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01c1c660 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, 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 | * Documentation/RCU | |
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> | |
38 | #include <linux/rcupdate.h> | |
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> | |
01c1c660 PM |
48 | #include <linux/cpu.h> |
49 | #include <linux/mutex.h> | |
67182ae1 | 50 | #include <linux/time.h> |
01c1c660 PM |
51 | |
52 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
53 | static struct lock_class_key rcu_lock_key; | |
54 | struct lockdep_map rcu_lock_map = | |
55 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); | |
56 | EXPORT_SYMBOL_GPL(rcu_lock_map); | |
57 | #endif | |
58 | ||
59 | ||
60 | /* Definition for rcupdate control block. */ | |
61 | static struct rcu_ctrlblk rcu_ctrlblk = { | |
62 | .cur = -300, | |
63 | .completed = -300, | |
3cac97cb | 64 | .pending = -300, |
01c1c660 PM |
65 | .lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock), |
66 | .cpumask = CPU_MASK_NONE, | |
67 | }; | |
68 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { | |
69 | .cur = -300, | |
70 | .completed = -300, | |
3cac97cb | 71 | .pending = -300, |
01c1c660 PM |
72 | .lock = __SPIN_LOCK_UNLOCKED(&rcu_bh_ctrlblk.lock), |
73 | .cpumask = CPU_MASK_NONE, | |
74 | }; | |
75 | ||
76 | DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L }; | |
77 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L }; | |
78 | ||
79 | static int blimit = 10; | |
80 | static int qhimark = 10000; | |
81 | static int qlowmark = 100; | |
82 | ||
83 | #ifdef CONFIG_SMP | |
84 | static void force_quiescent_state(struct rcu_data *rdp, | |
85 | struct rcu_ctrlblk *rcp) | |
86 | { | |
87 | int cpu; | |
88 | cpumask_t cpumask; | |
eff9b713 PM |
89 | unsigned long flags; |
90 | ||
01c1c660 | 91 | set_need_resched(); |
eff9b713 | 92 | spin_lock_irqsave(&rcp->lock, flags); |
01c1c660 PM |
93 | if (unlikely(!rcp->signaled)) { |
94 | rcp->signaled = 1; | |
95 | /* | |
96 | * Don't send IPI to itself. With irqs disabled, | |
97 | * rdp->cpu is the current cpu. | |
8558f8f8 GS |
98 | * |
99 | * cpu_online_map is updated by the _cpu_down() | |
9b1a4d38 RR |
100 | * using __stop_machine(). Since we're in irqs disabled |
101 | * section, __stop_machine() is not exectuting, hence | |
8558f8f8 GS |
102 | * the cpu_online_map is stable. |
103 | * | |
104 | * However, a cpu might have been offlined _just_ before | |
105 | * we disabled irqs while entering here. | |
106 | * And rcu subsystem might not yet have handled the CPU_DEAD | |
107 | * notification, leading to the offlined cpu's bit | |
108 | * being set in the rcp->cpumask. | |
109 | * | |
110 | * Hence cpumask = (rcp->cpumask & cpu_online_map) to prevent | |
111 | * sending smp_reschedule() to an offlined CPU. | |
01c1c660 | 112 | */ |
8558f8f8 | 113 | cpus_and(cpumask, rcp->cpumask, cpu_online_map); |
01c1c660 | 114 | cpu_clear(rdp->cpu, cpumask); |
363ab6f1 | 115 | for_each_cpu_mask_nr(cpu, cpumask) |
01c1c660 PM |
116 | smp_send_reschedule(cpu); |
117 | } | |
eff9b713 | 118 | spin_unlock_irqrestore(&rcp->lock, flags); |
01c1c660 PM |
119 | } |
120 | #else | |
121 | static inline void force_quiescent_state(struct rcu_data *rdp, | |
122 | struct rcu_ctrlblk *rcp) | |
123 | { | |
124 | set_need_resched(); | |
125 | } | |
126 | #endif | |
127 | ||
5127bed5 LJ |
128 | static void __call_rcu(struct rcu_head *head, struct rcu_ctrlblk *rcp, |
129 | struct rcu_data *rdp) | |
130 | { | |
131 | long batch; | |
1f7b94cd PM |
132 | |
133 | head->next = NULL; | |
134 | smp_mb(); /* Read of rcu->cur must happen after any change by caller. */ | |
5127bed5 LJ |
135 | |
136 | /* | |
137 | * Determine the batch number of this callback. | |
138 | * | |
139 | * Using ACCESS_ONCE to avoid the following error when gcc eliminates | |
140 | * local variable "batch" and emits codes like this: | |
141 | * 1) rdp->batch = rcp->cur + 1 # gets old value | |
142 | * ...... | |
143 | * 2)rcu_batch_after(rcp->cur + 1, rdp->batch) # gets new value | |
144 | * then [*nxttail[0], *nxttail[1]) may contain callbacks | |
145 | * that batch# = rdp->batch, see the comment of struct rcu_data. | |
146 | */ | |
147 | batch = ACCESS_ONCE(rcp->cur) + 1; | |
148 | ||
149 | if (rdp->nxtlist && rcu_batch_after(batch, rdp->batch)) { | |
150 | /* process callbacks */ | |
151 | rdp->nxttail[0] = rdp->nxttail[1]; | |
152 | rdp->nxttail[1] = rdp->nxttail[2]; | |
153 | if (rcu_batch_after(batch - 1, rdp->batch)) | |
154 | rdp->nxttail[0] = rdp->nxttail[2]; | |
155 | } | |
156 | ||
157 | rdp->batch = batch; | |
158 | *rdp->nxttail[2] = head; | |
159 | rdp->nxttail[2] = &head->next; | |
160 | ||
161 | if (unlikely(++rdp->qlen > qhimark)) { | |
162 | rdp->blimit = INT_MAX; | |
163 | force_quiescent_state(rdp, &rcu_ctrlblk); | |
164 | } | |
165 | } | |
166 | ||
2133b5d7 PM |
167 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
168 | ||
169 | static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp) | |
170 | { | |
171 | rcp->gp_start = jiffies; | |
172 | rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; | |
173 | } | |
174 | ||
175 | static void print_other_cpu_stall(struct rcu_ctrlblk *rcp) | |
176 | { | |
177 | int cpu; | |
178 | long delta; | |
179 | unsigned long flags; | |
180 | ||
181 | /* Only let one CPU complain about others per time interval. */ | |
182 | ||
183 | spin_lock_irqsave(&rcp->lock, flags); | |
184 | delta = jiffies - rcp->jiffies_stall; | |
185 | if (delta < 2 || rcp->cur != rcp->completed) { | |
186 | spin_unlock_irqrestore(&rcp->lock, flags); | |
187 | return; | |
188 | } | |
189 | rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
190 | spin_unlock_irqrestore(&rcp->lock, flags); | |
191 | ||
192 | /* OK, time to rat on our buddy... */ | |
193 | ||
194 | printk(KERN_ERR "RCU detected CPU stalls:"); | |
195 | for_each_possible_cpu(cpu) { | |
196 | if (cpu_isset(cpu, rcp->cpumask)) | |
197 | printk(" %d", cpu); | |
198 | } | |
199 | printk(" (detected by %d, t=%ld jiffies)\n", | |
200 | smp_processor_id(), (long)(jiffies - rcp->gp_start)); | |
201 | } | |
202 | ||
203 | static void print_cpu_stall(struct rcu_ctrlblk *rcp) | |
204 | { | |
205 | unsigned long flags; | |
206 | ||
207 | printk(KERN_ERR "RCU detected CPU %d stall (t=%lu/%lu jiffies)\n", | |
208 | smp_processor_id(), jiffies, | |
209 | jiffies - rcp->gp_start); | |
210 | dump_stack(); | |
211 | spin_lock_irqsave(&rcp->lock, flags); | |
212 | if ((long)(jiffies - rcp->jiffies_stall) >= 0) | |
213 | rcp->jiffies_stall = | |
214 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; | |
215 | spin_unlock_irqrestore(&rcp->lock, flags); | |
216 | set_need_resched(); /* kick ourselves to get things going. */ | |
217 | } | |
218 | ||
219 | static void check_cpu_stall(struct rcu_ctrlblk *rcp) | |
220 | { | |
221 | long delta; | |
222 | ||
223 | delta = jiffies - rcp->jiffies_stall; | |
224 | if (cpu_isset(smp_processor_id(), rcp->cpumask) && delta >= 0) { | |
225 | ||
226 | /* We haven't checked in, so go dump stack. */ | |
227 | print_cpu_stall(rcp); | |
228 | ||
229 | } else if (rcp->cur != rcp->completed && delta >= 2) { | |
230 | ||
231 | /* They had two seconds to dump stack, so complain. */ | |
232 | print_other_cpu_stall(rcp); | |
233 | } | |
234 | } | |
235 | ||
236 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
237 | ||
238 | static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp) | |
239 | { | |
240 | } | |
241 | ||
2ec2b482 | 242 | static inline void check_cpu_stall(struct rcu_ctrlblk *rcp) |
2133b5d7 PM |
243 | { |
244 | } | |
245 | ||
246 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
247 | ||
01c1c660 PM |
248 | /** |
249 | * call_rcu - Queue an RCU callback for invocation after a grace period. | |
250 | * @head: structure to be used for queueing the RCU updates. | |
251 | * @func: actual update function to be invoked after the grace period | |
252 | * | |
253 | * The update function will be invoked some time after a full grace | |
254 | * period elapses, in other words after all currently executing RCU | |
255 | * read-side critical sections have completed. RCU read-side critical | |
256 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
257 | * and may be nested. | |
258 | */ | |
259 | void call_rcu(struct rcu_head *head, | |
260 | void (*func)(struct rcu_head *rcu)) | |
261 | { | |
262 | unsigned long flags; | |
01c1c660 PM |
263 | |
264 | head->func = func; | |
01c1c660 | 265 | local_irq_save(flags); |
5127bed5 | 266 | __call_rcu(head, &rcu_ctrlblk, &__get_cpu_var(rcu_data)); |
01c1c660 PM |
267 | local_irq_restore(flags); |
268 | } | |
269 | EXPORT_SYMBOL_GPL(call_rcu); | |
270 | ||
271 | /** | |
272 | * call_rcu_bh - Queue an RCU for invocation after a quicker grace period. | |
273 | * @head: structure to be used for queueing the RCU updates. | |
274 | * @func: actual update function to be invoked after the grace period | |
275 | * | |
276 | * The update function will be invoked some time after a full grace | |
277 | * period elapses, in other words after all currently executing RCU | |
278 | * read-side critical sections have completed. call_rcu_bh() assumes | |
279 | * that the read-side critical sections end on completion of a softirq | |
280 | * handler. This means that read-side critical sections in process | |
281 | * context must not be interrupted by softirqs. This interface is to be | |
282 | * used when most of the read-side critical sections are in softirq context. | |
283 | * RCU read-side critical sections are delimited by rcu_read_lock() and | |
284 | * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh() | |
285 | * and rcu_read_unlock_bh(), if in process context. These may be nested. | |
286 | */ | |
287 | void call_rcu_bh(struct rcu_head *head, | |
288 | void (*func)(struct rcu_head *rcu)) | |
289 | { | |
290 | unsigned long flags; | |
01c1c660 PM |
291 | |
292 | head->func = func; | |
01c1c660 | 293 | local_irq_save(flags); |
5127bed5 | 294 | __call_rcu(head, &rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data)); |
01c1c660 PM |
295 | local_irq_restore(flags); |
296 | } | |
297 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
298 | ||
299 | /* | |
300 | * Return the number of RCU batches processed thus far. Useful | |
301 | * for debug and statistics. | |
302 | */ | |
303 | long rcu_batches_completed(void) | |
304 | { | |
305 | return rcu_ctrlblk.completed; | |
306 | } | |
307 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
308 | ||
309 | /* | |
310 | * Return the number of RCU batches processed thus far. Useful | |
311 | * for debug and statistics. | |
312 | */ | |
313 | long rcu_batches_completed_bh(void) | |
314 | { | |
315 | return rcu_bh_ctrlblk.completed; | |
316 | } | |
317 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
318 | ||
319 | /* Raises the softirq for processing rcu_callbacks. */ | |
320 | static inline void raise_rcu_softirq(void) | |
321 | { | |
322 | raise_softirq(RCU_SOFTIRQ); | |
01c1c660 PM |
323 | } |
324 | ||
325 | /* | |
326 | * Invoke the completed RCU callbacks. They are expected to be in | |
327 | * a per-cpu list. | |
328 | */ | |
329 | static void rcu_do_batch(struct rcu_data *rdp) | |
330 | { | |
275a89bd | 331 | unsigned long flags; |
01c1c660 PM |
332 | struct rcu_head *next, *list; |
333 | int count = 0; | |
334 | ||
335 | list = rdp->donelist; | |
336 | while (list) { | |
337 | next = list->next; | |
338 | prefetch(next); | |
339 | list->func(list); | |
340 | list = next; | |
341 | if (++count >= rdp->blimit) | |
342 | break; | |
343 | } | |
344 | rdp->donelist = list; | |
345 | ||
275a89bd | 346 | local_irq_save(flags); |
01c1c660 | 347 | rdp->qlen -= count; |
275a89bd | 348 | local_irq_restore(flags); |
01c1c660 PM |
349 | if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark) |
350 | rdp->blimit = blimit; | |
351 | ||
352 | if (!rdp->donelist) | |
353 | rdp->donetail = &rdp->donelist; | |
354 | else | |
355 | raise_rcu_softirq(); | |
356 | } | |
357 | ||
358 | /* | |
359 | * Grace period handling: | |
360 | * The grace period handling consists out of two steps: | |
361 | * - A new grace period is started. | |
362 | * This is done by rcu_start_batch. The start is not broadcasted to | |
363 | * all cpus, they must pick this up by comparing rcp->cur with | |
364 | * rdp->quiescbatch. All cpus are recorded in the | |
365 | * rcu_ctrlblk.cpumask bitmap. | |
366 | * - All cpus must go through a quiescent state. | |
367 | * Since the start of the grace period is not broadcasted, at least two | |
368 | * calls to rcu_check_quiescent_state are required: | |
369 | * The first call just notices that a new grace period is running. The | |
370 | * following calls check if there was a quiescent state since the beginning | |
371 | * of the grace period. If so, it updates rcu_ctrlblk.cpumask. If | |
372 | * the bitmap is empty, then the grace period is completed. | |
373 | * rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace | |
374 | * period (if necessary). | |
375 | */ | |
67182ae1 | 376 | |
01c1c660 PM |
377 | /* |
378 | * Register a new batch of callbacks, and start it up if there is currently no | |
379 | * active batch and the batch to be registered has not already occurred. | |
380 | * Caller must hold rcu_ctrlblk.lock. | |
381 | */ | |
382 | static void rcu_start_batch(struct rcu_ctrlblk *rcp) | |
383 | { | |
3cac97cb | 384 | if (rcp->cur != rcp->pending && |
01c1c660 | 385 | rcp->completed == rcp->cur) { |
01c1c660 | 386 | rcp->cur++; |
2133b5d7 | 387 | record_gp_stall_check_time(rcp); |
01c1c660 PM |
388 | |
389 | /* | |
390 | * Accessing nohz_cpu_mask before incrementing rcp->cur needs a | |
391 | * Barrier Otherwise it can cause tickless idle CPUs to be | |
392 | * included in rcp->cpumask, which will extend graceperiods | |
393 | * unnecessarily. | |
394 | */ | |
395 | smp_mb(); | |
396 | cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask); | |
397 | ||
398 | rcp->signaled = 0; | |
399 | } | |
400 | } | |
401 | ||
402 | /* | |
403 | * cpu went through a quiescent state since the beginning of the grace period. | |
404 | * Clear it from the cpu mask and complete the grace period if it was the last | |
405 | * cpu. Start another grace period if someone has further entries pending | |
406 | */ | |
407 | static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp) | |
408 | { | |
409 | cpu_clear(cpu, rcp->cpumask); | |
410 | if (cpus_empty(rcp->cpumask)) { | |
411 | /* batch completed ! */ | |
412 | rcp->completed = rcp->cur; | |
413 | rcu_start_batch(rcp); | |
414 | } | |
415 | } | |
416 | ||
417 | /* | |
418 | * Check if the cpu has gone through a quiescent state (say context | |
419 | * switch). If so and if it already hasn't done so in this RCU | |
420 | * quiescent cycle, then indicate that it has done so. | |
421 | */ | |
422 | static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp, | |
423 | struct rcu_data *rdp) | |
424 | { | |
eff9b713 PM |
425 | unsigned long flags; |
426 | ||
01c1c660 PM |
427 | if (rdp->quiescbatch != rcp->cur) { |
428 | /* start new grace period: */ | |
429 | rdp->qs_pending = 1; | |
430 | rdp->passed_quiesc = 0; | |
431 | rdp->quiescbatch = rcp->cur; | |
432 | return; | |
433 | } | |
434 | ||
435 | /* Grace period already completed for this cpu? | |
436 | * qs_pending is checked instead of the actual bitmap to avoid | |
437 | * cacheline trashing. | |
438 | */ | |
439 | if (!rdp->qs_pending) | |
440 | return; | |
441 | ||
442 | /* | |
443 | * Was there a quiescent state since the beginning of the grace | |
444 | * period? If no, then exit and wait for the next call. | |
445 | */ | |
446 | if (!rdp->passed_quiesc) | |
447 | return; | |
448 | rdp->qs_pending = 0; | |
449 | ||
eff9b713 | 450 | spin_lock_irqsave(&rcp->lock, flags); |
01c1c660 PM |
451 | /* |
452 | * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync | |
453 | * during cpu startup. Ignore the quiescent state. | |
454 | */ | |
455 | if (likely(rdp->quiescbatch == rcp->cur)) | |
456 | cpu_quiet(rdp->cpu, rcp); | |
457 | ||
eff9b713 | 458 | spin_unlock_irqrestore(&rcp->lock, flags); |
01c1c660 PM |
459 | } |
460 | ||
461 | ||
462 | #ifdef CONFIG_HOTPLUG_CPU | |
463 | ||
464 | /* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing | |
465 | * locking requirements, the list it's pulling from has to belong to a cpu | |
466 | * which is dead and hence not processing interrupts. | |
467 | */ | |
468 | static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list, | |
5127bed5 | 469 | struct rcu_head **tail, long batch) |
01c1c660 | 470 | { |
275a89bd PM |
471 | unsigned long flags; |
472 | ||
5127bed5 | 473 | if (list) { |
275a89bd | 474 | local_irq_save(flags); |
5127bed5 LJ |
475 | this_rdp->batch = batch; |
476 | *this_rdp->nxttail[2] = list; | |
477 | this_rdp->nxttail[2] = tail; | |
275a89bd | 478 | local_irq_restore(flags); |
5127bed5 | 479 | } |
01c1c660 PM |
480 | } |
481 | ||
482 | static void __rcu_offline_cpu(struct rcu_data *this_rdp, | |
483 | struct rcu_ctrlblk *rcp, struct rcu_data *rdp) | |
484 | { | |
eff9b713 PM |
485 | unsigned long flags; |
486 | ||
1f7b94cd PM |
487 | /* |
488 | * if the cpu going offline owns the grace period | |
01c1c660 PM |
489 | * we can block indefinitely waiting for it, so flush |
490 | * it here | |
491 | */ | |
eff9b713 | 492 | spin_lock_irqsave(&rcp->lock, flags); |
01c1c660 PM |
493 | if (rcp->cur != rcp->completed) |
494 | cpu_quiet(rdp->cpu, rcp); | |
5127bed5 LJ |
495 | rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail, rcp->cur + 1); |
496 | rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail[2], rcp->cur + 1); | |
eff9b713 | 497 | spin_unlock(&rcp->lock); |
199a9528 | 498 | |
199a9528 | 499 | this_rdp->qlen += rdp->qlen; |
eff9b713 | 500 | local_irq_restore(flags); |
01c1c660 PM |
501 | } |
502 | ||
503 | static void rcu_offline_cpu(int cpu) | |
504 | { | |
505 | struct rcu_data *this_rdp = &get_cpu_var(rcu_data); | |
506 | struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data); | |
507 | ||
508 | __rcu_offline_cpu(this_rdp, &rcu_ctrlblk, | |
509 | &per_cpu(rcu_data, cpu)); | |
510 | __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, | |
511 | &per_cpu(rcu_bh_data, cpu)); | |
512 | put_cpu_var(rcu_data); | |
513 | put_cpu_var(rcu_bh_data); | |
514 | } | |
515 | ||
516 | #else | |
517 | ||
518 | static void rcu_offline_cpu(int cpu) | |
519 | { | |
520 | } | |
521 | ||
522 | #endif | |
523 | ||
524 | /* | |
525 | * This does the RCU processing work from softirq context. | |
526 | */ | |
527 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, | |
528 | struct rcu_data *rdp) | |
529 | { | |
275a89bd | 530 | unsigned long flags; |
1f7b94cd PM |
531 | long completed_snap; |
532 | ||
5127bed5 | 533 | if (rdp->nxtlist) { |
275a89bd | 534 | local_irq_save(flags); |
1f7b94cd | 535 | completed_snap = ACCESS_ONCE(rcp->completed); |
01c1c660 PM |
536 | |
537 | /* | |
5127bed5 LJ |
538 | * move the other grace-period-completed entries to |
539 | * [rdp->nxtlist, *rdp->nxttail[0]) temporarily | |
540 | */ | |
1f7b94cd | 541 | if (!rcu_batch_before(completed_snap, rdp->batch)) |
5127bed5 | 542 | rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2]; |
1f7b94cd | 543 | else if (!rcu_batch_before(completed_snap, rdp->batch - 1)) |
5127bed5 LJ |
544 | rdp->nxttail[0] = rdp->nxttail[1]; |
545 | ||
546 | /* | |
547 | * the grace period for entries in | |
548 | * [rdp->nxtlist, *rdp->nxttail[0]) has completed and | |
549 | * move these entries to donelist | |
01c1c660 | 550 | */ |
5127bed5 LJ |
551 | if (rdp->nxttail[0] != &rdp->nxtlist) { |
552 | *rdp->donetail = rdp->nxtlist; | |
553 | rdp->donetail = rdp->nxttail[0]; | |
554 | rdp->nxtlist = *rdp->nxttail[0]; | |
555 | *rdp->donetail = NULL; | |
556 | ||
557 | if (rdp->nxttail[1] == rdp->nxttail[0]) | |
558 | rdp->nxttail[1] = &rdp->nxtlist; | |
559 | if (rdp->nxttail[2] == rdp->nxttail[0]) | |
560 | rdp->nxttail[2] = &rdp->nxtlist; | |
561 | rdp->nxttail[0] = &rdp->nxtlist; | |
562 | } | |
01c1c660 | 563 | |
275a89bd | 564 | local_irq_restore(flags); |
01c1c660 | 565 | |
3cac97cb | 566 | if (rcu_batch_after(rdp->batch, rcp->pending)) { |
3a72dc8e | 567 | unsigned long flags2; |
0c925d79 | 568 | |
01c1c660 | 569 | /* and start it/schedule start if it's a new batch */ |
3a72dc8e | 570 | spin_lock_irqsave(&rcp->lock, flags2); |
3cac97cb LJ |
571 | if (rcu_batch_after(rdp->batch, rcp->pending)) { |
572 | rcp->pending = rdp->batch; | |
573 | rcu_start_batch(rcp); | |
574 | } | |
3a72dc8e | 575 | spin_unlock_irqrestore(&rcp->lock, flags2); |
01c1c660 PM |
576 | } |
577 | } | |
578 | ||
579 | rcu_check_quiescent_state(rcp, rdp); | |
580 | if (rdp->donelist) | |
581 | rcu_do_batch(rdp); | |
582 | } | |
583 | ||
584 | static void rcu_process_callbacks(struct softirq_action *unused) | |
585 | { | |
1f7b94cd PM |
586 | /* |
587 | * Memory references from any prior RCU read-side critical sections | |
588 | * executed by the interrupted code must be see before any RCU | |
589 | * grace-period manupulations below. | |
590 | */ | |
591 | ||
592 | smp_mb(); /* See above block comment. */ | |
593 | ||
01c1c660 PM |
594 | __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data)); |
595 | __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data)); | |
1f7b94cd PM |
596 | |
597 | /* | |
598 | * Memory references from any later RCU read-side critical sections | |
599 | * executed by the interrupted code must be see after any RCU | |
600 | * grace-period manupulations above. | |
601 | */ | |
602 | ||
603 | smp_mb(); /* See above block comment. */ | |
01c1c660 PM |
604 | } |
605 | ||
606 | static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) | |
607 | { | |
67182ae1 | 608 | /* Check for CPU stalls, if enabled. */ |
2133b5d7 | 609 | check_cpu_stall(rcp); |
67182ae1 | 610 | |
5127bed5 | 611 | if (rdp->nxtlist) { |
1f7b94cd PM |
612 | long completed_snap = ACCESS_ONCE(rcp->completed); |
613 | ||
5127bed5 LJ |
614 | /* |
615 | * This cpu has pending rcu entries and the grace period | |
616 | * for them has completed. | |
617 | */ | |
1f7b94cd | 618 | if (!rcu_batch_before(completed_snap, rdp->batch)) |
5127bed5 | 619 | return 1; |
1f7b94cd | 620 | if (!rcu_batch_before(completed_snap, rdp->batch - 1) && |
5127bed5 LJ |
621 | rdp->nxttail[0] != rdp->nxttail[1]) |
622 | return 1; | |
623 | if (rdp->nxttail[0] != &rdp->nxtlist) | |
624 | return 1; | |
01c1c660 | 625 | |
5127bed5 LJ |
626 | /* |
627 | * This cpu has pending rcu entries and the new batch | |
628 | * for then hasn't been started nor scheduled start | |
629 | */ | |
630 | if (rcu_batch_after(rdp->batch, rcp->pending)) | |
631 | return 1; | |
632 | } | |
01c1c660 PM |
633 | |
634 | /* This cpu has finished callbacks to invoke */ | |
635 | if (rdp->donelist) | |
636 | return 1; | |
637 | ||
638 | /* The rcu core waits for a quiescent state from the cpu */ | |
639 | if (rdp->quiescbatch != rcp->cur || rdp->qs_pending) | |
640 | return 1; | |
641 | ||
642 | /* nothing to do */ | |
643 | return 0; | |
644 | } | |
645 | ||
646 | /* | |
647 | * Check to see if there is any immediate RCU-related work to be done | |
648 | * by the current CPU, returning 1 if so. This function is part of the | |
649 | * RCU implementation; it is -not- an exported member of the RCU API. | |
650 | */ | |
651 | int rcu_pending(int cpu) | |
652 | { | |
653 | return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) || | |
654 | __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu)); | |
655 | } | |
656 | ||
657 | /* | |
658 | * Check to see if any future RCU-related work will need to be done | |
659 | * by the current CPU, even if none need be done immediately, returning | |
660 | * 1 if so. This function is part of the RCU implementation; it is -not- | |
661 | * an exported member of the RCU API. | |
662 | */ | |
663 | int rcu_needs_cpu(int cpu) | |
664 | { | |
665 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); | |
666 | struct rcu_data *rdp_bh = &per_cpu(rcu_bh_data, cpu); | |
667 | ||
5127bed5 | 668 | return !!rdp->nxtlist || !!rdp_bh->nxtlist || rcu_pending(cpu); |
01c1c660 PM |
669 | } |
670 | ||
1f7b94cd PM |
671 | /* |
672 | * Top-level function driving RCU grace-period detection, normally | |
673 | * invoked from the scheduler-clock interrupt. This function simply | |
674 | * increments counters that are read only from softirq by this same | |
675 | * CPU, so there are no memory barriers required. | |
676 | */ | |
01c1c660 PM |
677 | void rcu_check_callbacks(int cpu, int user) |
678 | { | |
679 | if (user || | |
680 | (idle_cpu(cpu) && !in_softirq() && | |
681 | hardirq_count() <= (1 << HARDIRQ_SHIFT))) { | |
8db559b8 PM |
682 | |
683 | /* | |
684 | * Get here if this CPU took its interrupt from user | |
685 | * mode or from the idle loop, and if this is not a | |
686 | * nested interrupt. In this case, the CPU is in | |
687 | * a quiescent state, so count it. | |
688 | * | |
689 | * Also do a memory barrier. This is needed to handle | |
690 | * the case where writes from a preempt-disable section | |
691 | * of code get reordered into schedule() by this CPU's | |
692 | * write buffer. The memory barrier makes sure that | |
693 | * the rcu_qsctr_inc() and rcu_bh_qsctr_inc() are see | |
694 | * by other CPUs to happen after any such write. | |
695 | */ | |
696 | ||
697 | smp_mb(); /* See above block comment. */ | |
01c1c660 PM |
698 | rcu_qsctr_inc(cpu); |
699 | rcu_bh_qsctr_inc(cpu); | |
8db559b8 PM |
700 | |
701 | } else if (!in_softirq()) { | |
702 | ||
703 | /* | |
704 | * Get here if this CPU did not take its interrupt from | |
705 | * softirq, in other words, if it is not interrupting | |
706 | * a rcu_bh read-side critical section. This is an _bh | |
707 | * critical section, so count it. The memory barrier | |
708 | * is needed for the same reason as is the above one. | |
709 | */ | |
710 | ||
711 | smp_mb(); /* See above block comment. */ | |
01c1c660 | 712 | rcu_bh_qsctr_inc(cpu); |
8db559b8 | 713 | } |
01c1c660 PM |
714 | raise_rcu_softirq(); |
715 | } | |
716 | ||
717 | static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp, | |
718 | struct rcu_data *rdp) | |
719 | { | |
0cd418dd | 720 | unsigned long flags; |
cd958517 PM |
721 | |
722 | spin_lock_irqsave(&rcp->lock, flags); | |
01c1c660 | 723 | memset(rdp, 0, sizeof(*rdp)); |
5127bed5 | 724 | rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2] = &rdp->nxtlist; |
01c1c660 PM |
725 | rdp->donetail = &rdp->donelist; |
726 | rdp->quiescbatch = rcp->completed; | |
727 | rdp->qs_pending = 0; | |
728 | rdp->cpu = cpu; | |
729 | rdp->blimit = blimit; | |
cd958517 | 730 | spin_unlock_irqrestore(&rcp->lock, flags); |
01c1c660 PM |
731 | } |
732 | ||
733 | static void __cpuinit rcu_online_cpu(int cpu) | |
734 | { | |
735 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); | |
736 | struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu); | |
737 | ||
738 | rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp); | |
739 | rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp); | |
962cf36c | 740 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
01c1c660 PM |
741 | } |
742 | ||
743 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, | |
744 | unsigned long action, void *hcpu) | |
745 | { | |
746 | long cpu = (long)hcpu; | |
747 | ||
748 | switch (action) { | |
749 | case CPU_UP_PREPARE: | |
750 | case CPU_UP_PREPARE_FROZEN: | |
751 | rcu_online_cpu(cpu); | |
752 | break; | |
753 | case CPU_DEAD: | |
754 | case CPU_DEAD_FROZEN: | |
755 | rcu_offline_cpu(cpu); | |
756 | break; | |
757 | default: | |
758 | break; | |
759 | } | |
760 | return NOTIFY_OK; | |
761 | } | |
762 | ||
763 | static struct notifier_block __cpuinitdata rcu_nb = { | |
764 | .notifier_call = rcu_cpu_notify, | |
765 | }; | |
766 | ||
767 | /* | |
768 | * Initializes rcu mechanism. Assumed to be called early. | |
769 | * That is before local timer(SMP) or jiffie timer (uniproc) is setup. | |
770 | * Note that rcu_qsctr and friends are implicitly | |
771 | * initialized due to the choice of ``0'' for RCU_CTR_INVALID. | |
772 | */ | |
773 | void __init __rcu_init(void) | |
774 | { | |
2133b5d7 PM |
775 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
776 | printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); | |
777 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
01c1c660 PM |
778 | rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, |
779 | (void *)(long)smp_processor_id()); | |
780 | /* Register notifier for non-boot CPUs */ | |
781 | register_cpu_notifier(&rcu_nb); | |
782 | } | |
783 | ||
784 | module_param(blimit, int, 0); | |
785 | module_param(qhimark, int, 0); | |
786 | module_param(qlowmark, int, 0); |