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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> | |
49 | ||
9f77da9f PM |
50 | #include "rcutree.h" |
51 | ||
64db4cff PM |
52 | /* Data structures. */ |
53 | ||
54 | #define RCU_STATE_INITIALIZER(name) { \ | |
55 | .level = { &name.node[0] }, \ | |
56 | .levelcnt = { \ | |
57 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ | |
58 | NUM_RCU_LVL_1, \ | |
59 | NUM_RCU_LVL_2, \ | |
60 | NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \ | |
61 | }, \ | |
62 | .signaled = RCU_SIGNAL_INIT, \ | |
63 | .gpnum = -300, \ | |
64 | .completed = -300, \ | |
65 | .onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \ | |
66 | .fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \ | |
67 | .n_force_qs = 0, \ | |
68 | .n_force_qs_ngp = 0, \ | |
69 | } | |
70 | ||
d6714c22 PM |
71 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
72 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); | |
64db4cff | 73 | |
6258c4fb IM |
74 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
75 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); | |
b1f77b05 | 76 | |
f41d911f | 77 | |
fc2219d4 PM |
78 | /* |
79 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
80 | * permit this function to be invoked without holding the root rcu_node | |
81 | * structure's ->lock, but of course results can be subject to change. | |
82 | */ | |
83 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
84 | { | |
85 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
86 | } | |
87 | ||
b1f77b05 | 88 | /* |
d6714c22 | 89 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 90 | * how many quiescent states passed, just if there was at least |
d6714c22 | 91 | * one since the start of the grace period, this just sets a flag. |
b1f77b05 | 92 | */ |
d6714c22 | 93 | void rcu_sched_qs(int cpu) |
b1f77b05 | 94 | { |
f41d911f PM |
95 | struct rcu_data *rdp; |
96 | ||
f41d911f | 97 | rdp = &per_cpu(rcu_sched_data, cpu); |
b1f77b05 | 98 | rdp->passed_quiesc_completed = rdp->completed; |
c3422bea PM |
99 | barrier(); |
100 | rdp->passed_quiesc = 1; | |
101 | rcu_preempt_note_context_switch(cpu); | |
b1f77b05 IM |
102 | } |
103 | ||
d6714c22 | 104 | void rcu_bh_qs(int cpu) |
b1f77b05 | 105 | { |
f41d911f PM |
106 | struct rcu_data *rdp; |
107 | ||
f41d911f | 108 | rdp = &per_cpu(rcu_bh_data, cpu); |
b1f77b05 | 109 | rdp->passed_quiesc_completed = rdp->completed; |
c3422bea PM |
110 | barrier(); |
111 | rdp->passed_quiesc = 1; | |
b1f77b05 | 112 | } |
64db4cff PM |
113 | |
114 | #ifdef CONFIG_NO_HZ | |
90a4d2c0 PM |
115 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
116 | .dynticks_nesting = 1, | |
117 | .dynticks = 1, | |
118 | }; | |
64db4cff PM |
119 | #endif /* #ifdef CONFIG_NO_HZ */ |
120 | ||
121 | static int blimit = 10; /* Maximum callbacks per softirq. */ | |
122 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ | |
123 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
124 | ||
3d76c082 PM |
125 | module_param(blimit, int, 0); |
126 | module_param(qhimark, int, 0); | |
127 | module_param(qlowmark, int, 0); | |
128 | ||
64db4cff | 129 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
a157229c | 130 | static int rcu_pending(int cpu); |
64db4cff PM |
131 | |
132 | /* | |
d6714c22 | 133 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 134 | */ |
d6714c22 | 135 | long rcu_batches_completed_sched(void) |
64db4cff | 136 | { |
d6714c22 | 137 | return rcu_sched_state.completed; |
64db4cff | 138 | } |
d6714c22 | 139 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
140 | |
141 | /* | |
142 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
143 | */ | |
144 | long rcu_batches_completed_bh(void) | |
145 | { | |
146 | return rcu_bh_state.completed; | |
147 | } | |
148 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
149 | ||
150 | /* | |
151 | * Does the CPU have callbacks ready to be invoked? | |
152 | */ | |
153 | static int | |
154 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
155 | { | |
156 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
157 | } | |
158 | ||
159 | /* | |
160 | * Does the current CPU require a yet-as-unscheduled grace period? | |
161 | */ | |
162 | static int | |
163 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
164 | { | |
fc2219d4 | 165 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
64db4cff PM |
166 | } |
167 | ||
168 | /* | |
169 | * Return the root node of the specified rcu_state structure. | |
170 | */ | |
171 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
172 | { | |
173 | return &rsp->node[0]; | |
174 | } | |
175 | ||
176 | #ifdef CONFIG_SMP | |
177 | ||
178 | /* | |
179 | * If the specified CPU is offline, tell the caller that it is in | |
180 | * a quiescent state. Otherwise, whack it with a reschedule IPI. | |
181 | * Grace periods can end up waiting on an offline CPU when that | |
182 | * CPU is in the process of coming online -- it will be added to the | |
183 | * rcu_node bitmasks before it actually makes it online. The same thing | |
184 | * can happen while a CPU is in the process of coming online. Because this | |
185 | * race is quite rare, we check for it after detecting that the grace | |
186 | * period has been delayed rather than checking each and every CPU | |
187 | * each and every time we start a new grace period. | |
188 | */ | |
189 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) | |
190 | { | |
191 | /* | |
192 | * If the CPU is offline, it is in a quiescent state. We can | |
193 | * trust its state not to change because interrupts are disabled. | |
194 | */ | |
195 | if (cpu_is_offline(rdp->cpu)) { | |
196 | rdp->offline_fqs++; | |
197 | return 1; | |
198 | } | |
199 | ||
f41d911f PM |
200 | /* If preemptable RCU, no point in sending reschedule IPI. */ |
201 | if (rdp->preemptable) | |
202 | return 0; | |
203 | ||
64db4cff PM |
204 | /* The CPU is online, so send it a reschedule IPI. */ |
205 | if (rdp->cpu != smp_processor_id()) | |
206 | smp_send_reschedule(rdp->cpu); | |
207 | else | |
208 | set_need_resched(); | |
209 | rdp->resched_ipi++; | |
210 | return 0; | |
211 | } | |
212 | ||
213 | #endif /* #ifdef CONFIG_SMP */ | |
214 | ||
215 | #ifdef CONFIG_NO_HZ | |
64db4cff PM |
216 | |
217 | /** | |
218 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz | |
219 | * | |
220 | * Enter nohz mode, in other words, -leave- the mode in which RCU | |
221 | * read-side critical sections can occur. (Though RCU read-side | |
222 | * critical sections can occur in irq handlers in nohz mode, a possibility | |
223 | * handled by rcu_irq_enter() and rcu_irq_exit()). | |
224 | */ | |
225 | void rcu_enter_nohz(void) | |
226 | { | |
227 | unsigned long flags; | |
228 | struct rcu_dynticks *rdtp; | |
229 | ||
230 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
231 | local_irq_save(flags); | |
232 | rdtp = &__get_cpu_var(rcu_dynticks); | |
233 | rdtp->dynticks++; | |
234 | rdtp->dynticks_nesting--; | |
86848966 | 235 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
64db4cff PM |
236 | local_irq_restore(flags); |
237 | } | |
238 | ||
239 | /* | |
240 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz | |
241 | * | |
242 | * Exit nohz mode, in other words, -enter- the mode in which RCU | |
243 | * read-side critical sections normally occur. | |
244 | */ | |
245 | void rcu_exit_nohz(void) | |
246 | { | |
247 | unsigned long flags; | |
248 | struct rcu_dynticks *rdtp; | |
249 | ||
250 | local_irq_save(flags); | |
251 | rdtp = &__get_cpu_var(rcu_dynticks); | |
252 | rdtp->dynticks++; | |
253 | rdtp->dynticks_nesting++; | |
86848966 | 254 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
64db4cff PM |
255 | local_irq_restore(flags); |
256 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ | |
257 | } | |
258 | ||
259 | /** | |
260 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
261 | * | |
262 | * If the CPU was idle with dynamic ticks active, and there is no | |
263 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
264 | * RCU grace-period handling know that the CPU is active. | |
265 | */ | |
266 | void rcu_nmi_enter(void) | |
267 | { | |
268 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
269 | ||
270 | if (rdtp->dynticks & 0x1) | |
271 | return; | |
272 | rdtp->dynticks_nmi++; | |
86848966 | 273 | WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); |
64db4cff PM |
274 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
275 | } | |
276 | ||
277 | /** | |
278 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
279 | * | |
280 | * If the CPU was idle with dynamic ticks active, and there is no | |
281 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
282 | * RCU grace-period handling know that the CPU is no longer active. | |
283 | */ | |
284 | void rcu_nmi_exit(void) | |
285 | { | |
286 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
287 | ||
288 | if (rdtp->dynticks & 0x1) | |
289 | return; | |
290 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
291 | rdtp->dynticks_nmi++; | |
86848966 | 292 | WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); |
64db4cff PM |
293 | } |
294 | ||
295 | /** | |
296 | * rcu_irq_enter - inform RCU of entry to hard irq context | |
297 | * | |
298 | * If the CPU was idle with dynamic ticks active, this updates the | |
299 | * rdtp->dynticks to let the RCU handling know that the CPU is active. | |
300 | */ | |
301 | void rcu_irq_enter(void) | |
302 | { | |
303 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
304 | ||
305 | if (rdtp->dynticks_nesting++) | |
306 | return; | |
307 | rdtp->dynticks++; | |
86848966 | 308 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
64db4cff PM |
309 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
310 | } | |
311 | ||
312 | /** | |
313 | * rcu_irq_exit - inform RCU of exit from hard irq context | |
314 | * | |
315 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks | |
316 | * to put let the RCU handling be aware that the CPU is going back to idle | |
317 | * with no ticks. | |
318 | */ | |
319 | void rcu_irq_exit(void) | |
320 | { | |
321 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
322 | ||
323 | if (--rdtp->dynticks_nesting) | |
324 | return; | |
325 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
326 | rdtp->dynticks++; | |
86848966 | 327 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
64db4cff PM |
328 | |
329 | /* If the interrupt queued a callback, get out of dyntick mode. */ | |
d6714c22 | 330 | if (__get_cpu_var(rcu_sched_data).nxtlist || |
64db4cff PM |
331 | __get_cpu_var(rcu_bh_data).nxtlist) |
332 | set_need_resched(); | |
333 | } | |
334 | ||
335 | /* | |
336 | * Record the specified "completed" value, which is later used to validate | |
337 | * dynticks counter manipulations. Specify "rsp->completed - 1" to | |
338 | * unconditionally invalidate any future dynticks manipulations (which is | |
339 | * useful at the beginning of a grace period). | |
340 | */ | |
341 | static void dyntick_record_completed(struct rcu_state *rsp, long comp) | |
342 | { | |
343 | rsp->dynticks_completed = comp; | |
344 | } | |
345 | ||
346 | #ifdef CONFIG_SMP | |
347 | ||
348 | /* | |
349 | * Recall the previously recorded value of the completion for dynticks. | |
350 | */ | |
351 | static long dyntick_recall_completed(struct rcu_state *rsp) | |
352 | { | |
353 | return rsp->dynticks_completed; | |
354 | } | |
355 | ||
356 | /* | |
357 | * Snapshot the specified CPU's dynticks counter so that we can later | |
358 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 359 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
360 | */ |
361 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
362 | { | |
363 | int ret; | |
364 | int snap; | |
365 | int snap_nmi; | |
366 | ||
367 | snap = rdp->dynticks->dynticks; | |
368 | snap_nmi = rdp->dynticks->dynticks_nmi; | |
369 | smp_mb(); /* Order sampling of snap with end of grace period. */ | |
370 | rdp->dynticks_snap = snap; | |
371 | rdp->dynticks_nmi_snap = snap_nmi; | |
372 | ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); | |
373 | if (ret) | |
374 | rdp->dynticks_fqs++; | |
375 | return ret; | |
376 | } | |
377 | ||
378 | /* | |
379 | * Return true if the specified CPU has passed through a quiescent | |
380 | * state by virtue of being in or having passed through an dynticks | |
381 | * idle state since the last call to dyntick_save_progress_counter() | |
382 | * for this same CPU. | |
383 | */ | |
384 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
385 | { | |
386 | long curr; | |
387 | long curr_nmi; | |
388 | long snap; | |
389 | long snap_nmi; | |
390 | ||
391 | curr = rdp->dynticks->dynticks; | |
392 | snap = rdp->dynticks_snap; | |
393 | curr_nmi = rdp->dynticks->dynticks_nmi; | |
394 | snap_nmi = rdp->dynticks_nmi_snap; | |
395 | smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ | |
396 | ||
397 | /* | |
398 | * If the CPU passed through or entered a dynticks idle phase with | |
399 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
400 | * already acknowledged the request to pass through a quiescent | |
401 | * state. Either way, that CPU cannot possibly be in an RCU | |
402 | * read-side critical section that started before the beginning | |
403 | * of the current RCU grace period. | |
404 | */ | |
405 | if ((curr != snap || (curr & 0x1) == 0) && | |
406 | (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { | |
407 | rdp->dynticks_fqs++; | |
408 | return 1; | |
409 | } | |
410 | ||
411 | /* Go check for the CPU being offline. */ | |
412 | return rcu_implicit_offline_qs(rdp); | |
413 | } | |
414 | ||
415 | #endif /* #ifdef CONFIG_SMP */ | |
416 | ||
417 | #else /* #ifdef CONFIG_NO_HZ */ | |
418 | ||
419 | static void dyntick_record_completed(struct rcu_state *rsp, long comp) | |
420 | { | |
421 | } | |
422 | ||
423 | #ifdef CONFIG_SMP | |
424 | ||
425 | /* | |
426 | * If there are no dynticks, then the only way that a CPU can passively | |
427 | * be in a quiescent state is to be offline. Unlike dynticks idle, which | |
428 | * is a point in time during the prior (already finished) grace period, | |
429 | * an offline CPU is always in a quiescent state, and thus can be | |
430 | * unconditionally applied. So just return the current value of completed. | |
431 | */ | |
432 | static long dyntick_recall_completed(struct rcu_state *rsp) | |
433 | { | |
434 | return rsp->completed; | |
435 | } | |
436 | ||
437 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
438 | { | |
439 | return 0; | |
440 | } | |
441 | ||
442 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
443 | { | |
444 | return rcu_implicit_offline_qs(rdp); | |
445 | } | |
446 | ||
447 | #endif /* #ifdef CONFIG_SMP */ | |
448 | ||
449 | #endif /* #else #ifdef CONFIG_NO_HZ */ | |
450 | ||
451 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
452 | ||
453 | static void record_gp_stall_check_time(struct rcu_state *rsp) | |
454 | { | |
455 | rsp->gp_start = jiffies; | |
456 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; | |
457 | } | |
458 | ||
459 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
460 | { | |
461 | int cpu; | |
462 | long delta; | |
463 | unsigned long flags; | |
464 | struct rcu_node *rnp = rcu_get_root(rsp); | |
64db4cff PM |
465 | |
466 | /* Only let one CPU complain about others per time interval. */ | |
467 | ||
468 | spin_lock_irqsave(&rnp->lock, flags); | |
469 | delta = jiffies - rsp->jiffies_stall; | |
fc2219d4 | 470 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
64db4cff PM |
471 | spin_unlock_irqrestore(&rnp->lock, flags); |
472 | return; | |
473 | } | |
474 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
a0b6c9a7 PM |
475 | |
476 | /* | |
477 | * Now rat on any tasks that got kicked up to the root rcu_node | |
478 | * due to CPU offlining. | |
479 | */ | |
480 | rcu_print_task_stall(rnp); | |
64db4cff PM |
481 | spin_unlock_irqrestore(&rnp->lock, flags); |
482 | ||
483 | /* OK, time to rat on our buddy... */ | |
484 | ||
485 | printk(KERN_ERR "INFO: RCU detected CPU stalls:"); | |
a0b6c9a7 | 486 | rcu_for_each_leaf_node(rsp, rnp) { |
f41d911f | 487 | rcu_print_task_stall(rnp); |
a0b6c9a7 | 488 | if (rnp->qsmask == 0) |
64db4cff | 489 | continue; |
a0b6c9a7 PM |
490 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
491 | if (rnp->qsmask & (1UL << cpu)) | |
492 | printk(" %d", rnp->grplo + cpu); | |
64db4cff PM |
493 | } |
494 | printk(" (detected by %d, t=%ld jiffies)\n", | |
495 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); | |
c1dc0b9c IM |
496 | trigger_all_cpu_backtrace(); |
497 | ||
64db4cff PM |
498 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
499 | } | |
500 | ||
501 | static void print_cpu_stall(struct rcu_state *rsp) | |
502 | { | |
503 | unsigned long flags; | |
504 | struct rcu_node *rnp = rcu_get_root(rsp); | |
505 | ||
506 | printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n", | |
507 | smp_processor_id(), jiffies - rsp->gp_start); | |
c1dc0b9c IM |
508 | trigger_all_cpu_backtrace(); |
509 | ||
64db4cff PM |
510 | spin_lock_irqsave(&rnp->lock, flags); |
511 | if ((long)(jiffies - rsp->jiffies_stall) >= 0) | |
512 | rsp->jiffies_stall = | |
513 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
514 | spin_unlock_irqrestore(&rnp->lock, flags); | |
c1dc0b9c | 515 | |
64db4cff PM |
516 | set_need_resched(); /* kick ourselves to get things going. */ |
517 | } | |
518 | ||
519 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
520 | { | |
521 | long delta; | |
522 | struct rcu_node *rnp; | |
523 | ||
524 | delta = jiffies - rsp->jiffies_stall; | |
525 | rnp = rdp->mynode; | |
526 | if ((rnp->qsmask & rdp->grpmask) && delta >= 0) { | |
527 | ||
528 | /* We haven't checked in, so go dump stack. */ | |
529 | print_cpu_stall(rsp); | |
530 | ||
fc2219d4 | 531 | } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) { |
64db4cff PM |
532 | |
533 | /* They had two time units to dump stack, so complain. */ | |
534 | print_other_cpu_stall(rsp); | |
535 | } | |
536 | } | |
537 | ||
538 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
539 | ||
540 | static void record_gp_stall_check_time(struct rcu_state *rsp) | |
541 | { | |
542 | } | |
543 | ||
544 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
545 | { | |
546 | } | |
547 | ||
548 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
549 | ||
550 | /* | |
551 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
552 | * This is used both when we started the grace period and when we notice | |
553 | * that someone else started the grace period. | |
554 | */ | |
555 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) | |
556 | { | |
557 | rdp->qs_pending = 1; | |
558 | rdp->passed_quiesc = 0; | |
559 | rdp->gpnum = rsp->gpnum; | |
64db4cff PM |
560 | } |
561 | ||
562 | /* | |
563 | * Did someone else start a new RCU grace period start since we last | |
564 | * checked? Update local state appropriately if so. Must be called | |
565 | * on the CPU corresponding to rdp. | |
566 | */ | |
567 | static int | |
568 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
569 | { | |
570 | unsigned long flags; | |
571 | int ret = 0; | |
572 | ||
573 | local_irq_save(flags); | |
574 | if (rdp->gpnum != rsp->gpnum) { | |
575 | note_new_gpnum(rsp, rdp); | |
576 | ret = 1; | |
577 | } | |
578 | local_irq_restore(flags); | |
579 | return ret; | |
580 | } | |
581 | ||
582 | /* | |
583 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
584 | * in preparation for detecting the next grace period. The caller must hold | |
585 | * the root node's ->lock, which is released before return. Hard irqs must | |
586 | * be disabled. | |
587 | */ | |
588 | static void | |
589 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
590 | __releases(rcu_get_root(rsp)->lock) | |
591 | { | |
592 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; | |
593 | struct rcu_node *rnp = rcu_get_root(rsp); | |
64db4cff PM |
594 | |
595 | if (!cpu_needs_another_gp(rsp, rdp)) { | |
596 | spin_unlock_irqrestore(&rnp->lock, flags); | |
597 | return; | |
598 | } | |
599 | ||
600 | /* Advance to a new grace period and initialize state. */ | |
601 | rsp->gpnum++; | |
c3422bea | 602 | WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
64db4cff PM |
603 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
604 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
64db4cff PM |
605 | record_gp_stall_check_time(rsp); |
606 | dyntick_record_completed(rsp, rsp->completed - 1); | |
607 | note_new_gpnum(rsp, rdp); | |
608 | ||
609 | /* | |
1eba8f84 PM |
610 | * Because this CPU just now started the new grace period, we know |
611 | * that all of its callbacks will be covered by this upcoming grace | |
612 | * period, even the ones that were registered arbitrarily recently. | |
613 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. | |
614 | * | |
615 | * Other CPUs cannot be sure exactly when the grace period started. | |
616 | * Therefore, their recently registered callbacks must pass through | |
617 | * an additional RCU_NEXT_READY stage, so that they will be handled | |
618 | * by the next RCU grace period. | |
64db4cff PM |
619 | */ |
620 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
621 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
622 | ||
623 | /* Special-case the common single-level case. */ | |
624 | if (NUM_RCU_NODES == 1) { | |
b0e165c0 | 625 | rcu_preempt_check_blocked_tasks(rnp); |
28ecd580 | 626 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 627 | rnp->gpnum = rsp->gpnum; |
c12172c0 | 628 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
64db4cff PM |
629 | spin_unlock_irqrestore(&rnp->lock, flags); |
630 | return; | |
631 | } | |
632 | ||
633 | spin_unlock(&rnp->lock); /* leave irqs disabled. */ | |
634 | ||
635 | ||
636 | /* Exclude any concurrent CPU-hotplug operations. */ | |
637 | spin_lock(&rsp->onofflock); /* irqs already disabled. */ | |
638 | ||
639 | /* | |
b835db1f PM |
640 | * Set the quiescent-state-needed bits in all the rcu_node |
641 | * structures for all currently online CPUs in breadth-first | |
642 | * order, starting from the root rcu_node structure. This | |
643 | * operation relies on the layout of the hierarchy within the | |
644 | * rsp->node[] array. Note that other CPUs will access only | |
645 | * the leaves of the hierarchy, which still indicate that no | |
646 | * grace period is in progress, at least until the corresponding | |
647 | * leaf node has been initialized. In addition, we have excluded | |
648 | * CPU-hotplug operations. | |
64db4cff PM |
649 | * |
650 | * Note that the grace period cannot complete until we finish | |
651 | * the initialization process, as there will be at least one | |
652 | * qsmask bit set in the root node until that time, namely the | |
b835db1f PM |
653 | * one corresponding to this CPU, due to the fact that we have |
654 | * irqs disabled. | |
64db4cff | 655 | */ |
a0b6c9a7 | 656 | rcu_for_each_node_breadth_first(rsp, rnp) { |
49e29126 | 657 | spin_lock(&rnp->lock); /* irqs already disabled. */ |
b0e165c0 | 658 | rcu_preempt_check_blocked_tasks(rnp); |
49e29126 | 659 | rnp->qsmask = rnp->qsmaskinit; |
de078d87 | 660 | rnp->gpnum = rsp->gpnum; |
49e29126 | 661 | spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
662 | } |
663 | ||
664 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ | |
665 | spin_unlock_irqrestore(&rsp->onofflock, flags); | |
666 | } | |
667 | ||
668 | /* | |
669 | * Advance this CPU's callbacks, but only if the current grace period | |
670 | * has ended. This may be called only from the CPU to whom the rdp | |
671 | * belongs. | |
672 | */ | |
673 | static void | |
674 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
675 | { | |
676 | long completed_snap; | |
677 | unsigned long flags; | |
678 | ||
679 | local_irq_save(flags); | |
680 | completed_snap = ACCESS_ONCE(rsp->completed); /* outside of lock. */ | |
681 | ||
682 | /* Did another grace period end? */ | |
683 | if (rdp->completed != completed_snap) { | |
684 | ||
685 | /* Advance callbacks. No harm if list empty. */ | |
686 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
687 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
688 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
689 | ||
690 | /* Remember that we saw this grace-period completion. */ | |
691 | rdp->completed = completed_snap; | |
692 | } | |
693 | local_irq_restore(flags); | |
694 | } | |
695 | ||
f41d911f PM |
696 | /* |
697 | * Clean up after the prior grace period and let rcu_start_gp() start up | |
698 | * the next grace period if one is needed. Note that the caller must | |
699 | * hold rnp->lock, as required by rcu_start_gp(), which will release it. | |
700 | */ | |
701 | static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags) | |
fc2219d4 | 702 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 703 | { |
fc2219d4 | 704 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
f41d911f PM |
705 | rsp->completed = rsp->gpnum; |
706 | rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]); | |
707 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ | |
708 | } | |
709 | ||
64db4cff PM |
710 | /* |
711 | * Similar to cpu_quiet(), for which it is a helper function. Allows | |
712 | * a group of CPUs to be quieted at one go, though all the CPUs in the | |
713 | * group must be represented by the same leaf rcu_node structure. | |
714 | * That structure's lock must be held upon entry, and it is released | |
715 | * before return. | |
716 | */ | |
717 | static void | |
718 | cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, | |
719 | unsigned long flags) | |
720 | __releases(rnp->lock) | |
721 | { | |
28ecd580 PM |
722 | struct rcu_node *rnp_c; |
723 | ||
64db4cff PM |
724 | /* Walk up the rcu_node hierarchy. */ |
725 | for (;;) { | |
726 | if (!(rnp->qsmask & mask)) { | |
727 | ||
728 | /* Our bit has already been cleared, so done. */ | |
729 | spin_unlock_irqrestore(&rnp->lock, flags); | |
730 | return; | |
731 | } | |
732 | rnp->qsmask &= ~mask; | |
f41d911f | 733 | if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { |
64db4cff PM |
734 | |
735 | /* Other bits still set at this level, so done. */ | |
736 | spin_unlock_irqrestore(&rnp->lock, flags); | |
737 | return; | |
738 | } | |
739 | mask = rnp->grpmask; | |
740 | if (rnp->parent == NULL) { | |
741 | ||
742 | /* No more levels. Exit loop holding root lock. */ | |
743 | ||
744 | break; | |
745 | } | |
746 | spin_unlock_irqrestore(&rnp->lock, flags); | |
28ecd580 | 747 | rnp_c = rnp; |
64db4cff PM |
748 | rnp = rnp->parent; |
749 | spin_lock_irqsave(&rnp->lock, flags); | |
28ecd580 | 750 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
751 | } |
752 | ||
753 | /* | |
754 | * Get here if we are the last CPU to pass through a quiescent | |
f41d911f PM |
755 | * state for this grace period. Invoke cpu_quiet_msk_finish() |
756 | * to clean up and start the next grace period if one is needed. | |
64db4cff | 757 | */ |
f41d911f | 758 | cpu_quiet_msk_finish(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
759 | } |
760 | ||
761 | /* | |
762 | * Record a quiescent state for the specified CPU, which must either be | |
e7d8842e PM |
763 | * the current CPU. The lastcomp argument is used to make sure we are |
764 | * still in the grace period of interest. We don't want to end the current | |
765 | * grace period based on quiescent states detected in an earlier grace | |
766 | * period! | |
64db4cff PM |
767 | */ |
768 | static void | |
769 | cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) | |
770 | { | |
771 | unsigned long flags; | |
772 | unsigned long mask; | |
773 | struct rcu_node *rnp; | |
774 | ||
775 | rnp = rdp->mynode; | |
776 | spin_lock_irqsave(&rnp->lock, flags); | |
777 | if (lastcomp != ACCESS_ONCE(rsp->completed)) { | |
778 | ||
779 | /* | |
780 | * Someone beat us to it for this grace period, so leave. | |
781 | * The race with GP start is resolved by the fact that we | |
782 | * hold the leaf rcu_node lock, so that the per-CPU bits | |
783 | * cannot yet be initialized -- so we would simply find our | |
784 | * CPU's bit already cleared in cpu_quiet_msk() if this race | |
785 | * occurred. | |
786 | */ | |
787 | rdp->passed_quiesc = 0; /* try again later! */ | |
788 | spin_unlock_irqrestore(&rnp->lock, flags); | |
789 | return; | |
790 | } | |
791 | mask = rdp->grpmask; | |
792 | if ((rnp->qsmask & mask) == 0) { | |
793 | spin_unlock_irqrestore(&rnp->lock, flags); | |
794 | } else { | |
795 | rdp->qs_pending = 0; | |
796 | ||
797 | /* | |
798 | * This GP can't end until cpu checks in, so all of our | |
799 | * callbacks can be processed during the next GP. | |
800 | */ | |
64db4cff PM |
801 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
802 | ||
803 | cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */ | |
804 | } | |
805 | } | |
806 | ||
807 | /* | |
808 | * Check to see if there is a new grace period of which this CPU | |
809 | * is not yet aware, and if so, set up local rcu_data state for it. | |
810 | * Otherwise, see if this CPU has just passed through its first | |
811 | * quiescent state for this grace period, and record that fact if so. | |
812 | */ | |
813 | static void | |
814 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
815 | { | |
816 | /* If there is now a new grace period, record and return. */ | |
817 | if (check_for_new_grace_period(rsp, rdp)) | |
818 | return; | |
819 | ||
820 | /* | |
821 | * Does this CPU still need to do its part for current grace period? | |
822 | * If no, return and let the other CPUs do their part as well. | |
823 | */ | |
824 | if (!rdp->qs_pending) | |
825 | return; | |
826 | ||
827 | /* | |
828 | * Was there a quiescent state since the beginning of the grace | |
829 | * period? If no, then exit and wait for the next call. | |
830 | */ | |
831 | if (!rdp->passed_quiesc) | |
832 | return; | |
833 | ||
834 | /* Tell RCU we are done (but cpu_quiet() will be the judge of that). */ | |
835 | cpu_quiet(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); | |
836 | } | |
837 | ||
838 | #ifdef CONFIG_HOTPLUG_CPU | |
839 | ||
840 | /* | |
841 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy | |
842 | * and move all callbacks from the outgoing CPU to the current one. | |
843 | */ | |
844 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) | |
845 | { | |
846 | int i; | |
847 | unsigned long flags; | |
848 | long lastcomp; | |
849 | unsigned long mask; | |
850 | struct rcu_data *rdp = rsp->rda[cpu]; | |
851 | struct rcu_data *rdp_me; | |
852 | struct rcu_node *rnp; | |
853 | ||
854 | /* Exclude any attempts to start a new grace period. */ | |
855 | spin_lock_irqsave(&rsp->onofflock, flags); | |
856 | ||
857 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ | |
28ecd580 | 858 | rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
64db4cff PM |
859 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
860 | do { | |
861 | spin_lock(&rnp->lock); /* irqs already disabled. */ | |
862 | rnp->qsmaskinit &= ~mask; | |
863 | if (rnp->qsmaskinit != 0) { | |
f41d911f | 864 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
865 | break; |
866 | } | |
28ecd580 | 867 | rcu_preempt_offline_tasks(rsp, rnp, rdp); |
64db4cff | 868 | mask = rnp->grpmask; |
f41d911f | 869 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
870 | rnp = rnp->parent; |
871 | } while (rnp != NULL); | |
872 | lastcomp = rsp->completed; | |
873 | ||
874 | spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ | |
875 | ||
64db4cff PM |
876 | /* |
877 | * Move callbacks from the outgoing CPU to the running CPU. | |
1eba8f84 | 878 | * Note that the outgoing CPU is now quiescent, so it is now |
d6714c22 | 879 | * (uncharacteristically) safe to access its rcu_data structure. |
64db4cff PM |
880 | * Note also that we must carefully retain the order of the |
881 | * outgoing CPU's callbacks in order for rcu_barrier() to work | |
882 | * correctly. Finally, note that we start all the callbacks | |
883 | * afresh, even those that have passed through a grace period | |
884 | * and are therefore ready to invoke. The theory is that hotplug | |
885 | * events are rare, and that if they are frequent enough to | |
886 | * indefinitely delay callbacks, you have far worse things to | |
887 | * be worrying about. | |
888 | */ | |
64db4cff | 889 | if (rdp->nxtlist != NULL) { |
3d76c082 | 890 | rdp_me = rsp->rda[smp_processor_id()]; |
64db4cff PM |
891 | *rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist; |
892 | rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
893 | rdp->nxtlist = NULL; | |
894 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
895 | rdp->nxttail[i] = &rdp->nxtlist; | |
896 | rdp_me->qlen += rdp->qlen; | |
897 | rdp->qlen = 0; | |
898 | } | |
899 | local_irq_restore(flags); | |
900 | } | |
901 | ||
902 | /* | |
903 | * Remove the specified CPU from the RCU hierarchy and move any pending | |
904 | * callbacks that it might have to the current CPU. This code assumes | |
905 | * that at least one CPU in the system will remain running at all times. | |
906 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. | |
907 | */ | |
908 | static void rcu_offline_cpu(int cpu) | |
909 | { | |
d6714c22 | 910 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
64db4cff | 911 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
33f76148 | 912 | rcu_preempt_offline_cpu(cpu); |
64db4cff PM |
913 | } |
914 | ||
915 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
916 | ||
917 | static void rcu_offline_cpu(int cpu) | |
918 | { | |
919 | } | |
920 | ||
921 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
922 | ||
923 | /* | |
924 | * Invoke any RCU callbacks that have made it to the end of their grace | |
925 | * period. Thottle as specified by rdp->blimit. | |
926 | */ | |
927 | static void rcu_do_batch(struct rcu_data *rdp) | |
928 | { | |
929 | unsigned long flags; | |
930 | struct rcu_head *next, *list, **tail; | |
931 | int count; | |
932 | ||
933 | /* If no callbacks are ready, just return.*/ | |
934 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) | |
935 | return; | |
936 | ||
937 | /* | |
938 | * Extract the list of ready callbacks, disabling to prevent | |
939 | * races with call_rcu() from interrupt handlers. | |
940 | */ | |
941 | local_irq_save(flags); | |
942 | list = rdp->nxtlist; | |
943 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
944 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
945 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
946 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) | |
947 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) | |
948 | rdp->nxttail[count] = &rdp->nxtlist; | |
949 | local_irq_restore(flags); | |
950 | ||
951 | /* Invoke callbacks. */ | |
952 | count = 0; | |
953 | while (list) { | |
954 | next = list->next; | |
955 | prefetch(next); | |
956 | list->func(list); | |
957 | list = next; | |
958 | if (++count >= rdp->blimit) | |
959 | break; | |
960 | } | |
961 | ||
962 | local_irq_save(flags); | |
963 | ||
964 | /* Update count, and requeue any remaining callbacks. */ | |
965 | rdp->qlen -= count; | |
966 | if (list != NULL) { | |
967 | *tail = rdp->nxtlist; | |
968 | rdp->nxtlist = list; | |
969 | for (count = 0; count < RCU_NEXT_SIZE; count++) | |
970 | if (&rdp->nxtlist == rdp->nxttail[count]) | |
971 | rdp->nxttail[count] = tail; | |
972 | else | |
973 | break; | |
974 | } | |
975 | ||
976 | /* Reinstate batch limit if we have worked down the excess. */ | |
977 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
978 | rdp->blimit = blimit; | |
979 | ||
980 | local_irq_restore(flags); | |
981 | ||
982 | /* Re-raise the RCU softirq if there are callbacks remaining. */ | |
983 | if (cpu_has_callbacks_ready_to_invoke(rdp)) | |
984 | raise_softirq(RCU_SOFTIRQ); | |
985 | } | |
986 | ||
987 | /* | |
988 | * Check to see if this CPU is in a non-context-switch quiescent state | |
989 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
990 | * Also schedule the RCU softirq handler. | |
991 | * | |
992 | * This function must be called with hardirqs disabled. It is normally | |
993 | * invoked from the scheduling-clock interrupt. If rcu_pending returns | |
994 | * false, there is no point in invoking rcu_check_callbacks(). | |
995 | */ | |
996 | void rcu_check_callbacks(int cpu, int user) | |
997 | { | |
a157229c PM |
998 | if (!rcu_pending(cpu)) |
999 | return; /* if nothing for RCU to do. */ | |
64db4cff | 1000 | if (user || |
a6826048 PM |
1001 | (idle_cpu(cpu) && rcu_scheduler_active && |
1002 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
64db4cff PM |
1003 | |
1004 | /* | |
1005 | * Get here if this CPU took its interrupt from user | |
1006 | * mode or from the idle loop, and if this is not a | |
1007 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1008 | * a quiescent state, so note it. |
64db4cff PM |
1009 | * |
1010 | * No memory barrier is required here because both | |
d6714c22 PM |
1011 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1012 | * variables that other CPUs neither access nor modify, | |
1013 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1014 | */ |
1015 | ||
d6714c22 PM |
1016 | rcu_sched_qs(cpu); |
1017 | rcu_bh_qs(cpu); | |
64db4cff PM |
1018 | |
1019 | } else if (!in_softirq()) { | |
1020 | ||
1021 | /* | |
1022 | * Get here if this CPU did not take its interrupt from | |
1023 | * softirq, in other words, if it is not interrupting | |
1024 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1025 | * critical section, so note it. |
64db4cff PM |
1026 | */ |
1027 | ||
d6714c22 | 1028 | rcu_bh_qs(cpu); |
64db4cff | 1029 | } |
f41d911f | 1030 | rcu_preempt_check_callbacks(cpu); |
64db4cff PM |
1031 | raise_softirq(RCU_SOFTIRQ); |
1032 | } | |
1033 | ||
1034 | #ifdef CONFIG_SMP | |
1035 | ||
1036 | /* | |
1037 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1038 | * have not yet encountered a quiescent state, using the function specified. | |
1039 | * Returns 1 if the current grace period ends while scanning (possibly | |
1040 | * because we made it end). | |
1041 | */ | |
1042 | static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp, | |
1043 | int (*f)(struct rcu_data *)) | |
1044 | { | |
1045 | unsigned long bit; | |
1046 | int cpu; | |
1047 | unsigned long flags; | |
1048 | unsigned long mask; | |
a0b6c9a7 | 1049 | struct rcu_node *rnp; |
64db4cff | 1050 | |
a0b6c9a7 | 1051 | rcu_for_each_leaf_node(rsp, rnp) { |
64db4cff | 1052 | mask = 0; |
a0b6c9a7 | 1053 | spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 1054 | if (rsp->completed != lastcomp) { |
a0b6c9a7 | 1055 | spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1056 | return 1; |
1057 | } | |
a0b6c9a7 PM |
1058 | if (rnp->qsmask == 0) { |
1059 | spin_unlock_irqrestore(&rnp->lock, flags); | |
64db4cff PM |
1060 | continue; |
1061 | } | |
a0b6c9a7 | 1062 | cpu = rnp->grplo; |
64db4cff | 1063 | bit = 1; |
a0b6c9a7 PM |
1064 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
1065 | if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu])) | |
64db4cff PM |
1066 | mask |= bit; |
1067 | } | |
1068 | if (mask != 0 && rsp->completed == lastcomp) { | |
1069 | ||
a0b6c9a7 PM |
1070 | /* cpu_quiet_msk() releases rnp->lock. */ |
1071 | cpu_quiet_msk(mask, rsp, rnp, flags); | |
64db4cff PM |
1072 | continue; |
1073 | } | |
a0b6c9a7 | 1074 | spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1075 | } |
1076 | return 0; | |
1077 | } | |
1078 | ||
1079 | /* | |
1080 | * Force quiescent states on reluctant CPUs, and also detect which | |
1081 | * CPUs are in dyntick-idle mode. | |
1082 | */ | |
1083 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1084 | { | |
1085 | unsigned long flags; | |
1086 | long lastcomp; | |
64db4cff PM |
1087 | struct rcu_node *rnp = rcu_get_root(rsp); |
1088 | u8 signaled; | |
1089 | ||
fc2219d4 | 1090 | if (!rcu_gp_in_progress(rsp)) |
64db4cff PM |
1091 | return; /* No grace period in progress, nothing to force. */ |
1092 | if (!spin_trylock_irqsave(&rsp->fqslock, flags)) { | |
1093 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ | |
1094 | return; /* Someone else is already on the job. */ | |
1095 | } | |
1096 | if (relaxed && | |
ef631b0c | 1097 | (long)(rsp->jiffies_force_qs - jiffies) >= 0) |
64db4cff PM |
1098 | goto unlock_ret; /* no emergency and done recently. */ |
1099 | rsp->n_force_qs++; | |
1100 | spin_lock(&rnp->lock); | |
1101 | lastcomp = rsp->completed; | |
1102 | signaled = rsp->signaled; | |
1103 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
64db4cff PM |
1104 | if (lastcomp == rsp->gpnum) { |
1105 | rsp->n_force_qs_ngp++; | |
1106 | spin_unlock(&rnp->lock); | |
1107 | goto unlock_ret; /* no GP in progress, time updated. */ | |
1108 | } | |
1109 | spin_unlock(&rnp->lock); | |
1110 | switch (signaled) { | |
1111 | case RCU_GP_INIT: | |
1112 | ||
1113 | break; /* grace period still initializing, ignore. */ | |
1114 | ||
1115 | case RCU_SAVE_DYNTICK: | |
1116 | ||
1117 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) | |
1118 | break; /* So gcc recognizes the dead code. */ | |
1119 | ||
1120 | /* Record dyntick-idle state. */ | |
1121 | if (rcu_process_dyntick(rsp, lastcomp, | |
1122 | dyntick_save_progress_counter)) | |
1123 | goto unlock_ret; | |
1124 | ||
1125 | /* Update state, record completion counter. */ | |
1126 | spin_lock(&rnp->lock); | |
1127 | if (lastcomp == rsp->completed) { | |
1128 | rsp->signaled = RCU_FORCE_QS; | |
1129 | dyntick_record_completed(rsp, lastcomp); | |
1130 | } | |
1131 | spin_unlock(&rnp->lock); | |
1132 | break; | |
1133 | ||
1134 | case RCU_FORCE_QS: | |
1135 | ||
1136 | /* Check dyntick-idle state, send IPI to laggarts. */ | |
1137 | if (rcu_process_dyntick(rsp, dyntick_recall_completed(rsp), | |
1138 | rcu_implicit_dynticks_qs)) | |
1139 | goto unlock_ret; | |
1140 | ||
1141 | /* Leave state in case more forcing is required. */ | |
1142 | ||
1143 | break; | |
1144 | } | |
1145 | unlock_ret: | |
1146 | spin_unlock_irqrestore(&rsp->fqslock, flags); | |
1147 | } | |
1148 | ||
1149 | #else /* #ifdef CONFIG_SMP */ | |
1150 | ||
1151 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1152 | { | |
1153 | set_need_resched(); | |
1154 | } | |
1155 | ||
1156 | #endif /* #else #ifdef CONFIG_SMP */ | |
1157 | ||
1158 | /* | |
1159 | * This does the RCU processing work from softirq context for the | |
1160 | * specified rcu_state and rcu_data structures. This may be called | |
1161 | * only from the CPU to whom the rdp belongs. | |
1162 | */ | |
1163 | static void | |
1164 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) | |
1165 | { | |
1166 | unsigned long flags; | |
1167 | ||
2e597558 PM |
1168 | WARN_ON_ONCE(rdp->beenonline == 0); |
1169 | ||
64db4cff PM |
1170 | /* |
1171 | * If an RCU GP has gone long enough, go check for dyntick | |
1172 | * idle CPUs and, if needed, send resched IPIs. | |
1173 | */ | |
ef631b0c | 1174 | if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
64db4cff PM |
1175 | force_quiescent_state(rsp, 1); |
1176 | ||
1177 | /* | |
1178 | * Advance callbacks in response to end of earlier grace | |
1179 | * period that some other CPU ended. | |
1180 | */ | |
1181 | rcu_process_gp_end(rsp, rdp); | |
1182 | ||
1183 | /* Update RCU state based on any recent quiescent states. */ | |
1184 | rcu_check_quiescent_state(rsp, rdp); | |
1185 | ||
1186 | /* Does this CPU require a not-yet-started grace period? */ | |
1187 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1188 | spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); | |
1189 | rcu_start_gp(rsp, flags); /* releases above lock */ | |
1190 | } | |
1191 | ||
1192 | /* If there are callbacks ready, invoke them. */ | |
1193 | rcu_do_batch(rdp); | |
1194 | } | |
1195 | ||
1196 | /* | |
1197 | * Do softirq processing for the current CPU. | |
1198 | */ | |
1199 | static void rcu_process_callbacks(struct softirq_action *unused) | |
1200 | { | |
1201 | /* | |
1202 | * Memory references from any prior RCU read-side critical sections | |
1203 | * executed by the interrupted code must be seen before any RCU | |
1204 | * grace-period manipulations below. | |
1205 | */ | |
1206 | smp_mb(); /* See above block comment. */ | |
1207 | ||
d6714c22 PM |
1208 | __rcu_process_callbacks(&rcu_sched_state, |
1209 | &__get_cpu_var(rcu_sched_data)); | |
64db4cff | 1210 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
f41d911f | 1211 | rcu_preempt_process_callbacks(); |
64db4cff PM |
1212 | |
1213 | /* | |
1214 | * Memory references from any later RCU read-side critical sections | |
1215 | * executed by the interrupted code must be seen after any RCU | |
1216 | * grace-period manipulations above. | |
1217 | */ | |
1218 | smp_mb(); /* See above block comment. */ | |
1219 | } | |
1220 | ||
1221 | static void | |
1222 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
1223 | struct rcu_state *rsp) | |
1224 | { | |
1225 | unsigned long flags; | |
1226 | struct rcu_data *rdp; | |
1227 | ||
1228 | head->func = func; | |
1229 | head->next = NULL; | |
1230 | ||
1231 | smp_mb(); /* Ensure RCU update seen before callback registry. */ | |
1232 | ||
1233 | /* | |
1234 | * Opportunistically note grace-period endings and beginnings. | |
1235 | * Note that we might see a beginning right after we see an | |
1236 | * end, but never vice versa, since this CPU has to pass through | |
1237 | * a quiescent state betweentimes. | |
1238 | */ | |
1239 | local_irq_save(flags); | |
1240 | rdp = rsp->rda[smp_processor_id()]; | |
1241 | rcu_process_gp_end(rsp, rdp); | |
1242 | check_for_new_grace_period(rsp, rdp); | |
1243 | ||
1244 | /* Add the callback to our list. */ | |
1245 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
1246 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
1247 | ||
1248 | /* Start a new grace period if one not already started. */ | |
fc2219d4 | 1249 | if (!rcu_gp_in_progress(rsp)) { |
64db4cff PM |
1250 | unsigned long nestflag; |
1251 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
1252 | ||
1253 | spin_lock_irqsave(&rnp_root->lock, nestflag); | |
1254 | rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */ | |
1255 | } | |
1256 | ||
1257 | /* Force the grace period if too many callbacks or too long waiting. */ | |
1258 | if (unlikely(++rdp->qlen > qhimark)) { | |
1259 | rdp->blimit = LONG_MAX; | |
1260 | force_quiescent_state(rsp, 0); | |
ef631b0c | 1261 | } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
64db4cff PM |
1262 | force_quiescent_state(rsp, 1); |
1263 | local_irq_restore(flags); | |
1264 | } | |
1265 | ||
1266 | /* | |
d6714c22 | 1267 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 1268 | */ |
d6714c22 | 1269 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 1270 | { |
d6714c22 | 1271 | __call_rcu(head, func, &rcu_sched_state); |
64db4cff | 1272 | } |
d6714c22 | 1273 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
1274 | |
1275 | /* | |
1276 | * Queue an RCU for invocation after a quicker grace period. | |
1277 | */ | |
1278 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1279 | { | |
1280 | __call_rcu(head, func, &rcu_bh_state); | |
1281 | } | |
1282 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
1283 | ||
1284 | /* | |
1285 | * Check to see if there is any immediate RCU-related work to be done | |
1286 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
1287 | * The checks are in order of increasing expense: checks that can be | |
1288 | * carried out against CPU-local state are performed first. However, | |
1289 | * we must check for CPU stalls first, else we might not get a chance. | |
1290 | */ | |
1291 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
1292 | { | |
1293 | rdp->n_rcu_pending++; | |
1294 | ||
1295 | /* Check for CPU stalls, if enabled. */ | |
1296 | check_cpu_stall(rsp, rdp); | |
1297 | ||
1298 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
7ba5c840 PM |
1299 | if (rdp->qs_pending) { |
1300 | rdp->n_rp_qs_pending++; | |
64db4cff | 1301 | return 1; |
7ba5c840 | 1302 | } |
64db4cff PM |
1303 | |
1304 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
1305 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
1306 | rdp->n_rp_cb_ready++; | |
64db4cff | 1307 | return 1; |
7ba5c840 | 1308 | } |
64db4cff PM |
1309 | |
1310 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
1311 | if (cpu_needs_another_gp(rsp, rdp)) { |
1312 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 1313 | return 1; |
7ba5c840 | 1314 | } |
64db4cff PM |
1315 | |
1316 | /* Has another RCU grace period completed? */ | |
7ba5c840 PM |
1317 | if (ACCESS_ONCE(rsp->completed) != rdp->completed) { /* outside lock */ |
1318 | rdp->n_rp_gp_completed++; | |
64db4cff | 1319 | return 1; |
7ba5c840 | 1320 | } |
64db4cff PM |
1321 | |
1322 | /* Has a new RCU grace period started? */ | |
7ba5c840 PM |
1323 | if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) { /* outside lock */ |
1324 | rdp->n_rp_gp_started++; | |
64db4cff | 1325 | return 1; |
7ba5c840 | 1326 | } |
64db4cff PM |
1327 | |
1328 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ | |
fc2219d4 | 1329 | if (rcu_gp_in_progress(rsp) && |
7ba5c840 PM |
1330 | ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) { |
1331 | rdp->n_rp_need_fqs++; | |
64db4cff | 1332 | return 1; |
7ba5c840 | 1333 | } |
64db4cff PM |
1334 | |
1335 | /* nothing to do */ | |
7ba5c840 | 1336 | rdp->n_rp_need_nothing++; |
64db4cff PM |
1337 | return 0; |
1338 | } | |
1339 | ||
1340 | /* | |
1341 | * Check to see if there is any immediate RCU-related work to be done | |
1342 | * by the current CPU, returning 1 if so. This function is part of the | |
1343 | * RCU implementation; it is -not- an exported member of the RCU API. | |
1344 | */ | |
a157229c | 1345 | static int rcu_pending(int cpu) |
64db4cff | 1346 | { |
d6714c22 | 1347 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
f41d911f PM |
1348 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
1349 | rcu_preempt_pending(cpu); | |
64db4cff PM |
1350 | } |
1351 | ||
1352 | /* | |
1353 | * Check to see if any future RCU-related work will need to be done | |
1354 | * by the current CPU, even if none need be done immediately, returning | |
1355 | * 1 if so. This function is part of the RCU implementation; it is -not- | |
1356 | * an exported member of the RCU API. | |
1357 | */ | |
1358 | int rcu_needs_cpu(int cpu) | |
1359 | { | |
1360 | /* RCU callbacks either ready or pending? */ | |
d6714c22 | 1361 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
f41d911f PM |
1362 | per_cpu(rcu_bh_data, cpu).nxtlist || |
1363 | rcu_preempt_needs_cpu(cpu); | |
64db4cff PM |
1364 | } |
1365 | ||
1366 | /* | |
27569620 | 1367 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 1368 | */ |
27569620 PM |
1369 | static void __init |
1370 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
1371 | { |
1372 | unsigned long flags; | |
1373 | int i; | |
27569620 PM |
1374 | struct rcu_data *rdp = rsp->rda[cpu]; |
1375 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1376 | ||
1377 | /* Set up local state, ensuring consistent view of global state. */ | |
1378 | spin_lock_irqsave(&rnp->lock, flags); | |
1379 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); | |
1380 | rdp->nxtlist = NULL; | |
1381 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1382 | rdp->nxttail[i] = &rdp->nxtlist; | |
1383 | rdp->qlen = 0; | |
1384 | #ifdef CONFIG_NO_HZ | |
1385 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); | |
1386 | #endif /* #ifdef CONFIG_NO_HZ */ | |
1387 | rdp->cpu = cpu; | |
1388 | spin_unlock_irqrestore(&rnp->lock, flags); | |
1389 | } | |
1390 | ||
1391 | /* | |
1392 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
1393 | * offline event can be happening at a given time. Note also that we | |
1394 | * can accept some slop in the rsp->completed access due to the fact | |
1395 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 1396 | */ |
e4fa4c97 | 1397 | static void __cpuinit |
f41d911f | 1398 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
64db4cff PM |
1399 | { |
1400 | unsigned long flags; | |
64db4cff PM |
1401 | long lastcomp; |
1402 | unsigned long mask; | |
1403 | struct rcu_data *rdp = rsp->rda[cpu]; | |
1404 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1405 | ||
1406 | /* Set up local state, ensuring consistent view of global state. */ | |
1407 | spin_lock_irqsave(&rnp->lock, flags); | |
1408 | lastcomp = rsp->completed; | |
1409 | rdp->completed = lastcomp; | |
1410 | rdp->gpnum = lastcomp; | |
1411 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ | |
1412 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ | |
1413 | rdp->beenonline = 1; /* We have now been online. */ | |
f41d911f | 1414 | rdp->preemptable = preemptable; |
64db4cff | 1415 | rdp->passed_quiesc_completed = lastcomp - 1; |
64db4cff | 1416 | rdp->blimit = blimit; |
64db4cff PM |
1417 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
1418 | ||
1419 | /* | |
1420 | * A new grace period might start here. If so, we won't be part | |
1421 | * of it, but that is OK, as we are currently in a quiescent state. | |
1422 | */ | |
1423 | ||
1424 | /* Exclude any attempts to start a new GP on large systems. */ | |
1425 | spin_lock(&rsp->onofflock); /* irqs already disabled. */ | |
1426 | ||
1427 | /* Add CPU to rcu_node bitmasks. */ | |
1428 | rnp = rdp->mynode; | |
1429 | mask = rdp->grpmask; | |
1430 | do { | |
1431 | /* Exclude any attempts to start a new GP on small systems. */ | |
1432 | spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1433 | rnp->qsmaskinit |= mask; | |
1434 | mask = rnp->grpmask; | |
1435 | spin_unlock(&rnp->lock); /* irqs already disabled. */ | |
1436 | rnp = rnp->parent; | |
1437 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
1438 | ||
e7d8842e | 1439 | spin_unlock_irqrestore(&rsp->onofflock, flags); |
64db4cff PM |
1440 | } |
1441 | ||
1442 | static void __cpuinit rcu_online_cpu(int cpu) | |
1443 | { | |
f41d911f PM |
1444 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
1445 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); | |
1446 | rcu_preempt_init_percpu_data(cpu); | |
64db4cff PM |
1447 | } |
1448 | ||
1449 | /* | |
f41d911f | 1450 | * Handle CPU online/offline notification events. |
64db4cff | 1451 | */ |
2e597558 PM |
1452 | int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
1453 | unsigned long action, void *hcpu) | |
64db4cff PM |
1454 | { |
1455 | long cpu = (long)hcpu; | |
1456 | ||
1457 | switch (action) { | |
1458 | case CPU_UP_PREPARE: | |
1459 | case CPU_UP_PREPARE_FROZEN: | |
1460 | rcu_online_cpu(cpu); | |
1461 | break; | |
1462 | case CPU_DEAD: | |
1463 | case CPU_DEAD_FROZEN: | |
1464 | case CPU_UP_CANCELED: | |
1465 | case CPU_UP_CANCELED_FROZEN: | |
1466 | rcu_offline_cpu(cpu); | |
1467 | break; | |
1468 | default: | |
1469 | break; | |
1470 | } | |
1471 | return NOTIFY_OK; | |
1472 | } | |
1473 | ||
1474 | /* | |
1475 | * Compute the per-level fanout, either using the exact fanout specified | |
1476 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
1477 | */ | |
1478 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
1479 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1480 | { | |
1481 | int i; | |
1482 | ||
1483 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) | |
1484 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; | |
1485 | } | |
1486 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1487 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1488 | { | |
1489 | int ccur; | |
1490 | int cprv; | |
1491 | int i; | |
1492 | ||
1493 | cprv = NR_CPUS; | |
1494 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1495 | ccur = rsp->levelcnt[i]; | |
1496 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
1497 | cprv = ccur; | |
1498 | } | |
1499 | } | |
1500 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1501 | ||
1502 | /* | |
1503 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
1504 | */ | |
1505 | static void __init rcu_init_one(struct rcu_state *rsp) | |
1506 | { | |
1507 | int cpustride = 1; | |
1508 | int i; | |
1509 | int j; | |
1510 | struct rcu_node *rnp; | |
1511 | ||
1512 | /* Initialize the level-tracking arrays. */ | |
1513 | ||
1514 | for (i = 1; i < NUM_RCU_LVLS; i++) | |
1515 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; | |
1516 | rcu_init_levelspread(rsp); | |
1517 | ||
1518 | /* Initialize the elements themselves, starting from the leaves. */ | |
1519 | ||
1520 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1521 | cpustride *= rsp->levelspread[i]; | |
1522 | rnp = rsp->level[i]; | |
1523 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1524 | spin_lock_init(&rnp->lock); | |
f41d911f | 1525 | rnp->gpnum = 0; |
64db4cff PM |
1526 | rnp->qsmask = 0; |
1527 | rnp->qsmaskinit = 0; | |
1528 | rnp->grplo = j * cpustride; | |
1529 | rnp->grphi = (j + 1) * cpustride - 1; | |
1530 | if (rnp->grphi >= NR_CPUS) | |
1531 | rnp->grphi = NR_CPUS - 1; | |
1532 | if (i == 0) { | |
1533 | rnp->grpnum = 0; | |
1534 | rnp->grpmask = 0; | |
1535 | rnp->parent = NULL; | |
1536 | } else { | |
1537 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
1538 | rnp->grpmask = 1UL << rnp->grpnum; | |
1539 | rnp->parent = rsp->level[i - 1] + | |
1540 | j / rsp->levelspread[i - 1]; | |
1541 | } | |
1542 | rnp->level = i; | |
f41d911f PM |
1543 | INIT_LIST_HEAD(&rnp->blocked_tasks[0]); |
1544 | INIT_LIST_HEAD(&rnp->blocked_tasks[1]); | |
64db4cff PM |
1545 | } |
1546 | } | |
1547 | } | |
1548 | ||
1549 | /* | |
f41d911f PM |
1550 | * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used |
1551 | * nowhere else! Assigns leaf node pointers into each CPU's rcu_data | |
1552 | * structure. | |
64db4cff | 1553 | */ |
65cf8f86 | 1554 | #define RCU_INIT_FLAVOR(rsp, rcu_data) \ |
64db4cff | 1555 | do { \ |
a0b6c9a7 PM |
1556 | int i; \ |
1557 | int j; \ | |
1558 | struct rcu_node *rnp; \ | |
1559 | \ | |
65cf8f86 | 1560 | rcu_init_one(rsp); \ |
64db4cff PM |
1561 | rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \ |
1562 | j = 0; \ | |
1563 | for_each_possible_cpu(i) { \ | |
1564 | if (i > rnp[j].grphi) \ | |
1565 | j++; \ | |
1566 | per_cpu(rcu_data, i).mynode = &rnp[j]; \ | |
1567 | (rsp)->rda[i] = &per_cpu(rcu_data, i); \ | |
65cf8f86 | 1568 | rcu_boot_init_percpu_data(i, rsp); \ |
64db4cff PM |
1569 | } \ |
1570 | } while (0) | |
1571 | ||
64db4cff PM |
1572 | void __init __rcu_init(void) |
1573 | { | |
f41d911f | 1574 | rcu_bootup_announce(); |
64db4cff PM |
1575 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
1576 | printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); | |
1577 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
65cf8f86 PM |
1578 | RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); |
1579 | RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); | |
f41d911f | 1580 | __rcu_init_preempt(); |
2e597558 | 1581 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
64db4cff PM |
1582 | } |
1583 | ||
1eba8f84 | 1584 | #include "rcutree_plugin.h" |