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Commit | Line | Data |
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3d442233 JA |
1 | /* |
2 | * Generic helpers for smp ipi calls | |
3 | * | |
4 | * (C) Jens Axboe <jens.axboe@oracle.com> 2008 | |
3d442233 | 5 | */ |
3d442233 | 6 | #include <linux/rcupdate.h> |
59190f42 | 7 | #include <linux/rculist.h> |
641cd4cf | 8 | #include <linux/kernel.h> |
0b13fda1 IM |
9 | #include <linux/module.h> |
10 | #include <linux/percpu.h> | |
11 | #include <linux/init.h> | |
3d442233 | 12 | #include <linux/smp.h> |
8969a5ed | 13 | #include <linux/cpu.h> |
3d442233 JA |
14 | |
15 | static DEFINE_PER_CPU(struct call_single_queue, call_single_queue); | |
8969a5ed PZ |
16 | |
17 | static struct { | |
18 | struct list_head queue; | |
19 | spinlock_t lock; | |
0b13fda1 IM |
20 | } call_function __cacheline_aligned_in_smp = |
21 | { | |
22 | .queue = LIST_HEAD_INIT(call_function.queue), | |
23 | .lock = __SPIN_LOCK_UNLOCKED(call_function.lock), | |
24 | }; | |
3d442233 JA |
25 | |
26 | enum { | |
6e275637 | 27 | CSD_FLAG_LOCK = 0x01, |
3d442233 JA |
28 | }; |
29 | ||
30 | struct call_function_data { | |
0b13fda1 | 31 | struct call_single_data csd; |
54fdade1 | 32 | atomic_t refs; |
0b13fda1 | 33 | cpumask_var_t cpumask; |
3d442233 JA |
34 | }; |
35 | ||
36 | struct call_single_queue { | |
0b13fda1 IM |
37 | struct list_head list; |
38 | spinlock_t lock; | |
3d442233 JA |
39 | }; |
40 | ||
54fdade1 | 41 | static DEFINE_PER_CPU(struct call_function_data, cfd_data); |
8969a5ed PZ |
42 | |
43 | static int | |
44 | hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) | |
45 | { | |
46 | long cpu = (long)hcpu; | |
47 | struct call_function_data *cfd = &per_cpu(cfd_data, cpu); | |
48 | ||
49 | switch (action) { | |
50 | case CPU_UP_PREPARE: | |
51 | case CPU_UP_PREPARE_FROZEN: | |
eaa95840 | 52 | if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, |
8969a5ed PZ |
53 | cpu_to_node(cpu))) |
54 | return NOTIFY_BAD; | |
55 | break; | |
56 | ||
69dd647f | 57 | #ifdef CONFIG_HOTPLUG_CPU |
8969a5ed PZ |
58 | case CPU_UP_CANCELED: |
59 | case CPU_UP_CANCELED_FROZEN: | |
60 | ||
61 | case CPU_DEAD: | |
62 | case CPU_DEAD_FROZEN: | |
63 | free_cpumask_var(cfd->cpumask); | |
64 | break; | |
65 | #endif | |
66 | }; | |
67 | ||
68 | return NOTIFY_OK; | |
69 | } | |
70 | ||
71 | static struct notifier_block __cpuinitdata hotplug_cfd_notifier = { | |
0b13fda1 | 72 | .notifier_call = hotplug_cfd, |
8969a5ed PZ |
73 | }; |
74 | ||
7babe8db | 75 | static int __cpuinit init_call_single_data(void) |
3d442233 | 76 | { |
8969a5ed | 77 | void *cpu = (void *)(long)smp_processor_id(); |
3d442233 JA |
78 | int i; |
79 | ||
80 | for_each_possible_cpu(i) { | |
81 | struct call_single_queue *q = &per_cpu(call_single_queue, i); | |
82 | ||
83 | spin_lock_init(&q->lock); | |
84 | INIT_LIST_HEAD(&q->list); | |
85 | } | |
8969a5ed PZ |
86 | |
87 | hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); | |
88 | register_cpu_notifier(&hotplug_cfd_notifier); | |
89 | ||
7babe8db | 90 | return 0; |
3d442233 | 91 | } |
7babe8db | 92 | early_initcall(init_call_single_data); |
3d442233 | 93 | |
8969a5ed PZ |
94 | /* |
95 | * csd_lock/csd_unlock used to serialize access to per-cpu csd resources | |
96 | * | |
0b13fda1 IM |
97 | * For non-synchronous ipi calls the csd can still be in use by the |
98 | * previous function call. For multi-cpu calls its even more interesting | |
99 | * as we'll have to ensure no other cpu is observing our csd. | |
8969a5ed | 100 | */ |
6e275637 | 101 | static void csd_lock_wait(struct call_single_data *data) |
8969a5ed PZ |
102 | { |
103 | while (data->flags & CSD_FLAG_LOCK) | |
104 | cpu_relax(); | |
6e275637 PZ |
105 | } |
106 | ||
107 | static void csd_lock(struct call_single_data *data) | |
108 | { | |
109 | csd_lock_wait(data); | |
8969a5ed PZ |
110 | data->flags = CSD_FLAG_LOCK; |
111 | ||
112 | /* | |
0b13fda1 IM |
113 | * prevent CPU from reordering the above assignment |
114 | * to ->flags with any subsequent assignments to other | |
115 | * fields of the specified call_single_data structure: | |
8969a5ed | 116 | */ |
8969a5ed PZ |
117 | smp_mb(); |
118 | } | |
119 | ||
120 | static void csd_unlock(struct call_single_data *data) | |
121 | { | |
122 | WARN_ON(!(data->flags & CSD_FLAG_LOCK)); | |
0b13fda1 | 123 | |
8969a5ed | 124 | /* |
0b13fda1 | 125 | * ensure we're all done before releasing data: |
8969a5ed PZ |
126 | */ |
127 | smp_mb(); | |
0b13fda1 | 128 | |
8969a5ed | 129 | data->flags &= ~CSD_FLAG_LOCK; |
3d442233 JA |
130 | } |
131 | ||
132 | /* | |
0b13fda1 IM |
133 | * Insert a previously allocated call_single_data element |
134 | * for execution on the given CPU. data must already have | |
135 | * ->func, ->info, and ->flags set. | |
3d442233 | 136 | */ |
6e275637 PZ |
137 | static |
138 | void generic_exec_single(int cpu, struct call_single_data *data, int wait) | |
3d442233 JA |
139 | { |
140 | struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); | |
3d442233 | 141 | unsigned long flags; |
6e275637 | 142 | int ipi; |
3d442233 JA |
143 | |
144 | spin_lock_irqsave(&dst->lock, flags); | |
145 | ipi = list_empty(&dst->list); | |
146 | list_add_tail(&data->list, &dst->list); | |
147 | spin_unlock_irqrestore(&dst->lock, flags); | |
148 | ||
561920a0 | 149 | /* |
15d0d3b3 NP |
150 | * The list addition should be visible before sending the IPI |
151 | * handler locks the list to pull the entry off it because of | |
152 | * normal cache coherency rules implied by spinlocks. | |
153 | * | |
154 | * If IPIs can go out of order to the cache coherency protocol | |
155 | * in an architecture, sufficient synchronisation should be added | |
156 | * to arch code to make it appear to obey cache coherency WRT | |
0b13fda1 IM |
157 | * locking and barrier primitives. Generic code isn't really |
158 | * equipped to do the right thing... | |
561920a0 | 159 | */ |
3d442233 JA |
160 | if (ipi) |
161 | arch_send_call_function_single_ipi(cpu); | |
162 | ||
163 | if (wait) | |
6e275637 | 164 | csd_lock_wait(data); |
3d442233 JA |
165 | } |
166 | ||
167 | /* | |
168 | * Invoked by arch to handle an IPI for call function. Must be called with | |
169 | * interrupts disabled. | |
170 | */ | |
171 | void generic_smp_call_function_interrupt(void) | |
172 | { | |
173 | struct call_function_data *data; | |
174 | int cpu = get_cpu(); | |
175 | ||
269c861b SS |
176 | /* |
177 | * Shouldn't receive this interrupt on a cpu that is not yet online. | |
178 | */ | |
179 | WARN_ON_ONCE(!cpu_online(cpu)); | |
180 | ||
15d0d3b3 NP |
181 | /* |
182 | * Ensure entry is visible on call_function_queue after we have | |
183 | * entered the IPI. See comment in smp_call_function_many. | |
184 | * If we don't have this, then we may miss an entry on the list | |
185 | * and never get another IPI to process it. | |
186 | */ | |
187 | smp_mb(); | |
188 | ||
3d442233 | 189 | /* |
0b13fda1 IM |
190 | * It's ok to use list_for_each_rcu() here even though we may |
191 | * delete 'pos', since list_del_rcu() doesn't clear ->next | |
3d442233 | 192 | */ |
8969a5ed | 193 | list_for_each_entry_rcu(data, &call_function.queue, csd.list) { |
3d442233 JA |
194 | int refs; |
195 | ||
54fdade1 | 196 | if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) |
3d442233 JA |
197 | continue; |
198 | ||
199 | data->csd.func(data->csd.info); | |
200 | ||
54fdade1 XG |
201 | refs = atomic_dec_return(&data->refs); |
202 | WARN_ON(refs < 0); | |
8969a5ed PZ |
203 | if (!refs) { |
204 | spin_lock(&call_function.lock); | |
205 | list_del_rcu(&data->csd.list); | |
206 | spin_unlock(&call_function.lock); | |
207 | } | |
3d442233 JA |
208 | |
209 | if (refs) | |
210 | continue; | |
211 | ||
8969a5ed | 212 | csd_unlock(&data->csd); |
3d442233 | 213 | } |
3d442233 JA |
214 | |
215 | put_cpu(); | |
216 | } | |
217 | ||
218 | /* | |
0b13fda1 IM |
219 | * Invoked by arch to handle an IPI for call function single. Must be |
220 | * called from the arch with interrupts disabled. | |
3d442233 JA |
221 | */ |
222 | void generic_smp_call_function_single_interrupt(void) | |
223 | { | |
224 | struct call_single_queue *q = &__get_cpu_var(call_single_queue); | |
15d0d3b3 | 225 | unsigned int data_flags; |
0b13fda1 | 226 | LIST_HEAD(list); |
3d442233 | 227 | |
269c861b SS |
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 | ||
15d0d3b3 NP |
233 | spin_lock(&q->lock); |
234 | list_replace_init(&q->list, &list); | |
235 | spin_unlock(&q->lock); | |
3d442233 | 236 | |
15d0d3b3 NP |
237 | while (!list_empty(&list)) { |
238 | struct call_single_data *data; | |
3d442233 | 239 | |
0b13fda1 | 240 | data = list_entry(list.next, struct call_single_data, list); |
15d0d3b3 | 241 | list_del(&data->list); |
3d442233 | 242 | |
3d442233 | 243 | /* |
0b13fda1 IM |
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: | |
3d442233 | 247 | */ |
15d0d3b3 NP |
248 | data_flags = data->flags; |
249 | ||
250 | data->func(data->info); | |
251 | ||
8969a5ed | 252 | /* |
0b13fda1 | 253 | * Unlocked CSDs are valid through generic_exec_single(): |
8969a5ed PZ |
254 | */ |
255 | if (data_flags & CSD_FLAG_LOCK) | |
256 | csd_unlock(data); | |
3d442233 JA |
257 | } |
258 | } | |
259 | ||
d7240b98 SR |
260 | static DEFINE_PER_CPU(struct call_single_data, csd_data); |
261 | ||
3d442233 JA |
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. | |
3d442233 JA |
266 | * @wait: If true, wait until function has completed on other CPUs. |
267 | * | |
268 | * Returns 0 on success, else a negative status code. Note that @wait | |
269 | * will be implicitly turned on in case of allocation failures, since | |
270 | * we fall back to on-stack allocation. | |
271 | */ | |
272 | int smp_call_function_single(int cpu, void (*func) (void *info), void *info, | |
8691e5a8 | 273 | int wait) |
3d442233 | 274 | { |
8969a5ed PZ |
275 | struct call_single_data d = { |
276 | .flags = 0, | |
277 | }; | |
3d442233 | 278 | unsigned long flags; |
0b13fda1 | 279 | int this_cpu; |
f73be6de | 280 | int err = 0; |
3d442233 | 281 | |
0b13fda1 IM |
282 | /* |
283 | * prevent preemption and reschedule on another processor, | |
284 | * as well as CPU removal | |
285 | */ | |
286 | this_cpu = get_cpu(); | |
287 | ||
269c861b SS |
288 | /* |
289 | * Can deadlock when called with interrupts disabled. | |
290 | * We allow cpu's that are not yet online though, as no one else can | |
291 | * send smp call function interrupt to this cpu and as such deadlocks | |
292 | * can't happen. | |
293 | */ | |
294 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() | |
295 | && !oops_in_progress); | |
3d442233 | 296 | |
0b13fda1 | 297 | if (cpu == this_cpu) { |
3d442233 JA |
298 | local_irq_save(flags); |
299 | func(info); | |
300 | local_irq_restore(flags); | |
0b13fda1 IM |
301 | } else { |
302 | if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { | |
303 | struct call_single_data *data = &d; | |
3d442233 | 304 | |
0b13fda1 IM |
305 | if (!wait) |
306 | data = &__get_cpu_var(csd_data); | |
6e275637 | 307 | |
0b13fda1 | 308 | csd_lock(data); |
3d442233 | 309 | |
0b13fda1 IM |
310 | data->func = func; |
311 | data->info = info; | |
312 | generic_exec_single(cpu, data, wait); | |
313 | } else { | |
314 | err = -ENXIO; /* CPU not online */ | |
315 | } | |
3d442233 JA |
316 | } |
317 | ||
318 | put_cpu(); | |
0b13fda1 | 319 | |
f73be6de | 320 | return err; |
3d442233 JA |
321 | } |
322 | EXPORT_SYMBOL(smp_call_function_single); | |
323 | ||
324 | /** | |
325 | * __smp_call_function_single(): Run a function on another CPU | |
326 | * @cpu: The CPU to run on. | |
327 | * @data: Pre-allocated and setup data structure | |
328 | * | |
0b13fda1 IM |
329 | * Like smp_call_function_single(), but allow caller to pass in a |
330 | * pre-allocated data structure. Useful for embedding @data inside | |
331 | * other structures, for instance. | |
3d442233 | 332 | */ |
6e275637 PZ |
333 | void __smp_call_function_single(int cpu, struct call_single_data *data, |
334 | int wait) | |
3d442233 | 335 | { |
6e275637 PZ |
336 | csd_lock(data); |
337 | ||
269c861b SS |
338 | /* |
339 | * Can deadlock when called with interrupts disabled. | |
340 | * We allow cpu's that are not yet online though, as no one else can | |
341 | * send smp call function interrupt to this cpu and as such deadlocks | |
342 | * can't happen. | |
343 | */ | |
344 | WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() | |
345 | && !oops_in_progress); | |
3d442233 | 346 | |
6e275637 | 347 | generic_exec_single(cpu, data, wait); |
3d442233 JA |
348 | } |
349 | ||
350 | /** | |
54b11e6d RR |
351 | * smp_call_function_many(): Run a function on a set of other CPUs. |
352 | * @mask: The set of cpus to run on (only runs on online subset). | |
3d442233 JA |
353 | * @func: The function to run. This must be fast and non-blocking. |
354 | * @info: An arbitrary pointer to pass to the function. | |
0b13fda1 IM |
355 | * @wait: If true, wait (atomically) until function has completed |
356 | * on other CPUs. | |
3d442233 | 357 | * |
3d442233 JA |
358 | * If @wait is true, then returns once @func has returned. Note that @wait |
359 | * will be implicitly turned on in case of allocation failures, since | |
360 | * we fall back to on-stack allocation. | |
361 | * | |
362 | * You must not call this function with disabled interrupts or from a | |
363 | * hardware interrupt handler or from a bottom half handler. Preemption | |
364 | * must be disabled when calling this function. | |
365 | */ | |
54b11e6d | 366 | void smp_call_function_many(const struct cpumask *mask, |
0b13fda1 | 367 | void (*func)(void *), void *info, bool wait) |
3d442233 | 368 | { |
54b11e6d | 369 | struct call_function_data *data; |
3d442233 | 370 | unsigned long flags; |
0b13fda1 | 371 | int cpu, next_cpu, this_cpu = smp_processor_id(); |
3d442233 | 372 | |
269c861b SS |
373 | /* |
374 | * Can deadlock when called with interrupts disabled. | |
375 | * We allow cpu's that are not yet online though, as no one else can | |
376 | * send smp call function interrupt to this cpu and as such deadlocks | |
377 | * can't happen. | |
378 | */ | |
379 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() | |
380 | && !oops_in_progress); | |
3d442233 | 381 | |
0b13fda1 | 382 | /* So, what's a CPU they want? Ignoring this one. */ |
54b11e6d | 383 | cpu = cpumask_first_and(mask, cpu_online_mask); |
0b13fda1 | 384 | if (cpu == this_cpu) |
54b11e6d | 385 | cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
0b13fda1 | 386 | |
54b11e6d RR |
387 | /* No online cpus? We're done. */ |
388 | if (cpu >= nr_cpu_ids) | |
389 | return; | |
390 | ||
391 | /* Do we have another CPU which isn't us? */ | |
392 | next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); | |
0b13fda1 | 393 | if (next_cpu == this_cpu) |
54b11e6d RR |
394 | next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); |
395 | ||
396 | /* Fastpath: do that cpu by itself. */ | |
397 | if (next_cpu >= nr_cpu_ids) { | |
398 | smp_call_function_single(cpu, func, info, wait); | |
399 | return; | |
3d442233 JA |
400 | } |
401 | ||
8969a5ed PZ |
402 | data = &__get_cpu_var(cfd_data); |
403 | csd_lock(&data->csd); | |
3d442233 | 404 | |
3d442233 JA |
405 | data->csd.func = func; |
406 | data->csd.info = info; | |
8969a5ed | 407 | cpumask_and(data->cpumask, mask, cpu_online_mask); |
0b13fda1 | 408 | cpumask_clear_cpu(this_cpu, data->cpumask); |
54fdade1 | 409 | atomic_set(&data->refs, cpumask_weight(data->cpumask)); |
3d442233 | 410 | |
54fdade1 | 411 | spin_lock_irqsave(&call_function.lock, flags); |
8969a5ed PZ |
412 | /* |
413 | * Place entry at the _HEAD_ of the list, so that any cpu still | |
0b13fda1 IM |
414 | * observing the entry in generic_smp_call_function_interrupt() |
415 | * will not miss any other list entries: | |
8969a5ed PZ |
416 | */ |
417 | list_add_rcu(&data->csd.list, &call_function.queue); | |
54fdade1 | 418 | spin_unlock_irqrestore(&call_function.lock, flags); |
3d442233 | 419 | |
561920a0 SS |
420 | /* |
421 | * Make the list addition visible before sending the ipi. | |
0b13fda1 IM |
422 | * (IPIs must obey or appear to obey normal Linux cache |
423 | * coherency rules -- see comment in generic_exec_single). | |
561920a0 SS |
424 | */ |
425 | smp_mb(); | |
426 | ||
3d442233 | 427 | /* Send a message to all CPUs in the map */ |
8969a5ed | 428 | arch_send_call_function_ipi_mask(data->cpumask); |
3d442233 | 429 | |
0b13fda1 | 430 | /* Optionally wait for the CPUs to complete */ |
54b11e6d | 431 | if (wait) |
6e275637 | 432 | csd_lock_wait(&data->csd); |
3d442233 | 433 | } |
54b11e6d | 434 | EXPORT_SYMBOL(smp_call_function_many); |
3d442233 JA |
435 | |
436 | /** | |
437 | * smp_call_function(): Run a function on all other CPUs. | |
438 | * @func: The function to run. This must be fast and non-blocking. | |
439 | * @info: An arbitrary pointer to pass to the function. | |
0b13fda1 IM |
440 | * @wait: If true, wait (atomically) until function has completed |
441 | * on other CPUs. | |
3d442233 | 442 | * |
54b11e6d | 443 | * Returns 0. |
3d442233 JA |
444 | * |
445 | * If @wait is true, then returns once @func has returned; otherwise | |
446 | * it returns just before the target cpu calls @func. In case of allocation | |
447 | * failure, @wait will be implicitly turned on. | |
448 | * | |
449 | * You must not call this function with disabled interrupts or from a | |
450 | * hardware interrupt handler or from a bottom half handler. | |
451 | */ | |
8691e5a8 | 452 | int smp_call_function(void (*func)(void *), void *info, int wait) |
3d442233 | 453 | { |
3d442233 | 454 | preempt_disable(); |
54b11e6d | 455 | smp_call_function_many(cpu_online_mask, func, info, wait); |
3d442233 | 456 | preempt_enable(); |
0b13fda1 | 457 | |
54b11e6d | 458 | return 0; |
3d442233 JA |
459 | } |
460 | EXPORT_SYMBOL(smp_call_function); | |
461 | ||
462 | void ipi_call_lock(void) | |
463 | { | |
8969a5ed | 464 | spin_lock(&call_function.lock); |
3d442233 JA |
465 | } |
466 | ||
467 | void ipi_call_unlock(void) | |
468 | { | |
8969a5ed | 469 | spin_unlock(&call_function.lock); |
3d442233 JA |
470 | } |
471 | ||
472 | void ipi_call_lock_irq(void) | |
473 | { | |
8969a5ed | 474 | spin_lock_irq(&call_function.lock); |
3d442233 JA |
475 | } |
476 | ||
477 | void ipi_call_unlock_irq(void) | |
478 | { | |
8969a5ed | 479 | spin_unlock_irq(&call_function.lock); |
3d442233 | 480 | } |