1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Generic helpers for smp ipi calls
4 *
5 * (C) Jens Axboe <jens.axboe@oracle.com> 2008
6 */
7
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10 #include <linux/irq_work.h>
11 #include <linux/rcupdate.h>
12 #include <linux/rculist.h>
13 #include <linux/kernel.h>
14 #include <linux/export.h>
15 #include <linux/percpu.h>
16 #include <linux/init.h>
17 #include <linux/interrupt.h>
18 #include <linux/gfp.h>
19 #include <linux/smp.h>
20 #include <linux/cpu.h>
21 #include <linux/sched.h>
22 #include <linux/sched/idle.h>
23 #include <linux/hypervisor.h>
24 #include <linux/sched/clock.h>
25 #include <linux/nmi.h>
26 #include <linux/sched/debug.h>
27 #include <linux/jump_label.h>
28 #include <linux/string_choices.h>
29
30 #include <trace/events/ipi.h>
31 #define CREATE_TRACE_POINTS
32 #include <trace/events/csd.h>
33 #undef CREATE_TRACE_POINTS
34
35 #include "smpboot.h"
36 #include "sched/smp.h"
37
38 #define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK)
39
40 struct call_function_data {
41 call_single_data_t __percpu *csd;
42 cpumask_var_t cpumask;
43 cpumask_var_t cpumask_ipi;
44 };
45
46 static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data);
47
48 static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
49
50 static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1);
51
52 static void __flush_smp_call_function_queue(bool warn_cpu_offline);
53
54 int smpcfd_prepare_cpu(unsigned int cpu)
55 {
56 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
57
58 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
59 cpu_to_node(cpu)))
60 return -ENOMEM;
61 if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL,
62 cpu_to_node(cpu))) {
63 free_cpumask_var(cfd->cpumask);
64 return -ENOMEM;
65 }
66 cfd->csd = alloc_percpu(call_single_data_t);
67 if (!cfd->csd) {
68 free_cpumask_var(cfd->cpumask);
69 free_cpumask_var(cfd->cpumask_ipi);
70 return -ENOMEM;
71 }
72
73 return 0;
74 }
75
76 int smpcfd_dead_cpu(unsigned int cpu)
77 {
78 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
79
80 free_cpumask_var(cfd->cpumask);
81 free_cpumask_var(cfd->cpumask_ipi);
82 free_percpu(cfd->csd);
83 return 0;
84 }
85
86 int smpcfd_dying_cpu(unsigned int cpu)
87 {
88 /*
89 * The IPIs for the smp-call-function callbacks queued by other
90 * CPUs might arrive late, either due to hardware latencies or
91 * because this CPU disabled interrupts (inside stop-machine)
92 * before the IPIs were sent. So flush out any pending callbacks
93 * explicitly (without waiting for the IPIs to arrive), to
94 * ensure that the outgoing CPU doesn't go offline with work
95 * still pending.
96 */
97 __flush_smp_call_function_queue(false);
98 irq_work_run();
99 return 0;
100 }
101
102 void __init call_function_init(void)
103 {
104 int i;
105
106 for_each_possible_cpu(i)
107 init_llist_head(&per_cpu(call_single_queue, i));
108
109 smpcfd_prepare_cpu(smp_processor_id());
110 }
111
112 static __always_inline void
113 send_call_function_single_ipi(int cpu)
114 {
115 if (call_function_single_prep_ipi(cpu)) {
116 trace_ipi_send_cpu(cpu, _RET_IP_,
117 generic_smp_call_function_single_interrupt);
118 arch_send_call_function_single_ipi(cpu);
119 }
120 }
121
122 static __always_inline void
123 send_call_function_ipi_mask(struct cpumask *mask)
124 {
125 trace_ipi_send_cpumask(mask, _RET_IP_,
126 generic_smp_call_function_single_interrupt);
127 arch_send_call_function_ipi_mask(mask);
128 }
129
130 static __always_inline void
131 csd_do_func(smp_call_func_t func, void *info, call_single_data_t *csd)
132 {
133 trace_csd_function_entry(func, csd);
134 func(info);
135 trace_csd_function_exit(func, csd);
136 }
137
138 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
139
140 static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled);
141
142 /*
143 * Parse the csdlock_debug= kernel boot parameter.
144 *
145 * If you need to restore the old "ext" value that once provided
146 * additional debugging information, reapply the following commits:
147 *
148 * de7b09ef658d ("locking/csd_lock: Prepare more CSD lock debugging")
149 * a5aabace5fb8 ("locking/csd_lock: Add more data to CSD lock debugging")
150 */
151 static int __init csdlock_debug(char *str)
152 {
153 int ret;
154 unsigned int val = 0;
155
156 ret = get_option(&str, &val);
157 if (ret) {
158 if (val)
159 static_branch_enable(&csdlock_debug_enabled);
160 else
161 static_branch_disable(&csdlock_debug_enabled);
162 }
163
164 return 1;
165 }
166 __setup("csdlock_debug=", csdlock_debug);
167
168 static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
169 static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
170 static DEFINE_PER_CPU(void *, cur_csd_info);
171
172 static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */
173 module_param(csd_lock_timeout, ulong, 0444);
174 static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */
175 module_param(panic_on_ipistall, int, 0444);
176
177 static atomic_t csd_bug_count = ATOMIC_INIT(0);
178
179 /* Record current CSD work for current CPU, NULL to erase. */
180 static void __csd_lock_record(call_single_data_t *csd)
181 {
182 if (!csd) {
183 smp_mb(); /* NULL cur_csd after unlock. */
184 __this_cpu_write(cur_csd, NULL);
185 return;
186 }
187 __this_cpu_write(cur_csd_func, csd->func);
188 __this_cpu_write(cur_csd_info, csd->info);
189 smp_wmb(); /* func and info before csd. */
190 __this_cpu_write(cur_csd, csd);
191 smp_mb(); /* Update cur_csd before function call. */
192 /* Or before unlock, as the case may be. */
193 }
194
195 static __always_inline void csd_lock_record(call_single_data_t *csd)
196 {
197 if (static_branch_unlikely(&csdlock_debug_enabled))
198 __csd_lock_record(csd);
199 }
200
201 static int csd_lock_wait_getcpu(call_single_data_t *csd)
202 {
203 unsigned int csd_type;
204
205 csd_type = CSD_TYPE(csd);
206 if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC)
207 return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */
208 return -1;
209 }
210
211 /*
212 * Complain if too much time spent waiting. Note that only
213 * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU,
214 * so waiting on other types gets much less information.
215 */
216 static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id)
217 {
218 int cpu = -1;
219 int cpux;
220 bool firsttime;
221 u64 ts2, ts_delta;
222 call_single_data_t *cpu_cur_csd;
223 unsigned int flags = READ_ONCE(csd->node.u_flags);
224 unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC;
225
226 if (!(flags & CSD_FLAG_LOCK)) {
227 if (!unlikely(*bug_id))
228 return true;
229 cpu = csd_lock_wait_getcpu(csd);
230 pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n",
231 *bug_id, raw_smp_processor_id(), cpu);
232 return true;
233 }
234
235 ts2 = sched_clock();
236 /* How long since we last checked for a stuck CSD lock.*/
237 ts_delta = ts2 - *ts1;
238 if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0))
239 return false;
240
241 firsttime = !*bug_id;
242 if (firsttime)
243 *bug_id = atomic_inc_return(&csd_bug_count);
244 cpu = csd_lock_wait_getcpu(csd);
245 if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
246 cpux = 0;
247 else
248 cpux = cpu;
249 cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */
250 /* How long since this CSD lock was stuck. */
251 ts_delta = ts2 - ts0;
252 pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n",
253 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts_delta,
254 cpu, csd->func, csd->info);
255 /*
256 * If the CSD lock is still stuck after 5 minutes, it is unlikely
257 * to become unstuck. Use a signed comparison to avoid triggering
258 * on underflows when the TSC is out of sync between sockets.
259 */
260 BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC));
261 if (cpu_cur_csd && csd != cpu_cur_csd) {
262 pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n",
263 *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),
264 READ_ONCE(per_cpu(cur_csd_info, cpux)));
265 } else {
266 pr_alert("\tcsd: CSD lock (#%d) %s.\n",
267 *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request");
268 }
269 if (cpu >= 0) {
270 if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0))
271 dump_cpu_task(cpu);
272 if (!cpu_cur_csd) {
273 pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu);
274 arch_send_call_function_single_ipi(cpu);
275 }
276 }
277 if (firsttime)
278 dump_stack();
279 *ts1 = ts2;
280
281 return false;
282 }
283
284 /*
285 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
286 *
287 * For non-synchronous ipi calls the csd can still be in use by the
288 * previous function call. For multi-cpu calls its even more interesting
289 * as we'll have to ensure no other cpu is observing our csd.
290 */
291 static void __csd_lock_wait(call_single_data_t *csd)
292 {
293 int bug_id = 0;
294 u64 ts0, ts1;
295
296 ts1 = ts0 = sched_clock();
297 for (;;) {
298 if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id))
299 break;
300 cpu_relax();
301 }
302 smp_acquire__after_ctrl_dep();
303 }
304
305 static __always_inline void csd_lock_wait(call_single_data_t *csd)
306 {
307 if (static_branch_unlikely(&csdlock_debug_enabled)) {
308 __csd_lock_wait(csd);
309 return;
310 }
311
312 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));
313 }
314 #else
315 static void csd_lock_record(call_single_data_t *csd)
316 {
317 }
318
319 static __always_inline void csd_lock_wait(call_single_data_t *csd)
320 {
321 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));
322 }
323 #endif
324
325 static __always_inline void csd_lock(call_single_data_t *csd)
326 {
327 csd_lock_wait(csd);
328 csd->node.u_flags |= CSD_FLAG_LOCK;
329
330 /*
331 * prevent CPU from reordering the above assignment
332 * to ->flags with any subsequent assignments to other
333 * fields of the specified call_single_data_t structure:
334 */
335 smp_wmb();
336 }
337
338 static __always_inline void csd_unlock(call_single_data_t *csd)
339 {
340 WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK));
341
342 /*
343 * ensure we're all done before releasing data:
344 */
345 smp_store_release(&csd->node.u_flags, 0);
346 }
347
348 static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data);
349
350 void __smp_call_single_queue(int cpu, struct llist_node *node)
351 {
352 /*
353 * We have to check the type of the CSD before queueing it, because
354 * once queued it can have its flags cleared by
355 * flush_smp_call_function_queue()
356 * even if we haven't sent the smp_call IPI yet (e.g. the stopper
357 * executes migration_cpu_stop() on the remote CPU).
358 */
359 if (trace_csd_queue_cpu_enabled()) {
360 call_single_data_t *csd;
361 smp_call_func_t func;
362
363 csd = container_of(node, call_single_data_t, node.llist);
364 func = CSD_TYPE(csd) == CSD_TYPE_TTWU ?
365 sched_ttwu_pending : csd->func;
366
367 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
368 }
369
370 /*
371 * The list addition should be visible to the target CPU when it pops
372 * the head of the list to pull the entry off it in the IPI handler
373 * because of normal cache coherency rules implied by the underlying
374 * llist ops.
375 *
376 * If IPIs can go out of order to the cache coherency protocol
377 * in an architecture, sufficient synchronisation should be added
378 * to arch code to make it appear to obey cache coherency WRT
379 * locking and barrier primitives. Generic code isn't really
380 * equipped to do the right thing...
381 */
382 if (llist_add(node, &per_cpu(call_single_queue, cpu)))
383 send_call_function_single_ipi(cpu);
384 }
385
386 /*
387 * Insert a previously allocated call_single_data_t element
388 * for execution on the given CPU. data must already have
389 * ->func, ->info, and ->flags set.
390 */
391 static int generic_exec_single(int cpu, call_single_data_t *csd)
392 {
393 if (cpu == smp_processor_id()) {
394 smp_call_func_t func = csd->func;
395 void *info = csd->info;
396 unsigned long flags;
397
398 /*
399 * We can unlock early even for the synchronous on-stack case,
400 * since we're doing this from the same CPU..
401 */
402 csd_lock_record(csd);
403 csd_unlock(csd);
404 local_irq_save(flags);
405 csd_do_func(func, info, NULL);
406 csd_lock_record(NULL);
407 local_irq_restore(flags);
408 return 0;
409 }
410
411 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
412 csd_unlock(csd);
413 return -ENXIO;
414 }
415
416 __smp_call_single_queue(cpu, &csd->node.llist);
417
418 return 0;
419 }
420
421 /**
422 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
423 *
424 * Invoked by arch to handle an IPI for call function single.
425 * Must be called with interrupts disabled.
426 */
427 void generic_smp_call_function_single_interrupt(void)
428 {
429 __flush_smp_call_function_queue(true);
430 }
431
432 /**
433 * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks
434 *
435 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
436 * offline CPU. Skip this check if set to 'false'.
437 *
438 * Flush any pending smp-call-function callbacks queued on this CPU. This is
439 * invoked by the generic IPI handler, as well as by a CPU about to go offline,
440 * to ensure that all pending IPI callbacks are run before it goes completely
441 * offline.
442 *
443 * Loop through the call_single_queue and run all the queued callbacks.
444 * Must be called with interrupts disabled.
445 */
446 static void __flush_smp_call_function_queue(bool warn_cpu_offline)
447 {
448 call_single_data_t *csd, *csd_next;
449 struct llist_node *entry, *prev;
450 struct llist_head *head;
451 static bool warned;
452 atomic_t *tbt;
453
454 lockdep_assert_irqs_disabled();
455
456 /* Allow waiters to send backtrace NMI from here onwards */
457 tbt = this_cpu_ptr(&trigger_backtrace);
458 atomic_set_release(tbt, 1);
459
460 head = this_cpu_ptr(&call_single_queue);
461 entry = llist_del_all(head);
462 entry = llist_reverse_order(entry);
463
464 /* There shouldn't be any pending callbacks on an offline CPU. */
465 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
466 !warned && entry != NULL)) {
467 warned = true;
468 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
469
470 /*
471 * We don't have to use the _safe() variant here
472 * because we are not invoking the IPI handlers yet.
473 */
474 llist_for_each_entry(csd, entry, node.llist) {
475 switch (CSD_TYPE(csd)) {
476 case CSD_TYPE_ASYNC:
477 case CSD_TYPE_SYNC:
478 case CSD_TYPE_IRQ_WORK:
479 pr_warn("IPI callback %pS sent to offline CPU\n",
480 csd->func);
481 break;
482
483 case CSD_TYPE_TTWU:
484 pr_warn("IPI task-wakeup sent to offline CPU\n");
485 break;
486
487 default:
488 pr_warn("IPI callback, unknown type %d, sent to offline CPU\n",
489 CSD_TYPE(csd));
490 break;
491 }
492 }
493 }
494
495 /*
496 * First; run all SYNC callbacks, people are waiting for us.
497 */
498 prev = NULL;
499 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) {
500 /* Do we wait until *after* callback? */
501 if (CSD_TYPE(csd) == CSD_TYPE_SYNC) {
502 smp_call_func_t func = csd->func;
503 void *info = csd->info;
504
505 if (prev) {
506 prev->next = &csd_next->node.llist;
507 } else {
508 entry = &csd_next->node.llist;
509 }
510
511 csd_lock_record(csd);
512 csd_do_func(func, info, csd);
513 csd_unlock(csd);
514 csd_lock_record(NULL);
515 } else {
516 prev = &csd->node.llist;
517 }
518 }
519
520 if (!entry)
521 return;
522
523 /*
524 * Second; run all !SYNC callbacks.
525 */
526 prev = NULL;
527 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) {
528 int type = CSD_TYPE(csd);
529
530 if (type != CSD_TYPE_TTWU) {
531 if (prev) {
532 prev->next = &csd_next->node.llist;
533 } else {
534 entry = &csd_next->node.llist;
535 }
536
537 if (type == CSD_TYPE_ASYNC) {
538 smp_call_func_t func = csd->func;
539 void *info = csd->info;
540
541 csd_lock_record(csd);
542 csd_unlock(csd);
543 csd_do_func(func, info, csd);
544 csd_lock_record(NULL);
545 } else if (type == CSD_TYPE_IRQ_WORK) {
546 irq_work_single(csd);
547 }
548
549 } else {
550 prev = &csd->node.llist;
551 }
552 }
553
554 /*
555 * Third; only CSD_TYPE_TTWU is left, issue those.
556 */
557 if (entry) {
558 csd = llist_entry(entry, typeof(*csd), node.llist);
559 csd_do_func(sched_ttwu_pending, entry, csd);
560 }
561 }
562
563
564 /**
565 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
566 * from task context (idle, migration thread)
567 *
568 * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it
569 * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by
570 * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to
571 * handle queued SMP function calls before scheduling.
572 *
573 * The migration thread has to ensure that an eventually pending wakeup has
574 * been handled before it migrates a task.
575 */
576 void flush_smp_call_function_queue(void)
577 {
578 unsigned int was_pending;
579 unsigned long flags;
580
581 if (llist_empty(this_cpu_ptr(&call_single_queue)))
582 return;
583
584 local_irq_save(flags);
585 /* Get the already pending soft interrupts for RT enabled kernels */
586 was_pending = local_softirq_pending();
587 __flush_smp_call_function_queue(true);
588 if (local_softirq_pending())
589 do_softirq_post_smp_call_flush(was_pending);
590
591 local_irq_restore(flags);
592 }
593
594 /*
595 * smp_call_function_single - Run a function on a specific CPU
596 * @func: The function to run. This must be fast and non-blocking.
597 * @info: An arbitrary pointer to pass to the function.
598 * @wait: If true, wait until function has completed on other CPUs.
599 *
600 * Returns 0 on success, else a negative status code.
601 */
602 int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
603 int wait)
604 {
605 call_single_data_t *csd;
606 call_single_data_t csd_stack = {
607 .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, },
608 };
609 int this_cpu;
610 int err;
611
612 /*
613 * prevent preemption and reschedule on another processor,
614 * as well as CPU removal
615 */
616 this_cpu = get_cpu();
617
618 /*
619 * Can deadlock when called with interrupts disabled.
620 * We allow cpu's that are not yet online though, as no one else can
621 * send smp call function interrupt to this cpu and as such deadlocks
622 * can't happen.
623 */
624 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
625 && !oops_in_progress);
626
627 /*
628 * When @wait we can deadlock when we interrupt between llist_add() and
629 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
630 * csd_lock() on because the interrupt context uses the same csd
631 * storage.
632 */
633 WARN_ON_ONCE(!in_task());
634
635 csd = &csd_stack;
636 if (!wait) {
637 csd = this_cpu_ptr(&csd_data);
638 csd_lock(csd);
639 }
640
641 csd->func = func;
642 csd->info = info;
643 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
644 csd->node.src = smp_processor_id();
645 csd->node.dst = cpu;
646 #endif
647
648 err = generic_exec_single(cpu, csd);
649
650 if (wait)
651 csd_lock_wait(csd);
652
653 put_cpu();
654
655 return err;
656 }
657 EXPORT_SYMBOL(smp_call_function_single);
658
659 /**
660 * smp_call_function_single_async() - Run an asynchronous function on a
661 * specific CPU.
662 * @cpu: The CPU to run on.
663 * @csd: Pre-allocated and setup data structure
664 *
665 * Like smp_call_function_single(), but the call is asynchonous and
666 * can thus be done from contexts with disabled interrupts.
667 *
668 * The caller passes his own pre-allocated data structure
669 * (ie: embedded in an object) and is responsible for synchronizing it
670 * such that the IPIs performed on the @csd are strictly serialized.
671 *
672 * If the function is called with one csd which has not yet been
673 * processed by previous call to smp_call_function_single_async(), the
674 * function will return immediately with -EBUSY showing that the csd
675 * object is still in progress.
676 *
677 * NOTE: Be careful, there is unfortunately no current debugging facility to
678 * validate the correctness of this serialization.
679 *
680 * Return: %0 on success or negative errno value on error
681 */
682 int smp_call_function_single_async(int cpu, call_single_data_t *csd)
683 {
684 int err = 0;
685
686 preempt_disable();
687
688 if (csd->node.u_flags & CSD_FLAG_LOCK) {
689 err = -EBUSY;
690 goto out;
691 }
692
693 csd->node.u_flags = CSD_FLAG_LOCK;
694 smp_wmb();
695
696 err = generic_exec_single(cpu, csd);
697
698 out:
699 preempt_enable();
700
701 return err;
702 }
703 EXPORT_SYMBOL_GPL(smp_call_function_single_async);
704
705 /*
706 * smp_call_function_any - Run a function on any of the given cpus
707 * @mask: The mask of cpus it can run on.
708 * @func: The function to run. This must be fast and non-blocking.
709 * @info: An arbitrary pointer to pass to the function.
710 * @wait: If true, wait until function has completed.
711 *
712 * Returns 0 on success, else a negative status code (if no cpus were online).
713 *
714 * Selection preference:
715 * 1) current cpu if in @mask
716 * 2) any cpu of current node if in @mask
717 * 3) any other online cpu in @mask
718 */
719 int smp_call_function_any(const struct cpumask *mask,
720 smp_call_func_t func, void *info, int wait)
721 {
722 unsigned int cpu;
723 const struct cpumask *nodemask;
724 int ret;
725
726 /* Try for same CPU (cheapest) */
727 cpu = get_cpu();
728 if (cpumask_test_cpu(cpu, mask))
729 goto call;
730
731 /* Try for same node. */
732 nodemask = cpumask_of_node(cpu_to_node(cpu));
733 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
734 cpu = cpumask_next_and(cpu, nodemask, mask)) {
735 if (cpu_online(cpu))
736 goto call;
737 }
738
739 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
740 cpu = cpumask_any_and(mask, cpu_online_mask);
741 call:
742 ret = smp_call_function_single(cpu, func, info, wait);
743 put_cpu();
744 return ret;
745 }
746 EXPORT_SYMBOL_GPL(smp_call_function_any);
747
748 /*
749 * Flags to be used as scf_flags argument of smp_call_function_many_cond().
750 *
751 * %SCF_WAIT: Wait until function execution is completed
752 * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask
753 */
754 #define SCF_WAIT (1U << 0)
755 #define SCF_RUN_LOCAL (1U << 1)
756
757 static void smp_call_function_many_cond(const struct cpumask *mask,
758 smp_call_func_t func, void *info,
759 unsigned int scf_flags,
760 smp_cond_func_t cond_func)
761 {
762 int cpu, last_cpu, this_cpu = smp_processor_id();
763 struct call_function_data *cfd;
764 bool wait = scf_flags & SCF_WAIT;
765 int nr_cpus = 0;
766 bool run_remote = false;
767 bool run_local = false;
768
769 lockdep_assert_preemption_disabled();
770
771 /*
772 * Can deadlock when called with interrupts disabled.
773 * We allow cpu's that are not yet online though, as no one else can
774 * send smp call function interrupt to this cpu and as such deadlocks
775 * can't happen.
776 */
777 if (cpu_online(this_cpu) && !oops_in_progress &&
778 !early_boot_irqs_disabled)
779 lockdep_assert_irqs_enabled();
780
781 /*
782 * When @wait we can deadlock when we interrupt between llist_add() and
783 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
784 * csd_lock() on because the interrupt context uses the same csd
785 * storage.
786 */
787 WARN_ON_ONCE(!in_task());
788
789 /* Check if we need local execution. */
790 if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask))
791 run_local = true;
792
793 /* Check if we need remote execution, i.e., any CPU excluding this one. */
794 cpu = cpumask_first_and(mask, cpu_online_mask);
795 if (cpu == this_cpu)
796 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
797 if (cpu < nr_cpu_ids)
798 run_remote = true;
799
800 if (run_remote) {
801 cfd = this_cpu_ptr(&cfd_data);
802 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
803 __cpumask_clear_cpu(this_cpu, cfd->cpumask);
804
805 cpumask_clear(cfd->cpumask_ipi);
806 for_each_cpu(cpu, cfd->cpumask) {
807 call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu);
808
809 if (cond_func && !cond_func(cpu, info)) {
810 __cpumask_clear_cpu(cpu, cfd->cpumask);
811 continue;
812 }
813
814 csd_lock(csd);
815 if (wait)
816 csd->node.u_flags |= CSD_TYPE_SYNC;
817 csd->func = func;
818 csd->info = info;
819 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
820 csd->node.src = smp_processor_id();
821 csd->node.dst = cpu;
822 #endif
823 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
824
825 if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) {
826 __cpumask_set_cpu(cpu, cfd->cpumask_ipi);
827 nr_cpus++;
828 last_cpu = cpu;
829 }
830 }
831
832 /*
833 * Choose the most efficient way to send an IPI. Note that the
834 * number of CPUs might be zero due to concurrent changes to the
835 * provided mask.
836 */
837 if (nr_cpus == 1)
838 send_call_function_single_ipi(last_cpu);
839 else if (likely(nr_cpus > 1))
840 send_call_function_ipi_mask(cfd->cpumask_ipi);
841 }
842
843 if (run_local && (!cond_func || cond_func(this_cpu, info))) {
844 unsigned long flags;
845
846 local_irq_save(flags);
847 csd_do_func(func, info, NULL);
848 local_irq_restore(flags);
849 }
850
851 if (run_remote && wait) {
852 for_each_cpu(cpu, cfd->cpumask) {
853 call_single_data_t *csd;
854
855 csd = per_cpu_ptr(cfd->csd, cpu);
856 csd_lock_wait(csd);
857 }
858 }
859 }
860
861 /**
862 * smp_call_function_many(): Run a function on a set of CPUs.
863 * @mask: The set of cpus to run on (only runs on online subset).
864 * @func: The function to run. This must be fast and non-blocking.
865 * @info: An arbitrary pointer to pass to the function.
866 * @wait: Bitmask that controls the operation. If %SCF_WAIT is set, wait
867 * (atomically) until function has completed on other CPUs. If
868 * %SCF_RUN_LOCAL is set, the function will also be run locally
869 * if the local CPU is set in the @cpumask.
870 *
871 * If @wait is true, then returns once @func has returned.
872 *
873 * You must not call this function with disabled interrupts or from a
874 * hardware interrupt handler or from a bottom half handler. Preemption
875 * must be disabled when calling this function.
876 */
877 void smp_call_function_many(const struct cpumask *mask,
878 smp_call_func_t func, void *info, bool wait)
879 {
880 smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL);
881 }
882 EXPORT_SYMBOL(smp_call_function_many);
883
884 /**
885 * smp_call_function(): Run a function on all other CPUs.
886 * @func: The function to run. This must be fast and non-blocking.
887 * @info: An arbitrary pointer to pass to the function.
888 * @wait: If true, wait (atomically) until function has completed
889 * on other CPUs.
890 *
891 * Returns 0.
892 *
893 * If @wait is true, then returns once @func has returned; otherwise
894 * it returns just before the target cpu calls @func.
895 *
896 * You must not call this function with disabled interrupts or from a
897 * hardware interrupt handler or from a bottom half handler.
898 */
899 void smp_call_function(smp_call_func_t func, void *info, int wait)
900 {
901 preempt_disable();
902 smp_call_function_many(cpu_online_mask, func, info, wait);
903 preempt_enable();
904 }
905 EXPORT_SYMBOL(smp_call_function);
906
907 /* Setup configured maximum number of CPUs to activate */
908 unsigned int setup_max_cpus = NR_CPUS;
909 EXPORT_SYMBOL(setup_max_cpus);
910
911
912 /*
913 * Setup routine for controlling SMP activation
914 *
915 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
916 * activation entirely (the MPS table probe still happens, though).
917 *
918 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
919 * greater than 0, limits the maximum number of CPUs activated in
920 * SMP mode to <NUM>.
921 */
922
923 void __weak __init arch_disable_smp_support(void) { }
924
925 static int __init nosmp(char *str)
926 {
927 setup_max_cpus = 0;
928 arch_disable_smp_support();
929
930 return 0;
931 }
932
933 early_param("nosmp", nosmp);
934
935 /* this is hard limit */
936 static int __init nrcpus(char *str)
937 {
938 int nr_cpus;
939
940 if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids)
941 set_nr_cpu_ids(nr_cpus);
942
943 return 0;
944 }
945
946 early_param("nr_cpus", nrcpus);
947
948 static int __init maxcpus(char *str)
949 {
950 get_option(&str, &setup_max_cpus);
951 if (setup_max_cpus == 0)
952 arch_disable_smp_support();
953
954 return 0;
955 }
956
957 early_param("maxcpus", maxcpus);
958
959 #if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS)
960 /* Setup number of possible processor ids */
961 unsigned int nr_cpu_ids __read_mostly = NR_CPUS;
962 EXPORT_SYMBOL(nr_cpu_ids);
963 #endif
964
965 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
966 void __init setup_nr_cpu_ids(void)
967 {
968 set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1);
969 }
970
971 /* Called by boot processor to activate the rest. */
972 void __init smp_init(void)
973 {
974 int num_nodes, num_cpus;
975
976 idle_threads_init();
977 cpuhp_threads_init();
978
979 pr_info("Bringing up secondary CPUs ...\n");
980
981 bringup_nonboot_cpus(setup_max_cpus);
982
983 num_nodes = num_online_nodes();
984 num_cpus = num_online_cpus();
985 pr_info("Brought up %d node%s, %d CPU%s\n",
986 num_nodes, str_plural(num_nodes), num_cpus, str_plural(num_cpus));
987
988 /* Any cleanup work */
989 smp_cpus_done(setup_max_cpus);
990 }
991
992 /*
993 * on_each_cpu_cond(): Call a function on each processor for which
994 * the supplied function cond_func returns true, optionally waiting
995 * for all the required CPUs to finish. This may include the local
996 * processor.
997 * @cond_func: A callback function that is passed a cpu id and
998 * the info parameter. The function is called
999 * with preemption disabled. The function should
1000 * return a blooean value indicating whether to IPI
1001 * the specified CPU.
1002 * @func: The function to run on all applicable CPUs.
1003 * This must be fast and non-blocking.
1004 * @info: An arbitrary pointer to pass to both functions.
1005 * @wait: If true, wait (atomically) until function has
1006 * completed on other CPUs.
1007 *
1008 * Preemption is disabled to protect against CPUs going offline but not online.
1009 * CPUs going online during the call will not be seen or sent an IPI.
1010 *
1011 * You must not call this function with disabled interrupts or
1012 * from a hardware interrupt handler or from a bottom half handler.
1013 */
1014 void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
1015 void *info, bool wait, const struct cpumask *mask)
1016 {
1017 unsigned int scf_flags = SCF_RUN_LOCAL;
1018
1019 if (wait)
1020 scf_flags |= SCF_WAIT;
1021
1022 preempt_disable();
1023 smp_call_function_many_cond(mask, func, info, scf_flags, cond_func);
1024 preempt_enable();
1025 }
1026 EXPORT_SYMBOL(on_each_cpu_cond_mask);
1027
1028 static void do_nothing(void *unused)
1029 {
1030 }
1031
1032 /**
1033 * kick_all_cpus_sync - Force all cpus out of idle
1034 *
1035 * Used to synchronize the update of pm_idle function pointer. It's
1036 * called after the pointer is updated and returns after the dummy
1037 * callback function has been executed on all cpus. The execution of
1038 * the function can only happen on the remote cpus after they have
1039 * left the idle function which had been called via pm_idle function
1040 * pointer. So it's guaranteed that nothing uses the previous pointer
1041 * anymore.
1042 */
1043 void kick_all_cpus_sync(void)
1044 {
1045 /* Make sure the change is visible before we kick the cpus */
1046 smp_mb();
1047 smp_call_function(do_nothing, NULL, 1);
1048 }
1049 EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
1050
1051 /**
1052 * wake_up_all_idle_cpus - break all cpus out of idle
1053 * wake_up_all_idle_cpus try to break all cpus which is in idle state even
1054 * including idle polling cpus, for non-idle cpus, we will do nothing
1055 * for them.
1056 */
1057 void wake_up_all_idle_cpus(void)
1058 {
1059 int cpu;
1060
1061 for_each_possible_cpu(cpu) {
1062 preempt_disable();
1063 if (cpu != smp_processor_id() && cpu_online(cpu))
1064 wake_up_if_idle(cpu);
1065 preempt_enable();
1066 }
1067 }
1068 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
1069
1070 /**
1071 * struct smp_call_on_cpu_struct - Call a function on a specific CPU
1072 * @work: &work_struct
1073 * @done: &completion to signal
1074 * @func: function to call
1075 * @data: function's data argument
1076 * @ret: return value from @func
1077 * @cpu: target CPU (%-1 for any CPU)
1078 *
1079 * Used to call a function on a specific cpu and wait for it to return.
1080 * Optionally make sure the call is done on a specified physical cpu via vcpu
1081 * pinning in order to support virtualized environments.
1082 */
1083 struct smp_call_on_cpu_struct {
1084 struct work_struct work;
1085 struct completion done;
1086 int (*func)(void *);
1087 void *data;
1088 int ret;
1089 int cpu;
1090 };
1091
1092 static void smp_call_on_cpu_callback(struct work_struct *work)
1093 {
1094 struct smp_call_on_cpu_struct *sscs;
1095
1096 sscs = container_of(work, struct smp_call_on_cpu_struct, work);
1097 if (sscs->cpu >= 0)
1098 hypervisor_pin_vcpu(sscs->cpu);
1099 sscs->ret = sscs->func(sscs->data);
1100 if (sscs->cpu >= 0)
1101 hypervisor_pin_vcpu(-1);
1102
1103 complete(&sscs->done);
1104 }
1105
1106 int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
1107 {
1108 struct smp_call_on_cpu_struct sscs = {
1109 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done),
1110 .func = func,
1111 .data = par,
1112 .cpu = phys ? cpu : -1,
1113 };
1114
1115 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
1116
1117 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
1118 return -ENXIO;
1119
1120 queue_work_on(cpu, system_wq, &sscs.work);
1121 wait_for_completion(&sscs.done);
1122 destroy_work_on_stack(&sscs.work);
1123
1124 return sscs.ret;
1125 }
1126 EXPORT_SYMBOL_GPL(smp_call_on_cpu);
1127
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