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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 - | |
28 | * Documentation/RCU | |
29 | */ | |
30 | #include <linux/types.h> | |
31 | #include <linux/kernel.h> | |
32 | #include <linux/init.h> | |
33 | #include <linux/spinlock.h> | |
34 | #include <linux/smp.h> | |
35 | #include <linux/rcupdate.h> | |
36 | #include <linux/interrupt.h> | |
37 | #include <linux/sched.h> | |
38 | #include <asm/atomic.h> | |
39 | #include <linux/bitops.h> | |
40 | #include <linux/module.h> | |
41 | #include <linux/completion.h> | |
42 | #include <linux/moduleparam.h> | |
43 | #include <linux/percpu.h> | |
44 | #include <linux/notifier.h> | |
45 | #include <linux/cpu.h> | |
46 | #include <linux/mutex.h> | |
47 | #include <linux/time.h> | |
48 | ||
9f77da9f PM |
49 | #include "rcutree.h" |
50 | ||
64db4cff PM |
51 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
52 | static struct lock_class_key rcu_lock_key; | |
53 | struct lockdep_map rcu_lock_map = | |
54 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); | |
55 | EXPORT_SYMBOL_GPL(rcu_lock_map); | |
56 | #endif | |
57 | ||
58 | /* Data structures. */ | |
59 | ||
60 | #define RCU_STATE_INITIALIZER(name) { \ | |
61 | .level = { &name.node[0] }, \ | |
62 | .levelcnt = { \ | |
63 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ | |
64 | NUM_RCU_LVL_1, \ | |
65 | NUM_RCU_LVL_2, \ | |
66 | NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \ | |
67 | }, \ | |
68 | .signaled = RCU_SIGNAL_INIT, \ | |
69 | .gpnum = -300, \ | |
70 | .completed = -300, \ | |
71 | .onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \ | |
72 | .fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \ | |
73 | .n_force_qs = 0, \ | |
74 | .n_force_qs_ngp = 0, \ | |
75 | } | |
76 | ||
d6714c22 PM |
77 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
78 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); | |
64db4cff | 79 | |
6258c4fb IM |
80 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
81 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); | |
b1f77b05 | 82 | |
f41d911f PM |
83 | extern long rcu_batches_completed_sched(void); |
84 | static void cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, | |
85 | struct rcu_node *rnp, unsigned long flags); | |
86 | static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags); | |
33f76148 | 87 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp); |
f41d911f PM |
88 | static void __rcu_process_callbacks(struct rcu_state *rsp, |
89 | struct rcu_data *rdp); | |
90 | static void __call_rcu(struct rcu_head *head, | |
91 | void (*func)(struct rcu_head *rcu), | |
92 | struct rcu_state *rsp); | |
93 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp); | |
94 | static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_state *rsp, | |
95 | int preemptable); | |
96 | ||
97 | #include "rcutree_plugin.h" | |
98 | ||
b1f77b05 | 99 | /* |
d6714c22 | 100 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 101 | * how many quiescent states passed, just if there was at least |
d6714c22 | 102 | * one since the start of the grace period, this just sets a flag. |
b1f77b05 | 103 | */ |
d6714c22 | 104 | void rcu_sched_qs(int cpu) |
b1f77b05 | 105 | { |
f41d911f PM |
106 | unsigned long flags; |
107 | struct rcu_data *rdp; | |
108 | ||
109 | local_irq_save(flags); | |
110 | rdp = &per_cpu(rcu_sched_data, cpu); | |
b1f77b05 IM |
111 | rdp->passed_quiesc = 1; |
112 | rdp->passed_quiesc_completed = rdp->completed; | |
f41d911f PM |
113 | rcu_preempt_qs(cpu); |
114 | local_irq_restore(flags); | |
b1f77b05 IM |
115 | } |
116 | ||
d6714c22 | 117 | void rcu_bh_qs(int cpu) |
b1f77b05 | 118 | { |
f41d911f PM |
119 | unsigned long flags; |
120 | struct rcu_data *rdp; | |
121 | ||
122 | local_irq_save(flags); | |
123 | rdp = &per_cpu(rcu_bh_data, cpu); | |
b1f77b05 IM |
124 | rdp->passed_quiesc = 1; |
125 | rdp->passed_quiesc_completed = rdp->completed; | |
f41d911f | 126 | local_irq_restore(flags); |
b1f77b05 | 127 | } |
64db4cff PM |
128 | |
129 | #ifdef CONFIG_NO_HZ | |
90a4d2c0 PM |
130 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
131 | .dynticks_nesting = 1, | |
132 | .dynticks = 1, | |
133 | }; | |
64db4cff PM |
134 | #endif /* #ifdef CONFIG_NO_HZ */ |
135 | ||
136 | static int blimit = 10; /* Maximum callbacks per softirq. */ | |
137 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ | |
138 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
139 | ||
140 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); | |
a157229c | 141 | static int rcu_pending(int cpu); |
64db4cff | 142 | |
d6714c22 PM |
143 | /* |
144 | * Return the number of RCU-sched batches processed thus far for debug & stats. | |
145 | */ | |
146 | long rcu_batches_completed_sched(void) | |
147 | { | |
148 | return rcu_sched_state.completed; | |
149 | } | |
150 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); | |
151 | ||
64db4cff PM |
152 | /* |
153 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
154 | */ | |
155 | long rcu_batches_completed_bh(void) | |
156 | { | |
157 | return rcu_bh_state.completed; | |
158 | } | |
159 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
160 | ||
161 | /* | |
162 | * Does the CPU have callbacks ready to be invoked? | |
163 | */ | |
164 | static int | |
165 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
166 | { | |
167 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
168 | } | |
169 | ||
170 | /* | |
171 | * Does the current CPU require a yet-as-unscheduled grace period? | |
172 | */ | |
173 | static int | |
174 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
175 | { | |
176 | /* ACCESS_ONCE() because we are accessing outside of lock. */ | |
177 | return *rdp->nxttail[RCU_DONE_TAIL] && | |
178 | ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum); | |
179 | } | |
180 | ||
181 | /* | |
182 | * Return the root node of the specified rcu_state structure. | |
183 | */ | |
184 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
185 | { | |
186 | return &rsp->node[0]; | |
187 | } | |
188 | ||
189 | #ifdef CONFIG_SMP | |
190 | ||
191 | /* | |
192 | * If the specified CPU is offline, tell the caller that it is in | |
193 | * a quiescent state. Otherwise, whack it with a reschedule IPI. | |
194 | * Grace periods can end up waiting on an offline CPU when that | |
195 | * CPU is in the process of coming online -- it will be added to the | |
196 | * rcu_node bitmasks before it actually makes it online. The same thing | |
197 | * can happen while a CPU is in the process of coming online. Because this | |
198 | * race is quite rare, we check for it after detecting that the grace | |
199 | * period has been delayed rather than checking each and every CPU | |
200 | * each and every time we start a new grace period. | |
201 | */ | |
202 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) | |
203 | { | |
204 | /* | |
205 | * If the CPU is offline, it is in a quiescent state. We can | |
206 | * trust its state not to change because interrupts are disabled. | |
207 | */ | |
208 | if (cpu_is_offline(rdp->cpu)) { | |
209 | rdp->offline_fqs++; | |
210 | return 1; | |
211 | } | |
212 | ||
f41d911f PM |
213 | /* If preemptable RCU, no point in sending reschedule IPI. */ |
214 | if (rdp->preemptable) | |
215 | return 0; | |
216 | ||
64db4cff PM |
217 | /* The CPU is online, so send it a reschedule IPI. */ |
218 | if (rdp->cpu != smp_processor_id()) | |
219 | smp_send_reschedule(rdp->cpu); | |
220 | else | |
221 | set_need_resched(); | |
222 | rdp->resched_ipi++; | |
223 | return 0; | |
224 | } | |
225 | ||
226 | #endif /* #ifdef CONFIG_SMP */ | |
227 | ||
228 | #ifdef CONFIG_NO_HZ | |
229 | static DEFINE_RATELIMIT_STATE(rcu_rs, 10 * HZ, 5); | |
230 | ||
231 | /** | |
232 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz | |
233 | * | |
234 | * Enter nohz mode, in other words, -leave- the mode in which RCU | |
235 | * read-side critical sections can occur. (Though RCU read-side | |
236 | * critical sections can occur in irq handlers in nohz mode, a possibility | |
237 | * handled by rcu_irq_enter() and rcu_irq_exit()). | |
238 | */ | |
239 | void rcu_enter_nohz(void) | |
240 | { | |
241 | unsigned long flags; | |
242 | struct rcu_dynticks *rdtp; | |
243 | ||
244 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
245 | local_irq_save(flags); | |
246 | rdtp = &__get_cpu_var(rcu_dynticks); | |
247 | rdtp->dynticks++; | |
248 | rdtp->dynticks_nesting--; | |
249 | WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); | |
250 | local_irq_restore(flags); | |
251 | } | |
252 | ||
253 | /* | |
254 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz | |
255 | * | |
256 | * Exit nohz mode, in other words, -enter- the mode in which RCU | |
257 | * read-side critical sections normally occur. | |
258 | */ | |
259 | void rcu_exit_nohz(void) | |
260 | { | |
261 | unsigned long flags; | |
262 | struct rcu_dynticks *rdtp; | |
263 | ||
264 | local_irq_save(flags); | |
265 | rdtp = &__get_cpu_var(rcu_dynticks); | |
266 | rdtp->dynticks++; | |
267 | rdtp->dynticks_nesting++; | |
268 | WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs); | |
269 | local_irq_restore(flags); | |
270 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ | |
271 | } | |
272 | ||
273 | /** | |
274 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
275 | * | |
276 | * If the CPU was idle with dynamic ticks active, and there is no | |
277 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
278 | * RCU grace-period handling know that the CPU is active. | |
279 | */ | |
280 | void rcu_nmi_enter(void) | |
281 | { | |
282 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
283 | ||
284 | if (rdtp->dynticks & 0x1) | |
285 | return; | |
286 | rdtp->dynticks_nmi++; | |
287 | WARN_ON_RATELIMIT(!(rdtp->dynticks_nmi & 0x1), &rcu_rs); | |
288 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ | |
289 | } | |
290 | ||
291 | /** | |
292 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
293 | * | |
294 | * If the CPU was idle with dynamic ticks active, and there is no | |
295 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
296 | * RCU grace-period handling know that the CPU is no longer active. | |
297 | */ | |
298 | void rcu_nmi_exit(void) | |
299 | { | |
300 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
301 | ||
302 | if (rdtp->dynticks & 0x1) | |
303 | return; | |
304 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
305 | rdtp->dynticks_nmi++; | |
306 | WARN_ON_RATELIMIT(rdtp->dynticks_nmi & 0x1, &rcu_rs); | |
307 | } | |
308 | ||
309 | /** | |
310 | * rcu_irq_enter - inform RCU of entry to hard irq context | |
311 | * | |
312 | * If the CPU was idle with dynamic ticks active, this updates the | |
313 | * rdtp->dynticks to let the RCU handling know that the CPU is active. | |
314 | */ | |
315 | void rcu_irq_enter(void) | |
316 | { | |
317 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
318 | ||
319 | if (rdtp->dynticks_nesting++) | |
320 | return; | |
321 | rdtp->dynticks++; | |
322 | WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs); | |
323 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ | |
324 | } | |
325 | ||
326 | /** | |
327 | * rcu_irq_exit - inform RCU of exit from hard irq context | |
328 | * | |
329 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks | |
330 | * to put let the RCU handling be aware that the CPU is going back to idle | |
331 | * with no ticks. | |
332 | */ | |
333 | void rcu_irq_exit(void) | |
334 | { | |
335 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
336 | ||
337 | if (--rdtp->dynticks_nesting) | |
338 | return; | |
339 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ | |
340 | rdtp->dynticks++; | |
341 | WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); | |
342 | ||
343 | /* If the interrupt queued a callback, get out of dyntick mode. */ | |
d6714c22 | 344 | if (__get_cpu_var(rcu_sched_data).nxtlist || |
64db4cff PM |
345 | __get_cpu_var(rcu_bh_data).nxtlist) |
346 | set_need_resched(); | |
347 | } | |
348 | ||
349 | /* | |
350 | * Record the specified "completed" value, which is later used to validate | |
351 | * dynticks counter manipulations. Specify "rsp->completed - 1" to | |
352 | * unconditionally invalidate any future dynticks manipulations (which is | |
353 | * useful at the beginning of a grace period). | |
354 | */ | |
355 | static void dyntick_record_completed(struct rcu_state *rsp, long comp) | |
356 | { | |
357 | rsp->dynticks_completed = comp; | |
358 | } | |
359 | ||
360 | #ifdef CONFIG_SMP | |
361 | ||
362 | /* | |
363 | * Recall the previously recorded value of the completion for dynticks. | |
364 | */ | |
365 | static long dyntick_recall_completed(struct rcu_state *rsp) | |
366 | { | |
367 | return rsp->dynticks_completed; | |
368 | } | |
369 | ||
370 | /* | |
371 | * Snapshot the specified CPU's dynticks counter so that we can later | |
372 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
373 | * is already in a quiescent state courtesy of dynticks idle mode. | |
374 | */ | |
375 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
376 | { | |
377 | int ret; | |
378 | int snap; | |
379 | int snap_nmi; | |
380 | ||
381 | snap = rdp->dynticks->dynticks; | |
382 | snap_nmi = rdp->dynticks->dynticks_nmi; | |
383 | smp_mb(); /* Order sampling of snap with end of grace period. */ | |
384 | rdp->dynticks_snap = snap; | |
385 | rdp->dynticks_nmi_snap = snap_nmi; | |
386 | ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); | |
387 | if (ret) | |
388 | rdp->dynticks_fqs++; | |
389 | return ret; | |
390 | } | |
391 | ||
392 | /* | |
393 | * Return true if the specified CPU has passed through a quiescent | |
394 | * state by virtue of being in or having passed through an dynticks | |
395 | * idle state since the last call to dyntick_save_progress_counter() | |
396 | * for this same CPU. | |
397 | */ | |
398 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
399 | { | |
400 | long curr; | |
401 | long curr_nmi; | |
402 | long snap; | |
403 | long snap_nmi; | |
404 | ||
405 | curr = rdp->dynticks->dynticks; | |
406 | snap = rdp->dynticks_snap; | |
407 | curr_nmi = rdp->dynticks->dynticks_nmi; | |
408 | snap_nmi = rdp->dynticks_nmi_snap; | |
409 | smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ | |
410 | ||
411 | /* | |
412 | * If the CPU passed through or entered a dynticks idle phase with | |
413 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
414 | * already acknowledged the request to pass through a quiescent | |
415 | * state. Either way, that CPU cannot possibly be in an RCU | |
416 | * read-side critical section that started before the beginning | |
417 | * of the current RCU grace period. | |
418 | */ | |
419 | if ((curr != snap || (curr & 0x1) == 0) && | |
420 | (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { | |
421 | rdp->dynticks_fqs++; | |
422 | return 1; | |
423 | } | |
424 | ||
425 | /* Go check for the CPU being offline. */ | |
426 | return rcu_implicit_offline_qs(rdp); | |
427 | } | |
428 | ||
429 | #endif /* #ifdef CONFIG_SMP */ | |
430 | ||
431 | #else /* #ifdef CONFIG_NO_HZ */ | |
432 | ||
433 | static void dyntick_record_completed(struct rcu_state *rsp, long comp) | |
434 | { | |
435 | } | |
436 | ||
437 | #ifdef CONFIG_SMP | |
438 | ||
439 | /* | |
440 | * If there are no dynticks, then the only way that a CPU can passively | |
441 | * be in a quiescent state is to be offline. Unlike dynticks idle, which | |
442 | * is a point in time during the prior (already finished) grace period, | |
443 | * an offline CPU is always in a quiescent state, and thus can be | |
444 | * unconditionally applied. So just return the current value of completed. | |
445 | */ | |
446 | static long dyntick_recall_completed(struct rcu_state *rsp) | |
447 | { | |
448 | return rsp->completed; | |
449 | } | |
450 | ||
451 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
452 | { | |
453 | return 0; | |
454 | } | |
455 | ||
456 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
457 | { | |
458 | return rcu_implicit_offline_qs(rdp); | |
459 | } | |
460 | ||
461 | #endif /* #ifdef CONFIG_SMP */ | |
462 | ||
463 | #endif /* #else #ifdef CONFIG_NO_HZ */ | |
464 | ||
465 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
466 | ||
467 | static void record_gp_stall_check_time(struct rcu_state *rsp) | |
468 | { | |
469 | rsp->gp_start = jiffies; | |
470 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; | |
471 | } | |
472 | ||
473 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
474 | { | |
475 | int cpu; | |
476 | long delta; | |
477 | unsigned long flags; | |
478 | struct rcu_node *rnp = rcu_get_root(rsp); | |
479 | struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1]; | |
480 | struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES]; | |
481 | ||
482 | /* Only let one CPU complain about others per time interval. */ | |
483 | ||
484 | spin_lock_irqsave(&rnp->lock, flags); | |
485 | delta = jiffies - rsp->jiffies_stall; | |
486 | if (delta < RCU_STALL_RAT_DELAY || rsp->gpnum == rsp->completed) { | |
487 | spin_unlock_irqrestore(&rnp->lock, flags); | |
488 | return; | |
489 | } | |
490 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
491 | spin_unlock_irqrestore(&rnp->lock, flags); | |
492 | ||
493 | /* OK, time to rat on our buddy... */ | |
494 | ||
495 | printk(KERN_ERR "INFO: RCU detected CPU stalls:"); | |
496 | for (; rnp_cur < rnp_end; rnp_cur++) { | |
f41d911f | 497 | rcu_print_task_stall(rnp); |
64db4cff PM |
498 | if (rnp_cur->qsmask == 0) |
499 | continue; | |
500 | for (cpu = 0; cpu <= rnp_cur->grphi - rnp_cur->grplo; cpu++) | |
501 | if (rnp_cur->qsmask & (1UL << cpu)) | |
502 | printk(" %d", rnp_cur->grplo + cpu); | |
503 | } | |
504 | printk(" (detected by %d, t=%ld jiffies)\n", | |
505 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); | |
506 | force_quiescent_state(rsp, 0); /* Kick them all. */ | |
507 | } | |
508 | ||
509 | static void print_cpu_stall(struct rcu_state *rsp) | |
510 | { | |
511 | unsigned long flags; | |
512 | struct rcu_node *rnp = rcu_get_root(rsp); | |
513 | ||
514 | printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n", | |
515 | smp_processor_id(), jiffies - rsp->gp_start); | |
516 | dump_stack(); | |
517 | spin_lock_irqsave(&rnp->lock, flags); | |
518 | if ((long)(jiffies - rsp->jiffies_stall) >= 0) | |
519 | rsp->jiffies_stall = | |
520 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
521 | spin_unlock_irqrestore(&rnp->lock, flags); | |
522 | set_need_resched(); /* kick ourselves to get things going. */ | |
523 | } | |
524 | ||
525 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
526 | { | |
527 | long delta; | |
528 | struct rcu_node *rnp; | |
529 | ||
530 | delta = jiffies - rsp->jiffies_stall; | |
531 | rnp = rdp->mynode; | |
532 | if ((rnp->qsmask & rdp->grpmask) && delta >= 0) { | |
533 | ||
534 | /* We haven't checked in, so go dump stack. */ | |
535 | print_cpu_stall(rsp); | |
536 | ||
537 | } else if (rsp->gpnum != rsp->completed && | |
538 | delta >= RCU_STALL_RAT_DELAY) { | |
539 | ||
540 | /* They had two time units to dump stack, so complain. */ | |
541 | print_other_cpu_stall(rsp); | |
542 | } | |
543 | } | |
544 | ||
545 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
546 | ||
547 | static void record_gp_stall_check_time(struct rcu_state *rsp) | |
548 | { | |
549 | } | |
550 | ||
551 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
552 | { | |
553 | } | |
554 | ||
555 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
556 | ||
557 | /* | |
558 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
559 | * This is used both when we started the grace period and when we notice | |
560 | * that someone else started the grace period. | |
561 | */ | |
562 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) | |
563 | { | |
564 | rdp->qs_pending = 1; | |
565 | rdp->passed_quiesc = 0; | |
566 | rdp->gpnum = rsp->gpnum; | |
64db4cff PM |
567 | } |
568 | ||
569 | /* | |
570 | * Did someone else start a new RCU grace period start since we last | |
571 | * checked? Update local state appropriately if so. Must be called | |
572 | * on the CPU corresponding to rdp. | |
573 | */ | |
574 | static int | |
575 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
576 | { | |
577 | unsigned long flags; | |
578 | int ret = 0; | |
579 | ||
580 | local_irq_save(flags); | |
581 | if (rdp->gpnum != rsp->gpnum) { | |
582 | note_new_gpnum(rsp, rdp); | |
583 | ret = 1; | |
584 | } | |
585 | local_irq_restore(flags); | |
586 | return ret; | |
587 | } | |
588 | ||
589 | /* | |
590 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
591 | * in preparation for detecting the next grace period. The caller must hold | |
592 | * the root node's ->lock, which is released before return. Hard irqs must | |
593 | * be disabled. | |
594 | */ | |
595 | static void | |
596 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
597 | __releases(rcu_get_root(rsp)->lock) | |
598 | { | |
599 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; | |
600 | struct rcu_node *rnp = rcu_get_root(rsp); | |
601 | struct rcu_node *rnp_cur; | |
602 | struct rcu_node *rnp_end; | |
603 | ||
604 | if (!cpu_needs_another_gp(rsp, rdp)) { | |
605 | spin_unlock_irqrestore(&rnp->lock, flags); | |
606 | return; | |
607 | } | |
608 | ||
609 | /* Advance to a new grace period and initialize state. */ | |
610 | rsp->gpnum++; | |
611 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ | |
612 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
64db4cff PM |
613 | record_gp_stall_check_time(rsp); |
614 | dyntick_record_completed(rsp, rsp->completed - 1); | |
615 | note_new_gpnum(rsp, rdp); | |
616 | ||
617 | /* | |
618 | * Because we are first, we know that all our callbacks will | |
619 | * be covered by this upcoming grace period, even the ones | |
620 | * that were registered arbitrarily recently. | |
621 | */ | |
622 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
623 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
624 | ||
625 | /* Special-case the common single-level case. */ | |
626 | if (NUM_RCU_NODES == 1) { | |
627 | rnp->qsmask = rnp->qsmaskinit; | |
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 | /* | |
640 | * Set the quiescent-state-needed bits in all the non-leaf RCU | |
641 | * nodes for all currently online CPUs. This operation relies | |
642 | * on the layout of the hierarchy within the rsp->node[] array. | |
643 | * Note that other CPUs will access only the leaves of the | |
644 | * hierarchy, which still indicate that no grace period is in | |
645 | * progress. In addition, we have excluded CPU-hotplug operations. | |
646 | * | |
647 | * We therefore do not need to hold any locks. Any required | |
648 | * memory barriers will be supplied by the locks guarding the | |
649 | * leaf rcu_nodes in the hierarchy. | |
650 | */ | |
651 | ||
652 | rnp_end = rsp->level[NUM_RCU_LVLS - 1]; | |
653 | for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++) | |
654 | rnp_cur->qsmask = rnp_cur->qsmaskinit; | |
655 | ||
656 | /* | |
657 | * Now set up the leaf nodes. Here we must be careful. First, | |
658 | * we need to hold the lock in order to exclude other CPUs, which | |
659 | * might be contending for the leaf nodes' locks. Second, as | |
660 | * soon as we initialize a given leaf node, its CPUs might run | |
661 | * up the rest of the hierarchy. We must therefore acquire locks | |
662 | * for each node that we touch during this stage. (But we still | |
663 | * are excluding CPU-hotplug operations.) | |
664 | * | |
665 | * Note that the grace period cannot complete until we finish | |
666 | * the initialization process, as there will be at least one | |
667 | * qsmask bit set in the root node until that time, namely the | |
668 | * one corresponding to this CPU. | |
669 | */ | |
670 | rnp_end = &rsp->node[NUM_RCU_NODES]; | |
671 | rnp_cur = rsp->level[NUM_RCU_LVLS - 1]; | |
672 | for (; rnp_cur < rnp_end; rnp_cur++) { | |
673 | spin_lock(&rnp_cur->lock); /* irqs already disabled. */ | |
674 | rnp_cur->qsmask = rnp_cur->qsmaskinit; | |
675 | spin_unlock(&rnp_cur->lock); /* irqs already disabled. */ | |
676 | } | |
677 | ||
678 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ | |
679 | spin_unlock_irqrestore(&rsp->onofflock, flags); | |
680 | } | |
681 | ||
682 | /* | |
683 | * Advance this CPU's callbacks, but only if the current grace period | |
684 | * has ended. This may be called only from the CPU to whom the rdp | |
685 | * belongs. | |
686 | */ | |
687 | static void | |
688 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
689 | { | |
690 | long completed_snap; | |
691 | unsigned long flags; | |
692 | ||
693 | local_irq_save(flags); | |
694 | completed_snap = ACCESS_ONCE(rsp->completed); /* outside of lock. */ | |
695 | ||
696 | /* Did another grace period end? */ | |
697 | if (rdp->completed != completed_snap) { | |
698 | ||
699 | /* Advance callbacks. No harm if list empty. */ | |
700 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
701 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
702 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
703 | ||
704 | /* Remember that we saw this grace-period completion. */ | |
705 | rdp->completed = completed_snap; | |
706 | } | |
707 | local_irq_restore(flags); | |
708 | } | |
709 | ||
f41d911f PM |
710 | /* |
711 | * Clean up after the prior grace period and let rcu_start_gp() start up | |
712 | * the next grace period if one is needed. Note that the caller must | |
713 | * hold rnp->lock, as required by rcu_start_gp(), which will release it. | |
714 | */ | |
715 | static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags) | |
716 | __releases(rnp->lock) | |
717 | { | |
718 | rsp->completed = rsp->gpnum; | |
719 | rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]); | |
720 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ | |
721 | } | |
722 | ||
64db4cff PM |
723 | /* |
724 | * Similar to cpu_quiet(), for which it is a helper function. Allows | |
725 | * a group of CPUs to be quieted at one go, though all the CPUs in the | |
726 | * group must be represented by the same leaf rcu_node structure. | |
727 | * That structure's lock must be held upon entry, and it is released | |
728 | * before return. | |
729 | */ | |
730 | static void | |
731 | cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, | |
732 | unsigned long flags) | |
733 | __releases(rnp->lock) | |
734 | { | |
735 | /* Walk up the rcu_node hierarchy. */ | |
736 | for (;;) { | |
737 | if (!(rnp->qsmask & mask)) { | |
738 | ||
739 | /* Our bit has already been cleared, so done. */ | |
740 | spin_unlock_irqrestore(&rnp->lock, flags); | |
741 | return; | |
742 | } | |
743 | rnp->qsmask &= ~mask; | |
f41d911f | 744 | if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { |
64db4cff PM |
745 | |
746 | /* Other bits still set at this level, so done. */ | |
747 | spin_unlock_irqrestore(&rnp->lock, flags); | |
748 | return; | |
749 | } | |
750 | mask = rnp->grpmask; | |
751 | if (rnp->parent == NULL) { | |
752 | ||
753 | /* No more levels. Exit loop holding root lock. */ | |
754 | ||
755 | break; | |
756 | } | |
757 | spin_unlock_irqrestore(&rnp->lock, flags); | |
758 | rnp = rnp->parent; | |
759 | spin_lock_irqsave(&rnp->lock, flags); | |
760 | } | |
761 | ||
762 | /* | |
763 | * Get here if we are the last CPU to pass through a quiescent | |
f41d911f PM |
764 | * state for this grace period. Invoke cpu_quiet_msk_finish() |
765 | * to clean up and start the next grace period if one is needed. | |
64db4cff | 766 | */ |
f41d911f | 767 | cpu_quiet_msk_finish(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
768 | } |
769 | ||
770 | /* | |
771 | * Record a quiescent state for the specified CPU, which must either be | |
772 | * the current CPU or an offline CPU. The lastcomp argument is used to | |
773 | * make sure we are still in the grace period of interest. We don't want | |
774 | * to end the current grace period based on quiescent states detected in | |
775 | * an earlier grace period! | |
776 | */ | |
777 | static void | |
778 | cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) | |
779 | { | |
780 | unsigned long flags; | |
781 | unsigned long mask; | |
782 | struct rcu_node *rnp; | |
783 | ||
784 | rnp = rdp->mynode; | |
785 | spin_lock_irqsave(&rnp->lock, flags); | |
786 | if (lastcomp != ACCESS_ONCE(rsp->completed)) { | |
787 | ||
788 | /* | |
789 | * Someone beat us to it for this grace period, so leave. | |
790 | * The race with GP start is resolved by the fact that we | |
791 | * hold the leaf rcu_node lock, so that the per-CPU bits | |
792 | * cannot yet be initialized -- so we would simply find our | |
793 | * CPU's bit already cleared in cpu_quiet_msk() if this race | |
794 | * occurred. | |
795 | */ | |
796 | rdp->passed_quiesc = 0; /* try again later! */ | |
797 | spin_unlock_irqrestore(&rnp->lock, flags); | |
798 | return; | |
799 | } | |
800 | mask = rdp->grpmask; | |
801 | if ((rnp->qsmask & mask) == 0) { | |
802 | spin_unlock_irqrestore(&rnp->lock, flags); | |
803 | } else { | |
804 | rdp->qs_pending = 0; | |
805 | ||
806 | /* | |
807 | * This GP can't end until cpu checks in, so all of our | |
808 | * callbacks can be processed during the next GP. | |
809 | */ | |
810 | rdp = rsp->rda[smp_processor_id()]; | |
811 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
812 | ||
813 | cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */ | |
814 | } | |
815 | } | |
816 | ||
817 | /* | |
818 | * Check to see if there is a new grace period of which this CPU | |
819 | * is not yet aware, and if so, set up local rcu_data state for it. | |
820 | * Otherwise, see if this CPU has just passed through its first | |
821 | * quiescent state for this grace period, and record that fact if so. | |
822 | */ | |
823 | static void | |
824 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
825 | { | |
826 | /* If there is now a new grace period, record and return. */ | |
827 | if (check_for_new_grace_period(rsp, rdp)) | |
828 | return; | |
829 | ||
830 | /* | |
831 | * Does this CPU still need to do its part for current grace period? | |
832 | * If no, return and let the other CPUs do their part as well. | |
833 | */ | |
834 | if (!rdp->qs_pending) | |
835 | return; | |
836 | ||
837 | /* | |
838 | * Was there a quiescent state since the beginning of the grace | |
839 | * period? If no, then exit and wait for the next call. | |
840 | */ | |
841 | if (!rdp->passed_quiesc) | |
842 | return; | |
843 | ||
844 | /* Tell RCU we are done (but cpu_quiet() will be the judge of that). */ | |
845 | cpu_quiet(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); | |
846 | } | |
847 | ||
848 | #ifdef CONFIG_HOTPLUG_CPU | |
849 | ||
850 | /* | |
851 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy | |
852 | * and move all callbacks from the outgoing CPU to the current one. | |
853 | */ | |
854 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) | |
855 | { | |
856 | int i; | |
857 | unsigned long flags; | |
858 | long lastcomp; | |
859 | unsigned long mask; | |
860 | struct rcu_data *rdp = rsp->rda[cpu]; | |
861 | struct rcu_data *rdp_me; | |
862 | struct rcu_node *rnp; | |
863 | ||
864 | /* Exclude any attempts to start a new grace period. */ | |
865 | spin_lock_irqsave(&rsp->onofflock, flags); | |
866 | ||
867 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ | |
868 | rnp = rdp->mynode; | |
869 | mask = rdp->grpmask; /* rnp->grplo is constant. */ | |
870 | do { | |
871 | spin_lock(&rnp->lock); /* irqs already disabled. */ | |
872 | rnp->qsmaskinit &= ~mask; | |
873 | if (rnp->qsmaskinit != 0) { | |
f41d911f | 874 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
875 | break; |
876 | } | |
877 | mask = rnp->grpmask; | |
f41d911f | 878 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
879 | rnp = rnp->parent; |
880 | } while (rnp != NULL); | |
881 | lastcomp = rsp->completed; | |
882 | ||
883 | spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ | |
884 | ||
885 | /* Being offline is a quiescent state, so go record it. */ | |
886 | cpu_quiet(cpu, rsp, rdp, lastcomp); | |
887 | ||
888 | /* | |
889 | * Move callbacks from the outgoing CPU to the running CPU. | |
890 | * Note that the outgoing CPU is now quiscent, so it is now | |
d6714c22 | 891 | * (uncharacteristically) safe to access its rcu_data structure. |
64db4cff PM |
892 | * Note also that we must carefully retain the order of the |
893 | * outgoing CPU's callbacks in order for rcu_barrier() to work | |
894 | * correctly. Finally, note that we start all the callbacks | |
895 | * afresh, even those that have passed through a grace period | |
896 | * and are therefore ready to invoke. The theory is that hotplug | |
897 | * events are rare, and that if they are frequent enough to | |
898 | * indefinitely delay callbacks, you have far worse things to | |
899 | * be worrying about. | |
900 | */ | |
901 | rdp_me = rsp->rda[smp_processor_id()]; | |
902 | if (rdp->nxtlist != NULL) { | |
903 | *rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist; | |
904 | rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
905 | rdp->nxtlist = NULL; | |
906 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
907 | rdp->nxttail[i] = &rdp->nxtlist; | |
908 | rdp_me->qlen += rdp->qlen; | |
909 | rdp->qlen = 0; | |
910 | } | |
911 | local_irq_restore(flags); | |
912 | } | |
913 | ||
914 | /* | |
915 | * Remove the specified CPU from the RCU hierarchy and move any pending | |
916 | * callbacks that it might have to the current CPU. This code assumes | |
917 | * that at least one CPU in the system will remain running at all times. | |
918 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. | |
919 | */ | |
920 | static void rcu_offline_cpu(int cpu) | |
921 | { | |
d6714c22 | 922 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
64db4cff | 923 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
33f76148 | 924 | rcu_preempt_offline_cpu(cpu); |
64db4cff PM |
925 | } |
926 | ||
927 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
928 | ||
929 | static void rcu_offline_cpu(int cpu) | |
930 | { | |
931 | } | |
932 | ||
933 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
934 | ||
935 | /* | |
936 | * Invoke any RCU callbacks that have made it to the end of their grace | |
937 | * period. Thottle as specified by rdp->blimit. | |
938 | */ | |
939 | static void rcu_do_batch(struct rcu_data *rdp) | |
940 | { | |
941 | unsigned long flags; | |
942 | struct rcu_head *next, *list, **tail; | |
943 | int count; | |
944 | ||
945 | /* If no callbacks are ready, just return.*/ | |
946 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) | |
947 | return; | |
948 | ||
949 | /* | |
950 | * Extract the list of ready callbacks, disabling to prevent | |
951 | * races with call_rcu() from interrupt handlers. | |
952 | */ | |
953 | local_irq_save(flags); | |
954 | list = rdp->nxtlist; | |
955 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
956 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
957 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
958 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) | |
959 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) | |
960 | rdp->nxttail[count] = &rdp->nxtlist; | |
961 | local_irq_restore(flags); | |
962 | ||
963 | /* Invoke callbacks. */ | |
964 | count = 0; | |
965 | while (list) { | |
966 | next = list->next; | |
967 | prefetch(next); | |
968 | list->func(list); | |
969 | list = next; | |
970 | if (++count >= rdp->blimit) | |
971 | break; | |
972 | } | |
973 | ||
974 | local_irq_save(flags); | |
975 | ||
976 | /* Update count, and requeue any remaining callbacks. */ | |
977 | rdp->qlen -= count; | |
978 | if (list != NULL) { | |
979 | *tail = rdp->nxtlist; | |
980 | rdp->nxtlist = list; | |
981 | for (count = 0; count < RCU_NEXT_SIZE; count++) | |
982 | if (&rdp->nxtlist == rdp->nxttail[count]) | |
983 | rdp->nxttail[count] = tail; | |
984 | else | |
985 | break; | |
986 | } | |
987 | ||
988 | /* Reinstate batch limit if we have worked down the excess. */ | |
989 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
990 | rdp->blimit = blimit; | |
991 | ||
992 | local_irq_restore(flags); | |
993 | ||
994 | /* Re-raise the RCU softirq if there are callbacks remaining. */ | |
995 | if (cpu_has_callbacks_ready_to_invoke(rdp)) | |
996 | raise_softirq(RCU_SOFTIRQ); | |
997 | } | |
998 | ||
999 | /* | |
1000 | * Check to see if this CPU is in a non-context-switch quiescent state | |
1001 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
1002 | * Also schedule the RCU softirq handler. | |
1003 | * | |
1004 | * This function must be called with hardirqs disabled. It is normally | |
1005 | * invoked from the scheduling-clock interrupt. If rcu_pending returns | |
1006 | * false, there is no point in invoking rcu_check_callbacks(). | |
1007 | */ | |
1008 | void rcu_check_callbacks(int cpu, int user) | |
1009 | { | |
a157229c PM |
1010 | if (!rcu_pending(cpu)) |
1011 | return; /* if nothing for RCU to do. */ | |
64db4cff | 1012 | if (user || |
a6826048 PM |
1013 | (idle_cpu(cpu) && rcu_scheduler_active && |
1014 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
64db4cff PM |
1015 | |
1016 | /* | |
1017 | * Get here if this CPU took its interrupt from user | |
1018 | * mode or from the idle loop, and if this is not a | |
1019 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1020 | * a quiescent state, so note it. |
64db4cff PM |
1021 | * |
1022 | * No memory barrier is required here because both | |
d6714c22 PM |
1023 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1024 | * variables that other CPUs neither access nor modify, | |
1025 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1026 | */ |
1027 | ||
d6714c22 PM |
1028 | rcu_sched_qs(cpu); |
1029 | rcu_bh_qs(cpu); | |
64db4cff PM |
1030 | |
1031 | } else if (!in_softirq()) { | |
1032 | ||
1033 | /* | |
1034 | * Get here if this CPU did not take its interrupt from | |
1035 | * softirq, in other words, if it is not interrupting | |
1036 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1037 | * critical section, so note it. |
64db4cff PM |
1038 | */ |
1039 | ||
d6714c22 | 1040 | rcu_bh_qs(cpu); |
64db4cff | 1041 | } |
f41d911f | 1042 | rcu_preempt_check_callbacks(cpu); |
64db4cff PM |
1043 | raise_softirq(RCU_SOFTIRQ); |
1044 | } | |
1045 | ||
1046 | #ifdef CONFIG_SMP | |
1047 | ||
1048 | /* | |
1049 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1050 | * have not yet encountered a quiescent state, using the function specified. | |
1051 | * Returns 1 if the current grace period ends while scanning (possibly | |
1052 | * because we made it end). | |
1053 | */ | |
1054 | static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp, | |
1055 | int (*f)(struct rcu_data *)) | |
1056 | { | |
1057 | unsigned long bit; | |
1058 | int cpu; | |
1059 | unsigned long flags; | |
1060 | unsigned long mask; | |
1061 | struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1]; | |
1062 | struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES]; | |
1063 | ||
1064 | for (; rnp_cur < rnp_end; rnp_cur++) { | |
1065 | mask = 0; | |
1066 | spin_lock_irqsave(&rnp_cur->lock, flags); | |
1067 | if (rsp->completed != lastcomp) { | |
1068 | spin_unlock_irqrestore(&rnp_cur->lock, flags); | |
1069 | return 1; | |
1070 | } | |
1071 | if (rnp_cur->qsmask == 0) { | |
1072 | spin_unlock_irqrestore(&rnp_cur->lock, flags); | |
1073 | continue; | |
1074 | } | |
1075 | cpu = rnp_cur->grplo; | |
1076 | bit = 1; | |
1077 | for (; cpu <= rnp_cur->grphi; cpu++, bit <<= 1) { | |
1078 | if ((rnp_cur->qsmask & bit) != 0 && f(rsp->rda[cpu])) | |
1079 | mask |= bit; | |
1080 | } | |
1081 | if (mask != 0 && rsp->completed == lastcomp) { | |
1082 | ||
1083 | /* cpu_quiet_msk() releases rnp_cur->lock. */ | |
1084 | cpu_quiet_msk(mask, rsp, rnp_cur, flags); | |
1085 | continue; | |
1086 | } | |
1087 | spin_unlock_irqrestore(&rnp_cur->lock, flags); | |
1088 | } | |
1089 | return 0; | |
1090 | } | |
1091 | ||
1092 | /* | |
1093 | * Force quiescent states on reluctant CPUs, and also detect which | |
1094 | * CPUs are in dyntick-idle mode. | |
1095 | */ | |
1096 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1097 | { | |
1098 | unsigned long flags; | |
1099 | long lastcomp; | |
64db4cff PM |
1100 | struct rcu_node *rnp = rcu_get_root(rsp); |
1101 | u8 signaled; | |
1102 | ||
1103 | if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum)) | |
1104 | return; /* No grace period in progress, nothing to force. */ | |
1105 | if (!spin_trylock_irqsave(&rsp->fqslock, flags)) { | |
1106 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ | |
1107 | return; /* Someone else is already on the job. */ | |
1108 | } | |
1109 | if (relaxed && | |
ef631b0c | 1110 | (long)(rsp->jiffies_force_qs - jiffies) >= 0) |
64db4cff PM |
1111 | goto unlock_ret; /* no emergency and done recently. */ |
1112 | rsp->n_force_qs++; | |
1113 | spin_lock(&rnp->lock); | |
1114 | lastcomp = rsp->completed; | |
1115 | signaled = rsp->signaled; | |
1116 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; | |
64db4cff PM |
1117 | if (lastcomp == rsp->gpnum) { |
1118 | rsp->n_force_qs_ngp++; | |
1119 | spin_unlock(&rnp->lock); | |
1120 | goto unlock_ret; /* no GP in progress, time updated. */ | |
1121 | } | |
1122 | spin_unlock(&rnp->lock); | |
1123 | switch (signaled) { | |
1124 | case RCU_GP_INIT: | |
1125 | ||
1126 | break; /* grace period still initializing, ignore. */ | |
1127 | ||
1128 | case RCU_SAVE_DYNTICK: | |
1129 | ||
1130 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) | |
1131 | break; /* So gcc recognizes the dead code. */ | |
1132 | ||
1133 | /* Record dyntick-idle state. */ | |
1134 | if (rcu_process_dyntick(rsp, lastcomp, | |
1135 | dyntick_save_progress_counter)) | |
1136 | goto unlock_ret; | |
1137 | ||
1138 | /* Update state, record completion counter. */ | |
1139 | spin_lock(&rnp->lock); | |
1140 | if (lastcomp == rsp->completed) { | |
1141 | rsp->signaled = RCU_FORCE_QS; | |
1142 | dyntick_record_completed(rsp, lastcomp); | |
1143 | } | |
1144 | spin_unlock(&rnp->lock); | |
1145 | break; | |
1146 | ||
1147 | case RCU_FORCE_QS: | |
1148 | ||
1149 | /* Check dyntick-idle state, send IPI to laggarts. */ | |
1150 | if (rcu_process_dyntick(rsp, dyntick_recall_completed(rsp), | |
1151 | rcu_implicit_dynticks_qs)) | |
1152 | goto unlock_ret; | |
1153 | ||
1154 | /* Leave state in case more forcing is required. */ | |
1155 | ||
1156 | break; | |
1157 | } | |
1158 | unlock_ret: | |
1159 | spin_unlock_irqrestore(&rsp->fqslock, flags); | |
1160 | } | |
1161 | ||
1162 | #else /* #ifdef CONFIG_SMP */ | |
1163 | ||
1164 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) | |
1165 | { | |
1166 | set_need_resched(); | |
1167 | } | |
1168 | ||
1169 | #endif /* #else #ifdef CONFIG_SMP */ | |
1170 | ||
1171 | /* | |
1172 | * This does the RCU processing work from softirq context for the | |
1173 | * specified rcu_state and rcu_data structures. This may be called | |
1174 | * only from the CPU to whom the rdp belongs. | |
1175 | */ | |
1176 | static void | |
1177 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) | |
1178 | { | |
1179 | unsigned long flags; | |
1180 | ||
2e597558 PM |
1181 | WARN_ON_ONCE(rdp->beenonline == 0); |
1182 | ||
64db4cff PM |
1183 | /* |
1184 | * If an RCU GP has gone long enough, go check for dyntick | |
1185 | * idle CPUs and, if needed, send resched IPIs. | |
1186 | */ | |
ef631b0c | 1187 | if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
64db4cff PM |
1188 | force_quiescent_state(rsp, 1); |
1189 | ||
1190 | /* | |
1191 | * Advance callbacks in response to end of earlier grace | |
1192 | * period that some other CPU ended. | |
1193 | */ | |
1194 | rcu_process_gp_end(rsp, rdp); | |
1195 | ||
1196 | /* Update RCU state based on any recent quiescent states. */ | |
1197 | rcu_check_quiescent_state(rsp, rdp); | |
1198 | ||
1199 | /* Does this CPU require a not-yet-started grace period? */ | |
1200 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1201 | spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); | |
1202 | rcu_start_gp(rsp, flags); /* releases above lock */ | |
1203 | } | |
1204 | ||
1205 | /* If there are callbacks ready, invoke them. */ | |
1206 | rcu_do_batch(rdp); | |
1207 | } | |
1208 | ||
1209 | /* | |
1210 | * Do softirq processing for the current CPU. | |
1211 | */ | |
1212 | static void rcu_process_callbacks(struct softirq_action *unused) | |
1213 | { | |
1214 | /* | |
1215 | * Memory references from any prior RCU read-side critical sections | |
1216 | * executed by the interrupted code must be seen before any RCU | |
1217 | * grace-period manipulations below. | |
1218 | */ | |
1219 | smp_mb(); /* See above block comment. */ | |
1220 | ||
d6714c22 PM |
1221 | __rcu_process_callbacks(&rcu_sched_state, |
1222 | &__get_cpu_var(rcu_sched_data)); | |
64db4cff | 1223 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
f41d911f | 1224 | rcu_preempt_process_callbacks(); |
64db4cff PM |
1225 | |
1226 | /* | |
1227 | * Memory references from any later RCU read-side critical sections | |
1228 | * executed by the interrupted code must be seen after any RCU | |
1229 | * grace-period manipulations above. | |
1230 | */ | |
1231 | smp_mb(); /* See above block comment. */ | |
1232 | } | |
1233 | ||
1234 | static void | |
1235 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
1236 | struct rcu_state *rsp) | |
1237 | { | |
1238 | unsigned long flags; | |
1239 | struct rcu_data *rdp; | |
1240 | ||
1241 | head->func = func; | |
1242 | head->next = NULL; | |
1243 | ||
1244 | smp_mb(); /* Ensure RCU update seen before callback registry. */ | |
1245 | ||
1246 | /* | |
1247 | * Opportunistically note grace-period endings and beginnings. | |
1248 | * Note that we might see a beginning right after we see an | |
1249 | * end, but never vice versa, since this CPU has to pass through | |
1250 | * a quiescent state betweentimes. | |
1251 | */ | |
1252 | local_irq_save(flags); | |
1253 | rdp = rsp->rda[smp_processor_id()]; | |
1254 | rcu_process_gp_end(rsp, rdp); | |
1255 | check_for_new_grace_period(rsp, rdp); | |
1256 | ||
1257 | /* Add the callback to our list. */ | |
1258 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
1259 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
1260 | ||
1261 | /* Start a new grace period if one not already started. */ | |
1262 | if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum)) { | |
1263 | unsigned long nestflag; | |
1264 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
1265 | ||
1266 | spin_lock_irqsave(&rnp_root->lock, nestflag); | |
1267 | rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */ | |
1268 | } | |
1269 | ||
1270 | /* Force the grace period if too many callbacks or too long waiting. */ | |
1271 | if (unlikely(++rdp->qlen > qhimark)) { | |
1272 | rdp->blimit = LONG_MAX; | |
1273 | force_quiescent_state(rsp, 0); | |
ef631b0c | 1274 | } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
64db4cff PM |
1275 | force_quiescent_state(rsp, 1); |
1276 | local_irq_restore(flags); | |
1277 | } | |
1278 | ||
1279 | /* | |
d6714c22 PM |
1280 | * Queue an RCU-sched callback for invocation after a grace period. |
1281 | */ | |
1282 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1283 | { | |
1284 | __call_rcu(head, func, &rcu_sched_state); | |
1285 | } | |
1286 | EXPORT_SYMBOL_GPL(call_rcu_sched); | |
1287 | ||
64db4cff PM |
1288 | /* |
1289 | * Queue an RCU for invocation after a quicker grace period. | |
1290 | */ | |
1291 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1292 | { | |
1293 | __call_rcu(head, func, &rcu_bh_state); | |
1294 | } | |
1295 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
1296 | ||
1297 | /* | |
1298 | * Check to see if there is any immediate RCU-related work to be done | |
1299 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
1300 | * The checks are in order of increasing expense: checks that can be | |
1301 | * carried out against CPU-local state are performed first. However, | |
1302 | * we must check for CPU stalls first, else we might not get a chance. | |
1303 | */ | |
1304 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
1305 | { | |
1306 | rdp->n_rcu_pending++; | |
1307 | ||
1308 | /* Check for CPU stalls, if enabled. */ | |
1309 | check_cpu_stall(rsp, rdp); | |
1310 | ||
1311 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
7ba5c840 PM |
1312 | if (rdp->qs_pending) { |
1313 | rdp->n_rp_qs_pending++; | |
64db4cff | 1314 | return 1; |
7ba5c840 | 1315 | } |
64db4cff PM |
1316 | |
1317 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
1318 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
1319 | rdp->n_rp_cb_ready++; | |
64db4cff | 1320 | return 1; |
7ba5c840 | 1321 | } |
64db4cff PM |
1322 | |
1323 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
1324 | if (cpu_needs_another_gp(rsp, rdp)) { |
1325 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 1326 | return 1; |
7ba5c840 | 1327 | } |
64db4cff PM |
1328 | |
1329 | /* Has another RCU grace period completed? */ | |
7ba5c840 PM |
1330 | if (ACCESS_ONCE(rsp->completed) != rdp->completed) { /* outside lock */ |
1331 | rdp->n_rp_gp_completed++; | |
64db4cff | 1332 | return 1; |
7ba5c840 | 1333 | } |
64db4cff PM |
1334 | |
1335 | /* Has a new RCU grace period started? */ | |
7ba5c840 PM |
1336 | if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) { /* outside lock */ |
1337 | rdp->n_rp_gp_started++; | |
64db4cff | 1338 | return 1; |
7ba5c840 | 1339 | } |
64db4cff PM |
1340 | |
1341 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ | |
1342 | if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) && | |
7ba5c840 PM |
1343 | ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) { |
1344 | rdp->n_rp_need_fqs++; | |
64db4cff | 1345 | return 1; |
7ba5c840 | 1346 | } |
64db4cff PM |
1347 | |
1348 | /* nothing to do */ | |
7ba5c840 | 1349 | rdp->n_rp_need_nothing++; |
64db4cff PM |
1350 | return 0; |
1351 | } | |
1352 | ||
1353 | /* | |
1354 | * Check to see if there is any immediate RCU-related work to be done | |
1355 | * by the current CPU, returning 1 if so. This function is part of the | |
1356 | * RCU implementation; it is -not- an exported member of the RCU API. | |
1357 | */ | |
a157229c | 1358 | static int rcu_pending(int cpu) |
64db4cff | 1359 | { |
d6714c22 | 1360 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
f41d911f PM |
1361 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
1362 | rcu_preempt_pending(cpu); | |
64db4cff PM |
1363 | } |
1364 | ||
1365 | /* | |
1366 | * Check to see if any future RCU-related work will need to be done | |
1367 | * by the current CPU, even if none need be done immediately, returning | |
1368 | * 1 if so. This function is part of the RCU implementation; it is -not- | |
1369 | * an exported member of the RCU API. | |
1370 | */ | |
1371 | int rcu_needs_cpu(int cpu) | |
1372 | { | |
1373 | /* RCU callbacks either ready or pending? */ | |
d6714c22 | 1374 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
f41d911f PM |
1375 | per_cpu(rcu_bh_data, cpu).nxtlist || |
1376 | rcu_preempt_needs_cpu(cpu); | |
64db4cff PM |
1377 | } |
1378 | ||
1379 | /* | |
27569620 PM |
1380 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
1381 | */ | |
1382 | static void __init | |
1383 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
1384 | { | |
1385 | unsigned long flags; | |
1386 | int i; | |
1387 | struct rcu_data *rdp = rsp->rda[cpu]; | |
1388 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1389 | ||
1390 | /* Set up local state, ensuring consistent view of global state. */ | |
1391 | spin_lock_irqsave(&rnp->lock, flags); | |
1392 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); | |
1393 | rdp->nxtlist = NULL; | |
1394 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1395 | rdp->nxttail[i] = &rdp->nxtlist; | |
1396 | rdp->qlen = 0; | |
1397 | #ifdef CONFIG_NO_HZ | |
1398 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); | |
1399 | #endif /* #ifdef CONFIG_NO_HZ */ | |
1400 | rdp->cpu = cpu; | |
1401 | spin_unlock_irqrestore(&rnp->lock, flags); | |
1402 | } | |
1403 | ||
1404 | /* | |
1405 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
1406 | * offline event can be happening at a given time. Note also that we | |
1407 | * can accept some slop in the rsp->completed access due to the fact | |
1408 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 1409 | */ |
e4fa4c97 | 1410 | static void __cpuinit |
f41d911f | 1411 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
64db4cff PM |
1412 | { |
1413 | unsigned long flags; | |
64db4cff PM |
1414 | long lastcomp; |
1415 | unsigned long mask; | |
1416 | struct rcu_data *rdp = rsp->rda[cpu]; | |
1417 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1418 | ||
1419 | /* Set up local state, ensuring consistent view of global state. */ | |
1420 | spin_lock_irqsave(&rnp->lock, flags); | |
1421 | lastcomp = rsp->completed; | |
1422 | rdp->completed = lastcomp; | |
1423 | rdp->gpnum = lastcomp; | |
1424 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ | |
1425 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ | |
1426 | rdp->beenonline = 1; /* We have now been online. */ | |
f41d911f | 1427 | rdp->preemptable = preemptable; |
64db4cff | 1428 | rdp->passed_quiesc_completed = lastcomp - 1; |
64db4cff | 1429 | rdp->blimit = blimit; |
64db4cff PM |
1430 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
1431 | ||
1432 | /* | |
1433 | * A new grace period might start here. If so, we won't be part | |
1434 | * of it, but that is OK, as we are currently in a quiescent state. | |
1435 | */ | |
1436 | ||
1437 | /* Exclude any attempts to start a new GP on large systems. */ | |
1438 | spin_lock(&rsp->onofflock); /* irqs already disabled. */ | |
1439 | ||
1440 | /* Add CPU to rcu_node bitmasks. */ | |
1441 | rnp = rdp->mynode; | |
1442 | mask = rdp->grpmask; | |
1443 | do { | |
1444 | /* Exclude any attempts to start a new GP on small systems. */ | |
1445 | spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1446 | rnp->qsmaskinit |= mask; | |
1447 | mask = rnp->grpmask; | |
1448 | spin_unlock(&rnp->lock); /* irqs already disabled. */ | |
1449 | rnp = rnp->parent; | |
1450 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
1451 | ||
1452 | spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ | |
1453 | ||
1454 | /* | |
1455 | * A new grace period might start here. If so, we will be part of | |
1456 | * it, and its gpnum will be greater than ours, so we will | |
1457 | * participate. It is also possible for the gpnum to have been | |
1458 | * incremented before this function was called, and the bitmasks | |
1459 | * to not be filled out until now, in which case we will also | |
1460 | * participate due to our gpnum being behind. | |
1461 | */ | |
1462 | ||
1463 | /* Since it is coming online, the CPU is in a quiescent state. */ | |
1464 | cpu_quiet(cpu, rsp, rdp, lastcomp); | |
1465 | local_irq_restore(flags); | |
1466 | } | |
1467 | ||
1468 | static void __cpuinit rcu_online_cpu(int cpu) | |
1469 | { | |
f41d911f PM |
1470 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
1471 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); | |
1472 | rcu_preempt_init_percpu_data(cpu); | |
64db4cff PM |
1473 | } |
1474 | ||
1475 | /* | |
f41d911f | 1476 | * Handle CPU online/offline notification events. |
64db4cff | 1477 | */ |
2e597558 PM |
1478 | int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
1479 | unsigned long action, void *hcpu) | |
64db4cff PM |
1480 | { |
1481 | long cpu = (long)hcpu; | |
1482 | ||
1483 | switch (action) { | |
1484 | case CPU_UP_PREPARE: | |
1485 | case CPU_UP_PREPARE_FROZEN: | |
1486 | rcu_online_cpu(cpu); | |
1487 | break; | |
1488 | case CPU_DEAD: | |
1489 | case CPU_DEAD_FROZEN: | |
1490 | case CPU_UP_CANCELED: | |
1491 | case CPU_UP_CANCELED_FROZEN: | |
1492 | rcu_offline_cpu(cpu); | |
1493 | break; | |
1494 | default: | |
1495 | break; | |
1496 | } | |
1497 | return NOTIFY_OK; | |
1498 | } | |
1499 | ||
1500 | /* | |
1501 | * Compute the per-level fanout, either using the exact fanout specified | |
1502 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
1503 | */ | |
1504 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
1505 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1506 | { | |
1507 | int i; | |
1508 | ||
1509 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) | |
1510 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; | |
1511 | } | |
1512 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1513 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
1514 | { | |
1515 | int ccur; | |
1516 | int cprv; | |
1517 | int i; | |
1518 | ||
1519 | cprv = NR_CPUS; | |
1520 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1521 | ccur = rsp->levelcnt[i]; | |
1522 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
1523 | cprv = ccur; | |
1524 | } | |
1525 | } | |
1526 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
1527 | ||
1528 | /* | |
1529 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
1530 | */ | |
1531 | static void __init rcu_init_one(struct rcu_state *rsp) | |
1532 | { | |
1533 | int cpustride = 1; | |
1534 | int i; | |
1535 | int j; | |
1536 | struct rcu_node *rnp; | |
1537 | ||
1538 | /* Initialize the level-tracking arrays. */ | |
1539 | ||
1540 | for (i = 1; i < NUM_RCU_LVLS; i++) | |
1541 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; | |
1542 | rcu_init_levelspread(rsp); | |
1543 | ||
1544 | /* Initialize the elements themselves, starting from the leaves. */ | |
1545 | ||
1546 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { | |
1547 | cpustride *= rsp->levelspread[i]; | |
1548 | rnp = rsp->level[i]; | |
1549 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1550 | spin_lock_init(&rnp->lock); | |
f41d911f | 1551 | rnp->gpnum = 0; |
64db4cff PM |
1552 | rnp->qsmask = 0; |
1553 | rnp->qsmaskinit = 0; | |
1554 | rnp->grplo = j * cpustride; | |
1555 | rnp->grphi = (j + 1) * cpustride - 1; | |
1556 | if (rnp->grphi >= NR_CPUS) | |
1557 | rnp->grphi = NR_CPUS - 1; | |
1558 | if (i == 0) { | |
1559 | rnp->grpnum = 0; | |
1560 | rnp->grpmask = 0; | |
1561 | rnp->parent = NULL; | |
1562 | } else { | |
1563 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
1564 | rnp->grpmask = 1UL << rnp->grpnum; | |
1565 | rnp->parent = rsp->level[i - 1] + | |
1566 | j / rsp->levelspread[i - 1]; | |
1567 | } | |
1568 | rnp->level = i; | |
f41d911f PM |
1569 | INIT_LIST_HEAD(&rnp->blocked_tasks[0]); |
1570 | INIT_LIST_HEAD(&rnp->blocked_tasks[1]); | |
64db4cff PM |
1571 | } |
1572 | } | |
1573 | } | |
1574 | ||
1575 | /* | |
f41d911f PM |
1576 | * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used |
1577 | * nowhere else! Assigns leaf node pointers into each CPU's rcu_data | |
1578 | * structure. | |
64db4cff | 1579 | */ |
65cf8f86 | 1580 | #define RCU_INIT_FLAVOR(rsp, rcu_data) \ |
64db4cff | 1581 | do { \ |
65cf8f86 | 1582 | rcu_init_one(rsp); \ |
64db4cff PM |
1583 | rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \ |
1584 | j = 0; \ | |
1585 | for_each_possible_cpu(i) { \ | |
1586 | if (i > rnp[j].grphi) \ | |
1587 | j++; \ | |
1588 | per_cpu(rcu_data, i).mynode = &rnp[j]; \ | |
1589 | (rsp)->rda[i] = &per_cpu(rcu_data, i); \ | |
65cf8f86 | 1590 | rcu_boot_init_percpu_data(i, rsp); \ |
64db4cff PM |
1591 | } \ |
1592 | } while (0) | |
1593 | ||
f41d911f PM |
1594 | #ifdef CONFIG_TREE_PREEMPT_RCU |
1595 | ||
1596 | void __init __rcu_init_preempt(void) | |
1597 | { | |
1598 | int i; /* All used by RCU_INIT_FLAVOR(). */ | |
1599 | int j; | |
1600 | struct rcu_node *rnp; | |
1601 | ||
1602 | RCU_INIT_FLAVOR(&rcu_preempt_state, rcu_preempt_data); | |
1603 | } | |
1604 | ||
1605 | #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ | |
1606 | ||
1607 | void __init __rcu_init_preempt(void) | |
1608 | { | |
1609 | } | |
1610 | ||
1611 | #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ | |
1612 | ||
64db4cff PM |
1613 | void __init __rcu_init(void) |
1614 | { | |
f41d911f | 1615 | int i; /* All used by RCU_INIT_FLAVOR(). */ |
64db4cff PM |
1616 | int j; |
1617 | struct rcu_node *rnp; | |
1618 | ||
f41d911f | 1619 | rcu_bootup_announce(); |
64db4cff PM |
1620 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
1621 | printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); | |
1622 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
65cf8f86 PM |
1623 | RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); |
1624 | RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); | |
f41d911f | 1625 | __rcu_init_preempt(); |
2e597558 | 1626 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
64db4cff PM |
1627 | } |
1628 | ||
1629 | module_param(blimit, int, 0); | |
1630 | module_param(qhimark, int, 0); | |
1631 | module_param(qlowmark, int, 0); |