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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 | spinlock_t lock; |
33 | unsigned int refs; |
34 | cpumask_var_t cpumask; |
35 | }; |
36 | |
37 | struct call_single_queue { |
38 | struct list_head list; |
39 | spinlock_t lock; |
40 | }; |
41 | |
42 | static DEFINE_PER_CPU(struct call_function_data, cfd_data) = { |
43 | .lock = __SPIN_LOCK_UNLOCKED(cfd_data.lock), |
44 | }; |
45 | |
46 | static int |
47 | hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) |
48 | { |
49 | long cpu = (long)hcpu; |
50 | struct call_function_data *cfd = &per_cpu(cfd_data, cpu); |
51 | |
52 | switch (action) { |
53 | case CPU_UP_PREPARE: |
54 | case CPU_UP_PREPARE_FROZEN: |
55 | if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, |
56 | cpu_to_node(cpu))) |
57 | return NOTIFY_BAD; |
58 | break; |
59 | |
60 | #ifdef CONFIG_HOTPLUG_CPU |
61 | case CPU_UP_CANCELED: |
62 | case CPU_UP_CANCELED_FROZEN: |
63 | |
64 | case CPU_DEAD: |
65 | case CPU_DEAD_FROZEN: |
66 | free_cpumask_var(cfd->cpumask); |
67 | break; |
68 | #endif |
69 | }; |
70 | |
71 | return NOTIFY_OK; |
72 | } |
73 | |
74 | static struct notifier_block __cpuinitdata hotplug_cfd_notifier = { |
75 | .notifier_call = hotplug_cfd, |
76 | }; |
77 | |
78 | static int __cpuinit init_call_single_data(void) |
79 | { |
80 | void *cpu = (void *)(long)smp_processor_id(); |
81 | int i; |
82 | |
83 | for_each_possible_cpu(i) { |
84 | struct call_single_queue *q = &per_cpu(call_single_queue, i); |
85 | |
86 | spin_lock_init(&q->lock); |
87 | INIT_LIST_HEAD(&q->list); |
88 | } |
89 | |
90 | hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); |
91 | register_cpu_notifier(&hotplug_cfd_notifier); |
92 | |
93 | return 0; |
94 | } |
95 | early_initcall(init_call_single_data); |
96 | |
97 | /* |
98 | * csd_lock/csd_unlock used to serialize access to per-cpu csd resources |
99 | * |
100 | * For non-synchronous ipi calls the csd can still be in use by the |
101 | * previous function call. For multi-cpu calls its even more interesting |
102 | * as we'll have to ensure no other cpu is observing our csd. |
103 | */ |
104 | static void csd_lock_wait(struct call_single_data *data) |
105 | { |
106 | while (data->flags & CSD_FLAG_LOCK) |
107 | cpu_relax(); |
108 | } |
109 | |
110 | static void csd_lock(struct call_single_data *data) |
111 | { |
112 | csd_lock_wait(data); |
113 | data->flags = CSD_FLAG_LOCK; |
114 | |
115 | /* |
116 | * prevent CPU from reordering the above assignment |
117 | * to ->flags with any subsequent assignments to other |
118 | * fields of the specified call_single_data structure: |
119 | */ |
120 | smp_mb(); |
121 | } |
122 | |
123 | static void csd_unlock(struct call_single_data *data) |
124 | { |
125 | WARN_ON(!(data->flags & CSD_FLAG_LOCK)); |
126 | |
127 | /* |
128 | * ensure we're all done before releasing data: |
129 | */ |
130 | smp_mb(); |
131 | |
132 | data->flags &= ~CSD_FLAG_LOCK; |
133 | } |
134 | |
135 | /* |
136 | * Insert a previously allocated call_single_data element |
137 | * for execution on the given CPU. data must already have |
138 | * ->func, ->info, and ->flags set. |
139 | */ |
140 | static |
141 | void generic_exec_single(int cpu, struct call_single_data *data, int wait) |
142 | { |
143 | struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); |
144 | unsigned long flags; |
145 | int ipi; |
146 | |
147 | spin_lock_irqsave(&dst->lock, flags); |
148 | ipi = list_empty(&dst->list); |
149 | list_add_tail(&data->list, &dst->list); |
150 | spin_unlock_irqrestore(&dst->lock, flags); |
151 | |
152 | /* |
153 | * The list addition should be visible before sending the IPI |
154 | * handler locks the list to pull the entry off it because of |
155 | * normal cache coherency rules implied by spinlocks. |
156 | * |
157 | * If IPIs can go out of order to the cache coherency protocol |
158 | * in an architecture, sufficient synchronisation should be added |
159 | * to arch code to make it appear to obey cache coherency WRT |
160 | * locking and barrier primitives. Generic code isn't really |
161 | * equipped to do the right thing... |
162 | */ |
163 | if (ipi) |
164 | arch_send_call_function_single_ipi(cpu); |
165 | |
166 | if (wait) |
167 | csd_lock_wait(data); |
168 | } |
169 | |
170 | /* |
171 | * Invoked by arch to handle an IPI for call function. Must be called with |
172 | * interrupts disabled. |
173 | */ |
174 | void generic_smp_call_function_interrupt(void) |
175 | { |
176 | struct call_function_data *data; |
177 | int cpu = get_cpu(); |
178 | |
179 | /* |
180 | * Ensure entry is visible on call_function_queue after we have |
181 | * entered the IPI. See comment in smp_call_function_many. |
182 | * If we don't have this, then we may miss an entry on the list |
183 | * and never get another IPI to process it. |
184 | */ |
185 | smp_mb(); |
186 | |
187 | /* |
188 | * It's ok to use list_for_each_rcu() here even though we may |
189 | * delete 'pos', since list_del_rcu() doesn't clear ->next |
190 | */ |
191 | list_for_each_entry_rcu(data, &call_function.queue, csd.list) { |
192 | int refs; |
193 | |
194 | spin_lock(&data->lock); |
195 | if (!cpumask_test_cpu(cpu, data->cpumask)) { |
196 | spin_unlock(&data->lock); |
197 | continue; |
198 | } |
199 | cpumask_clear_cpu(cpu, data->cpumask); |
200 | spin_unlock(&data->lock); |
201 | |
202 | data->csd.func(data->csd.info); |
203 | |
204 | spin_lock(&data->lock); |
205 | WARN_ON(data->refs == 0); |
206 | refs = --data->refs; |
207 | if (!refs) { |
208 | spin_lock(&call_function.lock); |
209 | list_del_rcu(&data->csd.list); |
210 | spin_unlock(&call_function.lock); |
211 | } |
212 | spin_unlock(&data->lock); |
213 | |
214 | if (refs) |
215 | continue; |
216 | |
217 | csd_unlock(&data->csd); |
218 | } |
219 | |
220 | put_cpu(); |
221 | } |
222 | |
223 | /* |
224 | * Invoked by arch to handle an IPI for call function single. Must be |
225 | * called from the arch with interrupts disabled. |
226 | */ |
227 | void generic_smp_call_function_single_interrupt(void) |
228 | { |
229 | struct call_single_queue *q = &__get_cpu_var(call_single_queue); |
230 | unsigned int data_flags; |
231 | LIST_HEAD(list); |
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 | /* Can deadlock when called with interrupts disabled */ |
289 | WARN_ON_ONCE(irqs_disabled() && !oops_in_progress); |
290 | |
291 | if (cpu == this_cpu) { |
292 | local_irq_save(flags); |
293 | func(info); |
294 | local_irq_restore(flags); |
295 | } else { |
296 | if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { |
297 | struct call_single_data *data = &d; |
298 | |
299 | if (!wait) |
300 | data = &__get_cpu_var(csd_data); |
301 | |
302 | csd_lock(data); |
303 | |
304 | data->func = func; |
305 | data->info = info; |
306 | generic_exec_single(cpu, data, wait); |
307 | } else { |
308 | err = -ENXIO; /* CPU not online */ |
309 | } |
310 | } |
311 | |
312 | put_cpu(); |
313 | |
314 | return err; |
315 | } |
316 | EXPORT_SYMBOL(smp_call_function_single); |
317 | |
318 | /** |
319 | * __smp_call_function_single(): Run a function on another CPU |
320 | * @cpu: The CPU to run on. |
321 | * @data: Pre-allocated and setup data structure |
322 | * |
323 | * Like smp_call_function_single(), but allow caller to pass in a |
324 | * pre-allocated data structure. Useful for embedding @data inside |
325 | * other structures, for instance. |
326 | */ |
327 | void __smp_call_function_single(int cpu, struct call_single_data *data, |
328 | int wait) |
329 | { |
330 | csd_lock(data); |
331 | |
332 | /* Can deadlock when called with interrupts disabled */ |
333 | WARN_ON_ONCE(wait && irqs_disabled() && !oops_in_progress); |
334 | |
335 | generic_exec_single(cpu, data, wait); |
336 | } |
337 | |
338 | /* Deprecated: shim for archs using old arch_send_call_function_ipi API. */ |
339 | |
340 | #ifndef arch_send_call_function_ipi_mask |
341 | # define arch_send_call_function_ipi_mask(maskp) \ |
342 | arch_send_call_function_ipi(*(maskp)) |
343 | #endif |
344 | |
345 | /** |
346 | * smp_call_function_many(): Run a function on a set of other CPUs. |
347 | * @mask: The set of cpus to run on (only runs on online subset). |
348 | * @func: The function to run. This must be fast and non-blocking. |
349 | * @info: An arbitrary pointer to pass to the function. |
350 | * @wait: If true, wait (atomically) until function has completed |
351 | * on other CPUs. |
352 | * |
353 | * If @wait is true, then returns once @func has returned. Note that @wait |
354 | * will be implicitly turned on in case of allocation failures, since |
355 | * we fall back to on-stack allocation. |
356 | * |
357 | * You must not call this function with disabled interrupts or from a |
358 | * hardware interrupt handler or from a bottom half handler. Preemption |
359 | * must be disabled when calling this function. |
360 | */ |
361 | void smp_call_function_many(const struct cpumask *mask, |
362 | void (*func)(void *), void *info, bool wait) |
363 | { |
364 | struct call_function_data *data; |
365 | unsigned long flags; |
366 | int cpu, next_cpu, this_cpu = smp_processor_id(); |
367 | |
368 | /* Can deadlock when called with interrupts disabled */ |
369 | WARN_ON_ONCE(irqs_disabled() && !oops_in_progress); |
370 | |
371 | /* So, what's a CPU they want? Ignoring this one. */ |
372 | cpu = cpumask_first_and(mask, cpu_online_mask); |
373 | if (cpu == this_cpu) |
374 | cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
375 | |
376 | /* No online cpus? We're done. */ |
377 | if (cpu >= nr_cpu_ids) |
378 | return; |
379 | |
380 | /* Do we have another CPU which isn't us? */ |
381 | next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
382 | if (next_cpu == this_cpu) |
383 | next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); |
384 | |
385 | /* Fastpath: do that cpu by itself. */ |
386 | if (next_cpu >= nr_cpu_ids) { |
387 | smp_call_function_single(cpu, func, info, wait); |
388 | return; |
389 | } |
390 | |
391 | data = &__get_cpu_var(cfd_data); |
392 | csd_lock(&data->csd); |
393 | |
394 | spin_lock_irqsave(&data->lock, flags); |
395 | data->csd.func = func; |
396 | data->csd.info = info; |
397 | cpumask_and(data->cpumask, mask, cpu_online_mask); |
398 | cpumask_clear_cpu(this_cpu, data->cpumask); |
399 | data->refs = cpumask_weight(data->cpumask); |
400 | |
401 | spin_lock(&call_function.lock); |
402 | /* |
403 | * Place entry at the _HEAD_ of the list, so that any cpu still |
404 | * observing the entry in generic_smp_call_function_interrupt() |
405 | * will not miss any other list entries: |
406 | */ |
407 | list_add_rcu(&data->csd.list, &call_function.queue); |
408 | spin_unlock(&call_function.lock); |
409 | |
410 | spin_unlock_irqrestore(&data->lock, flags); |
411 | |
412 | /* |
413 | * Make the list addition visible before sending the ipi. |
414 | * (IPIs must obey or appear to obey normal Linux cache |
415 | * coherency rules -- see comment in generic_exec_single). |
416 | */ |
417 | smp_mb(); |
418 | |
419 | /* Send a message to all CPUs in the map */ |
420 | arch_send_call_function_ipi_mask(data->cpumask); |
421 | |
422 | /* Optionally wait for the CPUs to complete */ |
423 | if (wait) |
424 | csd_lock_wait(&data->csd); |
425 | } |
426 | EXPORT_SYMBOL(smp_call_function_many); |
427 | |
428 | /** |
429 | * smp_call_function(): Run a function on all other CPUs. |
430 | * @func: The function to run. This must be fast and non-blocking. |
431 | * @info: An arbitrary pointer to pass to the function. |
432 | * @wait: If true, wait (atomically) until function has completed |
433 | * on other CPUs. |
434 | * |
435 | * Returns 0. |
436 | * |
437 | * If @wait is true, then returns once @func has returned; otherwise |
438 | * it returns just before the target cpu calls @func. In case of allocation |
439 | * failure, @wait will be implicitly turned on. |
440 | * |
441 | * You must not call this function with disabled interrupts or from a |
442 | * hardware interrupt handler or from a bottom half handler. |
443 | */ |
444 | int smp_call_function(void (*func)(void *), void *info, int wait) |
445 | { |
446 | preempt_disable(); |
447 | smp_call_function_many(cpu_online_mask, func, info, wait); |
448 | preempt_enable(); |
449 | |
450 | return 0; |
451 | } |
452 | EXPORT_SYMBOL(smp_call_function); |
453 | |
454 | void ipi_call_lock(void) |
455 | { |
456 | spin_lock(&call_function.lock); |
457 | } |
458 | |
459 | void ipi_call_unlock(void) |
460 | { |
461 | spin_unlock(&call_function.lock); |
462 | } |
463 | |
464 | void ipi_call_lock_irq(void) |
465 | { |
466 | spin_lock_irq(&call_function.lock); |
467 | } |
468 | |
469 | void ipi_call_unlock_irq(void) |
470 | { |
471 | spin_unlock_irq(&call_function.lock); |
472 | } |
473 |
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