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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> | |
bbad9379 | 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 | |
4300aa64 PM |
57 | #define RCU_STATE_INITIALIZER(structname) { \ |
58 | .level = { &structname.node[0] }, \ | |
64db4cff PM |
59 | .levelcnt = { \ |
60 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ | |
61 | NUM_RCU_LVL_1, \ | |
62 | NUM_RCU_LVL_2, \ | |
cf244dc0 PM |
63 | NUM_RCU_LVL_3, \ |
64 | NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ | |
64db4cff | 65 | }, \ |
83f5b01f | 66 | .signaled = RCU_GP_IDLE, \ |
64db4cff PM |
67 | .gpnum = -300, \ |
68 | .completed = -300, \ | |
4300aa64 | 69 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \ |
4300aa64 | 70 | .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \ |
64db4cff PM |
71 | .n_force_qs = 0, \ |
72 | .n_force_qs_ngp = 0, \ | |
4300aa64 | 73 | .name = #structname, \ |
64db4cff PM |
74 | } |
75 | ||
d6714c22 PM |
76 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
77 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); | |
64db4cff | 78 | |
6258c4fb IM |
79 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
80 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); | |
b1f77b05 | 81 | |
bbad9379 PM |
82 | int rcu_scheduler_active __read_mostly; |
83 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
84 | ||
fc2219d4 PM |
85 | /* |
86 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
87 | * permit this function to be invoked without holding the root rcu_node | |
88 | * structure's ->lock, but of course results can be subject to change. | |
89 | */ | |
90 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
91 | { | |
92 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
93 | } | |
94 | ||
b1f77b05 | 95 | /* |
d6714c22 | 96 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 97 | * how many quiescent states passed, just if there was at least |
d6714c22 | 98 | * one since the start of the grace period, this just sets a flag. |
b1f77b05 | 99 | */ |
d6714c22 | 100 | void rcu_sched_qs(int cpu) |
b1f77b05 | 101 | { |
25502a6c | 102 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
f41d911f | 103 | |
c64ac3ce | 104 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
c3422bea PM |
105 | barrier(); |
106 | rdp->passed_quiesc = 1; | |
b1f77b05 IM |
107 | } |
108 | ||
d6714c22 | 109 | void rcu_bh_qs(int cpu) |
b1f77b05 | 110 | { |
25502a6c | 111 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
f41d911f | 112 | |
c64ac3ce | 113 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
c3422bea PM |
114 | barrier(); |
115 | rdp->passed_quiesc = 1; | |
b1f77b05 | 116 | } |
64db4cff | 117 | |
25502a6c PM |
118 | /* |
119 | * Note a context switch. This is a quiescent state for RCU-sched, | |
120 | * and requires special handling for preemptible RCU. | |
121 | */ | |
122 | void rcu_note_context_switch(int cpu) | |
123 | { | |
124 | rcu_sched_qs(cpu); | |
125 | rcu_preempt_note_context_switch(cpu); | |
126 | } | |
127 | ||
64db4cff | 128 | #ifdef CONFIG_NO_HZ |
90a4d2c0 PM |
129 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
130 | .dynticks_nesting = 1, | |
131 | .dynticks = 1, | |
132 | }; | |
64db4cff PM |
133 | #endif /* #ifdef CONFIG_NO_HZ */ |
134 | ||
135 | static int blimit = 10; /* Maximum callbacks per softirq. */ | |
136 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ | |
137 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
138 | ||
3d76c082 PM |
139 | module_param(blimit, int, 0); |
140 | module_param(qhimark, int, 0); | |
141 | module_param(qlowmark, int, 0); | |
142 | ||
742734ee | 143 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
910b1b7e | 144 | int rcu_cpu_stall_suppress __read_mostly = RCU_CPU_STALL_SUPPRESS_INIT; |
f2e0dd70 | 145 | module_param(rcu_cpu_stall_suppress, int, 0644); |
742734ee PM |
146 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
147 | ||
64db4cff | 148 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
a157229c | 149 | static int rcu_pending(int cpu); |
64db4cff PM |
150 | |
151 | /* | |
d6714c22 | 152 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 153 | */ |
d6714c22 | 154 | long rcu_batches_completed_sched(void) |
64db4cff | 155 | { |
d6714c22 | 156 | return rcu_sched_state.completed; |
64db4cff | 157 | } |
d6714c22 | 158 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
159 | |
160 | /* | |
161 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
162 | */ | |
163 | long rcu_batches_completed_bh(void) | |
164 | { | |
165 | return rcu_bh_state.completed; | |
166 | } | |
167 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
168 | ||
bf66f18e PM |
169 | /* |
170 | * Force a quiescent state for RCU BH. | |
171 | */ | |
172 | void rcu_bh_force_quiescent_state(void) | |
173 | { | |
174 | force_quiescent_state(&rcu_bh_state, 0); | |
175 | } | |
176 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
177 | ||
178 | /* | |
179 | * Force a quiescent state for RCU-sched. | |
180 | */ | |
181 | void rcu_sched_force_quiescent_state(void) | |
182 | { | |
183 | force_quiescent_state(&rcu_sched_state, 0); | |
184 | } | |
185 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
186 | ||
64db4cff PM |
187 | /* |
188 | * Does the CPU have callbacks ready to be invoked? | |
189 | */ | |
190 | static int | |
191 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
192 | { | |
193 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
194 | } | |
195 | ||
196 | /* | |
197 | * Does the current CPU require a yet-as-unscheduled grace period? | |
198 | */ | |
199 | static int | |
200 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
201 | { | |
fc2219d4 | 202 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
64db4cff PM |
203 | } |
204 | ||
205 | /* | |
206 | * Return the root node of the specified rcu_state structure. | |
207 | */ | |
208 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
209 | { | |
210 | return &rsp->node[0]; | |
211 | } | |
212 | ||
213 | #ifdef CONFIG_SMP | |
214 | ||
215 | /* | |
216 | * If the specified CPU is offline, tell the caller that it is in | |
217 | * a quiescent state. Otherwise, whack it with a reschedule IPI. | |
218 | * Grace periods can end up waiting on an offline CPU when that | |
219 | * CPU is in the process of coming online -- it will be added to the | |
220 | * rcu_node bitmasks before it actually makes it online. The same thing | |
221 | * can happen while a CPU is in the process of coming online. Because this | |
222 | * race is quite rare, we check for it after detecting that the grace | |
223 | * period has been delayed rather than checking each and every CPU | |
224 | * each and every time we start a new grace period. | |
225 | */ | |
226 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) | |
227 | { | |
228 | /* | |
229 | * If the CPU is offline, it is in a quiescent state. We can | |
230 | * trust its state not to change because interrupts are disabled. | |
231 | */ | |
232 | if (cpu_is_offline(rdp->cpu)) { | |
233 | rdp->offline_fqs++; | |
234 | return 1; | |
235 | } | |
236 | ||
f41d911f PM |
237 | /* If preemptable RCU, no point in sending reschedule IPI. */ |
238 | if (rdp->preemptable) | |
239 | return 0; | |
240 | ||
64db4cff PM |
241 | /* The CPU is online, so send it a reschedule IPI. */ |
242 | if (rdp->cpu != smp_processor_id()) | |
243 | smp_send_reschedule(rdp->cpu); | |
244 | else | |
245 | set_need_resched(); | |
246 | rdp->resched_ipi++; | |
247 | return 0; | |
248 | } | |
249 | ||
250 | #endif /* #ifdef CONFIG_SMP */ | |
251 | ||
252 | #ifdef CONFIG_NO_HZ | |
64db4cff PM |
253 | |
254 | /** | |
255 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz | |
256 | * | |
257 | * Enter nohz mode, in other words, -leave- the mode in which RCU | |
258 | * read-side critical sections can occur. (Though RCU read-side | |
259 | * critical sections can occur in irq handlers in nohz mode, a possibility | |
260 | * handled by rcu_irq_enter() and rcu_irq_exit()). | |
261 | */ | |
262 | void rcu_enter_nohz(void) | |
263 | { | |
264 | unsigned long flags; | |
265 | struct rcu_dynticks *rdtp; | |
266 | ||
267 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
268 | local_irq_save(flags); | |
269 | rdtp = &__get_cpu_var(rcu_dynticks); | |
270 | rdtp->dynticks++; | |
271 | rdtp->dynticks_nesting--; | |
86848966 | 272 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
64db4cff PM |
273 | local_irq_restore(flags); |
274 | } | |
275 | ||
276 | /* | |
277 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz | |
278 | * | |
279 | * Exit nohz mode, in other words, -enter- the mode in which RCU | |
280 | * read-side critical sections normally occur. | |
281 | */ | |
282 | void rcu_exit_nohz(void) | |
283 | { | |
284 | unsigned long flags; | |
285 | struct rcu_dynticks *rdtp; | |
286 | ||
287 | local_irq_save(flags); | |
288 | rdtp = &__get_cpu_var(rcu_dynticks); | |
289 | rdtp->dynticks++; | |
290 | rdtp->dynticks_nesting++; | |
86848966 | 291 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
64db4cff PM |
292 | local_irq_restore(flags); |
293 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ | |
294 | } | |
295 | ||
296 | /** | |
297 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
298 | * | |
299 | * If the CPU was idle with dynamic ticks active, and there is no | |
300 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
301 | * RCU grace-period handling know that the CPU is active. | |
302 | */ | |
303 | void rcu_nmi_enter(void) | |
304 | { | |
305 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
306 | ||
307 | if (rdtp->dynticks & 0x1) | |
308 | return; | |
309 | rdtp->dynticks_nmi++; | |
86848966 | 310 | WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); |
64db4cff PM |
311 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
312 | } | |
313 | ||
314 | /** | |
315 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
316 | * | |
317 | * If the CPU was idle with dynamic ticks active, and there is no | |
318 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
319 | * RCU grace-period handling know that the CPU is no longer active. | |
320 | */ | |
321 | void rcu_nmi_exit(void) | |
322 | { | |
323 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
324 | ||
325 | if (rdtp->dynticks & 0x1) | |
326 | return; | |
327 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
328 | rdtp->dynticks_nmi++; | |
86848966 | 329 | WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); |
64db4cff PM |
330 | } |
331 | ||
332 | /** | |
333 | * rcu_irq_enter - inform RCU of entry to hard irq context | |
334 | * | |
335 | * If the CPU was idle with dynamic ticks active, this updates the | |
336 | * rdtp->dynticks to let the RCU handling know that the CPU is active. | |
337 | */ | |
338 | void rcu_irq_enter(void) | |
339 | { | |
340 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
341 | ||
342 | if (rdtp->dynticks_nesting++) | |
343 | return; | |
344 | rdtp->dynticks++; | |
86848966 | 345 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
64db4cff PM |
346 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
347 | } | |
348 | ||
349 | /** | |
350 | * rcu_irq_exit - inform RCU of exit from hard irq context | |
351 | * | |
352 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks | |
353 | * to put let the RCU handling be aware that the CPU is going back to idle | |
354 | * with no ticks. | |
355 | */ | |
356 | void rcu_irq_exit(void) | |
357 | { | |
358 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
359 | ||
360 | if (--rdtp->dynticks_nesting) | |
361 | return; | |
362 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
363 | rdtp->dynticks++; | |
86848966 | 364 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
64db4cff PM |
365 | |
366 | /* If the interrupt queued a callback, get out of dyntick mode. */ | |
909ea964 CL |
367 | if (__this_cpu_read(rcu_sched_data.nxtlist) || |
368 | __this_cpu_read(rcu_bh_data.nxtlist)) | |
64db4cff PM |
369 | set_need_resched(); |
370 | } | |
371 | ||
64db4cff PM |
372 | #ifdef CONFIG_SMP |
373 | ||
64db4cff PM |
374 | /* |
375 | * Snapshot the specified CPU's dynticks counter so that we can later | |
376 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 377 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
378 | */ |
379 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
380 | { | |
381 | int ret; | |
382 | int snap; | |
383 | int snap_nmi; | |
384 | ||
385 | snap = rdp->dynticks->dynticks; | |
386 | snap_nmi = rdp->dynticks->dynticks_nmi; | |
387 | smp_mb(); /* Order sampling of snap with end of grace period. */ | |
388 | rdp->dynticks_snap = snap; | |
389 | rdp->dynticks_nmi_snap = snap_nmi; | |
390 | ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); | |
391 | if (ret) | |
392 | rdp->dynticks_fqs++; | |
393 | return ret; | |
394 | } | |
395 | ||
396 | /* | |
397 | * Return true if the specified CPU has passed through a quiescent | |
398 | * state by virtue of being in or having passed through an dynticks | |
399 | * idle state since the last call to dyntick_save_progress_counter() | |
400 | * for this same CPU. | |
401 | */ | |
402 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
403 | { | |
404 | long curr; | |
405 | long curr_nmi; | |
406 | long snap; | |
407 | long snap_nmi; | |
408 | ||
409 | curr = rdp->dynticks->dynticks; | |
410 | snap = rdp->dynticks_snap; | |
411 | curr_nmi = rdp->dynticks->dynticks_nmi; | |
412 | snap_nmi = rdp->dynticks_nmi_snap; | |
413 | smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ | |
414 | ||
415 | /* | |
416 | * If the CPU passed through or entered a dynticks idle phase with | |
417 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
418 | * already acknowledged the request to pass through a quiescent | |
419 | * state. Either way, that CPU cannot possibly be in an RCU | |
420 | * read-side critical section that started before the beginning | |
421 | * of the current RCU grace period. | |
422 | */ | |
423 | if ((curr != snap || (curr & 0x1) == 0) && | |
424 | (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { | |
425 | rdp->dynticks_fqs++; | |
426 | return 1; | |
427 | } | |
428 | ||
429 | /* Go check for the CPU being offline. */ | |
430 | return rcu_implicit_offline_qs(rdp); | |
431 | } | |
432 | ||
433 | #endif /* #ifdef CONFIG_SMP */ | |
434 | ||
435 | #else /* #ifdef CONFIG_NO_HZ */ | |
436 | ||
64db4cff PM |
437 | #ifdef CONFIG_SMP |
438 | ||
64db4cff PM |
439 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
440 | { | |
441 | return 0; | |
442 | } | |
443 | ||
444 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
445 | { | |
446 | return rcu_implicit_offline_qs(rdp); | |
447 | } | |
448 | ||
449 | #endif /* #ifdef CONFIG_SMP */ | |
450 | ||
451 | #endif /* #else #ifdef CONFIG_NO_HZ */ | |
452 | ||
453 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
454 | ||
742734ee | 455 | int rcu_cpu_stall_suppress __read_mostly; |
c68de209 | 456 | |
64db4cff PM |
457 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
458 | { | |
459 | rsp->gp_start = jiffies; | |
460 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; | |
461 | } | |
462 | ||
463 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
464 | { | |
465 | int cpu; | |
466 | long delta; | |
467 | unsigned long flags; | |
468 | struct rcu_node *rnp = rcu_get_root(rsp); | |
64db4cff PM |
469 | |
470 | /* Only let one CPU complain about others per time interval. */ | |
471 | ||
1304afb2 | 472 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 473 | delta = jiffies - rsp->jiffies_stall; |
fc2219d4 | 474 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 475 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
476 | return; |
477 | } | |
478 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
a0b6c9a7 PM |
479 | |
480 | /* | |
481 | * Now rat on any tasks that got kicked up to the root rcu_node | |
482 | * due to CPU offlining. | |
483 | */ | |
484 | rcu_print_task_stall(rnp); | |
1304afb2 | 485 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 486 | |
8cdd32a9 PM |
487 | /* |
488 | * OK, time to rat on our buddy... | |
489 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
490 | * RCU CPU stall warnings. | |
491 | */ | |
4300aa64 PM |
492 | printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {", |
493 | rsp->name); | |
a0b6c9a7 | 494 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 495 | raw_spin_lock_irqsave(&rnp->lock, flags); |
f41d911f | 496 | rcu_print_task_stall(rnp); |
3acd9eb3 | 497 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
a0b6c9a7 | 498 | if (rnp->qsmask == 0) |
64db4cff | 499 | continue; |
a0b6c9a7 PM |
500 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
501 | if (rnp->qsmask & (1UL << cpu)) | |
502 | printk(" %d", rnp->grplo + cpu); | |
64db4cff | 503 | } |
4300aa64 | 504 | printk("} (detected by %d, t=%ld jiffies)\n", |
64db4cff | 505 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
c1dc0b9c IM |
506 | trigger_all_cpu_backtrace(); |
507 | ||
1ed509a2 PM |
508 | /* If so configured, complain about tasks blocking the grace period. */ |
509 | ||
510 | rcu_print_detail_task_stall(rsp); | |
511 | ||
64db4cff PM |
512 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
513 | } | |
514 | ||
515 | static void print_cpu_stall(struct rcu_state *rsp) | |
516 | { | |
517 | unsigned long flags; | |
518 | struct rcu_node *rnp = rcu_get_root(rsp); | |
519 | ||
8cdd32a9 PM |
520 | /* |
521 | * OK, time to rat on ourselves... | |
522 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
523 | * RCU CPU stall warnings. | |
524 | */ | |
4300aa64 PM |
525 | printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n", |
526 | rsp->name, smp_processor_id(), jiffies - rsp->gp_start); | |
c1dc0b9c IM |
527 | trigger_all_cpu_backtrace(); |
528 | ||
1304afb2 | 529 | raw_spin_lock_irqsave(&rnp->lock, flags); |
20133cfc | 530 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
64db4cff PM |
531 | rsp->jiffies_stall = |
532 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
1304afb2 | 533 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 534 | |
64db4cff PM |
535 | set_need_resched(); /* kick ourselves to get things going. */ |
536 | } | |
537 | ||
538 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
539 | { | |
540 | long delta; | |
541 | struct rcu_node *rnp; | |
542 | ||
742734ee | 543 | if (rcu_cpu_stall_suppress) |
c68de209 | 544 | return; |
4ee0a603 | 545 | delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall); |
64db4cff | 546 | rnp = rdp->mynode; |
4ee0a603 | 547 | if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) { |
64db4cff PM |
548 | |
549 | /* We haven't checked in, so go dump stack. */ | |
550 | print_cpu_stall(rsp); | |
551 | ||
fc2219d4 | 552 | } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) { |
64db4cff PM |
553 | |
554 | /* They had two time units to dump stack, so complain. */ | |
555 | print_other_cpu_stall(rsp); | |
556 | } | |
557 | } | |
558 | ||
c68de209 PM |
559 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
560 | { | |
742734ee | 561 | rcu_cpu_stall_suppress = 1; |
c68de209 PM |
562 | return NOTIFY_DONE; |
563 | } | |
564 | ||
53d84e00 PM |
565 | /** |
566 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
567 | * | |
568 | * Set the stall-warning timeout way off into the future, thus preventing | |
569 | * any RCU CPU stall-warning messages from appearing in the current set of | |
570 | * RCU grace periods. | |
571 | * | |
572 | * The caller must disable hard irqs. | |
573 | */ | |
574 | void rcu_cpu_stall_reset(void) | |
575 | { | |
576 | rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2; | |
577 | rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2; | |
578 | rcu_preempt_stall_reset(); | |
579 | } | |
580 | ||
c68de209 PM |
581 | static struct notifier_block rcu_panic_block = { |
582 | .notifier_call = rcu_panic, | |
583 | }; | |
584 | ||
585 | static void __init check_cpu_stall_init(void) | |
586 | { | |
587 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); | |
588 | } | |
589 | ||
64db4cff PM |
590 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
591 | ||
592 | static void record_gp_stall_check_time(struct rcu_state *rsp) | |
593 | { | |
594 | } | |
595 | ||
596 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
597 | { | |
598 | } | |
599 | ||
53d84e00 PM |
600 | void rcu_cpu_stall_reset(void) |
601 | { | |
602 | } | |
603 | ||
c68de209 PM |
604 | static void __init check_cpu_stall_init(void) |
605 | { | |
606 | } | |
607 | ||
64db4cff PM |
608 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
609 | ||
610 | /* | |
611 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
612 | * This is used both when we started the grace period and when we notice | |
9160306e PM |
613 | * that someone else started the grace period. The caller must hold the |
614 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, | |
615 | * and must have irqs disabled. | |
64db4cff | 616 | */ |
9160306e PM |
617 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
618 | { | |
619 | if (rdp->gpnum != rnp->gpnum) { | |
121dfc4b PM |
620 | /* |
621 | * If the current grace period is waiting for this CPU, | |
622 | * set up to detect a quiescent state, otherwise don't | |
623 | * go looking for one. | |
624 | */ | |
9160306e | 625 | rdp->gpnum = rnp->gpnum; |
121dfc4b PM |
626 | if (rnp->qsmask & rdp->grpmask) { |
627 | rdp->qs_pending = 1; | |
628 | rdp->passed_quiesc = 0; | |
629 | } else | |
630 | rdp->qs_pending = 0; | |
9160306e PM |
631 | } |
632 | } | |
633 | ||
64db4cff PM |
634 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
635 | { | |
9160306e PM |
636 | unsigned long flags; |
637 | struct rcu_node *rnp; | |
638 | ||
639 | local_irq_save(flags); | |
640 | rnp = rdp->mynode; | |
641 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ | |
1304afb2 | 642 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
9160306e PM |
643 | local_irq_restore(flags); |
644 | return; | |
645 | } | |
646 | __note_new_gpnum(rsp, rnp, rdp); | |
1304afb2 | 647 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
648 | } |
649 | ||
650 | /* | |
651 | * Did someone else start a new RCU grace period start since we last | |
652 | * checked? Update local state appropriately if so. Must be called | |
653 | * on the CPU corresponding to rdp. | |
654 | */ | |
655 | static int | |
656 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
657 | { | |
658 | unsigned long flags; | |
659 | int ret = 0; | |
660 | ||
661 | local_irq_save(flags); | |
662 | if (rdp->gpnum != rsp->gpnum) { | |
663 | note_new_gpnum(rsp, rdp); | |
664 | ret = 1; | |
665 | } | |
666 | local_irq_restore(flags); | |
667 | return ret; | |
668 | } | |
669 | ||
d09b62df PM |
670 | /* |
671 | * Advance this CPU's callbacks, but only if the current grace period | |
672 | * has ended. This may be called only from the CPU to whom the rdp | |
673 | * belongs. In addition, the corresponding leaf rcu_node structure's | |
674 | * ->lock must be held by the caller, with irqs disabled. | |
675 | */ | |
676 | static void | |
677 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
678 | { | |
679 | /* Did another grace period end? */ | |
680 | if (rdp->completed != rnp->completed) { | |
681 | ||
682 | /* Advance callbacks. No harm if list empty. */ | |
683 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
684 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
685 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
686 | ||
687 | /* Remember that we saw this grace-period completion. */ | |
688 | rdp->completed = rnp->completed; | |
20377f32 | 689 | |
5ff8e6f0 FW |
690 | /* |
691 | * If we were in an extended quiescent state, we may have | |
121dfc4b | 692 | * missed some grace periods that others CPUs handled on |
5ff8e6f0 | 693 | * our behalf. Catch up with this state to avoid noting |
121dfc4b PM |
694 | * spurious new grace periods. If another grace period |
695 | * has started, then rnp->gpnum will have advanced, so | |
696 | * we will detect this later on. | |
5ff8e6f0 | 697 | */ |
121dfc4b | 698 | if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) |
5ff8e6f0 FW |
699 | rdp->gpnum = rdp->completed; |
700 | ||
20377f32 | 701 | /* |
121dfc4b PM |
702 | * If RCU does not need a quiescent state from this CPU, |
703 | * then make sure that this CPU doesn't go looking for one. | |
20377f32 | 704 | */ |
121dfc4b | 705 | if ((rnp->qsmask & rdp->grpmask) == 0) |
20377f32 | 706 | rdp->qs_pending = 0; |
d09b62df PM |
707 | } |
708 | } | |
709 | ||
710 | /* | |
711 | * Advance this CPU's callbacks, but only if the current grace period | |
712 | * has ended. This may be called only from the CPU to whom the rdp | |
713 | * belongs. | |
714 | */ | |
715 | static void | |
716 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
717 | { | |
718 | unsigned long flags; | |
719 | struct rcu_node *rnp; | |
720 | ||
721 | local_irq_save(flags); | |
722 | rnp = rdp->mynode; | |
723 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ | |
1304afb2 | 724 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
d09b62df PM |
725 | local_irq_restore(flags); |
726 | return; | |
727 | } | |
728 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1304afb2 | 729 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d09b62df PM |
730 | } |
731 | ||
732 | /* | |
733 | * Do per-CPU grace-period initialization for running CPU. The caller | |
734 | * must hold the lock of the leaf rcu_node structure corresponding to | |
735 | * this CPU. | |
736 | */ | |
737 | static void | |
738 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
739 | { | |
740 | /* Prior grace period ended, so advance callbacks for current CPU. */ | |
741 | __rcu_process_gp_end(rsp, rnp, rdp); | |
742 | ||
743 | /* | |
744 | * Because this CPU just now started the new grace period, we know | |
745 | * that all of its callbacks will be covered by this upcoming grace | |
746 | * period, even the ones that were registered arbitrarily recently. | |
747 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. | |
748 | * | |
749 | * Other CPUs cannot be sure exactly when the grace period started. | |
750 | * Therefore, their recently registered callbacks must pass through | |
751 | * an additional RCU_NEXT_READY stage, so that they will be handled | |
752 | * by the next RCU grace period. | |
753 | */ | |
754 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
755 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
9160306e PM |
756 | |
757 | /* Set state so that this CPU will detect the next quiescent state. */ | |
758 | __note_new_gpnum(rsp, rnp, rdp); | |
d09b62df PM |
759 | } |
760 | ||
64db4cff PM |
761 | /* |
762 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
763 | * in preparation for detecting the next grace period. The caller must hold | |
764 | * the root node's ->lock, which is released before return. Hard irqs must | |
765 | * be disabled. | |
766 | */ | |
767 | static void | |
768 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
769 | __releases(rcu_get_root(rsp)->lock) | |
770 | { | |
394f99a9 | 771 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
64db4cff | 772 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 773 | |
07079d53 | 774 | if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { |
46a1e34e PM |
775 | if (cpu_needs_another_gp(rsp, rdp)) |
776 | rsp->fqs_need_gp = 1; | |
b32e9eb6 | 777 | if (rnp->completed == rsp->completed) { |
1304afb2 | 778 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b32e9eb6 PM |
779 | return; |
780 | } | |
1304afb2 | 781 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
b32e9eb6 PM |
782 | |
783 | /* | |
784 | * Propagate new ->completed value to rcu_node structures | |
785 | * so that other CPUs don't have to wait until the start | |
786 | * of the next grace period to process their callbacks. | |
787 | */ | |
788 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
1304afb2 | 789 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
b32e9eb6 | 790 | rnp->completed = rsp->completed; |
1304afb2 | 791 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
b32e9eb6 PM |
792 | } |
793 | local_irq_restore(flags); | |
64db4cff PM |
794 | return; |
795 | } | |
796 | ||
797 | /* Advance to a new grace period and initialize state. */ | |
798 | rsp->gpnum++; | |
c3422bea | 799 | WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
64db4cff PM |
800 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
801 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
64db4cff | 802 | record_gp_stall_check_time(rsp); |
64db4cff | 803 | |
64db4cff PM |
804 | /* Special-case the common single-level case. */ |
805 | if (NUM_RCU_NODES == 1) { | |
b0e165c0 | 806 | rcu_preempt_check_blocked_tasks(rnp); |
28ecd580 | 807 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 808 | rnp->gpnum = rsp->gpnum; |
d09b62df | 809 | rnp->completed = rsp->completed; |
c12172c0 | 810 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
d09b62df | 811 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
1304afb2 | 812 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
813 | return; |
814 | } | |
815 | ||
1304afb2 | 816 | raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
64db4cff PM |
817 | |
818 | ||
819 | /* Exclude any concurrent CPU-hotplug operations. */ | |
1304afb2 | 820 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
821 | |
822 | /* | |
b835db1f PM |
823 | * Set the quiescent-state-needed bits in all the rcu_node |
824 | * structures for all currently online CPUs in breadth-first | |
825 | * order, starting from the root rcu_node structure. This | |
826 | * operation relies on the layout of the hierarchy within the | |
827 | * rsp->node[] array. Note that other CPUs will access only | |
828 | * the leaves of the hierarchy, which still indicate that no | |
829 | * grace period is in progress, at least until the corresponding | |
830 | * leaf node has been initialized. In addition, we have excluded | |
831 | * CPU-hotplug operations. | |
64db4cff PM |
832 | * |
833 | * Note that the grace period cannot complete until we finish | |
834 | * the initialization process, as there will be at least one | |
835 | * qsmask bit set in the root node until that time, namely the | |
b835db1f PM |
836 | * one corresponding to this CPU, due to the fact that we have |
837 | * irqs disabled. | |
64db4cff | 838 | */ |
a0b6c9a7 | 839 | rcu_for_each_node_breadth_first(rsp, rnp) { |
1304afb2 | 840 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
b0e165c0 | 841 | rcu_preempt_check_blocked_tasks(rnp); |
49e29126 | 842 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 843 | rnp->gpnum = rsp->gpnum; |
d09b62df PM |
844 | rnp->completed = rsp->completed; |
845 | if (rnp == rdp->mynode) | |
846 | rcu_start_gp_per_cpu(rsp, rnp, rdp); | |
1304afb2 | 847 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
848 | } |
849 | ||
83f5b01f | 850 | rnp = rcu_get_root(rsp); |
1304afb2 | 851 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff | 852 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
1304afb2 PM |
853 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
854 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); | |
64db4cff PM |
855 | } |
856 | ||
f41d911f | 857 | /* |
d3f6bad3 PM |
858 | * Report a full set of quiescent states to the specified rcu_state |
859 | * data structure. This involves cleaning up after the prior grace | |
860 | * period and letting rcu_start_gp() start up the next grace period | |
861 | * if one is needed. Note that the caller must hold rnp->lock, as | |
862 | * required by rcu_start_gp(), which will release it. | |
f41d911f | 863 | */ |
d3f6bad3 | 864 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 865 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 866 | { |
fc2219d4 | 867 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
f41d911f | 868 | rsp->completed = rsp->gpnum; |
83f5b01f | 869 | rsp->signaled = RCU_GP_IDLE; |
f41d911f PM |
870 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
871 | } | |
872 | ||
64db4cff | 873 | /* |
d3f6bad3 PM |
874 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
875 | * Allows quiescent states for a group of CPUs to be reported at one go | |
876 | * to the specified rcu_node structure, though all the CPUs in the group | |
877 | * must be represented by the same rcu_node structure (which need not be | |
878 | * a leaf rcu_node structure, though it often will be). That structure's | |
879 | * lock must be held upon entry, and it is released before return. | |
64db4cff PM |
880 | */ |
881 | static void | |
d3f6bad3 PM |
882 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
883 | struct rcu_node *rnp, unsigned long flags) | |
64db4cff PM |
884 | __releases(rnp->lock) |
885 | { | |
28ecd580 PM |
886 | struct rcu_node *rnp_c; |
887 | ||
64db4cff PM |
888 | /* Walk up the rcu_node hierarchy. */ |
889 | for (;;) { | |
890 | if (!(rnp->qsmask & mask)) { | |
891 | ||
892 | /* Our bit has already been cleared, so done. */ | |
1304afb2 | 893 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
894 | return; |
895 | } | |
896 | rnp->qsmask &= ~mask; | |
f41d911f | 897 | if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { |
64db4cff PM |
898 | |
899 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 900 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
901 | return; |
902 | } | |
903 | mask = rnp->grpmask; | |
904 | if (rnp->parent == NULL) { | |
905 | ||
906 | /* No more levels. Exit loop holding root lock. */ | |
907 | ||
908 | break; | |
909 | } | |
1304afb2 | 910 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 911 | rnp_c = rnp; |
64db4cff | 912 | rnp = rnp->parent; |
1304afb2 | 913 | raw_spin_lock_irqsave(&rnp->lock, flags); |
28ecd580 | 914 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
915 | } |
916 | ||
917 | /* | |
918 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 919 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 920 | * to clean up and start the next grace period if one is needed. |
64db4cff | 921 | */ |
d3f6bad3 | 922 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
923 | } |
924 | ||
925 | /* | |
d3f6bad3 PM |
926 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
927 | * structure. This must be either called from the specified CPU, or | |
928 | * called when the specified CPU is known to be offline (and when it is | |
929 | * also known that no other CPU is concurrently trying to help the offline | |
930 | * CPU). The lastcomp argument is used to make sure we are still in the | |
931 | * grace period of interest. We don't want to end the current grace period | |
932 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
933 | */ |
934 | static void | |
d3f6bad3 | 935 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
64db4cff PM |
936 | { |
937 | unsigned long flags; | |
938 | unsigned long mask; | |
939 | struct rcu_node *rnp; | |
940 | ||
941 | rnp = rdp->mynode; | |
1304afb2 | 942 | raw_spin_lock_irqsave(&rnp->lock, flags); |
560d4bc0 | 943 | if (lastcomp != rnp->completed) { |
64db4cff PM |
944 | |
945 | /* | |
946 | * Someone beat us to it for this grace period, so leave. | |
947 | * The race with GP start is resolved by the fact that we | |
948 | * hold the leaf rcu_node lock, so that the per-CPU bits | |
949 | * cannot yet be initialized -- so we would simply find our | |
d3f6bad3 PM |
950 | * CPU's bit already cleared in rcu_report_qs_rnp() if this |
951 | * race occurred. | |
64db4cff PM |
952 | */ |
953 | rdp->passed_quiesc = 0; /* try again later! */ | |
1304afb2 | 954 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
955 | return; |
956 | } | |
957 | mask = rdp->grpmask; | |
958 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 959 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
960 | } else { |
961 | rdp->qs_pending = 0; | |
962 | ||
963 | /* | |
964 | * This GP can't end until cpu checks in, so all of our | |
965 | * callbacks can be processed during the next GP. | |
966 | */ | |
64db4cff PM |
967 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
968 | ||
d3f6bad3 | 969 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
64db4cff PM |
970 | } |
971 | } | |
972 | ||
973 | /* | |
974 | * Check to see if there is a new grace period of which this CPU | |
975 | * is not yet aware, and if so, set up local rcu_data state for it. | |
976 | * Otherwise, see if this CPU has just passed through its first | |
977 | * quiescent state for this grace period, and record that fact if so. | |
978 | */ | |
979 | static void | |
980 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
981 | { | |
982 | /* If there is now a new grace period, record and return. */ | |
983 | if (check_for_new_grace_period(rsp, rdp)) | |
984 | return; | |
985 | ||
986 | /* | |
987 | * Does this CPU still need to do its part for current grace period? | |
988 | * If no, return and let the other CPUs do their part as well. | |
989 | */ | |
990 | if (!rdp->qs_pending) | |
991 | return; | |
992 | ||
993 | /* | |
994 | * Was there a quiescent state since the beginning of the grace | |
995 | * period? If no, then exit and wait for the next call. | |
996 | */ | |
997 | if (!rdp->passed_quiesc) | |
998 | return; | |
999 | ||
d3f6bad3 PM |
1000 | /* |
1001 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
1002 | * judge of that). | |
1003 | */ | |
1004 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); | |
64db4cff PM |
1005 | } |
1006 | ||
1007 | #ifdef CONFIG_HOTPLUG_CPU | |
1008 | ||
e74f4c45 | 1009 | /* |
29494be7 LJ |
1010 | * Move a dying CPU's RCU callbacks to online CPU's callback list. |
1011 | * Synchronization is not required because this function executes | |
1012 | * in stop_machine() context. | |
e74f4c45 | 1013 | */ |
29494be7 | 1014 | static void rcu_send_cbs_to_online(struct rcu_state *rsp) |
e74f4c45 PM |
1015 | { |
1016 | int i; | |
29494be7 LJ |
1017 | /* current DYING CPU is cleared in the cpu_online_mask */ |
1018 | int receive_cpu = cpumask_any(cpu_online_mask); | |
394f99a9 | 1019 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
29494be7 | 1020 | struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu); |
e74f4c45 PM |
1021 | |
1022 | if (rdp->nxtlist == NULL) | |
1023 | return; /* irqs disabled, so comparison is stable. */ | |
29494be7 LJ |
1024 | |
1025 | *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist; | |
1026 | receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
1027 | receive_rdp->qlen += rdp->qlen; | |
1028 | receive_rdp->n_cbs_adopted += rdp->qlen; | |
1029 | rdp->n_cbs_orphaned += rdp->qlen; | |
1030 | ||
e74f4c45 PM |
1031 | rdp->nxtlist = NULL; |
1032 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1033 | rdp->nxttail[i] = &rdp->nxtlist; | |
e74f4c45 | 1034 | rdp->qlen = 0; |
e74f4c45 PM |
1035 | } |
1036 | ||
64db4cff PM |
1037 | /* |
1038 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy | |
1039 | * and move all callbacks from the outgoing CPU to the current one. | |
1040 | */ | |
1041 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) | |
1042 | { | |
64db4cff | 1043 | unsigned long flags; |
64db4cff | 1044 | unsigned long mask; |
d9a3da06 | 1045 | int need_report = 0; |
394f99a9 | 1046 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
1047 | struct rcu_node *rnp; |
1048 | ||
1049 | /* Exclude any attempts to start a new grace period. */ | |
1304afb2 | 1050 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
64db4cff PM |
1051 | |
1052 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ | |
28ecd580 | 1053 | rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
64db4cff PM |
1054 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
1055 | do { | |
1304afb2 | 1056 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
1057 | rnp->qsmaskinit &= ~mask; |
1058 | if (rnp->qsmaskinit != 0) { | |
b668c9cf | 1059 | if (rnp != rdp->mynode) |
1304afb2 | 1060 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
1061 | break; |
1062 | } | |
b668c9cf | 1063 | if (rnp == rdp->mynode) |
d9a3da06 | 1064 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); |
b668c9cf | 1065 | else |
1304afb2 | 1066 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff | 1067 | mask = rnp->grpmask; |
64db4cff PM |
1068 | rnp = rnp->parent; |
1069 | } while (rnp != NULL); | |
64db4cff | 1070 | |
b668c9cf PM |
1071 | /* |
1072 | * We still hold the leaf rcu_node structure lock here, and | |
1073 | * irqs are still disabled. The reason for this subterfuge is | |
d3f6bad3 PM |
1074 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock |
1075 | * held leads to deadlock. | |
b668c9cf | 1076 | */ |
1304afb2 | 1077 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
b668c9cf | 1078 | rnp = rdp->mynode; |
d9a3da06 | 1079 | if (need_report & RCU_OFL_TASKS_NORM_GP) |
d3f6bad3 | 1080 | rcu_report_unblock_qs_rnp(rnp, flags); |
b668c9cf | 1081 | else |
1304afb2 | 1082 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da06 PM |
1083 | if (need_report & RCU_OFL_TASKS_EXP_GP) |
1084 | rcu_report_exp_rnp(rsp, rnp); | |
64db4cff PM |
1085 | } |
1086 | ||
1087 | /* | |
1088 | * Remove the specified CPU from the RCU hierarchy and move any pending | |
1089 | * callbacks that it might have to the current CPU. This code assumes | |
1090 | * that at least one CPU in the system will remain running at all times. | |
1091 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. | |
1092 | */ | |
1093 | static void rcu_offline_cpu(int cpu) | |
1094 | { | |
d6714c22 | 1095 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
64db4cff | 1096 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
33f76148 | 1097 | rcu_preempt_offline_cpu(cpu); |
64db4cff PM |
1098 | } |
1099 | ||
1100 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1101 | ||
29494be7 | 1102 | static void rcu_send_cbs_to_online(struct rcu_state *rsp) |
e74f4c45 PM |
1103 | { |
1104 | } | |
1105 | ||
64db4cff PM |
1106 | static void rcu_offline_cpu(int cpu) |
1107 | { | |
1108 | } | |
1109 | ||
1110 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
1111 | ||
1112 | /* | |
1113 | * Invoke any RCU callbacks that have made it to the end of their grace | |
1114 | * period. Thottle as specified by rdp->blimit. | |
1115 | */ | |
37c72e56 | 1116 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1117 | { |
1118 | unsigned long flags; | |
1119 | struct rcu_head *next, *list, **tail; | |
1120 | int count; | |
1121 | ||
1122 | /* If no callbacks are ready, just return.*/ | |
1123 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) | |
1124 | return; | |
1125 | ||
1126 | /* | |
1127 | * Extract the list of ready callbacks, disabling to prevent | |
1128 | * races with call_rcu() from interrupt handlers. | |
1129 | */ | |
1130 | local_irq_save(flags); | |
1131 | list = rdp->nxtlist; | |
1132 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
1133 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
1134 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
1135 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) | |
1136 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) | |
1137 | rdp->nxttail[count] = &rdp->nxtlist; | |
1138 | local_irq_restore(flags); | |
1139 | ||
1140 | /* Invoke callbacks. */ | |
1141 | count = 0; | |
1142 | while (list) { | |
1143 | next = list->next; | |
1144 | prefetch(next); | |
551d55a9 | 1145 | debug_rcu_head_unqueue(list); |
64db4cff PM |
1146 | list->func(list); |
1147 | list = next; | |
1148 | if (++count >= rdp->blimit) | |
1149 | break; | |
1150 | } | |
1151 | ||
1152 | local_irq_save(flags); | |
1153 | ||
1154 | /* Update count, and requeue any remaining callbacks. */ | |
1155 | rdp->qlen -= count; | |
269dcc1c | 1156 | rdp->n_cbs_invoked += count; |
64db4cff PM |
1157 | if (list != NULL) { |
1158 | *tail = rdp->nxtlist; | |
1159 | rdp->nxtlist = list; | |
1160 | for (count = 0; count < RCU_NEXT_SIZE; count++) | |
1161 | if (&rdp->nxtlist == rdp->nxttail[count]) | |
1162 | rdp->nxttail[count] = tail; | |
1163 | else | |
1164 | break; | |
1165 | } | |
1166 | ||
1167 | /* Reinstate batch limit if we have worked down the excess. */ | |
1168 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
1169 | rdp->blimit = blimit; | |
1170 | ||
37c72e56 PM |
1171 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1172 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
1173 | rdp->qlen_last_fqs_check = 0; | |
1174 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1175 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
1176 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1177 | ||
64db4cff PM |
1178 | local_irq_restore(flags); |
1179 | ||
1180 | /* Re-raise the RCU softirq if there are callbacks remaining. */ | |
1181 | if (cpu_has_callbacks_ready_to_invoke(rdp)) | |
1182 | raise_softirq(RCU_SOFTIRQ); | |
1183 | } | |
1184 | ||
1185 | /* | |
1186 | * Check to see if this CPU is in a non-context-switch quiescent state | |
1187 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
1188 | * Also schedule the RCU softirq handler. | |
1189 | * | |
1190 | * This function must be called with hardirqs disabled. It is normally | |
1191 | * invoked from the scheduling-clock interrupt. If rcu_pending returns | |
1192 | * false, there is no point in invoking rcu_check_callbacks(). | |
1193 | */ | |
1194 | void rcu_check_callbacks(int cpu, int user) | |
1195 | { | |
1196 | if (user || | |
a6826048 PM |
1197 | (idle_cpu(cpu) && rcu_scheduler_active && |
1198 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
64db4cff PM |
1199 | |
1200 | /* | |
1201 | * Get here if this CPU took its interrupt from user | |
1202 | * mode or from the idle loop, and if this is not a | |
1203 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1204 | * a quiescent state, so note it. |
64db4cff PM |
1205 | * |
1206 | * No memory barrier is required here because both | |
d6714c22 PM |
1207 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1208 | * variables that other CPUs neither access nor modify, | |
1209 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1210 | */ |
1211 | ||
d6714c22 PM |
1212 | rcu_sched_qs(cpu); |
1213 | rcu_bh_qs(cpu); | |
64db4cff PM |
1214 | |
1215 | } else if (!in_softirq()) { | |
1216 | ||
1217 | /* | |
1218 | * Get here if this CPU did not take its interrupt from | |
1219 | * softirq, in other words, if it is not interrupting | |
1220 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1221 | * critical section, so note it. |
64db4cff PM |
1222 | */ |
1223 | ||
d6714c22 | 1224 | rcu_bh_qs(cpu); |
64db4cff | 1225 | } |
f41d911f | 1226 | rcu_preempt_check_callbacks(cpu); |
d21670ac PM |
1227 | if (rcu_pending(cpu)) |
1228 | raise_softirq(RCU_SOFTIRQ); | |
64db4cff PM |
1229 | } |
1230 | ||
1231 | #ifdef CONFIG_SMP | |
1232 | ||
1233 | /* | |
1234 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1235 | * have not yet encountered a quiescent state, using the function specified. | |
ee47eb9f | 1236 | * The caller must have suppressed start of new grace periods. |
64db4cff | 1237 | */ |
45f014c5 | 1238 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
64db4cff PM |
1239 | { |
1240 | unsigned long bit; | |
1241 | int cpu; | |
1242 | unsigned long flags; | |
1243 | unsigned long mask; | |
a0b6c9a7 | 1244 | struct rcu_node *rnp; |
64db4cff | 1245 | |
a0b6c9a7 | 1246 | rcu_for_each_leaf_node(rsp, rnp) { |
64db4cff | 1247 | mask = 0; |
1304afb2 | 1248 | raw_spin_lock_irqsave(&rnp->lock, flags); |
ee47eb9f | 1249 | if (!rcu_gp_in_progress(rsp)) { |
1304afb2 | 1250 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
0f10dc82 | 1251 | return; |
64db4cff | 1252 | } |
a0b6c9a7 | 1253 | if (rnp->qsmask == 0) { |
1304afb2 | 1254 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1255 | continue; |
1256 | } | |
a0b6c9a7 | 1257 | cpu = rnp->grplo; |
64db4cff | 1258 | bit = 1; |
a0b6c9a7 | 1259 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
394f99a9 LJ |
1260 | if ((rnp->qsmask & bit) != 0 && |
1261 | f(per_cpu_ptr(rsp->rda, cpu))) | |
64db4cff PM |
1262 | mask |= bit; |
1263 | } | |
45f014c5 | 1264 | if (mask != 0) { |
64db4cff | 1265 | |
d3f6bad3 PM |
1266 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
1267 | rcu_report_qs_rnp(mask, rsp, rnp, flags); | |
64db4cff PM |
1268 | continue; |
1269 | } | |
1304afb2 | 1270 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 1271 | } |
64db4cff PM |
1272 | } |
1273 | ||
1274 | /* | |
1275 | * Force quiescent states on reluctant CPUs, and also detect which | |
1276 | * CPUs are in dyntick-idle mode. | |
1277 | */ | |
1278 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1279 | { | |
1280 | unsigned long flags; | |
64db4cff | 1281 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 1282 | |
fc2219d4 | 1283 | if (!rcu_gp_in_progress(rsp)) |
64db4cff | 1284 | return; /* No grace period in progress, nothing to force. */ |
1304afb2 | 1285 | if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { |
64db4cff PM |
1286 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
1287 | return; /* Someone else is already on the job. */ | |
1288 | } | |
20133cfc | 1289 | if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) |
f96e9232 | 1290 | goto unlock_fqs_ret; /* no emergency and done recently. */ |
64db4cff | 1291 | rsp->n_force_qs++; |
1304afb2 | 1292 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
64db4cff | 1293 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
560d4bc0 | 1294 | if(!rcu_gp_in_progress(rsp)) { |
64db4cff | 1295 | rsp->n_force_qs_ngp++; |
1304afb2 | 1296 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
f96e9232 | 1297 | goto unlock_fqs_ret; /* no GP in progress, time updated. */ |
64db4cff | 1298 | } |
07079d53 | 1299 | rsp->fqs_active = 1; |
f3a8b5c6 | 1300 | switch (rsp->signaled) { |
83f5b01f | 1301 | case RCU_GP_IDLE: |
64db4cff PM |
1302 | case RCU_GP_INIT: |
1303 | ||
83f5b01f | 1304 | break; /* grace period idle or initializing, ignore. */ |
64db4cff PM |
1305 | |
1306 | case RCU_SAVE_DYNTICK: | |
64db4cff PM |
1307 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
1308 | break; /* So gcc recognizes the dead code. */ | |
1309 | ||
f261414f LJ |
1310 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
1311 | ||
64db4cff | 1312 | /* Record dyntick-idle state. */ |
45f014c5 | 1313 | force_qs_rnp(rsp, dyntick_save_progress_counter); |
1304afb2 | 1314 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
ee47eb9f | 1315 | if (rcu_gp_in_progress(rsp)) |
64db4cff | 1316 | rsp->signaled = RCU_FORCE_QS; |
ee47eb9f | 1317 | break; |
64db4cff PM |
1318 | |
1319 | case RCU_FORCE_QS: | |
1320 | ||
1321 | /* Check dyntick-idle state, send IPI to laggarts. */ | |
1304afb2 | 1322 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
45f014c5 | 1323 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
64db4cff PM |
1324 | |
1325 | /* Leave state in case more forcing is required. */ | |
1326 | ||
1304afb2 | 1327 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
f96e9232 | 1328 | break; |
64db4cff | 1329 | } |
07079d53 | 1330 | rsp->fqs_active = 0; |
46a1e34e | 1331 | if (rsp->fqs_need_gp) { |
1304afb2 | 1332 | raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ |
46a1e34e PM |
1333 | rsp->fqs_need_gp = 0; |
1334 | rcu_start_gp(rsp, flags); /* releases rnp->lock */ | |
1335 | return; | |
1336 | } | |
1304afb2 | 1337 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
f96e9232 | 1338 | unlock_fqs_ret: |
1304afb2 | 1339 | raw_spin_unlock_irqrestore(&rsp->fqslock, flags); |
64db4cff PM |
1340 | } |
1341 | ||
1342 | #else /* #ifdef CONFIG_SMP */ | |
1343 | ||
1344 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1345 | { | |
1346 | set_need_resched(); | |
1347 | } | |
1348 | ||
1349 | #endif /* #else #ifdef CONFIG_SMP */ | |
1350 | ||
1351 | /* | |
1352 | * This does the RCU processing work from softirq context for the | |
1353 | * specified rcu_state and rcu_data structures. This may be called | |
1354 | * only from the CPU to whom the rdp belongs. | |
1355 | */ | |
1356 | static void | |
1357 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) | |
1358 | { | |
1359 | unsigned long flags; | |
1360 | ||
2e597558 PM |
1361 | WARN_ON_ONCE(rdp->beenonline == 0); |
1362 | ||
64db4cff PM |
1363 | /* |
1364 | * If an RCU GP has gone long enough, go check for dyntick | |
1365 | * idle CPUs and, if needed, send resched IPIs. | |
1366 | */ | |
20133cfc | 1367 | if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
64db4cff PM |
1368 | force_quiescent_state(rsp, 1); |
1369 | ||
1370 | /* | |
1371 | * Advance callbacks in response to end of earlier grace | |
1372 | * period that some other CPU ended. | |
1373 | */ | |
1374 | rcu_process_gp_end(rsp, rdp); | |
1375 | ||
1376 | /* Update RCU state based on any recent quiescent states. */ | |
1377 | rcu_check_quiescent_state(rsp, rdp); | |
1378 | ||
1379 | /* Does this CPU require a not-yet-started grace period? */ | |
1380 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1304afb2 | 1381 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
64db4cff PM |
1382 | rcu_start_gp(rsp, flags); /* releases above lock */ |
1383 | } | |
1384 | ||
1385 | /* If there are callbacks ready, invoke them. */ | |
37c72e56 | 1386 | rcu_do_batch(rsp, rdp); |
64db4cff PM |
1387 | } |
1388 | ||
1389 | /* | |
1390 | * Do softirq processing for the current CPU. | |
1391 | */ | |
1392 | static void rcu_process_callbacks(struct softirq_action *unused) | |
1393 | { | |
1394 | /* | |
1395 | * Memory references from any prior RCU read-side critical sections | |
1396 | * executed by the interrupted code must be seen before any RCU | |
1397 | * grace-period manipulations below. | |
1398 | */ | |
1399 | smp_mb(); /* See above block comment. */ | |
1400 | ||
d6714c22 PM |
1401 | __rcu_process_callbacks(&rcu_sched_state, |
1402 | &__get_cpu_var(rcu_sched_data)); | |
64db4cff | 1403 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
f41d911f | 1404 | rcu_preempt_process_callbacks(); |
64db4cff PM |
1405 | |
1406 | /* | |
1407 | * Memory references from any later RCU read-side critical sections | |
1408 | * executed by the interrupted code must be seen after any RCU | |
1409 | * grace-period manipulations above. | |
1410 | */ | |
1411 | smp_mb(); /* See above block comment. */ | |
a47cd880 PM |
1412 | |
1413 | /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ | |
1414 | rcu_needs_cpu_flush(); | |
64db4cff PM |
1415 | } |
1416 | ||
1417 | static void | |
1418 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
1419 | struct rcu_state *rsp) | |
1420 | { | |
1421 | unsigned long flags; | |
1422 | struct rcu_data *rdp; | |
1423 | ||
551d55a9 | 1424 | debug_rcu_head_queue(head); |
64db4cff PM |
1425 | head->func = func; |
1426 | head->next = NULL; | |
1427 | ||
1428 | smp_mb(); /* Ensure RCU update seen before callback registry. */ | |
1429 | ||
1430 | /* | |
1431 | * Opportunistically note grace-period endings and beginnings. | |
1432 | * Note that we might see a beginning right after we see an | |
1433 | * end, but never vice versa, since this CPU has to pass through | |
1434 | * a quiescent state betweentimes. | |
1435 | */ | |
1436 | local_irq_save(flags); | |
394f99a9 | 1437 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
1438 | |
1439 | /* Add the callback to our list. */ | |
1440 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
1441 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
1442 | ||
37c72e56 PM |
1443 | /* |
1444 | * Force the grace period if too many callbacks or too long waiting. | |
1445 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
1446 | * if some other CPU has recently done so. Also, don't bother | |
1447 | * invoking force_quiescent_state() if the newly enqueued callback | |
1448 | * is the only one waiting for a grace period to complete. | |
1449 | */ | |
1450 | if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { | |
b52573d2 PM |
1451 | |
1452 | /* Are we ignoring a completed grace period? */ | |
1453 | rcu_process_gp_end(rsp, rdp); | |
1454 | check_for_new_grace_period(rsp, rdp); | |
1455 | ||
1456 | /* Start a new grace period if one not already started. */ | |
1457 | if (!rcu_gp_in_progress(rsp)) { | |
1458 | unsigned long nestflag; | |
1459 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
1460 | ||
1461 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); | |
1462 | rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */ | |
1463 | } else { | |
1464 | /* Give the grace period a kick. */ | |
1465 | rdp->blimit = LONG_MAX; | |
1466 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
1467 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
1468 | force_quiescent_state(rsp, 0); | |
1469 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1470 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1471 | } | |
20133cfc | 1472 | } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
64db4cff PM |
1473 | force_quiescent_state(rsp, 1); |
1474 | local_irq_restore(flags); | |
1475 | } | |
1476 | ||
1477 | /* | |
d6714c22 | 1478 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 1479 | */ |
d6714c22 | 1480 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 1481 | { |
d6714c22 | 1482 | __call_rcu(head, func, &rcu_sched_state); |
64db4cff | 1483 | } |
d6714c22 | 1484 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
1485 | |
1486 | /* | |
1487 | * Queue an RCU for invocation after a quicker grace period. | |
1488 | */ | |
1489 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1490 | { | |
1491 | __call_rcu(head, func, &rcu_bh_state); | |
1492 | } | |
1493 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
1494 | ||
6ebb237b PM |
1495 | /** |
1496 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
1497 | * | |
1498 | * Control will return to the caller some time after a full rcu-sched | |
1499 | * grace period has elapsed, in other words after all currently executing | |
1500 | * rcu-sched read-side critical sections have completed. These read-side | |
1501 | * critical sections are delimited by rcu_read_lock_sched() and | |
1502 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
1503 | * local_irq_disable(), and so on may be used in place of | |
1504 | * rcu_read_lock_sched(). | |
1505 | * | |
1506 | * This means that all preempt_disable code sequences, including NMI and | |
1507 | * hardware-interrupt handlers, in progress on entry will have completed | |
1508 | * before this primitive returns. However, this does not guarantee that | |
1509 | * softirq handlers will have completed, since in some kernels, these | |
1510 | * handlers can run in process context, and can block. | |
1511 | * | |
1512 | * This primitive provides the guarantees made by the (now removed) | |
1513 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
1514 | * guarantees that rcu_read_lock() sections will have completed. | |
1515 | * In "classic RCU", these two guarantees happen to be one and | |
1516 | * the same, but can differ in realtime RCU implementations. | |
1517 | */ | |
1518 | void synchronize_sched(void) | |
1519 | { | |
1520 | struct rcu_synchronize rcu; | |
1521 | ||
1522 | if (rcu_blocking_is_gp()) | |
1523 | return; | |
1524 | ||
72d5a9f7 | 1525 | init_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1526 | init_completion(&rcu.completion); |
1527 | /* Will wake me after RCU finished. */ | |
1528 | call_rcu_sched(&rcu.head, wakeme_after_rcu); | |
1529 | /* Wait for it. */ | |
1530 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 1531 | destroy_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1532 | } |
1533 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
1534 | ||
1535 | /** | |
1536 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
1537 | * | |
1538 | * Control will return to the caller some time after a full rcu_bh grace | |
1539 | * period has elapsed, in other words after all currently executing rcu_bh | |
1540 | * read-side critical sections have completed. RCU read-side critical | |
1541 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
1542 | * and may be nested. | |
1543 | */ | |
1544 | void synchronize_rcu_bh(void) | |
1545 | { | |
1546 | struct rcu_synchronize rcu; | |
1547 | ||
1548 | if (rcu_blocking_is_gp()) | |
1549 | return; | |
1550 | ||
72d5a9f7 | 1551 | init_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1552 | init_completion(&rcu.completion); |
1553 | /* Will wake me after RCU finished. */ | |
1554 | call_rcu_bh(&rcu.head, wakeme_after_rcu); | |
1555 | /* Wait for it. */ | |
1556 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 1557 | destroy_rcu_head_on_stack(&rcu.head); |
6ebb237b PM |
1558 | } |
1559 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
1560 | ||
64db4cff PM |
1561 | /* |
1562 | * Check to see if there is any immediate RCU-related work to be done | |
1563 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
1564 | * The checks are in order of increasing expense: checks that can be | |
1565 | * carried out against CPU-local state are performed first. However, | |
1566 | * we must check for CPU stalls first, else we might not get a chance. | |
1567 | */ | |
1568 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
1569 | { | |
2f51f988 PM |
1570 | struct rcu_node *rnp = rdp->mynode; |
1571 | ||
64db4cff PM |
1572 | rdp->n_rcu_pending++; |
1573 | ||
1574 | /* Check for CPU stalls, if enabled. */ | |
1575 | check_cpu_stall(rsp, rdp); | |
1576 | ||
1577 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
d21670ac | 1578 | if (rdp->qs_pending && !rdp->passed_quiesc) { |
d25eb944 PM |
1579 | |
1580 | /* | |
1581 | * If force_quiescent_state() coming soon and this CPU | |
1582 | * needs a quiescent state, and this is either RCU-sched | |
1583 | * or RCU-bh, force a local reschedule. | |
1584 | */ | |
d21670ac | 1585 | rdp->n_rp_qs_pending++; |
d25eb944 PM |
1586 | if (!rdp->preemptable && |
1587 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, | |
1588 | jiffies)) | |
1589 | set_need_resched(); | |
d21670ac PM |
1590 | } else if (rdp->qs_pending && rdp->passed_quiesc) { |
1591 | rdp->n_rp_report_qs++; | |
64db4cff | 1592 | return 1; |
7ba5c840 | 1593 | } |
64db4cff PM |
1594 | |
1595 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
1596 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
1597 | rdp->n_rp_cb_ready++; | |
64db4cff | 1598 | return 1; |
7ba5c840 | 1599 | } |
64db4cff PM |
1600 | |
1601 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
1602 | if (cpu_needs_another_gp(rsp, rdp)) { |
1603 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 1604 | return 1; |
7ba5c840 | 1605 | } |
64db4cff PM |
1606 | |
1607 | /* Has another RCU grace period completed? */ | |
2f51f988 | 1608 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 1609 | rdp->n_rp_gp_completed++; |
64db4cff | 1610 | return 1; |
7ba5c840 | 1611 | } |
64db4cff PM |
1612 | |
1613 | /* Has a new RCU grace period started? */ | |
2f51f988 | 1614 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 1615 | rdp->n_rp_gp_started++; |
64db4cff | 1616 | return 1; |
7ba5c840 | 1617 | } |
64db4cff PM |
1618 | |
1619 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ | |
fc2219d4 | 1620 | if (rcu_gp_in_progress(rsp) && |
20133cfc | 1621 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { |
7ba5c840 | 1622 | rdp->n_rp_need_fqs++; |
64db4cff | 1623 | return 1; |
7ba5c840 | 1624 | } |
64db4cff PM |
1625 | |
1626 | /* nothing to do */ | |
7ba5c840 | 1627 | rdp->n_rp_need_nothing++; |
64db4cff PM |
1628 | return 0; |
1629 | } | |
1630 | ||
1631 | /* | |
1632 | * Check to see if there is any immediate RCU-related work to be done | |
1633 | * by the current CPU, returning 1 if so. This function is part of the | |
1634 | * RCU implementation; it is -not- an exported member of the RCU API. | |
1635 | */ | |
a157229c | 1636 | static int rcu_pending(int cpu) |
64db4cff | 1637 | { |
d6714c22 | 1638 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
f41d911f PM |
1639 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
1640 | rcu_preempt_pending(cpu); | |
64db4cff PM |
1641 | } |
1642 | ||
1643 | /* | |
1644 | * Check to see if any future RCU-related work will need to be done | |
1645 | * by the current CPU, even if none need be done immediately, returning | |
8bd93a2c | 1646 | * 1 if so. |
64db4cff | 1647 | */ |
8bd93a2c | 1648 | static int rcu_needs_cpu_quick_check(int cpu) |
64db4cff PM |
1649 | { |
1650 | /* RCU callbacks either ready or pending? */ | |
d6714c22 | 1651 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
f41d911f PM |
1652 | per_cpu(rcu_bh_data, cpu).nxtlist || |
1653 | rcu_preempt_needs_cpu(cpu); | |
64db4cff PM |
1654 | } |
1655 | ||
d0ec774c PM |
1656 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
1657 | static atomic_t rcu_barrier_cpu_count; | |
1658 | static DEFINE_MUTEX(rcu_barrier_mutex); | |
1659 | static struct completion rcu_barrier_completion; | |
d0ec774c PM |
1660 | |
1661 | static void rcu_barrier_callback(struct rcu_head *notused) | |
1662 | { | |
1663 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
1664 | complete(&rcu_barrier_completion); | |
1665 | } | |
1666 | ||
1667 | /* | |
1668 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
1669 | */ | |
1670 | static void rcu_barrier_func(void *type) | |
1671 | { | |
1672 | int cpu = smp_processor_id(); | |
1673 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); | |
1674 | void (*call_rcu_func)(struct rcu_head *head, | |
1675 | void (*func)(struct rcu_head *head)); | |
1676 | ||
1677 | atomic_inc(&rcu_barrier_cpu_count); | |
1678 | call_rcu_func = type; | |
1679 | call_rcu_func(head, rcu_barrier_callback); | |
1680 | } | |
1681 | ||
d0ec774c PM |
1682 | /* |
1683 | * Orchestrate the specified type of RCU barrier, waiting for all | |
1684 | * RCU callbacks of the specified type to complete. | |
1685 | */ | |
e74f4c45 PM |
1686 | static void _rcu_barrier(struct rcu_state *rsp, |
1687 | void (*call_rcu_func)(struct rcu_head *head, | |
d0ec774c PM |
1688 | void (*func)(struct rcu_head *head))) |
1689 | { | |
1690 | BUG_ON(in_interrupt()); | |
e74f4c45 | 1691 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
d0ec774c PM |
1692 | mutex_lock(&rcu_barrier_mutex); |
1693 | init_completion(&rcu_barrier_completion); | |
1694 | /* | |
1695 | * Initialize rcu_barrier_cpu_count to 1, then invoke | |
1696 | * rcu_barrier_func() on each CPU, so that each CPU also has | |
1697 | * incremented rcu_barrier_cpu_count. Only then is it safe to | |
1698 | * decrement rcu_barrier_cpu_count -- otherwise the first CPU | |
1699 | * might complete its grace period before all of the other CPUs | |
1700 | * did their increment, causing this function to return too | |
2d999e03 PM |
1701 | * early. Note that on_each_cpu() disables irqs, which prevents |
1702 | * any CPUs from coming online or going offline until each online | |
1703 | * CPU has queued its RCU-barrier callback. | |
d0ec774c PM |
1704 | */ |
1705 | atomic_set(&rcu_barrier_cpu_count, 1); | |
1706 | on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); | |
1707 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
1708 | complete(&rcu_barrier_completion); | |
1709 | wait_for_completion(&rcu_barrier_completion); | |
1710 | mutex_unlock(&rcu_barrier_mutex); | |
d0ec774c | 1711 | } |
d0ec774c PM |
1712 | |
1713 | /** | |
1714 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
1715 | */ | |
1716 | void rcu_barrier_bh(void) | |
1717 | { | |
e74f4c45 | 1718 | _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
d0ec774c PM |
1719 | } |
1720 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
1721 | ||
1722 | /** | |
1723 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
1724 | */ | |
1725 | void rcu_barrier_sched(void) | |
1726 | { | |
e74f4c45 | 1727 | _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
d0ec774c PM |
1728 | } |
1729 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
1730 | ||
64db4cff | 1731 | /* |
27569620 | 1732 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 1733 | */ |
27569620 PM |
1734 | static void __init |
1735 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
1736 | { |
1737 | unsigned long flags; | |
1738 | int i; | |
394f99a9 | 1739 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
1740 | struct rcu_node *rnp = rcu_get_root(rsp); |
1741 | ||
1742 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 1743 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 PM |
1744 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
1745 | rdp->nxtlist = NULL; | |
1746 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1747 | rdp->nxttail[i] = &rdp->nxtlist; | |
1748 | rdp->qlen = 0; | |
1749 | #ifdef CONFIG_NO_HZ | |
1750 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); | |
1751 | #endif /* #ifdef CONFIG_NO_HZ */ | |
1752 | rdp->cpu = cpu; | |
1304afb2 | 1753 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
1754 | } |
1755 | ||
1756 | /* | |
1757 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
1758 | * offline event can be happening at a given time. Note also that we | |
1759 | * can accept some slop in the rsp->completed access due to the fact | |
1760 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 1761 | */ |
e4fa4c97 | 1762 | static void __cpuinit |
f41d911f | 1763 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
64db4cff PM |
1764 | { |
1765 | unsigned long flags; | |
64db4cff | 1766 | unsigned long mask; |
394f99a9 | 1767 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
1768 | struct rcu_node *rnp = rcu_get_root(rsp); |
1769 | ||
1770 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 1771 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff PM |
1772 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
1773 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ | |
1774 | rdp->beenonline = 1; /* We have now been online. */ | |
f41d911f | 1775 | rdp->preemptable = preemptable; |
37c72e56 PM |
1776 | rdp->qlen_last_fqs_check = 0; |
1777 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 1778 | rdp->blimit = blimit; |
1304afb2 | 1779 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
1780 | |
1781 | /* | |
1782 | * A new grace period might start here. If so, we won't be part | |
1783 | * of it, but that is OK, as we are currently in a quiescent state. | |
1784 | */ | |
1785 | ||
1786 | /* Exclude any attempts to start a new GP on large systems. */ | |
1304afb2 | 1787 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
1788 | |
1789 | /* Add CPU to rcu_node bitmasks. */ | |
1790 | rnp = rdp->mynode; | |
1791 | mask = rdp->grpmask; | |
1792 | do { | |
1793 | /* Exclude any attempts to start a new GP on small systems. */ | |
1304afb2 | 1794 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
1795 | rnp->qsmaskinit |= mask; |
1796 | mask = rnp->grpmask; | |
d09b62df PM |
1797 | if (rnp == rdp->mynode) { |
1798 | rdp->gpnum = rnp->completed; /* if GP in progress... */ | |
1799 | rdp->completed = rnp->completed; | |
1800 | rdp->passed_quiesc_completed = rnp->completed - 1; | |
1801 | } | |
1304afb2 | 1802 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
1803 | rnp = rnp->parent; |
1804 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
1805 | ||
1304afb2 | 1806 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
64db4cff PM |
1807 | } |
1808 | ||
1809 | static void __cpuinit rcu_online_cpu(int cpu) | |
1810 | { | |
f41d911f PM |
1811 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
1812 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); | |
1813 | rcu_preempt_init_percpu_data(cpu); | |
64db4cff PM |
1814 | } |
1815 | ||
1816 | /* | |
f41d911f | 1817 | * Handle CPU online/offline notification events. |
64db4cff | 1818 | */ |
9f680ab4 PM |
1819 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
1820 | unsigned long action, void *hcpu) | |
64db4cff PM |
1821 | { |
1822 | long cpu = (long)hcpu; | |
1823 | ||
1824 | switch (action) { | |
1825 | case CPU_UP_PREPARE: | |
1826 | case CPU_UP_PREPARE_FROZEN: | |
1827 | rcu_online_cpu(cpu); | |
1828 | break; | |
d0ec774c PM |
1829 | case CPU_DYING: |
1830 | case CPU_DYING_FROZEN: | |
1831 | /* | |
2d999e03 PM |
1832 | * The whole machine is "stopped" except this CPU, so we can |
1833 | * touch any data without introducing corruption. We send the | |
1834 | * dying CPU's callbacks to an arbitrarily chosen online CPU. | |
d0ec774c | 1835 | */ |
29494be7 LJ |
1836 | rcu_send_cbs_to_online(&rcu_bh_state); |
1837 | rcu_send_cbs_to_online(&rcu_sched_state); | |
1838 | rcu_preempt_send_cbs_to_online(); | |
d0ec774c | 1839 | break; |
64db4cff PM |
1840 | case CPU_DEAD: |
1841 | case CPU_DEAD_FROZEN: | |
1842 | case CPU_UP_CANCELED: | |
1843 | case CPU_UP_CANCELED_FROZEN: | |
1844 | rcu_offline_cpu(cpu); | |
1845 | break; | |
1846 | default: | |
1847 | break; | |
1848 | } | |
1849 | return NOTIFY_OK; | |
1850 | } | |
1851 | ||
bbad9379 PM |
1852 | /* |
1853 | * This function is invoked towards the end of the scheduler's initialization | |
1854 | * process. Before this is called, the idle task might contain | |
1855 | * RCU read-side critical sections (during which time, this idle | |
1856 | * task is booting the system). After this function is called, the | |
1857 | * idle tasks are prohibited from containing RCU read-side critical | |
1858 | * sections. This function also enables RCU lockdep checking. | |
1859 | */ | |
1860 | void rcu_scheduler_starting(void) | |
1861 | { | |
1862 | WARN_ON(num_online_cpus() != 1); | |
1863 | WARN_ON(nr_context_switches() > 0); | |
1864 | rcu_scheduler_active = 1; | |
1865 | } | |
1866 | ||
64db4cff PM |
1867 | /* |
1868 | * Compute the per-level fanout, either using the exact fanout specified | |
1869 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
1870 | */ | |
1871 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
1872 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1873 | { | |
1874 | int i; | |
1875 | ||
0209f649 | 1876 | for (i = NUM_RCU_LVLS - 1; i > 0; i--) |
64db4cff | 1877 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
0209f649 | 1878 | rsp->levelspread[0] = RCU_FANOUT_LEAF; |
64db4cff PM |
1879 | } |
1880 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1881 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1882 | { | |
1883 | int ccur; | |
1884 | int cprv; | |
1885 | int i; | |
1886 | ||
1887 | cprv = NR_CPUS; | |
1888 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1889 | ccur = rsp->levelcnt[i]; | |
1890 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
1891 | cprv = ccur; | |
1892 | } | |
1893 | } | |
1894 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1895 | ||
1896 | /* | |
1897 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
1898 | */ | |
394f99a9 LJ |
1899 | static void __init rcu_init_one(struct rcu_state *rsp, |
1900 | struct rcu_data __percpu *rda) | |
64db4cff | 1901 | { |
b6407e86 PM |
1902 | static char *buf[] = { "rcu_node_level_0", |
1903 | "rcu_node_level_1", | |
1904 | "rcu_node_level_2", | |
1905 | "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ | |
64db4cff PM |
1906 | int cpustride = 1; |
1907 | int i; | |
1908 | int j; | |
1909 | struct rcu_node *rnp; | |
1910 | ||
b6407e86 PM |
1911 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
1912 | ||
64db4cff PM |
1913 | /* Initialize the level-tracking arrays. */ |
1914 | ||
1915 | for (i = 1; i < NUM_RCU_LVLS; i++) | |
1916 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; | |
1917 | rcu_init_levelspread(rsp); | |
1918 | ||
1919 | /* Initialize the elements themselves, starting from the leaves. */ | |
1920 | ||
1921 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1922 | cpustride *= rsp->levelspread[i]; | |
1923 | rnp = rsp->level[i]; | |
1924 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1304afb2 | 1925 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
1926 | lockdep_set_class_and_name(&rnp->lock, |
1927 | &rcu_node_class[i], buf[i]); | |
f41d911f | 1928 | rnp->gpnum = 0; |
64db4cff PM |
1929 | rnp->qsmask = 0; |
1930 | rnp->qsmaskinit = 0; | |
1931 | rnp->grplo = j * cpustride; | |
1932 | rnp->grphi = (j + 1) * cpustride - 1; | |
1933 | if (rnp->grphi >= NR_CPUS) | |
1934 | rnp->grphi = NR_CPUS - 1; | |
1935 | if (i == 0) { | |
1936 | rnp->grpnum = 0; | |
1937 | rnp->grpmask = 0; | |
1938 | rnp->parent = NULL; | |
1939 | } else { | |
1940 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
1941 | rnp->grpmask = 1UL << rnp->grpnum; | |
1942 | rnp->parent = rsp->level[i - 1] + | |
1943 | j / rsp->levelspread[i - 1]; | |
1944 | } | |
1945 | rnp->level = i; | |
f41d911f PM |
1946 | INIT_LIST_HEAD(&rnp->blocked_tasks[0]); |
1947 | INIT_LIST_HEAD(&rnp->blocked_tasks[1]); | |
d9a3da06 PM |
1948 | INIT_LIST_HEAD(&rnp->blocked_tasks[2]); |
1949 | INIT_LIST_HEAD(&rnp->blocked_tasks[3]); | |
64db4cff PM |
1950 | } |
1951 | } | |
0c34029a | 1952 | |
394f99a9 | 1953 | rsp->rda = rda; |
0c34029a LJ |
1954 | rnp = rsp->level[NUM_RCU_LVLS - 1]; |
1955 | for_each_possible_cpu(i) { | |
4a90a068 | 1956 | while (i > rnp->grphi) |
0c34029a | 1957 | rnp++; |
394f99a9 | 1958 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
1959 | rcu_boot_init_percpu_data(i, rsp); |
1960 | } | |
64db4cff PM |
1961 | } |
1962 | ||
9f680ab4 | 1963 | void __init rcu_init(void) |
64db4cff | 1964 | { |
017c4261 | 1965 | int cpu; |
9f680ab4 | 1966 | |
f41d911f | 1967 | rcu_bootup_announce(); |
394f99a9 LJ |
1968 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
1969 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); | |
f41d911f | 1970 | __rcu_init_preempt(); |
2e597558 | 1971 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
1972 | |
1973 | /* | |
1974 | * We don't need protection against CPU-hotplug here because | |
1975 | * this is called early in boot, before either interrupts | |
1976 | * or the scheduler are operational. | |
1977 | */ | |
1978 | cpu_notifier(rcu_cpu_notify, 0); | |
017c4261 PM |
1979 | for_each_online_cpu(cpu) |
1980 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
c68de209 | 1981 | check_cpu_stall_init(); |
64db4cff PM |
1982 | } |
1983 | ||
1eba8f84 | 1984 | #include "rcutree_plugin.h" |