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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, smp_call_func_t func, 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 | smp_call_func_t func, 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 a specific CPU |
369 | * @cpu: The CPU to run on. |
370 | * @data: Pre-allocated and setup data structure |
371 | * @wait: If true, wait until function has completed on specified CPU. |
372 | * |
373 | * Like smp_call_function_single(), but allow caller to pass in a |
374 | * pre-allocated data structure. Useful for embedding @data inside |
375 | * other structures, for instance. |
376 | */ |
377 | void __smp_call_function_single(int cpu, struct call_single_data *data, |
378 | int wait) |
379 | { |
380 | unsigned int this_cpu; |
381 | unsigned long flags; |
382 | |
383 | this_cpu = get_cpu(); |
384 | /* |
385 | * Can deadlock when called with interrupts disabled. |
386 | * We allow cpu's that are not yet online though, as no one else can |
387 | * send smp call function interrupt to this cpu and as such deadlocks |
388 | * can't happen. |
389 | */ |
390 | WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() |
391 | && !oops_in_progress); |
392 | |
393 | if (cpu == this_cpu) { |
394 | local_irq_save(flags); |
395 | data->func(data->info); |
396 | local_irq_restore(flags); |
397 | } else { |
398 | csd_lock(data); |
399 | generic_exec_single(cpu, data, wait); |
400 | } |
401 | put_cpu(); |
402 | } |
403 | |
404 | /** |
405 | * smp_call_function_many(): Run a function on a set of other CPUs. |
406 | * @mask: The set of cpus to run on (only runs on online subset). |
407 | * @func: The function to run. This must be fast and non-blocking. |
408 | * @info: An arbitrary pointer to pass to the function. |
409 | * @wait: If true, wait (atomically) until function has completed |
410 | * on other CPUs. |
411 | * |
412 | * If @wait is true, then returns once @func has returned. |
413 | * |
414 | * You must not call this function with disabled interrupts or from a |
415 | * hardware interrupt handler or from a bottom half handler. Preemption |
416 | * must be disabled when calling this function. |
417 | */ |
418 | void smp_call_function_many(const struct cpumask *mask, |
419 | smp_call_func_t func, void *info, bool wait) |
420 | { |
421 | struct call_function_data *data; |
422 | unsigned long flags; |
423 | int cpu, next_cpu, this_cpu = smp_processor_id(); |
424 | |
425 | /* |
426 | * Can deadlock when called with interrupts disabled. |
427 | * We allow cpu's that are not yet online though, as no one else can |
428 | * send smp call function interrupt to this cpu and as such deadlocks |
429 | * can't happen. |
430 | */ |
431 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() |
432 | && !oops_in_progress); |
433 | |
434 | /* So, what's a CPU they want? Ignoring this one. */ |
435 | cpu = cpumask_first_and(mask, cpu_online_mask); |
436 | if (cpu == this_cpu) |
437 | cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
438 | |
439 | /* No online cpus? We're done. */ |
440 | if (cpu >= nr_cpu_ids) |
441 | return; |
442 | |
443 | /* Do we have another CPU which isn't us? */ |
444 | next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
445 | if (next_cpu == this_cpu) |
446 | next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); |
447 | |
448 | /* Fastpath: do that cpu by itself. */ |
449 | if (next_cpu >= nr_cpu_ids) { |
450 | smp_call_function_single(cpu, func, info, wait); |
451 | return; |
452 | } |
453 | |
454 | data = &__get_cpu_var(cfd_data); |
455 | csd_lock(&data->csd); |
456 | |
457 | data->csd.func = func; |
458 | data->csd.info = info; |
459 | cpumask_and(data->cpumask, mask, cpu_online_mask); |
460 | cpumask_clear_cpu(this_cpu, data->cpumask); |
461 | atomic_set(&data->refs, cpumask_weight(data->cpumask)); |
462 | |
463 | raw_spin_lock_irqsave(&call_function.lock, flags); |
464 | /* |
465 | * Place entry at the _HEAD_ of the list, so that any cpu still |
466 | * observing the entry in generic_smp_call_function_interrupt() |
467 | * will not miss any other list entries: |
468 | */ |
469 | list_add_rcu(&data->csd.list, &call_function.queue); |
470 | raw_spin_unlock_irqrestore(&call_function.lock, flags); |
471 | |
472 | /* |
473 | * Make the list addition visible before sending the ipi. |
474 | * (IPIs must obey or appear to obey normal Linux cache |
475 | * coherency rules -- see comment in generic_exec_single). |
476 | */ |
477 | smp_mb(); |
478 | |
479 | /* Send a message to all CPUs in the map */ |
480 | arch_send_call_function_ipi_mask(data->cpumask); |
481 | |
482 | /* Optionally wait for the CPUs to complete */ |
483 | if (wait) |
484 | csd_lock_wait(&data->csd); |
485 | } |
486 | EXPORT_SYMBOL(smp_call_function_many); |
487 | |
488 | /** |
489 | * smp_call_function(): Run a function on all other CPUs. |
490 | * @func: The function to run. This must be fast and non-blocking. |
491 | * @info: An arbitrary pointer to pass to the function. |
492 | * @wait: If true, wait (atomically) until function has completed |
493 | * on other CPUs. |
494 | * |
495 | * Returns 0. |
496 | * |
497 | * If @wait is true, then returns once @func has returned; otherwise |
498 | * it returns just before the target cpu calls @func. |
499 | * |
500 | * You must not call this function with disabled interrupts or from a |
501 | * hardware interrupt handler or from a bottom half handler. |
502 | */ |
503 | int smp_call_function(smp_call_func_t func, void *info, int wait) |
504 | { |
505 | preempt_disable(); |
506 | smp_call_function_many(cpu_online_mask, func, info, wait); |
507 | preempt_enable(); |
508 | |
509 | return 0; |
510 | } |
511 | EXPORT_SYMBOL(smp_call_function); |
512 | |
513 | void ipi_call_lock(void) |
514 | { |
515 | raw_spin_lock(&call_function.lock); |
516 | } |
517 | |
518 | void ipi_call_unlock(void) |
519 | { |
520 | raw_spin_unlock(&call_function.lock); |
521 | } |
522 | |
523 | void ipi_call_lock_irq(void) |
524 | { |
525 | raw_spin_lock_irq(&call_function.lock); |
526 | } |
527 | |
528 | void ipi_call_unlock_irq(void) |
529 | { |
530 | raw_spin_unlock_irq(&call_function.lock); |
531 | } |
532 |
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