Commit | Line | Data |
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1da177e4 LT |
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 (C) IBM Corporation, 2001 | |
19 | * | |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
22 | * | |
23 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> | |
24 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
25 | * Papers: | |
26 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf | |
27 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) | |
28 | * | |
29 | * For detailed explanation of Read-Copy Update mechanism see - | |
30 | * http://lse.sourceforge.net/locking/rcupdate.html | |
31 | * | |
32 | */ | |
33 | #include <linux/types.h> | |
34 | #include <linux/kernel.h> | |
35 | #include <linux/init.h> | |
36 | #include <linux/spinlock.h> | |
37 | #include <linux/smp.h> | |
e56d0903 | 38 | #include <linux/rcupdate.h> |
1da177e4 LT |
39 | #include <linux/interrupt.h> |
40 | #include <linux/sched.h> | |
41 | #include <asm/atomic.h> | |
42 | #include <linux/bitops.h> | |
43 | #include <linux/module.h> | |
44 | #include <linux/completion.h> | |
45 | #include <linux/moduleparam.h> | |
46 | #include <linux/percpu.h> | |
47 | #include <linux/notifier.h> | |
48 | #include <linux/rcupdate.h> | |
49 | #include <linux/cpu.h> | |
50 | ||
51 | /* Definition for rcupdate control block. */ | |
69a0b315 ON |
52 | struct rcu_ctrlblk rcu_ctrlblk = { |
53 | .cur = -300, | |
54 | .completed = -300, | |
55 | .lock = SPIN_LOCK_UNLOCKED, | |
56 | .cpumask = CPU_MASK_NONE, | |
57 | }; | |
58 | struct rcu_ctrlblk rcu_bh_ctrlblk = { | |
59 | .cur = -300, | |
60 | .completed = -300, | |
61 | .lock = SPIN_LOCK_UNLOCKED, | |
62 | .cpumask = CPU_MASK_NONE, | |
1da177e4 | 63 | }; |
1da177e4 LT |
64 | |
65 | DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L }; | |
66 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L }; | |
67 | ||
68 | /* Fake initialization required by compiler */ | |
69 | static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL}; | |
2cc78eb5 | 70 | static int maxbatch = 10000; |
1da177e4 LT |
71 | |
72 | /** | |
73 | * call_rcu - Queue an RCU callback for invocation after a grace period. | |
74 | * @head: structure to be used for queueing the RCU updates. | |
75 | * @func: actual update function to be invoked after the grace period | |
76 | * | |
77 | * The update function will be invoked some time after a full grace | |
78 | * period elapses, in other words after all currently executing RCU | |
79 | * read-side critical sections have completed. RCU read-side critical | |
80 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
81 | * and may be nested. | |
82 | */ | |
83 | void fastcall call_rcu(struct rcu_head *head, | |
84 | void (*func)(struct rcu_head *rcu)) | |
85 | { | |
86 | unsigned long flags; | |
87 | struct rcu_data *rdp; | |
88 | ||
89 | head->func = func; | |
90 | head->next = NULL; | |
91 | local_irq_save(flags); | |
92 | rdp = &__get_cpu_var(rcu_data); | |
93 | *rdp->nxttail = head; | |
94 | rdp->nxttail = &head->next; | |
5ee832db ED |
95 | |
96 | if (unlikely(++rdp->count > 10000)) | |
97 | set_need_resched(); | |
98 | ||
1da177e4 LT |
99 | local_irq_restore(flags); |
100 | } | |
101 | ||
ab4720ec DS |
102 | static atomic_t rcu_barrier_cpu_count; |
103 | static struct semaphore rcu_barrier_sema; | |
104 | static struct completion rcu_barrier_completion; | |
105 | ||
1da177e4 LT |
106 | /** |
107 | * call_rcu_bh - Queue an RCU for invocation after a quicker grace period. | |
108 | * @head: structure to be used for queueing the RCU updates. | |
109 | * @func: actual update function to be invoked after the grace period | |
110 | * | |
111 | * The update function will be invoked some time after a full grace | |
112 | * period elapses, in other words after all currently executing RCU | |
113 | * read-side critical sections have completed. call_rcu_bh() assumes | |
114 | * that the read-side critical sections end on completion of a softirq | |
115 | * handler. This means that read-side critical sections in process | |
116 | * context must not be interrupted by softirqs. This interface is to be | |
117 | * used when most of the read-side critical sections are in softirq context. | |
118 | * RCU read-side critical sections are delimited by rcu_read_lock() and | |
119 | * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh() | |
120 | * and rcu_read_unlock_bh(), if in process context. These may be nested. | |
121 | */ | |
122 | void fastcall call_rcu_bh(struct rcu_head *head, | |
123 | void (*func)(struct rcu_head *rcu)) | |
124 | { | |
125 | unsigned long flags; | |
126 | struct rcu_data *rdp; | |
127 | ||
128 | head->func = func; | |
129 | head->next = NULL; | |
130 | local_irq_save(flags); | |
131 | rdp = &__get_cpu_var(rcu_bh_data); | |
132 | *rdp->nxttail = head; | |
133 | rdp->nxttail = &head->next; | |
5ee832db ED |
134 | rdp->count++; |
135 | /* | |
136 | * Should we directly call rcu_do_batch() here ? | |
137 | * if (unlikely(rdp->count > 10000)) | |
138 | * rcu_do_batch(rdp); | |
139 | */ | |
1da177e4 LT |
140 | local_irq_restore(flags); |
141 | } | |
142 | ||
a241ec65 PM |
143 | /* |
144 | * Return the number of RCU batches processed thus far. Useful | |
145 | * for debug and statistics. | |
146 | */ | |
147 | long rcu_batches_completed(void) | |
148 | { | |
149 | return rcu_ctrlblk.completed; | |
150 | } | |
151 | ||
ab4720ec DS |
152 | static void rcu_barrier_callback(struct rcu_head *notused) |
153 | { | |
154 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
155 | complete(&rcu_barrier_completion); | |
156 | } | |
157 | ||
158 | /* | |
159 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
160 | */ | |
161 | static void rcu_barrier_func(void *notused) | |
162 | { | |
163 | int cpu = smp_processor_id(); | |
164 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); | |
165 | struct rcu_head *head; | |
166 | ||
167 | head = &rdp->barrier; | |
168 | atomic_inc(&rcu_barrier_cpu_count); | |
169 | call_rcu(head, rcu_barrier_callback); | |
170 | } | |
171 | ||
172 | /** | |
173 | * rcu_barrier - Wait until all the in-flight RCUs are complete. | |
174 | */ | |
175 | void rcu_barrier(void) | |
176 | { | |
177 | BUG_ON(in_interrupt()); | |
178 | /* Take cpucontrol semaphore to protect against CPU hotplug */ | |
179 | down(&rcu_barrier_sema); | |
180 | init_completion(&rcu_barrier_completion); | |
181 | atomic_set(&rcu_barrier_cpu_count, 0); | |
182 | on_each_cpu(rcu_barrier_func, NULL, 0, 1); | |
183 | wait_for_completion(&rcu_barrier_completion); | |
184 | up(&rcu_barrier_sema); | |
185 | } | |
186 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
187 | ||
1da177e4 LT |
188 | /* |
189 | * Invoke the completed RCU callbacks. They are expected to be in | |
190 | * a per-cpu list. | |
191 | */ | |
192 | static void rcu_do_batch(struct rcu_data *rdp) | |
193 | { | |
194 | struct rcu_head *next, *list; | |
195 | int count = 0; | |
196 | ||
197 | list = rdp->donelist; | |
198 | while (list) { | |
199 | next = rdp->donelist = list->next; | |
200 | list->func(list); | |
201 | list = next; | |
5ee832db | 202 | rdp->count--; |
1da177e4 LT |
203 | if (++count >= maxbatch) |
204 | break; | |
205 | } | |
206 | if (!rdp->donelist) | |
207 | rdp->donetail = &rdp->donelist; | |
208 | else | |
209 | tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu)); | |
210 | } | |
211 | ||
212 | /* | |
213 | * Grace period handling: | |
214 | * The grace period handling consists out of two steps: | |
215 | * - A new grace period is started. | |
216 | * This is done by rcu_start_batch. The start is not broadcasted to | |
217 | * all cpus, they must pick this up by comparing rcp->cur with | |
218 | * rdp->quiescbatch. All cpus are recorded in the | |
69a0b315 | 219 | * rcu_ctrlblk.cpumask bitmap. |
1da177e4 LT |
220 | * - All cpus must go through a quiescent state. |
221 | * Since the start of the grace period is not broadcasted, at least two | |
222 | * calls to rcu_check_quiescent_state are required: | |
223 | * The first call just notices that a new grace period is running. The | |
224 | * following calls check if there was a quiescent state since the beginning | |
69a0b315 | 225 | * of the grace period. If so, it updates rcu_ctrlblk.cpumask. If |
1da177e4 LT |
226 | * the bitmap is empty, then the grace period is completed. |
227 | * rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace | |
228 | * period (if necessary). | |
229 | */ | |
230 | /* | |
231 | * Register a new batch of callbacks, and start it up if there is currently no | |
232 | * active batch and the batch to be registered has not already occurred. | |
69a0b315 | 233 | * Caller must hold rcu_ctrlblk.lock. |
1da177e4 | 234 | */ |
69a0b315 | 235 | static void rcu_start_batch(struct rcu_ctrlblk *rcp) |
1da177e4 | 236 | { |
1da177e4 LT |
237 | if (rcp->next_pending && |
238 | rcp->completed == rcp->cur) { | |
1da177e4 | 239 | rcp->next_pending = 0; |
c3f59023 SV |
240 | /* |
241 | * next_pending == 0 must be visible in | |
242 | * __rcu_process_callbacks() before it can see new value of cur. | |
1da177e4 LT |
243 | */ |
244 | smp_wmb(); | |
245 | rcp->cur++; | |
c3f59023 SV |
246 | |
247 | /* | |
248 | * Accessing nohz_cpu_mask before incrementing rcp->cur needs a | |
249 | * Barrier Otherwise it can cause tickless idle CPUs to be | |
69a0b315 | 250 | * included in rcp->cpumask, which will extend graceperiods |
c3f59023 SV |
251 | * unnecessarily. |
252 | */ | |
253 | smp_mb(); | |
69a0b315 | 254 | cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask); |
c3f59023 | 255 | |
1da177e4 LT |
256 | } |
257 | } | |
258 | ||
259 | /* | |
260 | * cpu went through a quiescent state since the beginning of the grace period. | |
261 | * Clear it from the cpu mask and complete the grace period if it was the last | |
262 | * cpu. Start another grace period if someone has further entries pending | |
263 | */ | |
69a0b315 | 264 | static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp) |
1da177e4 | 265 | { |
69a0b315 ON |
266 | cpu_clear(cpu, rcp->cpumask); |
267 | if (cpus_empty(rcp->cpumask)) { | |
1da177e4 LT |
268 | /* batch completed ! */ |
269 | rcp->completed = rcp->cur; | |
69a0b315 | 270 | rcu_start_batch(rcp); |
1da177e4 LT |
271 | } |
272 | } | |
273 | ||
274 | /* | |
275 | * Check if the cpu has gone through a quiescent state (say context | |
276 | * switch). If so and if it already hasn't done so in this RCU | |
277 | * quiescent cycle, then indicate that it has done so. | |
278 | */ | |
279 | static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp, | |
69a0b315 | 280 | struct rcu_data *rdp) |
1da177e4 LT |
281 | { |
282 | if (rdp->quiescbatch != rcp->cur) { | |
283 | /* start new grace period: */ | |
284 | rdp->qs_pending = 1; | |
285 | rdp->passed_quiesc = 0; | |
286 | rdp->quiescbatch = rcp->cur; | |
287 | return; | |
288 | } | |
289 | ||
290 | /* Grace period already completed for this cpu? | |
291 | * qs_pending is checked instead of the actual bitmap to avoid | |
292 | * cacheline trashing. | |
293 | */ | |
294 | if (!rdp->qs_pending) | |
295 | return; | |
296 | ||
297 | /* | |
298 | * Was there a quiescent state since the beginning of the grace | |
299 | * period? If no, then exit and wait for the next call. | |
300 | */ | |
301 | if (!rdp->passed_quiesc) | |
302 | return; | |
303 | rdp->qs_pending = 0; | |
304 | ||
69a0b315 | 305 | spin_lock(&rcp->lock); |
1da177e4 LT |
306 | /* |
307 | * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync | |
308 | * during cpu startup. Ignore the quiescent state. | |
309 | */ | |
310 | if (likely(rdp->quiescbatch == rcp->cur)) | |
69a0b315 | 311 | cpu_quiet(rdp->cpu, rcp); |
1da177e4 | 312 | |
69a0b315 | 313 | spin_unlock(&rcp->lock); |
1da177e4 LT |
314 | } |
315 | ||
316 | ||
317 | #ifdef CONFIG_HOTPLUG_CPU | |
318 | ||
319 | /* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing | |
320 | * locking requirements, the list it's pulling from has to belong to a cpu | |
321 | * which is dead and hence not processing interrupts. | |
322 | */ | |
323 | static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list, | |
324 | struct rcu_head **tail) | |
325 | { | |
326 | local_irq_disable(); | |
327 | *this_rdp->nxttail = list; | |
328 | if (list) | |
329 | this_rdp->nxttail = tail; | |
330 | local_irq_enable(); | |
331 | } | |
332 | ||
333 | static void __rcu_offline_cpu(struct rcu_data *this_rdp, | |
69a0b315 | 334 | struct rcu_ctrlblk *rcp, struct rcu_data *rdp) |
1da177e4 LT |
335 | { |
336 | /* if the cpu going offline owns the grace period | |
337 | * we can block indefinitely waiting for it, so flush | |
338 | * it here | |
339 | */ | |
69a0b315 | 340 | spin_lock_bh(&rcp->lock); |
1da177e4 | 341 | if (rcp->cur != rcp->completed) |
69a0b315 ON |
342 | cpu_quiet(rdp->cpu, rcp); |
343 | spin_unlock_bh(&rcp->lock); | |
1da177e4 LT |
344 | rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail); |
345 | rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail); | |
a9c82815 | 346 | rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail); |
1da177e4 | 347 | } |
a9c82815 | 348 | |
1da177e4 LT |
349 | static void rcu_offline_cpu(int cpu) |
350 | { | |
351 | struct rcu_data *this_rdp = &get_cpu_var(rcu_data); | |
352 | struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data); | |
353 | ||
69a0b315 | 354 | __rcu_offline_cpu(this_rdp, &rcu_ctrlblk, |
1da177e4 | 355 | &per_cpu(rcu_data, cpu)); |
69a0b315 | 356 | __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, |
1da177e4 LT |
357 | &per_cpu(rcu_bh_data, cpu)); |
358 | put_cpu_var(rcu_data); | |
359 | put_cpu_var(rcu_bh_data); | |
360 | tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu); | |
361 | } | |
362 | ||
363 | #else | |
364 | ||
365 | static void rcu_offline_cpu(int cpu) | |
366 | { | |
367 | } | |
368 | ||
369 | #endif | |
370 | ||
371 | /* | |
372 | * This does the RCU processing work from tasklet context. | |
373 | */ | |
374 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, | |
69a0b315 | 375 | struct rcu_data *rdp) |
1da177e4 LT |
376 | { |
377 | if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) { | |
378 | *rdp->donetail = rdp->curlist; | |
379 | rdp->donetail = rdp->curtail; | |
380 | rdp->curlist = NULL; | |
381 | rdp->curtail = &rdp->curlist; | |
382 | } | |
383 | ||
384 | local_irq_disable(); | |
385 | if (rdp->nxtlist && !rdp->curlist) { | |
386 | rdp->curlist = rdp->nxtlist; | |
387 | rdp->curtail = rdp->nxttail; | |
388 | rdp->nxtlist = NULL; | |
389 | rdp->nxttail = &rdp->nxtlist; | |
390 | local_irq_enable(); | |
391 | ||
392 | /* | |
393 | * start the next batch of callbacks | |
394 | */ | |
395 | ||
396 | /* determine batch number */ | |
397 | rdp->batch = rcp->cur + 1; | |
398 | /* see the comment and corresponding wmb() in | |
399 | * the rcu_start_batch() | |
400 | */ | |
401 | smp_rmb(); | |
402 | ||
403 | if (!rcp->next_pending) { | |
404 | /* and start it/schedule start if it's a new batch */ | |
69a0b315 | 405 | spin_lock(&rcp->lock); |
dbc1651f | 406 | rcp->next_pending = 1; |
69a0b315 ON |
407 | rcu_start_batch(rcp); |
408 | spin_unlock(&rcp->lock); | |
1da177e4 LT |
409 | } |
410 | } else { | |
411 | local_irq_enable(); | |
412 | } | |
69a0b315 | 413 | rcu_check_quiescent_state(rcp, rdp); |
1da177e4 LT |
414 | if (rdp->donelist) |
415 | rcu_do_batch(rdp); | |
416 | } | |
417 | ||
418 | static void rcu_process_callbacks(unsigned long unused) | |
419 | { | |
69a0b315 ON |
420 | __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data)); |
421 | __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data)); | |
1da177e4 LT |
422 | } |
423 | ||
67751777 ON |
424 | static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) |
425 | { | |
426 | /* This cpu has pending rcu entries and the grace period | |
427 | * for them has completed. | |
428 | */ | |
429 | if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) | |
430 | return 1; | |
431 | ||
432 | /* This cpu has no pending entries, but there are new entries */ | |
433 | if (!rdp->curlist && rdp->nxtlist) | |
434 | return 1; | |
435 | ||
436 | /* This cpu has finished callbacks to invoke */ | |
437 | if (rdp->donelist) | |
438 | return 1; | |
439 | ||
440 | /* The rcu core waits for a quiescent state from the cpu */ | |
441 | if (rdp->quiescbatch != rcp->cur || rdp->qs_pending) | |
442 | return 1; | |
443 | ||
444 | /* nothing to do */ | |
445 | return 0; | |
446 | } | |
447 | ||
448 | int rcu_pending(int cpu) | |
449 | { | |
450 | return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) || | |
451 | __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu)); | |
452 | } | |
453 | ||
1da177e4 LT |
454 | void rcu_check_callbacks(int cpu, int user) |
455 | { | |
456 | if (user || | |
457 | (idle_cpu(cpu) && !in_softirq() && | |
458 | hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
459 | rcu_qsctr_inc(cpu); | |
460 | rcu_bh_qsctr_inc(cpu); | |
461 | } else if (!in_softirq()) | |
462 | rcu_bh_qsctr_inc(cpu); | |
463 | tasklet_schedule(&per_cpu(rcu_tasklet, cpu)); | |
464 | } | |
465 | ||
466 | static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp, | |
467 | struct rcu_data *rdp) | |
468 | { | |
469 | memset(rdp, 0, sizeof(*rdp)); | |
470 | rdp->curtail = &rdp->curlist; | |
471 | rdp->nxttail = &rdp->nxtlist; | |
472 | rdp->donetail = &rdp->donelist; | |
473 | rdp->quiescbatch = rcp->completed; | |
474 | rdp->qs_pending = 0; | |
475 | rdp->cpu = cpu; | |
476 | } | |
477 | ||
478 | static void __devinit rcu_online_cpu(int cpu) | |
479 | { | |
480 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); | |
481 | struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu); | |
482 | ||
483 | rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp); | |
484 | rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp); | |
485 | tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL); | |
486 | } | |
487 | ||
488 | static int __devinit rcu_cpu_notify(struct notifier_block *self, | |
489 | unsigned long action, void *hcpu) | |
490 | { | |
491 | long cpu = (long)hcpu; | |
492 | switch (action) { | |
493 | case CPU_UP_PREPARE: | |
494 | rcu_online_cpu(cpu); | |
495 | break; | |
496 | case CPU_DEAD: | |
497 | rcu_offline_cpu(cpu); | |
498 | break; | |
499 | default: | |
500 | break; | |
501 | } | |
502 | return NOTIFY_OK; | |
503 | } | |
504 | ||
505 | static struct notifier_block __devinitdata rcu_nb = { | |
506 | .notifier_call = rcu_cpu_notify, | |
507 | }; | |
508 | ||
509 | /* | |
510 | * Initializes rcu mechanism. Assumed to be called early. | |
511 | * That is before local timer(SMP) or jiffie timer (uniproc) is setup. | |
512 | * Note that rcu_qsctr and friends are implicitly | |
513 | * initialized due to the choice of ``0'' for RCU_CTR_INVALID. | |
514 | */ | |
515 | void __init rcu_init(void) | |
516 | { | |
ab4720ec | 517 | sema_init(&rcu_barrier_sema, 1); |
1da177e4 LT |
518 | rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, |
519 | (void *)(long)smp_processor_id()); | |
520 | /* Register notifier for non-boot CPUs */ | |
521 | register_cpu_notifier(&rcu_nb); | |
522 | } | |
523 | ||
524 | struct rcu_synchronize { | |
525 | struct rcu_head head; | |
526 | struct completion completion; | |
527 | }; | |
528 | ||
529 | /* Because of FASTCALL declaration of complete, we use this wrapper */ | |
530 | static void wakeme_after_rcu(struct rcu_head *head) | |
531 | { | |
532 | struct rcu_synchronize *rcu; | |
533 | ||
534 | rcu = container_of(head, struct rcu_synchronize, head); | |
535 | complete(&rcu->completion); | |
536 | } | |
537 | ||
538 | /** | |
9b06e818 | 539 | * synchronize_rcu - wait until a grace period has elapsed. |
1da177e4 LT |
540 | * |
541 | * Control will return to the caller some time after a full grace | |
542 | * period has elapsed, in other words after all currently executing RCU | |
543 | * read-side critical sections have completed. RCU read-side critical | |
544 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
545 | * and may be nested. | |
9b06e818 PM |
546 | * |
547 | * If your read-side code is not protected by rcu_read_lock(), do -not- | |
548 | * use synchronize_rcu(). | |
1da177e4 | 549 | */ |
9b06e818 | 550 | void synchronize_rcu(void) |
1da177e4 LT |
551 | { |
552 | struct rcu_synchronize rcu; | |
553 | ||
554 | init_completion(&rcu.completion); | |
555 | /* Will wake me after RCU finished */ | |
556 | call_rcu(&rcu.head, wakeme_after_rcu); | |
557 | ||
558 | /* Wait for it */ | |
559 | wait_for_completion(&rcu.completion); | |
560 | } | |
561 | ||
9b06e818 PM |
562 | /* |
563 | * Deprecated, use synchronize_rcu() or synchronize_sched() instead. | |
564 | */ | |
565 | void synchronize_kernel(void) | |
566 | { | |
567 | synchronize_rcu(); | |
568 | } | |
569 | ||
1da177e4 | 570 | module_param(maxbatch, int, 0); |
a241ec65 | 571 | EXPORT_SYMBOL_GPL(rcu_batches_completed); |
66cf8f14 PM |
572 | EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */ |
573 | EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */ | |
9b06e818 | 574 | EXPORT_SYMBOL_GPL(synchronize_rcu); |
66cf8f14 | 575 | EXPORT_SYMBOL(synchronize_kernel); /* WARNING: GPL-only in April 2006. */ |