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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> | |
9331b315 | 50 | #include <linux/mutex.h> |
1da177e4 LT |
51 | |
52 | /* Definition for rcupdate control block. */ | |
2178426d | 53 | static struct rcu_ctrlblk rcu_ctrlblk = { |
69a0b315 ON |
54 | .cur = -300, |
55 | .completed = -300, | |
56 | .lock = SPIN_LOCK_UNLOCKED, | |
57 | .cpumask = CPU_MASK_NONE, | |
58 | }; | |
2178426d | 59 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { |
69a0b315 ON |
60 | .cur = -300, |
61 | .completed = -300, | |
62 | .lock = SPIN_LOCK_UNLOCKED, | |
63 | .cpumask = CPU_MASK_NONE, | |
1da177e4 | 64 | }; |
1da177e4 LT |
65 | |
66 | DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L }; | |
67 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L }; | |
68 | ||
69 | /* Fake initialization required by compiler */ | |
70 | static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL}; | |
21a1ea9e DS |
71 | static int blimit = 10; |
72 | static int qhimark = 10000; | |
73 | static int qlowmark = 100; | |
74 | #ifdef CONFIG_SMP | |
75 | static int rsinterval = 1000; | |
76 | #endif | |
77 | ||
78 | static atomic_t rcu_barrier_cpu_count; | |
9331b315 | 79 | static DEFINE_MUTEX(rcu_barrier_mutex); |
21a1ea9e DS |
80 | static struct completion rcu_barrier_completion; |
81 | ||
82 | #ifdef CONFIG_SMP | |
83 | static void force_quiescent_state(struct rcu_data *rdp, | |
84 | struct rcu_ctrlblk *rcp) | |
85 | { | |
86 | int cpu; | |
87 | cpumask_t cpumask; | |
88 | set_need_resched(); | |
89 | if (unlikely(rdp->qlen - rdp->last_rs_qlen > rsinterval)) { | |
90 | rdp->last_rs_qlen = rdp->qlen; | |
91 | /* | |
92 | * Don't send IPI to itself. With irqs disabled, | |
93 | * rdp->cpu is the current cpu. | |
94 | */ | |
95 | cpumask = rcp->cpumask; | |
96 | cpu_clear(rdp->cpu, cpumask); | |
97 | for_each_cpu_mask(cpu, cpumask) | |
98 | smp_send_reschedule(cpu); | |
99 | } | |
100 | } | |
101 | #else | |
102 | static inline void force_quiescent_state(struct rcu_data *rdp, | |
103 | struct rcu_ctrlblk *rcp) | |
104 | { | |
105 | set_need_resched(); | |
106 | } | |
107 | #endif | |
1da177e4 LT |
108 | |
109 | /** | |
110 | * call_rcu - Queue an RCU callback for invocation after a grace period. | |
111 | * @head: structure to be used for queueing the RCU updates. | |
112 | * @func: actual update function to be invoked after the grace period | |
113 | * | |
114 | * The update function will be invoked some time after a full grace | |
115 | * period elapses, in other words after all currently executing RCU | |
116 | * read-side critical sections have completed. RCU read-side critical | |
117 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
118 | * and may be nested. | |
119 | */ | |
120 | void fastcall call_rcu(struct rcu_head *head, | |
121 | void (*func)(struct rcu_head *rcu)) | |
122 | { | |
123 | unsigned long flags; | |
124 | struct rcu_data *rdp; | |
125 | ||
126 | head->func = func; | |
127 | head->next = NULL; | |
128 | local_irq_save(flags); | |
129 | rdp = &__get_cpu_var(rcu_data); | |
130 | *rdp->nxttail = head; | |
131 | rdp->nxttail = &head->next; | |
21a1ea9e DS |
132 | if (unlikely(++rdp->qlen > qhimark)) { |
133 | rdp->blimit = INT_MAX; | |
134 | force_quiescent_state(rdp, &rcu_ctrlblk); | |
135 | } | |
1da177e4 LT |
136 | local_irq_restore(flags); |
137 | } | |
138 | ||
139 | /** | |
140 | * call_rcu_bh - Queue an RCU for invocation after a quicker grace period. | |
141 | * @head: structure to be used for queueing the RCU updates. | |
142 | * @func: actual update function to be invoked after the grace period | |
143 | * | |
144 | * The update function will be invoked some time after a full grace | |
145 | * period elapses, in other words after all currently executing RCU | |
146 | * read-side critical sections have completed. call_rcu_bh() assumes | |
147 | * that the read-side critical sections end on completion of a softirq | |
148 | * handler. This means that read-side critical sections in process | |
149 | * context must not be interrupted by softirqs. This interface is to be | |
150 | * used when most of the read-side critical sections are in softirq context. | |
151 | * RCU read-side critical sections are delimited by rcu_read_lock() and | |
152 | * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh() | |
153 | * and rcu_read_unlock_bh(), if in process context. These may be nested. | |
154 | */ | |
155 | void fastcall call_rcu_bh(struct rcu_head *head, | |
156 | void (*func)(struct rcu_head *rcu)) | |
157 | { | |
158 | unsigned long flags; | |
159 | struct rcu_data *rdp; | |
160 | ||
161 | head->func = func; | |
162 | head->next = NULL; | |
163 | local_irq_save(flags); | |
164 | rdp = &__get_cpu_var(rcu_bh_data); | |
165 | *rdp->nxttail = head; | |
166 | rdp->nxttail = &head->next; | |
21a1ea9e DS |
167 | |
168 | if (unlikely(++rdp->qlen > qhimark)) { | |
169 | rdp->blimit = INT_MAX; | |
170 | force_quiescent_state(rdp, &rcu_bh_ctrlblk); | |
171 | } | |
172 | ||
1da177e4 LT |
173 | local_irq_restore(flags); |
174 | } | |
175 | ||
a241ec65 PM |
176 | /* |
177 | * Return the number of RCU batches processed thus far. Useful | |
178 | * for debug and statistics. | |
179 | */ | |
180 | long rcu_batches_completed(void) | |
181 | { | |
182 | return rcu_ctrlblk.completed; | |
183 | } | |
184 | ||
ab4720ec DS |
185 | static void rcu_barrier_callback(struct rcu_head *notused) |
186 | { | |
187 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
188 | complete(&rcu_barrier_completion); | |
189 | } | |
190 | ||
191 | /* | |
192 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
193 | */ | |
194 | static void rcu_barrier_func(void *notused) | |
195 | { | |
196 | int cpu = smp_processor_id(); | |
197 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); | |
198 | struct rcu_head *head; | |
199 | ||
200 | head = &rdp->barrier; | |
201 | atomic_inc(&rcu_barrier_cpu_count); | |
202 | call_rcu(head, rcu_barrier_callback); | |
203 | } | |
204 | ||
205 | /** | |
206 | * rcu_barrier - Wait until all the in-flight RCUs are complete. | |
207 | */ | |
208 | void rcu_barrier(void) | |
209 | { | |
210 | BUG_ON(in_interrupt()); | |
9331b315 IM |
211 | /* Take cpucontrol mutex to protect against CPU hotplug */ |
212 | mutex_lock(&rcu_barrier_mutex); | |
ab4720ec DS |
213 | init_completion(&rcu_barrier_completion); |
214 | atomic_set(&rcu_barrier_cpu_count, 0); | |
215 | on_each_cpu(rcu_barrier_func, NULL, 0, 1); | |
216 | wait_for_completion(&rcu_barrier_completion); | |
9331b315 | 217 | mutex_unlock(&rcu_barrier_mutex); |
ab4720ec DS |
218 | } |
219 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
220 | ||
1da177e4 LT |
221 | /* |
222 | * Invoke the completed RCU callbacks. They are expected to be in | |
223 | * a per-cpu list. | |
224 | */ | |
225 | static void rcu_do_batch(struct rcu_data *rdp) | |
226 | { | |
227 | struct rcu_head *next, *list; | |
228 | int count = 0; | |
229 | ||
230 | list = rdp->donelist; | |
231 | while (list) { | |
232 | next = rdp->donelist = list->next; | |
233 | list->func(list); | |
234 | list = next; | |
21a1ea9e DS |
235 | rdp->qlen--; |
236 | if (++count >= rdp->blimit) | |
1da177e4 LT |
237 | break; |
238 | } | |
21a1ea9e DS |
239 | if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark) |
240 | rdp->blimit = blimit; | |
1da177e4 LT |
241 | if (!rdp->donelist) |
242 | rdp->donetail = &rdp->donelist; | |
243 | else | |
244 | tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu)); | |
245 | } | |
246 | ||
247 | /* | |
248 | * Grace period handling: | |
249 | * The grace period handling consists out of two steps: | |
250 | * - A new grace period is started. | |
251 | * This is done by rcu_start_batch. The start is not broadcasted to | |
252 | * all cpus, they must pick this up by comparing rcp->cur with | |
253 | * rdp->quiescbatch. All cpus are recorded in the | |
69a0b315 | 254 | * rcu_ctrlblk.cpumask bitmap. |
1da177e4 LT |
255 | * - All cpus must go through a quiescent state. |
256 | * Since the start of the grace period is not broadcasted, at least two | |
257 | * calls to rcu_check_quiescent_state are required: | |
258 | * The first call just notices that a new grace period is running. The | |
259 | * following calls check if there was a quiescent state since the beginning | |
69a0b315 | 260 | * of the grace period. If so, it updates rcu_ctrlblk.cpumask. If |
1da177e4 LT |
261 | * the bitmap is empty, then the grace period is completed. |
262 | * rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace | |
263 | * period (if necessary). | |
264 | */ | |
265 | /* | |
266 | * Register a new batch of callbacks, and start it up if there is currently no | |
267 | * active batch and the batch to be registered has not already occurred. | |
69a0b315 | 268 | * Caller must hold rcu_ctrlblk.lock. |
1da177e4 | 269 | */ |
69a0b315 | 270 | static void rcu_start_batch(struct rcu_ctrlblk *rcp) |
1da177e4 | 271 | { |
1da177e4 LT |
272 | if (rcp->next_pending && |
273 | rcp->completed == rcp->cur) { | |
1da177e4 | 274 | rcp->next_pending = 0; |
c3f59023 SV |
275 | /* |
276 | * next_pending == 0 must be visible in | |
277 | * __rcu_process_callbacks() before it can see new value of cur. | |
1da177e4 LT |
278 | */ |
279 | smp_wmb(); | |
280 | rcp->cur++; | |
c3f59023 SV |
281 | |
282 | /* | |
283 | * Accessing nohz_cpu_mask before incrementing rcp->cur needs a | |
284 | * Barrier Otherwise it can cause tickless idle CPUs to be | |
69a0b315 | 285 | * included in rcp->cpumask, which will extend graceperiods |
c3f59023 SV |
286 | * unnecessarily. |
287 | */ | |
288 | smp_mb(); | |
69a0b315 | 289 | cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask); |
c3f59023 | 290 | |
1da177e4 LT |
291 | } |
292 | } | |
293 | ||
294 | /* | |
295 | * cpu went through a quiescent state since the beginning of the grace period. | |
296 | * Clear it from the cpu mask and complete the grace period if it was the last | |
297 | * cpu. Start another grace period if someone has further entries pending | |
298 | */ | |
69a0b315 | 299 | static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp) |
1da177e4 | 300 | { |
69a0b315 ON |
301 | cpu_clear(cpu, rcp->cpumask); |
302 | if (cpus_empty(rcp->cpumask)) { | |
1da177e4 LT |
303 | /* batch completed ! */ |
304 | rcp->completed = rcp->cur; | |
69a0b315 | 305 | rcu_start_batch(rcp); |
1da177e4 LT |
306 | } |
307 | } | |
308 | ||
309 | /* | |
310 | * Check if the cpu has gone through a quiescent state (say context | |
311 | * switch). If so and if it already hasn't done so in this RCU | |
312 | * quiescent cycle, then indicate that it has done so. | |
313 | */ | |
314 | static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp, | |
69a0b315 | 315 | struct rcu_data *rdp) |
1da177e4 LT |
316 | { |
317 | if (rdp->quiescbatch != rcp->cur) { | |
318 | /* start new grace period: */ | |
319 | rdp->qs_pending = 1; | |
320 | rdp->passed_quiesc = 0; | |
321 | rdp->quiescbatch = rcp->cur; | |
322 | return; | |
323 | } | |
324 | ||
325 | /* Grace period already completed for this cpu? | |
326 | * qs_pending is checked instead of the actual bitmap to avoid | |
327 | * cacheline trashing. | |
328 | */ | |
329 | if (!rdp->qs_pending) | |
330 | return; | |
331 | ||
332 | /* | |
333 | * Was there a quiescent state since the beginning of the grace | |
334 | * period? If no, then exit and wait for the next call. | |
335 | */ | |
336 | if (!rdp->passed_quiesc) | |
337 | return; | |
338 | rdp->qs_pending = 0; | |
339 | ||
69a0b315 | 340 | spin_lock(&rcp->lock); |
1da177e4 LT |
341 | /* |
342 | * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync | |
343 | * during cpu startup. Ignore the quiescent state. | |
344 | */ | |
345 | if (likely(rdp->quiescbatch == rcp->cur)) | |
69a0b315 | 346 | cpu_quiet(rdp->cpu, rcp); |
1da177e4 | 347 | |
69a0b315 | 348 | spin_unlock(&rcp->lock); |
1da177e4 LT |
349 | } |
350 | ||
351 | ||
352 | #ifdef CONFIG_HOTPLUG_CPU | |
353 | ||
354 | /* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing | |
355 | * locking requirements, the list it's pulling from has to belong to a cpu | |
356 | * which is dead and hence not processing interrupts. | |
357 | */ | |
358 | static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list, | |
359 | struct rcu_head **tail) | |
360 | { | |
361 | local_irq_disable(); | |
362 | *this_rdp->nxttail = list; | |
363 | if (list) | |
364 | this_rdp->nxttail = tail; | |
365 | local_irq_enable(); | |
366 | } | |
367 | ||
368 | static void __rcu_offline_cpu(struct rcu_data *this_rdp, | |
69a0b315 | 369 | struct rcu_ctrlblk *rcp, struct rcu_data *rdp) |
1da177e4 LT |
370 | { |
371 | /* if the cpu going offline owns the grace period | |
372 | * we can block indefinitely waiting for it, so flush | |
373 | * it here | |
374 | */ | |
69a0b315 | 375 | spin_lock_bh(&rcp->lock); |
1da177e4 | 376 | if (rcp->cur != rcp->completed) |
69a0b315 ON |
377 | cpu_quiet(rdp->cpu, rcp); |
378 | spin_unlock_bh(&rcp->lock); | |
1da177e4 LT |
379 | rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail); |
380 | rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail); | |
a9c82815 | 381 | rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail); |
1da177e4 | 382 | } |
a9c82815 | 383 | |
1da177e4 LT |
384 | static void rcu_offline_cpu(int cpu) |
385 | { | |
386 | struct rcu_data *this_rdp = &get_cpu_var(rcu_data); | |
387 | struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data); | |
388 | ||
69a0b315 | 389 | __rcu_offline_cpu(this_rdp, &rcu_ctrlblk, |
1da177e4 | 390 | &per_cpu(rcu_data, cpu)); |
69a0b315 | 391 | __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, |
1da177e4 LT |
392 | &per_cpu(rcu_bh_data, cpu)); |
393 | put_cpu_var(rcu_data); | |
394 | put_cpu_var(rcu_bh_data); | |
395 | tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu); | |
396 | } | |
397 | ||
398 | #else | |
399 | ||
400 | static void rcu_offline_cpu(int cpu) | |
401 | { | |
402 | } | |
403 | ||
404 | #endif | |
405 | ||
406 | /* | |
407 | * This does the RCU processing work from tasklet context. | |
408 | */ | |
409 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, | |
69a0b315 | 410 | struct rcu_data *rdp) |
1da177e4 LT |
411 | { |
412 | if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) { | |
413 | *rdp->donetail = rdp->curlist; | |
414 | rdp->donetail = rdp->curtail; | |
415 | rdp->curlist = NULL; | |
416 | rdp->curtail = &rdp->curlist; | |
417 | } | |
418 | ||
1da177e4 | 419 | if (rdp->nxtlist && !rdp->curlist) { |
caa9ee77 | 420 | local_irq_disable(); |
1da177e4 LT |
421 | rdp->curlist = rdp->nxtlist; |
422 | rdp->curtail = rdp->nxttail; | |
423 | rdp->nxtlist = NULL; | |
424 | rdp->nxttail = &rdp->nxtlist; | |
425 | local_irq_enable(); | |
426 | ||
427 | /* | |
428 | * start the next batch of callbacks | |
429 | */ | |
430 | ||
431 | /* determine batch number */ | |
432 | rdp->batch = rcp->cur + 1; | |
433 | /* see the comment and corresponding wmb() in | |
434 | * the rcu_start_batch() | |
435 | */ | |
436 | smp_rmb(); | |
437 | ||
438 | if (!rcp->next_pending) { | |
439 | /* and start it/schedule start if it's a new batch */ | |
69a0b315 | 440 | spin_lock(&rcp->lock); |
dbc1651f | 441 | rcp->next_pending = 1; |
69a0b315 ON |
442 | rcu_start_batch(rcp); |
443 | spin_unlock(&rcp->lock); | |
1da177e4 | 444 | } |
1da177e4 | 445 | } |
caa9ee77 | 446 | |
69a0b315 | 447 | rcu_check_quiescent_state(rcp, rdp); |
1da177e4 LT |
448 | if (rdp->donelist) |
449 | rcu_do_batch(rdp); | |
450 | } | |
451 | ||
452 | static void rcu_process_callbacks(unsigned long unused) | |
453 | { | |
69a0b315 ON |
454 | __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data)); |
455 | __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data)); | |
1da177e4 LT |
456 | } |
457 | ||
67751777 ON |
458 | static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) |
459 | { | |
460 | /* This cpu has pending rcu entries and the grace period | |
461 | * for them has completed. | |
462 | */ | |
463 | if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) | |
464 | return 1; | |
465 | ||
466 | /* This cpu has no pending entries, but there are new entries */ | |
467 | if (!rdp->curlist && rdp->nxtlist) | |
468 | return 1; | |
469 | ||
470 | /* This cpu has finished callbacks to invoke */ | |
471 | if (rdp->donelist) | |
472 | return 1; | |
473 | ||
474 | /* The rcu core waits for a quiescent state from the cpu */ | |
475 | if (rdp->quiescbatch != rcp->cur || rdp->qs_pending) | |
476 | return 1; | |
477 | ||
478 | /* nothing to do */ | |
479 | return 0; | |
480 | } | |
481 | ||
482 | int rcu_pending(int cpu) | |
483 | { | |
484 | return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) || | |
485 | __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu)); | |
486 | } | |
487 | ||
1da177e4 LT |
488 | void rcu_check_callbacks(int cpu, int user) |
489 | { | |
490 | if (user || | |
491 | (idle_cpu(cpu) && !in_softirq() && | |
492 | hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
493 | rcu_qsctr_inc(cpu); | |
494 | rcu_bh_qsctr_inc(cpu); | |
495 | } else if (!in_softirq()) | |
496 | rcu_bh_qsctr_inc(cpu); | |
497 | tasklet_schedule(&per_cpu(rcu_tasklet, cpu)); | |
498 | } | |
499 | ||
500 | static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp, | |
501 | struct rcu_data *rdp) | |
502 | { | |
503 | memset(rdp, 0, sizeof(*rdp)); | |
504 | rdp->curtail = &rdp->curlist; | |
505 | rdp->nxttail = &rdp->nxtlist; | |
506 | rdp->donetail = &rdp->donelist; | |
507 | rdp->quiescbatch = rcp->completed; | |
508 | rdp->qs_pending = 0; | |
509 | rdp->cpu = cpu; | |
21a1ea9e | 510 | rdp->blimit = blimit; |
1da177e4 LT |
511 | } |
512 | ||
513 | static void __devinit rcu_online_cpu(int cpu) | |
514 | { | |
515 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); | |
516 | struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu); | |
517 | ||
518 | rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp); | |
519 | rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp); | |
520 | tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL); | |
521 | } | |
522 | ||
523 | static int __devinit rcu_cpu_notify(struct notifier_block *self, | |
524 | unsigned long action, void *hcpu) | |
525 | { | |
526 | long cpu = (long)hcpu; | |
527 | switch (action) { | |
528 | case CPU_UP_PREPARE: | |
529 | rcu_online_cpu(cpu); | |
530 | break; | |
531 | case CPU_DEAD: | |
532 | rcu_offline_cpu(cpu); | |
533 | break; | |
534 | default: | |
535 | break; | |
536 | } | |
537 | return NOTIFY_OK; | |
538 | } | |
539 | ||
540 | static struct notifier_block __devinitdata rcu_nb = { | |
541 | .notifier_call = rcu_cpu_notify, | |
542 | }; | |
543 | ||
544 | /* | |
545 | * Initializes rcu mechanism. Assumed to be called early. | |
546 | * That is before local timer(SMP) or jiffie timer (uniproc) is setup. | |
547 | * Note that rcu_qsctr and friends are implicitly | |
548 | * initialized due to the choice of ``0'' for RCU_CTR_INVALID. | |
549 | */ | |
550 | void __init rcu_init(void) | |
551 | { | |
552 | rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, | |
553 | (void *)(long)smp_processor_id()); | |
554 | /* Register notifier for non-boot CPUs */ | |
555 | register_cpu_notifier(&rcu_nb); | |
556 | } | |
557 | ||
558 | struct rcu_synchronize { | |
559 | struct rcu_head head; | |
560 | struct completion completion; | |
561 | }; | |
562 | ||
563 | /* Because of FASTCALL declaration of complete, we use this wrapper */ | |
564 | static void wakeme_after_rcu(struct rcu_head *head) | |
565 | { | |
566 | struct rcu_synchronize *rcu; | |
567 | ||
568 | rcu = container_of(head, struct rcu_synchronize, head); | |
569 | complete(&rcu->completion); | |
570 | } | |
571 | ||
572 | /** | |
9b06e818 | 573 | * synchronize_rcu - wait until a grace period has elapsed. |
1da177e4 LT |
574 | * |
575 | * Control will return to the caller some time after a full grace | |
576 | * period has elapsed, in other words after all currently executing RCU | |
577 | * read-side critical sections have completed. RCU read-side critical | |
578 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
579 | * and may be nested. | |
9b06e818 PM |
580 | * |
581 | * If your read-side code is not protected by rcu_read_lock(), do -not- | |
582 | * use synchronize_rcu(). | |
1da177e4 | 583 | */ |
9b06e818 | 584 | void synchronize_rcu(void) |
1da177e4 LT |
585 | { |
586 | struct rcu_synchronize rcu; | |
587 | ||
588 | init_completion(&rcu.completion); | |
589 | /* Will wake me after RCU finished */ | |
590 | call_rcu(&rcu.head, wakeme_after_rcu); | |
591 | ||
592 | /* Wait for it */ | |
593 | wait_for_completion(&rcu.completion); | |
594 | } | |
595 | ||
9b06e818 PM |
596 | /* |
597 | * Deprecated, use synchronize_rcu() or synchronize_sched() instead. | |
598 | */ | |
599 | void synchronize_kernel(void) | |
600 | { | |
601 | synchronize_rcu(); | |
602 | } | |
603 | ||
21a1ea9e DS |
604 | module_param(blimit, int, 0); |
605 | module_param(qhimark, int, 0); | |
606 | module_param(qlowmark, int, 0); | |
607 | #ifdef CONFIG_SMP | |
608 | module_param(rsinterval, int, 0); | |
609 | #endif | |
a241ec65 | 610 | EXPORT_SYMBOL_GPL(rcu_batches_completed); |
01ca70dc GKH |
611 | EXPORT_SYMBOL_GPL_FUTURE(call_rcu); /* WARNING: GPL-only in April 2006. */ |
612 | EXPORT_SYMBOL_GPL_FUTURE(call_rcu_bh); /* WARNING: GPL-only in April 2006. */ | |
9b06e818 | 613 | EXPORT_SYMBOL_GPL(synchronize_rcu); |
01ca70dc | 614 | EXPORT_SYMBOL_GPL_FUTURE(synchronize_kernel); /* WARNING: GPL-only in April 2006. */ |