
a0b6c9a7 PM |
1155 | if (rnp->qsmask == 0) { |
1156 | spin_unlock_irqrestore(&rnp->lock, flags); | |
64db4cff PM |
1157 | continue; |
1158 | } | |
a0b6c9a7 | 1159 | cpu = rnp->grplo; |
64db4cff | 1160 | bit = 1; |
a0b6c9a7 PM |
1161 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
1162 | if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu])) | |
64db4cff PM |
1163 | mask |= bit; |
1164 | } | |
560d4bc0 | 1165 | if (mask != 0 && rnp->completed == lastcomp) { |
64db4cff | 1166 | |
a0b6c9a7 PM |
1167 | /* cpu_quiet_msk() releases rnp->lock. */ |
1168 | cpu_quiet_msk(mask, rsp, rnp, flags); | |
64db4cff PM |
1169 | continue; |
1170 | } | |
a0b6c9a7 | 1171 | spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1172 | } |
1173 | return 0; | |
1174 | } | |
1175 | ||
1176 | /* | |
1177 | * Force quiescent states on reluctant CPUs, and also detect which | |
1178 | * CPUs are in dyntick-idle mode. | |
1179 | */ | |
1180 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1181 | { | |
1182 | unsigned long flags; | |
1183 | long lastcomp; | |
64db4cff PM |
1184 | struct rcu_node *rnp = rcu_get_root(rsp); |
1185 | u8 signaled; | |
281d150c | 1186 | u8 forcenow; |
64db4cff | 1187 | |
fc2219d4 | 1188 | if (!rcu_gp_in_progress(rsp)) |
64db4cff PM |
1189 | return; /* No grace period in progress, nothing to force. */ |
1190 | if (!spin_trylock_irqsave(&rsp->fqslock, flags)) { | |
1191 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ | |
1192 | return; /* Someone else is already on the job. */ | |
1193 | } | |
1194 | if (relaxed && | |
ef631b0c | 1195 | (long)(rsp->jiffies_force_qs - jiffies) >= 0) |
64db4cff PM |
1196 | goto unlock_ret; /* no emergency and done recently. */ |
1197 | rsp->n_force_qs++; | |
1198 | spin_lock(&rnp->lock); | |
8e9aa8f0 | 1199 | lastcomp = rsp->gpnum - 1; |
64db4cff PM |
1200 | signaled = rsp->signaled; |
1201 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
560d4bc0 | 1202 | if(!rcu_gp_in_progress(rsp)) { |
64db4cff PM |
1203 | rsp->n_force_qs_ngp++; |
1204 | spin_unlock(&rnp->lock); | |
1205 | goto unlock_ret; /* no GP in progress, time updated. */ | |
1206 | } | |
1207 | spin_unlock(&rnp->lock); | |
1208 | switch (signaled) { | |
83f5b01f | 1209 | case RCU_GP_IDLE: |
64db4cff PM |
1210 | case RCU_GP_INIT: |
1211 | ||
83f5b01f | 1212 | break; /* grace period idle or initializing, ignore. */ |
64db4cff PM |
1213 | |
1214 | case RCU_SAVE_DYNTICK: | |
1215 | ||
1216 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) | |
1217 | break; /* So gcc recognizes the dead code. */ | |
1218 | ||
1219 | /* Record dyntick-idle state. */ | |
1220 | if (rcu_process_dyntick(rsp, lastcomp, | |
1221 | dyntick_save_progress_counter)) | |
1222 | goto unlock_ret; | |
281d150c PM |
1223 | /* fall into next case. */ |
1224 | ||
1225 | case RCU_SAVE_COMPLETED: | |
64db4cff PM |
1226 | |
1227 | /* Update state, record completion counter. */ | |
281d150c | 1228 | forcenow = 0; |
64db4cff | 1229 | spin_lock(&rnp->lock); |
560d4bc0 PM |
1230 | if (lastcomp + 1 == rsp->gpnum && |
1231 | lastcomp == rsp->completed && | |
281d150c | 1232 | rsp->signaled == signaled) { |
64db4cff | 1233 | rsp->signaled = RCU_FORCE_QS; |
8e9aa8f0 | 1234 | rsp->completed_fqs = lastcomp; |
281d150c | 1235 | forcenow = signaled == RCU_SAVE_COMPLETED; |
64db4cff PM |
1236 | } |
1237 | spin_unlock(&rnp->lock); | |
281d150c PM |
1238 | if (!forcenow) |
1239 | break; | |
1240 | /* fall into next case. */ | |
64db4cff PM |
1241 | |
1242 | case RCU_FORCE_QS: | |
1243 | ||
1244 | /* Check dyntick-idle state, send IPI to laggarts. */ | |
8e9aa8f0 | 1245 | if (rcu_process_dyntick(rsp, rsp->completed_fqs, |
64db4cff PM |
1246 | rcu_implicit_dynticks_qs)) |
1247 | goto unlock_ret; | |
1248 | ||
1249 | /* Leave state in case more forcing is required. */ | |
1250 | ||
1251 | break; | |
1252 | } | |
1253 | unlock_ret: | |
1254 | spin_unlock_irqrestore(&rsp->fqslock, flags); | |
1255 | } | |
1256 | ||
1257 | #else /* #ifdef CONFIG_SMP */ | |
1258 | ||
1259 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1260 | { | |
1261 | set_need_resched(); | |
1262 | } | |
1263 | ||
1264 | #endif /* #else #ifdef CONFIG_SMP */ | |
1265 | ||
1266 | /* | |
1267 | * This does the RCU processing work from softirq context for the | |
1268 | * specified rcu_state and rcu_data structures. This may be called | |
1269 | * only from the CPU to whom the rdp belongs. | |
1270 | */ | |
1271 | static void | |
1272 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) | |
1273 | { | |
1274 | unsigned long flags; | |
1275 | ||
2e597558 PM |
1276 | WARN_ON_ONCE(rdp->beenonline == 0); |
1277 | ||
64db4cff PM |
1278 | /* |
1279 | * If an RCU GP has gone long enough, go check for dyntick | |
1280 | * idle CPUs and, if needed, send resched IPIs. | |
1281 | */ | |
ef631b0c | 1282 | if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
64db4cff PM |
1283 | force_quiescent_state(rsp, 1); |
1284 | ||
1285 | /* | |
1286 | * Advance callbacks in response to end of earlier grace | |
1287 | * period that some other CPU ended. | |
1288 | */ | |
1289 | rcu_process_gp_end(rsp, rdp); | |
1290 | ||
1291 | /* Update RCU state based on any recent quiescent states. */ | |
1292 | rcu_check_quiescent_state(rsp, rdp); | |
1293 | ||
1294 | /* Does this CPU require a not-yet-started grace period? */ | |
1295 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1296 | spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); | |
1297 | rcu_start_gp(rsp, flags); /* releases above lock */ | |
1298 | } | |
1299 | ||
1300 | /* If there are callbacks ready, invoke them. */ | |
37c72e56 | 1301 | rcu_do_batch(rsp, rdp); |
64db4cff PM |
1302 | } |
1303 | ||
1304 | /* | |
1305 | * Do softirq processing for the current CPU. | |
1306 | */ | |
1307 | static void rcu_process_callbacks(struct softirq_action *unused) | |
1308 | { | |
1309 | /* | |
1310 | * Memory references from any prior RCU read-side critical sections | |
1311 | * executed by the interrupted code must be seen before any RCU | |
1312 | * grace-period manipulations below. | |
1313 | */ | |
1314 | smp_mb(); /* See above block comment. */ | |
1315 | ||
d6714c22 PM |
1316 | __rcu_process_callbacks(&rcu_sched_state, |
1317 | &__get_cpu_var(rcu_sched_data)); | |
64db4cff | 1318 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
f41d911f | 1319 | rcu_preempt_process_callbacks(); |
64db4cff PM |
1320 | |
1321 | /* | |
1322 | * Memory references from any later RCU read-side critical sections | |
1323 | * executed by the interrupted code must be seen after any RCU | |
1324 | * grace-period manipulations above. | |
1325 | */ | |
1326 | smp_mb(); /* See above block comment. */ | |
1327 | } | |
1328 | ||
1329 | static void | |
1330 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
1331 | struct rcu_state *rsp) | |
1332 | { | |
1333 | unsigned long flags; | |
1334 | struct rcu_data *rdp; | |
1335 | ||
1336 | head->func = func; | |
1337 | head->next = NULL; | |
1338 | ||
1339 | smp_mb(); /* Ensure RCU update seen before callback registry. */ | |
1340 | ||
1341 | /* | |
1342 | * Opportunistically note grace-period endings and beginnings. | |
1343 | * Note that we might see a beginning right after we see an | |
1344 | * end, but never vice versa, since this CPU has to pass through | |
1345 | * a quiescent state betweentimes. | |
1346 | */ | |
1347 | local_irq_save(flags); | |
1348 | rdp = rsp->rda[smp_processor_id()]; | |
1349 | rcu_process_gp_end(rsp, rdp); | |
1350 | check_for_new_grace_period(rsp, rdp); | |
1351 | ||
1352 | /* Add the callback to our list. */ | |
1353 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
1354 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
1355 | ||
1356 | /* Start a new grace period if one not already started. */ | |
fc2219d4 | 1357 | if (!rcu_gp_in_progress(rsp)) { |
64db4cff PM |
1358 | unsigned long nestflag; |
1359 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
1360 | ||
1361 | spin_lock_irqsave(&rnp_root->lock, nestflag); | |
1362 | rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */ | |
1363 | } | |
1364 | ||
37c72e56 PM |
1365 | /* |
1366 | * Force the grace period if too many callbacks or too long waiting. | |
1367 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
1368 | * if some other CPU has recently done so. Also, don't bother | |
1369 | * invoking force_quiescent_state() if the newly enqueued callback | |
1370 | * is the only one waiting for a grace period to complete. | |
1371 | */ | |
1372 | if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { | |
64db4cff | 1373 | rdp->blimit = LONG_MAX; |
37c72e56 PM |
1374 | if (rsp->n_force_qs == rdp->n_force_qs_snap && |
1375 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
1376 | force_quiescent_state(rsp, 0); | |
1377 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1378 | rdp->qlen_last_fqs_check = rdp->qlen; | |
ef631b0c | 1379 | } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
64db4cff PM |
1380 | force_quiescent_state(rsp, 1); |
1381 | local_irq_restore(flags); | |
1382 | } | |
1383 | ||
1384 | /* | |
d6714c22 | 1385 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 1386 | */ |
d6714c22 | 1387 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 1388 | { |
d6714c22 | 1389 | __call_rcu(head, func, &rcu_sched_state); |
64db4cff | 1390 | } |
d6714c22 | 1391 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
1392 | |
1393 | /* | |
1394 | * Queue an RCU for invocation after a quicker grace period. | |
1395 | */ | |
1396 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1397 | { | |
1398 | __call_rcu(head, func, &rcu_bh_state); | |
1399 | } | |
1400 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
1401 | ||
6ebb237b PM |
1402 | /** |
1403 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
1404 | * | |
1405 | * Control will return to the caller some time after a full rcu-sched | |
1406 | * grace period has elapsed, in other words after all currently executing | |
1407 | * rcu-sched read-side critical sections have completed. These read-side | |
1408 | * critical sections are delimited by rcu_read_lock_sched() and | |
1409 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
1410 | * local_irq_disable(), and so on may be used in place of | |
1411 | * rcu_read_lock_sched(). | |
1412 | * | |
1413 | * This means that all preempt_disable code sequences, including NMI and | |
1414 | * hardware-interrupt handlers, in progress on entry will have completed | |
1415 | * before this primitive returns. However, this does not guarantee that | |
1416 | * softirq handlers will have completed, since in some kernels, these | |
1417 | * handlers can run in process context, and can block. | |
1418 | * | |
1419 | * This primitive provides the guarantees made by the (now removed) | |
1420 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
1421 | * guarantees that rcu_read_lock() sections will have completed. | |
1422 | * In "classic RCU", these two guarantees happen to be one and | |
1423 | * the same, but can differ in realtime RCU implementations. | |
1424 | */ | |
1425 | void synchronize_sched(void) | |
1426 | { | |
1427 | struct rcu_synchronize rcu; | |
1428 | ||
1429 | if (rcu_blocking_is_gp()) | |
1430 | return; | |
1431 | ||
1432 | init_completion(&rcu.completion); | |
1433 | /* Will wake me after RCU finished. */ | |
1434 | call_rcu_sched(&rcu.head, wakeme_after_rcu); | |
1435 | /* Wait for it. */ | |
1436 | wait_for_completion(&rcu.completion); | |
1437 | } | |
1438 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
1439 | ||
1440 | /** | |
1441 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
1442 | * | |
1443 | * Control will return to the caller some time after a full rcu_bh grace | |
1444 | * period has elapsed, in other words after all currently executing rcu_bh | |
1445 | * read-side critical sections have completed. RCU read-side critical | |
1446 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
1447 | * and may be nested. | |
1448 | */ | |
1449 | void synchronize_rcu_bh(void) | |
1450 | { | |
1451 | struct rcu_synchronize rcu; | |
1452 | ||
1453 | if (rcu_blocking_is_gp()) | |
1454 | return; | |
1455 | ||
1456 | init_completion(&rcu.completion); | |
1457 | /* Will wake me after RCU finished. */ | |
1458 | call_rcu_bh(&rcu.head, wakeme_after_rcu); | |
1459 | /* Wait for it. */ | |
1460 | wait_for_completion(&rcu.completion); | |
1461 | } | |
1462 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
1463 | ||
64db4cff PM |
1464 | /* |
1465 | * Check to see if there is any immediate RCU-related work to be done | |
1466 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
1467 | * The checks are in order of increasing expense: checks that can be | |
1468 | * carried out against CPU-local state are performed first. However, | |
1469 | * we must check for CPU stalls first, else we might not get a chance. | |
1470 | */ | |
1471 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
1472 | { | |
2f51f988 PM |
1473 | struct rcu_node *rnp = rdp->mynode; |
1474 | ||
64db4cff PM |
1475 | rdp->n_rcu_pending++; |
1476 | ||
1477 | /* Check for CPU stalls, if enabled. */ | |
1478 | check_cpu_stall(rsp, rdp); | |
1479 | ||
1480 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
7ba5c840 PM |
1481 | if (rdp->qs_pending) { |
1482 | rdp->n_rp_qs_pending++; | |
64db4cff | 1483 | return 1; |
7ba5c840 | 1484 | } |
64db4cff PM |
1485 | |
1486 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
1487 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
1488 | rdp->n_rp_cb_ready++; | |
64db4cff | 1489 | return 1; |
7ba5c840 | 1490 | } |
64db4cff PM |
1491 | |
1492 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
1493 | if (cpu_needs_another_gp(rsp, rdp)) { |
1494 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 1495 | return 1; |
7ba5c840 | 1496 | } |
64db4cff PM |
1497 | |
1498 | /* Has another RCU grace period completed? */ | |
2f51f988 | 1499 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 1500 | rdp->n_rp_gp_completed++; |
64db4cff | 1501 | return 1; |
7ba5c840 | 1502 | } |
64db4cff PM |
1503 | |
1504 | /* Has a new RCU grace period started? */ | |
2f51f988 | 1505 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 1506 | rdp->n_rp_gp_started++; |
64db4cff | 1507 | return 1; |
7ba5c840 | 1508 | } |
64db4cff PM |
1509 | |
1510 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ | |
fc2219d4 | 1511 | if (rcu_gp_in_progress(rsp) && |
7ba5c840 PM |
1512 | ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) { |
1513 | rdp->n_rp_need_fqs++; | |
64db4cff | 1514 | return 1; |
7ba5c840 | 1515 | } |
64db4cff PM |
1516 | |
1517 | /* nothing to do */ | |
7ba5c840 | 1518 | rdp->n_rp_need_nothing++; |
64db4cff PM |
1519 | return 0; |
1520 | } | |
1521 | ||
1522 | /* | |
1523 | * Check to see if there is any immediate RCU-related work to be done | |
1524 | * by the current CPU, returning 1 if so. This function is part of the | |
1525 | * RCU implementation; it is -not- an exported member of the RCU API. | |
1526 | */ | |
a157229c | 1527 | static int rcu_pending(int cpu) |
64db4cff | 1528 | { |
d6714c22 | 1529 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
f41d911f PM |
1530 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
1531 | rcu_preempt_pending(cpu); | |
64db4cff PM |
1532 | } |
1533 | ||
1534 | /* | |
1535 | * Check to see if any future RCU-related work will need to be done | |
1536 | * by the current CPU, even if none need be done immediately, returning | |
1537 | * 1 if so. This function is part of the RCU implementation; it is -not- | |
1538 | * an exported member of the RCU API. | |
1539 | */ | |
1540 | int rcu_needs_cpu(int cpu) | |
1541 | { | |
1542 | /* RCU callbacks either ready or pending? */ | |
d6714c22 | 1543 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
f41d911f PM |
1544 | per_cpu(rcu_bh_data, cpu).nxtlist || |
1545 | rcu_preempt_needs_cpu(cpu); | |
64db4cff PM |
1546 | } |
1547 | ||
6ebb237b PM |
1548 | /* |
1549 | * This function is invoked towards the end of the scheduler's initialization | |
1550 | * process. Before this is called, the idle task might contain | |
1551 | * RCU read-side critical sections (during which time, this idle | |
1552 | * task is booting the system). After this function is called, the | |
1553 | * idle tasks are prohibited from containing RCU read-side critical | |
1554 | * sections. | |
1555 | */ | |
1556 | void rcu_scheduler_starting(void) | |
1557 | { | |
1558 | WARN_ON(num_online_cpus() != 1); | |
1559 | WARN_ON(nr_context_switches() > 0); | |
1560 | rcu_scheduler_active = 1; | |
1561 | } | |
1562 | ||
d0ec774c PM |
1563 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
1564 | static atomic_t rcu_barrier_cpu_count; | |
1565 | static DEFINE_MUTEX(rcu_barrier_mutex); | |
1566 | static struct completion rcu_barrier_completion; | |
d0ec774c PM |
1567 | |
1568 | static void rcu_barrier_callback(struct rcu_head *notused) | |
1569 | { | |
1570 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
1571 | complete(&rcu_barrier_completion); | |
1572 | } | |
1573 | ||
1574 | /* | |
1575 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
1576 | */ | |
1577 | static void rcu_barrier_func(void *type) | |
1578 | { | |
1579 | int cpu = smp_processor_id(); | |
1580 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); | |
1581 | void (*call_rcu_func)(struct rcu_head *head, | |
1582 | void (*func)(struct rcu_head *head)); | |
1583 | ||
1584 | atomic_inc(&rcu_barrier_cpu_count); | |
1585 | call_rcu_func = type; | |
1586 | call_rcu_func(head, rcu_barrier_callback); | |
1587 | } | |
1588 | ||
d0ec774c PM |
1589 | /* |
1590 | * Orchestrate the specified type of RCU barrier, waiting for all | |
1591 | * RCU callbacks of the specified type to complete. | |
1592 | */ | |
e74f4c45 PM |
1593 | static void _rcu_barrier(struct rcu_state *rsp, |
1594 | void (*call_rcu_func)(struct rcu_head *head, | |
d0ec774c PM |
1595 | void (*func)(struct rcu_head *head))) |
1596 | { | |
1597 | BUG_ON(in_interrupt()); | |
e74f4c45 | 1598 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
d0ec774c PM |
1599 | mutex_lock(&rcu_barrier_mutex); |
1600 | init_completion(&rcu_barrier_completion); | |
1601 | /* | |
1602 | * Initialize rcu_barrier_cpu_count to 1, then invoke | |
1603 | * rcu_barrier_func() on each CPU, so that each CPU also has | |
1604 | * incremented rcu_barrier_cpu_count. Only then is it safe to | |
1605 | * decrement rcu_barrier_cpu_count -- otherwise the first CPU | |
1606 | * might complete its grace period before all of the other CPUs | |
1607 | * did their increment, causing this function to return too | |
1608 | * early. | |
1609 | */ | |
1610 | atomic_set(&rcu_barrier_cpu_count, 1); | |
e74f4c45 PM |
1611 | preempt_disable(); /* stop CPU_DYING from filling orphan_cbs_list */ |
1612 | rcu_adopt_orphan_cbs(rsp); | |
d0ec774c | 1613 | on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); |
e74f4c45 | 1614 | preempt_enable(); /* CPU_DYING can again fill orphan_cbs_list */ |
d0ec774c PM |
1615 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
1616 | complete(&rcu_barrier_completion); | |
1617 | wait_for_completion(&rcu_barrier_completion); | |
1618 | mutex_unlock(&rcu_barrier_mutex); | |
d0ec774c | 1619 | } |
d0ec774c PM |
1620 | |
1621 | /** | |
1622 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
1623 | */ | |
1624 | void rcu_barrier_bh(void) | |
1625 | { | |
e74f4c45 | 1626 | _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
d0ec774c PM |
1627 | } |
1628 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
1629 | ||
1630 | /** | |
1631 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
1632 | */ | |
1633 | void rcu_barrier_sched(void) | |
1634 | { | |
e74f4c45 | 1635 | _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
d0ec774c PM |
1636 | } |
1637 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
1638 | ||
64db4cff | 1639 | /* |
27569620 | 1640 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 1641 | */ |
27569620 PM |
1642 | static void __init |
1643 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
1644 | { |
1645 | unsigned long flags; | |
1646 | int i; | |
27569620 PM |
1647 | struct rcu_data *rdp = rsp->rda[cpu]; |
1648 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1649 | ||
1650 | /* Set up local state, ensuring consistent view of global state. */ | |
1651 | spin_lock_irqsave(&rnp->lock, flags); | |
1652 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); | |
1653 | rdp->nxtlist = NULL; | |
1654 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1655 | rdp->nxttail[i] = &rdp->nxtlist; | |
1656 | rdp->qlen = 0; | |
1657 | #ifdef CONFIG_NO_HZ | |
1658 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); | |
1659 | #endif /* #ifdef CONFIG_NO_HZ */ | |
1660 | rdp->cpu = cpu; | |
1661 | spin_unlock_irqrestore(&rnp->lock, flags); | |
1662 | } | |
1663 | ||
1664 | /* | |
1665 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
1666 | * offline event can be happening at a given time. Note also that we | |
1667 | * can accept some slop in the rsp->completed access due to the fact | |
1668 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 1669 | */ |
e4fa4c97 | 1670 | static void __cpuinit |
f41d911f | 1671 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
64db4cff PM |
1672 | { |
1673 | unsigned long flags; | |
64db4cff PM |
1674 | unsigned long mask; |
1675 | struct rcu_data *rdp = rsp->rda[cpu]; | |
1676 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1677 | ||
1678 | /* Set up local state, ensuring consistent view of global state. */ | |
1679 | spin_lock_irqsave(&rnp->lock, flags); | |
64db4cff PM |
1680 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
1681 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ | |
1682 | rdp->beenonline = 1; /* We have now been online. */ | |
f41d911f | 1683 | rdp->preemptable = preemptable; |
37c72e56 PM |
1684 | rdp->qlen_last_fqs_check = 0; |
1685 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 1686 | rdp->blimit = blimit; |
64db4cff PM |
1687 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
1688 | ||
1689 | /* | |
1690 | * A new grace period might start here. If so, we won't be part | |
1691 | * of it, but that is OK, as we are currently in a quiescent state. | |
1692 | */ | |
1693 | ||
1694 | /* Exclude any attempts to start a new GP on large systems. */ | |
1695 | spin_lock(&rsp->onofflock); /* irqs already disabled. */ | |
1696 | ||
1697 | /* Add CPU to rcu_node bitmasks. */ | |
1698 | rnp = rdp->mynode; | |
1699 | mask = rdp->grpmask; | |
1700 | do { | |
1701 | /* Exclude any attempts to start a new GP on small systems. */ | |
1702 | spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1703 | rnp->qsmaskinit |= mask; | |
1704 | mask = rnp->grpmask; | |
d09b62df PM |
1705 | if (rnp == rdp->mynode) { |
1706 | rdp->gpnum = rnp->completed; /* if GP in progress... */ | |
1707 | rdp->completed = rnp->completed; | |
1708 | rdp->passed_quiesc_completed = rnp->completed - 1; | |
1709 | } | |
64db4cff PM |
1710 | spin_unlock(&rnp->lock); /* irqs already disabled. */ |
1711 | rnp = rnp->parent; | |
1712 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
1713 | ||
e7d8842e | 1714 | spin_unlock_irqrestore(&rsp->onofflock, flags); |
64db4cff PM |
1715 | } |
1716 | ||
1717 | static void __cpuinit rcu_online_cpu(int cpu) | |
1718 | { | |
f41d911f PM |
1719 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
1720 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); | |
1721 | rcu_preempt_init_percpu_data(cpu); | |
64db4cff PM |
1722 | } |
1723 | ||
1724 | /* | |
f41d911f | 1725 | * Handle CPU online/offline notification events. |
64db4cff | 1726 | */ |
9f680ab4 PM |
1727 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
1728 | unsigned long action, void *hcpu) | |
64db4cff PM |
1729 | { |
1730 | long cpu = (long)hcpu; | |
1731 | ||
1732 | switch (action) { | |
1733 | case CPU_UP_PREPARE: | |
1734 | case CPU_UP_PREPARE_FROZEN: | |
1735 | rcu_online_cpu(cpu); | |
1736 | break; | |
d0ec774c PM |
1737 | case CPU_DYING: |
1738 | case CPU_DYING_FROZEN: | |
1739 | /* | |
e74f4c45 | 1740 | * preempt_disable() in _rcu_barrier() prevents stop_machine(), |
d0ec774c | 1741 | * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);" |
e74f4c45 PM |
1742 | * returns, all online cpus have queued rcu_barrier_func(). |
1743 | * The dying CPU clears its cpu_online_mask bit and | |
1744 | * moves all of its RCU callbacks to ->orphan_cbs_list | |
1745 | * in the context of stop_machine(), so subsequent calls | |
1746 | * to _rcu_barrier() will adopt these callbacks and only | |
1747 | * then queue rcu_barrier_func() on all remaining CPUs. | |
d0ec774c | 1748 | */ |
e74f4c45 PM |
1749 | rcu_send_cbs_to_orphanage(&rcu_bh_state); |
1750 | rcu_send_cbs_to_orphanage(&rcu_sched_state); | |
1751 | rcu_preempt_send_cbs_to_orphanage(); | |
d0ec774c | 1752 | break; |
64db4cff PM |
1753 | case CPU_DEAD: |
1754 | case CPU_DEAD_FROZEN: | |
1755 | case CPU_UP_CANCELED: | |
1756 | case CPU_UP_CANCELED_FROZEN: | |
1757 | rcu_offline_cpu(cpu); | |
1758 | break; | |
1759 | default: | |
1760 | break; | |
1761 | } | |
1762 | return NOTIFY_OK; | |
1763 | } | |
1764 | ||
1765 | /* | |
1766 | * Compute the per-level fanout, either using the exact fanout specified | |
1767 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
1768 | */ | |
1769 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
1770 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1771 | { | |
1772 | int i; | |
1773 | ||
1774 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) | |
1775 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; | |
1776 | } | |
1777 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1778 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1779 | { | |
1780 | int ccur; | |
1781 | int cprv; | |
1782 | int i; | |
1783 | ||
1784 | cprv = NR_CPUS; | |
1785 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1786 | ccur = rsp->levelcnt[i]; | |
1787 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
1788 | cprv = ccur; | |
1789 | } | |
1790 | } | |
1791 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1792 | ||
1793 | /* | |
1794 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
1795 | */ | |
1796 | static void __init rcu_init_one(struct rcu_state *rsp) | |
1797 | { | |
1798 | int cpustride = 1; | |
1799 | int i; | |
1800 | int j; | |
1801 | struct rcu_node *rnp; | |
1802 | ||
1803 | /* Initialize the level-tracking arrays. */ | |
1804 | ||
1805 | for (i = 1; i < NUM_RCU_LVLS; i++) | |
1806 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; | |
1807 | rcu_init_levelspread(rsp); | |
1808 | ||
1809 | /* Initialize the elements themselves, starting from the leaves. */ | |
1810 | ||
1811 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1812 | cpustride *= rsp->levelspread[i]; | |
1813 | rnp = rsp->level[i]; | |
1814 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
88b91c7c | 1815 | spin_lock_init(&rnp->lock); |
b668c9cf | 1816 | lockdep_set_class(&rnp->lock, &rcu_node_class[i]); |
f41d911f | 1817 | rnp->gpnum = 0; |
64db4cff PM |
1818 | rnp->qsmask = 0; |
1819 | rnp->qsmaskinit = 0; | |
1820 | rnp->grplo = j * cpustride; | |
1821 | rnp->grphi = (j + 1) * cpustride - 1; | |
1822 | if (rnp->grphi >= NR_CPUS) | |
1823 | rnp->grphi = NR_CPUS - 1; | |
1824 | if (i == 0) { | |
1825 | rnp->grpnum = 0; | |
1826 | rnp->grpmask = 0; | |
1827 | rnp->parent = NULL; | |
1828 | } else { | |
1829 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
1830 | rnp->grpmask = 1UL << rnp->grpnum; | |
1831 | rnp->parent = rsp->level[i - 1] + | |
1832 | j / rsp->levelspread[i - 1]; | |
1833 | } | |
1834 | rnp->level = i; | |
f41d911f PM |
1835 | INIT_LIST_HEAD(&rnp->blocked_tasks[0]); |
1836 | INIT_LIST_HEAD(&rnp->blocked_tasks[1]); | |
64db4cff PM |
1837 | } |
1838 | } | |
1839 | } | |
1840 | ||
1841 | /* | |
f41d911f PM |
1842 | * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used |
1843 | * nowhere else! Assigns leaf node pointers into each CPU's rcu_data | |
1844 | * structure. | |
64db4cff | 1845 | */ |
65cf8f86 | 1846 | #define RCU_INIT_FLAVOR(rsp, rcu_data) \ |
64db4cff | 1847 | do { \ |
a0b6c9a7 PM |
1848 | int i; \ |
1849 | int j; \ | |
1850 | struct rcu_node *rnp; \ | |
1851 | \ | |
65cf8f86 | 1852 | rcu_init_one(rsp); \ |
64db4cff PM |
1853 | rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \ |
1854 | j = 0; \ | |
1855 | for_each_possible_cpu(i) { \ | |
1856 | if (i > rnp[j].grphi) \ | |
1857 | j++; \ | |
1858 | per_cpu(rcu_data, i).mynode = &rnp[j]; \ | |
1859 | (rsp)->rda[i] = &per_cpu(rcu_data, i); \ | |
65cf8f86 | 1860 | rcu_boot_init_percpu_data(i, rsp); \ |
64db4cff PM |
1861 | } \ |
1862 | } while (0) | |
1863 | ||
9f680ab4 | 1864 | void __init rcu_init(void) |
64db4cff | 1865 | { |
9f680ab4 PM |
1866 | int i; |
1867 | ||
f41d911f | 1868 | rcu_bootup_announce(); |
64db4cff PM |
1869 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
1870 | printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); | |
1871 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
65cf8f86 PM |
1872 | RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); |
1873 | RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); | |
f41d911f | 1874 | __rcu_init_preempt(); |
2e597558 | 1875 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
1876 | |
1877 | /* | |
1878 | * We don't need protection against CPU-hotplug here because | |
1879 | * this is called early in boot, before either interrupts | |
1880 | * or the scheduler are operational. | |
1881 | */ | |
1882 | cpu_notifier(rcu_cpu_notify, 0); | |
1883 | for_each_online_cpu(i) | |
1884 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)i); | |
64db4cff PM |
1885 | } |
1886 | ||
1eba8f84 | 1887 | #include "rcutree_plugin.h" |