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1 | /* | |
2 | * Generic helpers for smp ipi calls | |
3 | * | |
4 | * (C) Jens Axboe <jens.axboe@oracle.com> 2008 | |
5 | */ | |
6 | #include <linux/rcupdate.h> | |
7 | #include <linux/rculist.h> | |
8 | #include <linux/kernel.h> | |
9 | #include <linux/module.h> | |
10 | #include <linux/percpu.h> | |
11 | #include <linux/init.h> | |
12 | #include <linux/gfp.h> | |
13 | #include <linux/smp.h> | |
14 | #include <linux/cpu.h> | |
15 | ||
16 | static struct { | |
17 | struct list_head queue; | |
18 | raw_spinlock_t lock; | |
19 | } call_function __cacheline_aligned_in_smp = | |
20 | { | |
21 | .queue = LIST_HEAD_INIT(call_function.queue), | |
22 | .lock = __RAW_SPIN_LOCK_UNLOCKED(call_function.lock), | |
23 | }; | |
24 | ||
25 | enum { | |
26 | CSD_FLAG_LOCK = 0x01, | |
27 | }; | |
28 | ||
29 | struct call_function_data { | |
30 | struct call_single_data csd; | |
31 | atomic_t refs; | |
32 | cpumask_var_t cpumask; | |
33 | }; | |
34 | ||
35 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); | |
36 | ||
37 | struct call_single_queue { | |
38 | struct list_head list; | |
39 | raw_spinlock_t lock; | |
40 | }; | |
41 | ||
42 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue); | |
43 | ||
44 | static int | |
45 | hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) | |
46 | { | |
47 | long cpu = (long)hcpu; | |
48 | struct call_function_data *cfd = &per_cpu(cfd_data, cpu); | |
49 | ||
50 | switch (action) { | |
51 | case CPU_UP_PREPARE: | |
52 | case CPU_UP_PREPARE_FROZEN: | |
53 | if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, | |
54 | cpu_to_node(cpu))) | |
55 | return notifier_from_errno(-ENOMEM); | |
56 | break; | |
57 | ||
58 | #ifdef CONFIG_HOTPLUG_CPU | |
59 | case CPU_UP_CANCELED: | |
60 | case CPU_UP_CANCELED_FROZEN: | |
61 | ||
62 | case CPU_DEAD: | |
63 | case CPU_DEAD_FROZEN: | |
64 | free_cpumask_var(cfd->cpumask); | |
65 | break; | |
66 | #endif | |
67 | }; | |
68 | ||
69 | return NOTIFY_OK; | |
70 | } | |
71 | ||
72 | static struct notifier_block __cpuinitdata hotplug_cfd_notifier = { | |
73 | .notifier_call = hotplug_cfd, | |
74 | }; | |
75 | ||
76 | static int __cpuinit init_call_single_data(void) | |
77 | { | |
78 | void *cpu = (void *)(long)smp_processor_id(); | |
79 | int i; | |
80 | ||
81 | for_each_possible_cpu(i) { | |
82 | struct call_single_queue *q = &per_cpu(call_single_queue, i); | |
83 | ||
84 | raw_spin_lock_init(&q->lock); | |
85 | INIT_LIST_HEAD(&q->list); | |
86 | } | |
87 | ||
88 | hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); | |
89 | register_cpu_notifier(&hotplug_cfd_notifier); | |
90 | ||
91 | return 0; | |
92 | } | |
93 | early_initcall(init_call_single_data); | |
94 | ||
95 | /* | |
96 | * csd_lock/csd_unlock used to serialize access to per-cpu csd resources | |
97 | * | |
98 | * For non-synchronous ipi calls the csd can still be in use by the | |
99 | * previous function call. For multi-cpu calls its even more interesting | |
100 | * as we'll have to ensure no other cpu is observing our csd. | |
101 | */ | |
102 | static void csd_lock_wait(struct call_single_data *data) | |
103 | { | |
104 | while (data->flags & CSD_FLAG_LOCK) | |
105 | cpu_relax(); | |
106 | } | |
107 | ||
108 | static void csd_lock(struct call_single_data *data) | |
109 | { | |
110 | csd_lock_wait(data); | |
111 | data->flags = CSD_FLAG_LOCK; | |
112 | ||
113 | /* | |
114 | * prevent CPU from reordering the above assignment | |
115 | * to ->flags with any subsequent assignments to other | |
116 | * fields of the specified call_single_data structure: | |
117 | */ | |
118 | smp_mb(); | |
119 | } | |
120 | ||
121 | static void csd_unlock(struct call_single_data *data) | |
122 | { | |
123 | WARN_ON(!(data->flags & CSD_FLAG_LOCK)); | |
124 | ||
125 | /* | |
126 | * ensure we're all done before releasing data: | |
127 | */ | |
128 | smp_mb(); | |
129 | ||
130 | data->flags &= ~CSD_FLAG_LOCK; | |
131 | } | |
132 | ||
133 | /* | |
134 | * Insert a previously allocated call_single_data element | |
135 | * for execution on the given CPU. data must already have | |
136 | * ->func, ->info, and ->flags set. | |
137 | */ | |
138 | static | |
139 | void generic_exec_single(int cpu, struct call_single_data *data, int wait) | |
140 | { | |
141 | struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); | |
142 | unsigned long flags; | |
143 | int ipi; | |
144 | ||
145 | raw_spin_lock_irqsave(&dst->lock, flags); | |
146 | ipi = list_empty(&dst->list); | |
147 | list_add_tail(&data->list, &dst->list); | |
148 | raw_spin_unlock_irqrestore(&dst->lock, flags); | |
149 | ||
150 | /* | |
151 | * The list addition should be visible before sending the IPI | |
152 | * handler locks the list to pull the entry off it because of | |
153 | * normal cache coherency rules implied by spinlocks. | |
154 | * | |
155 | * If IPIs can go out of order to the cache coherency protocol | |
156 | * in an architecture, sufficient synchronisation should be added | |
157 | * to arch code to make it appear to obey cache coherency WRT | |
158 | * locking and barrier primitives. Generic code isn't really | |
159 | * equipped to do the right thing... | |
160 | */ | |
161 | if (ipi) | |
162 | arch_send_call_function_single_ipi(cpu); | |
163 | ||
164 | if (wait) | |
165 | csd_lock_wait(data); | |
166 | } | |
167 | ||
168 | /* | |
169 | * Invoked by arch to handle an IPI for call function. Must be called with | |
170 | * interrupts disabled. | |
171 | */ | |
172 | void generic_smp_call_function_interrupt(void) | |
173 | { | |
174 | struct call_function_data *data; | |
175 | int cpu = smp_processor_id(); | |
176 | ||
177 | /* | |
178 | * Shouldn't receive this interrupt on a cpu that is not yet online. | |
179 | */ | |
180 | WARN_ON_ONCE(!cpu_online(cpu)); | |
181 | ||
182 | /* | |
183 | * Ensure entry is visible on call_function_queue after we have | |
184 | * entered the IPI. See comment in smp_call_function_many. | |
185 | * If we don't have this, then we may miss an entry on the list | |
186 | * and never get another IPI to process it. | |
187 | */ | |
188 | smp_mb(); | |
189 | ||
190 | /* | |
191 | * It's ok to use list_for_each_rcu() here even though we may | |
192 | * delete 'pos', since list_del_rcu() doesn't clear ->next | |
193 | */ | |
194 | list_for_each_entry_rcu(data, &call_function.queue, csd.list) { | |
195 | int refs; | |
196 | ||
197 | if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) | |
198 | continue; | |
199 | ||
200 | data->csd.func(data->csd.info); | |
201 | ||
202 | refs = atomic_dec_return(&data->refs); | |
203 | WARN_ON(refs < 0); | |
204 | if (!refs) { | |
205 | raw_spin_lock(&call_function.lock); | |
206 | list_del_rcu(&data->csd.list); | |
207 | raw_spin_unlock(&call_function.lock); | |
208 | } | |
209 | ||
210 | if (refs) | |
211 | continue; | |
212 | ||
213 | csd_unlock(&data->csd); | |
214 | } | |
215 | ||
216 | } | |
217 | ||
218 | /* | |
219 | * Invoked by arch to handle an IPI for call function single. Must be | |
220 | * called from the arch with interrupts disabled. | |
221 | */ | |
222 | void generic_smp_call_function_single_interrupt(void) | |
223 | { | |
224 | struct call_single_queue *q = &__get_cpu_var(call_single_queue); | |
225 | unsigned int data_flags; | |
226 | LIST_HEAD(list); | |
227 | ||
228 | /* | |
229 | * Shouldn't receive this interrupt on a cpu that is not yet online. | |
230 | */ | |
231 | WARN_ON_ONCE(!cpu_online(smp_processor_id())); | |
232 | ||
233 | raw_spin_lock(&q->lock); | |
234 | list_replace_init(&q->list, &list); | |
235 | raw_spin_unlock(&q->lock); | |
236 | ||
237 | while (!list_empty(&list)) { | |
238 | struct call_single_data *data; | |
239 | ||
240 | data = list_entry(list.next, struct call_single_data, list); | |
241 | list_del(&data->list); | |
242 | ||
243 | /* | |
244 | * 'data' can be invalid after this call if flags == 0 | |
245 | * (when called through generic_exec_single()), | |
246 | * so save them away before making the call: | |
247 | */ | |
248 | data_flags = data->flags; | |
249 | ||
250 | data->func(data->info); | |
251 | ||
252 | /* | |
253 | * Unlocked CSDs are valid through generic_exec_single(): | |
254 | */ | |
255 | if (data_flags & CSD_FLAG_LOCK) | |
256 | csd_unlock(data); | |
257 | } | |
258 | } | |
259 | ||
260 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data); | |
261 | ||
262 | /* | |
263 | * smp_call_function_single - Run a function on a specific CPU | |
264 | * @func: The function to run. This must be fast and non-blocking. | |
265 | * @info: An arbitrary pointer to pass to the function. | |
266 | * @wait: If true, wait until function has completed on other CPUs. | |
267 | * | |
268 | * Returns 0 on success, else a negative status code. | |
269 | */ | |
270 | int smp_call_function_single(int cpu, void (*func) (void *info), void *info, | |
271 | int wait) | |
272 | { | |
273 | struct call_single_data d = { | |
274 | .flags = 0, | |
275 | }; | |
276 | unsigned long flags; | |
277 | int this_cpu; | |
278 | int err = 0; | |
279 | ||
280 | /* | |
281 | * prevent preemption and reschedule on another processor, | |
282 | * as well as CPU removal | |
283 | */ | |
284 | this_cpu = get_cpu(); | |
285 | ||
286 | /* | |
287 | * Can deadlock when called with interrupts disabled. | |
288 | * We allow cpu's that are not yet online though, as no one else can | |
289 | * send smp call function interrupt to this cpu and as such deadlocks | |
290 | * can't happen. | |
291 | */ | |
292 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() | |
293 | && !oops_in_progress); | |
294 | ||
295 | if (cpu == this_cpu) { | |
296 | local_irq_save(flags); | |
297 | func(info); | |
298 | local_irq_restore(flags); | |
299 | } else { | |
300 | if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { | |
301 | struct call_single_data *data = &d; | |
302 | ||
303 | if (!wait) | |
304 | data = &__get_cpu_var(csd_data); | |
305 | ||
306 | csd_lock(data); | |
307 | ||
308 | data->func = func; | |
309 | data->info = info; | |
310 | generic_exec_single(cpu, data, wait); | |
311 | } else { | |
312 | err = -ENXIO; /* CPU not online */ | |
313 | } | |
314 | } | |
315 | ||
316 | put_cpu(); | |
317 | ||
318 | return err; | |
319 | } | |
320 | EXPORT_SYMBOL(smp_call_function_single); | |
321 | ||
322 | /* | |
323 | * smp_call_function_any - Run a function on any of the given cpus | |
324 | * @mask: The mask of cpus it can run on. | |
325 | * @func: The function to run. This must be fast and non-blocking. | |
326 | * @info: An arbitrary pointer to pass to the function. | |
327 | * @wait: If true, wait until function has completed. | |
328 | * | |
329 | * Returns 0 on success, else a negative status code (if no cpus were online). | |
330 | * Note that @wait will be implicitly turned on in case of allocation failures, | |
331 | * since we fall back to on-stack allocation. | |
332 | * | |
333 | * Selection preference: | |
334 | * 1) current cpu if in @mask | |
335 | * 2) any cpu of current node if in @mask | |
336 | * 3) any other online cpu in @mask | |
337 | */ | |
338 | int smp_call_function_any(const struct cpumask *mask, | |
339 | void (*func)(void *info), void *info, int wait) | |
340 | { | |
341 | unsigned int cpu; | |
342 | const struct cpumask *nodemask; | |
343 | int ret; | |
344 | ||
345 | /* Try for same CPU (cheapest) */ | |
346 | cpu = get_cpu(); | |
347 | if (cpumask_test_cpu(cpu, mask)) | |
348 | goto call; | |
349 | ||
350 | /* Try for same node. */ | |
351 | nodemask = cpumask_of_node(cpu_to_node(cpu)); | |
352 | for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; | |
353 | cpu = cpumask_next_and(cpu, nodemask, mask)) { | |
354 | if (cpu_online(cpu)) | |
355 | goto call; | |
356 | } | |
357 | ||
358 | /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ | |
359 | cpu = cpumask_any_and(mask, cpu_online_mask); | |
360 | call: | |
361 | ret = smp_call_function_single(cpu, func, info, wait); | |
362 | put_cpu(); | |
363 | return ret; | |
364 | } | |
365 | EXPORT_SYMBOL_GPL(smp_call_function_any); | |
366 | ||
367 | /** | |
368 | * __smp_call_function_single(): Run a function on another CPU | |
369 | * @cpu: The CPU to run on. | |
370 | * @data: Pre-allocated and setup data structure | |
371 | * | |
372 | * Like smp_call_function_single(), but allow caller to pass in a | |
373 | * pre-allocated data structure. Useful for embedding @data inside | |
374 | * other structures, for instance. | |
375 | */ | |
376 | void __smp_call_function_single(int cpu, struct call_single_data *data, | |
377 | int wait) | |
378 | { | |
379 | csd_lock(data); | |
380 | ||
381 | /* | |
382 | * Can deadlock when called with interrupts disabled. | |
383 | * We allow cpu's that are not yet online though, as no one else can | |
384 | * send smp call function interrupt to this cpu and as such deadlocks | |
385 | * can't happen. | |
386 | */ | |
387 | WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() | |
388 | && !oops_in_progress); | |
389 | ||
390 | generic_exec_single(cpu, data, wait); | |
391 | } | |
392 | ||
393 | /** | |
394 | * smp_call_function_many(): Run a function on a set of other CPUs. | |
395 | * @mask: The set of cpus to run on (only runs on online subset). | |
396 | * @func: The function to run. This must be fast and non-blocking. | |
397 | * @info: An arbitrary pointer to pass to the function. | |
398 | * @wait: If true, wait (atomically) until function has completed | |
399 | * on other CPUs. | |
400 | * | |
401 | * If @wait is true, then returns once @func has returned. | |
402 | * | |
403 | * You must not call this function with disabled interrupts or from a | |
404 | * hardware interrupt handler or from a bottom half handler. Preemption | |
405 | * must be disabled when calling this function. | |
406 | */ | |
407 | void smp_call_function_many(const struct cpumask *mask, | |
408 | void (*func)(void *), void *info, bool wait) | |
409 | { | |
410 | struct call_function_data *data; | |
411 | unsigned long flags; | |
412 | int cpu, next_cpu, this_cpu = smp_processor_id(); | |
413 | ||
414 | /* | |
415 | * Can deadlock when called with interrupts disabled. | |
416 | * We allow cpu's that are not yet online though, as no one else can | |
417 | * send smp call function interrupt to this cpu and as such deadlocks | |
418 | * can't happen. | |
419 | */ | |
420 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() | |
421 | && !oops_in_progress); | |
422 | ||
423 | /* So, what's a CPU they want? Ignoring this one. */ | |
424 | cpu = cpumask_first_and(mask, cpu_online_mask); | |
425 | if (cpu == this_cpu) | |
426 | cpu = cpumask_next_and(cpu, mask, cpu_online_mask); | |
427 | ||
428 | /* No online cpus? We're done. */ | |
429 | if (cpu >= nr_cpu_ids) | |
430 | return; | |
431 | ||
432 | /* Do we have another CPU which isn't us? */ | |
433 | next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); | |
434 | if (next_cpu == this_cpu) | |
435 | next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); | |
436 | ||
437 | /* Fastpath: do that cpu by itself. */ | |
438 | if (next_cpu >= nr_cpu_ids) { | |
439 | smp_call_function_single(cpu, func, info, wait); | |
440 | return; | |
441 | } | |
442 | ||
443 | data = &__get_cpu_var(cfd_data); | |
444 | csd_lock(&data->csd); | |
445 | ||
446 | data->csd.func = func; | |
447 | data->csd.info = info; | |
448 | cpumask_and(data->cpumask, mask, cpu_online_mask); | |
449 | cpumask_clear_cpu(this_cpu, data->cpumask); | |
450 | atomic_set(&data->refs, cpumask_weight(data->cpumask)); | |
451 | ||
452 | raw_spin_lock_irqsave(&call_function.lock, flags); | |
453 | /* | |
454 | * Place entry at the _HEAD_ of the list, so that any cpu still | |
455 | * observing the entry in generic_smp_call_function_interrupt() | |
456 | * will not miss any other list entries: | |
457 | */ | |
458 | list_add_rcu(&data->csd.list, &call_function.queue); | |
459 | raw_spin_unlock_irqrestore(&call_function.lock, flags); | |
460 | ||
461 | /* | |
462 | * Make the list addition visible before sending the ipi. | |
463 | * (IPIs must obey or appear to obey normal Linux cache | |
464 | * coherency rules -- see comment in generic_exec_single). | |
465 | */ | |
466 | smp_mb(); | |
467 | ||
468 | /* Send a message to all CPUs in the map */ | |
469 | arch_send_call_function_ipi_mask(data->cpumask); | |
470 | ||
471 | /* Optionally wait for the CPUs to complete */ | |
472 | if (wait) | |
473 | csd_lock_wait(&data->csd); | |
474 | } | |
475 | EXPORT_SYMBOL(smp_call_function_many); | |
476 | ||
477 | /** | |
478 | * smp_call_function(): Run a function on all other CPUs. | |
479 | * @func: The function to run. This must be fast and non-blocking. | |
480 | * @info: An arbitrary pointer to pass to the function. | |
481 | * @wait: If true, wait (atomically) until function has completed | |
482 | * on other CPUs. | |
483 | * | |
484 | * Returns 0. | |
485 | * | |
486 | * If @wait is true, then returns once @func has returned; otherwise | |
487 | * it returns just before the target cpu calls @func. | |
488 | * | |
489 | * You must not call this function with disabled interrupts or from a | |
490 | * hardware interrupt handler or from a bottom half handler. | |
491 | */ | |
492 | int smp_call_function(void (*func)(void *), void *info, int wait) | |
493 | { | |
494 | preempt_disable(); | |
495 | smp_call_function_many(cpu_online_mask, func, info, wait); | |
496 | preempt_enable(); | |
497 | ||
498 | return 0; | |
499 | } | |
500 | EXPORT_SYMBOL(smp_call_function); | |
501 | ||
502 | void ipi_call_lock(void) | |
503 | { | |
504 | raw_spin_lock(&call_function.lock); | |
505 | } | |
506 | ||
507 | void ipi_call_unlock(void) | |
508 | { | |
509 | raw_spin_unlock(&call_function.lock); | |
510 | } | |
511 | ||
512 | void ipi_call_lock_irq(void) | |
513 | { | |
514 | raw_spin_lock_irq(&call_function.lock); | |
515 | } | |
516 | ||
517 | void ipi_call_unlock_irq(void) | |
518 | { | |
519 | raw_spin_unlock_irq(&call_function.lock); | |
520 | } |