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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/smp.h> |
13 | #include <linux/cpu.h> |
14 | |
15 | static DEFINE_PER_CPU(struct call_single_queue, call_single_queue); |
16 | |
17 | static struct { |
18 | struct list_head queue; |
19 | spinlock_t lock; |
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 | }; |
25 | |
26 | enum { |
27 | CSD_FLAG_LOCK = 0x01, |
28 | }; |
29 | |
30 | struct call_function_data { |
31 | struct call_single_data csd; |
32 | atomic_t refs; |
33 | cpumask_var_t cpumask; |
34 | }; |
35 | |
36 | struct call_single_queue { |
37 | struct list_head list; |
38 | spinlock_t lock; |
39 | }; |
40 | |
41 | static DEFINE_PER_CPU(struct call_function_data, cfd_data); |
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: |
52 | if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, |
53 | cpu_to_node(cpu))) |
54 | return NOTIFY_BAD; |
55 | break; |
56 | |
57 | #ifdef CONFIG_HOTPLUG_CPU |
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 = { |
72 | .notifier_call = hotplug_cfd, |
73 | }; |
74 | |
75 | static int __cpuinit init_call_single_data(void) |
76 | { |
77 | void *cpu = (void *)(long)smp_processor_id(); |
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 | } |
86 | |
87 | hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); |
88 | register_cpu_notifier(&hotplug_cfd_notifier); |
89 | |
90 | return 0; |
91 | } |
92 | early_initcall(init_call_single_data); |
93 | |
94 | /* |
95 | * csd_lock/csd_unlock used to serialize access to per-cpu csd resources |
96 | * |
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. |
100 | */ |
101 | static void csd_lock_wait(struct call_single_data *data) |
102 | { |
103 | while (data->flags & CSD_FLAG_LOCK) |
104 | cpu_relax(); |
105 | } |
106 | |
107 | static void csd_lock(struct call_single_data *data) |
108 | { |
109 | csd_lock_wait(data); |
110 | data->flags = CSD_FLAG_LOCK; |
111 | |
112 | /* |
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: |
116 | */ |
117 | smp_mb(); |
118 | } |
119 | |
120 | static void csd_unlock(struct call_single_data *data) |
121 | { |
122 | WARN_ON(!(data->flags & CSD_FLAG_LOCK)); |
123 | |
124 | /* |
125 | * ensure we're all done before releasing data: |
126 | */ |
127 | smp_mb(); |
128 | |
129 | data->flags &= ~CSD_FLAG_LOCK; |
130 | } |
131 | |
132 | /* |
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. |
136 | */ |
137 | static |
138 | void generic_exec_single(int cpu, struct call_single_data *data, int wait) |
139 | { |
140 | struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); |
141 | unsigned long flags; |
142 | int ipi; |
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 | |
149 | /* |
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 |
157 | * locking and barrier primitives. Generic code isn't really |
158 | * equipped to do the right thing... |
159 | */ |
160 | if (ipi) |
161 | arch_send_call_function_single_ipi(cpu); |
162 | |
163 | if (wait) |
164 | csd_lock_wait(data); |
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 | |
176 | /* |
177 | * Shouldn't receive this interrupt on a cpu that is not yet online. |
178 | */ |
179 | WARN_ON_ONCE(!cpu_online(cpu)); |
180 | |
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 | |
189 | /* |
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 |
192 | */ |
193 | list_for_each_entry_rcu(data, &call_function.queue, csd.list) { |
194 | int refs; |
195 | |
196 | if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) |
197 | continue; |
198 | |
199 | data->csd.func(data->csd.info); |
200 | |
201 | refs = atomic_dec_return(&data->refs); |
202 | WARN_ON(refs < 0); |
203 | if (!refs) { |
204 | spin_lock(&call_function.lock); |
205 | list_del_rcu(&data->csd.list); |
206 | spin_unlock(&call_function.lock); |
207 | } |
208 | |
209 | if (refs) |
210 | continue; |
211 | |
212 | csd_unlock(&data->csd); |
213 | } |
214 | |
215 | put_cpu(); |
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 | spin_lock(&q->lock); |
234 | list_replace_init(&q->list, &list); |
235 | 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(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. 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, |
273 | int wait) |
274 | { |
275 | struct call_single_data d = { |
276 | .flags = 0, |
277 | }; |
278 | unsigned long flags; |
279 | int this_cpu; |
280 | int err = 0; |
281 | |
282 | /* |
283 | * prevent preemption and reschedule on another processor, |
284 | * as well as CPU removal |
285 | */ |
286 | this_cpu = get_cpu(); |
287 | |
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); |
296 | |
297 | if (cpu == this_cpu) { |
298 | local_irq_save(flags); |
299 | func(info); |
300 | local_irq_restore(flags); |
301 | } else { |
302 | if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { |
303 | struct call_single_data *data = &d; |
304 | |
305 | if (!wait) |
306 | data = &__get_cpu_var(csd_data); |
307 | |
308 | csd_lock(data); |
309 | |
310 | data->func = func; |
311 | data->info = info; |
312 | generic_exec_single(cpu, data, wait); |
313 | } else { |
314 | err = -ENXIO; /* CPU not online */ |
315 | } |
316 | } |
317 | |
318 | put_cpu(); |
319 | |
320 | return err; |
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 | * |
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. |
332 | */ |
333 | void __smp_call_function_single(int cpu, struct call_single_data *data, |
334 | int wait) |
335 | { |
336 | csd_lock(data); |
337 | |
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); |
346 | |
347 | generic_exec_single(cpu, data, wait); |
348 | } |
349 | |
350 | /** |
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). |
353 | * @func: The function to run. This must be fast and non-blocking. |
354 | * @info: An arbitrary pointer to pass to the function. |
355 | * @wait: If true, wait (atomically) until function has completed |
356 | * on other CPUs. |
357 | * |
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 | */ |
366 | void smp_call_function_many(const struct cpumask *mask, |
367 | void (*func)(void *), void *info, bool wait) |
368 | { |
369 | struct call_function_data *data; |
370 | unsigned long flags; |
371 | int cpu, next_cpu, this_cpu = smp_processor_id(); |
372 | |
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); |
381 | |
382 | /* So, what's a CPU they want? Ignoring this one. */ |
383 | cpu = cpumask_first_and(mask, cpu_online_mask); |
384 | if (cpu == this_cpu) |
385 | cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
386 | |
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); |
393 | if (next_cpu == this_cpu) |
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; |
400 | } |
401 | |
402 | data = &__get_cpu_var(cfd_data); |
403 | csd_lock(&data->csd); |
404 | |
405 | data->csd.func = func; |
406 | data->csd.info = info; |
407 | cpumask_and(data->cpumask, mask, cpu_online_mask); |
408 | cpumask_clear_cpu(this_cpu, data->cpumask); |
409 | atomic_set(&data->refs, cpumask_weight(data->cpumask)); |
410 | |
411 | spin_lock_irqsave(&call_function.lock, flags); |
412 | /* |
413 | * Place entry at the _HEAD_ of the list, so that any cpu still |
414 | * observing the entry in generic_smp_call_function_interrupt() |
415 | * will not miss any other list entries: |
416 | */ |
417 | list_add_rcu(&data->csd.list, &call_function.queue); |
418 | spin_unlock_irqrestore(&call_function.lock, flags); |
419 | |
420 | /* |
421 | * Make the list addition visible before sending the ipi. |
422 | * (IPIs must obey or appear to obey normal Linux cache |
423 | * coherency rules -- see comment in generic_exec_single). |
424 | */ |
425 | smp_mb(); |
426 | |
427 | /* Send a message to all CPUs in the map */ |
428 | arch_send_call_function_ipi_mask(data->cpumask); |
429 | |
430 | /* Optionally wait for the CPUs to complete */ |
431 | if (wait) |
432 | csd_lock_wait(&data->csd); |
433 | } |
434 | EXPORT_SYMBOL(smp_call_function_many); |
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. |
440 | * @wait: If true, wait (atomically) until function has completed |
441 | * on other CPUs. |
442 | * |
443 | * Returns 0. |
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 | */ |
452 | int smp_call_function(void (*func)(void *), void *info, int wait) |
453 | { |
454 | preempt_disable(); |
455 | smp_call_function_many(cpu_online_mask, func, info, wait); |
456 | preempt_enable(); |
457 | |
458 | return 0; |
459 | } |
460 | EXPORT_SYMBOL(smp_call_function); |
461 | |
462 | void ipi_call_lock(void) |
463 | { |
464 | spin_lock(&call_function.lock); |
465 | } |
466 | |
467 | void ipi_call_unlock(void) |
468 | { |
469 | spin_unlock(&call_function.lock); |
470 | } |
471 | |
472 | void ipi_call_lock_irq(void) |
473 | { |
474 | spin_lock_irq(&call_function.lock); |
475 | } |
476 | |
477 | void ipi_call_unlock_irq(void) |
478 | { |
479 | spin_unlock_irq(&call_function.lock); |
480 | } |
481 |
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