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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
29#include "smpboot.h"
30#include "sched/smp.h"
31
32#define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK)
33
34#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
35union cfd_seq_cnt {
36 u64 val;
37 struct {
38 u64 src:16;
39 u64 dst:16;
40#define CFD_SEQ_NOCPU 0xffff
41 u64 type:4;
42#define CFD_SEQ_QUEUE 0
43#define CFD_SEQ_IPI 1
44#define CFD_SEQ_NOIPI 2
45#define CFD_SEQ_PING 3
46#define CFD_SEQ_PINGED 4
47#define CFD_SEQ_HANDLE 5
48#define CFD_SEQ_DEQUEUE 6
49#define CFD_SEQ_IDLE 7
50#define CFD_SEQ_GOTIPI 8
51#define CFD_SEQ_HDLEND 9
52 u64 cnt:28;
53 } u;
54};
55
56static char *seq_type[] = {
57 [CFD_SEQ_QUEUE] = "queue",
58 [CFD_SEQ_IPI] = "ipi",
59 [CFD_SEQ_NOIPI] = "noipi",
60 [CFD_SEQ_PING] = "ping",
61 [CFD_SEQ_PINGED] = "pinged",
62 [CFD_SEQ_HANDLE] = "handle",
63 [CFD_SEQ_DEQUEUE] = "dequeue (src CPU 0 == empty)",
64 [CFD_SEQ_IDLE] = "idle",
65 [CFD_SEQ_GOTIPI] = "gotipi",
66 [CFD_SEQ_HDLEND] = "hdlend (src CPU 0 == early)",
67};
68
69struct cfd_seq_local {
70 u64 ping;
71 u64 pinged;
72 u64 handle;
73 u64 dequeue;
74 u64 idle;
75 u64 gotipi;
76 u64 hdlend;
77};
78#endif
79
80struct cfd_percpu {
81 call_single_data_t csd;
82#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
83 u64 seq_queue;
84 u64 seq_ipi;
85 u64 seq_noipi;
86#endif
87};
88
89struct call_function_data {
90 struct cfd_percpu __percpu *pcpu;
91 cpumask_var_t cpumask;
92 cpumask_var_t cpumask_ipi;
93};
94
95static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data);
96
97static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
98
99static void __flush_smp_call_function_queue(bool warn_cpu_offline);
100
101int smpcfd_prepare_cpu(unsigned int cpu)
102{
103 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
104
105 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
106 cpu_to_node(cpu)))
107 return -ENOMEM;
108 if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL,
109 cpu_to_node(cpu))) {
110 free_cpumask_var(cfd->cpumask);
111 return -ENOMEM;
112 }
113 cfd->pcpu = alloc_percpu(struct cfd_percpu);
114 if (!cfd->pcpu) {
115 free_cpumask_var(cfd->cpumask);
116 free_cpumask_var(cfd->cpumask_ipi);
117 return -ENOMEM;
118 }
119
120 return 0;
121}
122
123int smpcfd_dead_cpu(unsigned int cpu)
124{
125 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
126
127 free_cpumask_var(cfd->cpumask);
128 free_cpumask_var(cfd->cpumask_ipi);
129 free_percpu(cfd->pcpu);
130 return 0;
131}
132
133int smpcfd_dying_cpu(unsigned int cpu)
134{
135 /*
136 * The IPIs for the smp-call-function callbacks queued by other
137 * CPUs might arrive late, either due to hardware latencies or
138 * because this CPU disabled interrupts (inside stop-machine)
139 * before the IPIs were sent. So flush out any pending callbacks
140 * explicitly (without waiting for the IPIs to arrive), to
141 * ensure that the outgoing CPU doesn't go offline with work
142 * still pending.
143 */
144 __flush_smp_call_function_queue(false);
145 irq_work_run();
146 return 0;
147}
148
149void __init call_function_init(void)
150{
151 int i;
152
153 for_each_possible_cpu(i)
154 init_llist_head(&per_cpu(call_single_queue, i));
155
156 smpcfd_prepare_cpu(smp_processor_id());
157}
158
159#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
160
161static DEFINE_STATIC_KEY_FALSE(csdlock_debug_enabled);
162static DEFINE_STATIC_KEY_FALSE(csdlock_debug_extended);
163
164static int __init csdlock_debug(char *str)
165{
166 unsigned int val = 0;
167
168 if (str && !strcmp(str, "ext")) {
169 val = 1;
170 static_branch_enable(&csdlock_debug_extended);
171 } else
172 get_option(&str, &val);
173
174 if (val)
175 static_branch_enable(&csdlock_debug_enabled);
176
177 return 1;
178}
179__setup("csdlock_debug=", csdlock_debug);
180
181static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
182static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
183static DEFINE_PER_CPU(void *, cur_csd_info);
184static DEFINE_PER_CPU(struct cfd_seq_local, cfd_seq_local);
185
186static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */
187module_param(csd_lock_timeout, ulong, 0444);
188
189static atomic_t csd_bug_count = ATOMIC_INIT(0);
190static u64 cfd_seq;
191
192#define CFD_SEQ(s, d, t, c) \
193 (union cfd_seq_cnt){ .u.src = s, .u.dst = d, .u.type = t, .u.cnt = c }
194
195static u64 cfd_seq_inc(unsigned int src, unsigned int dst, unsigned int type)
196{
197 union cfd_seq_cnt new, old;
198
199 new = CFD_SEQ(src, dst, type, 0);
200
201 do {
202 old.val = READ_ONCE(cfd_seq);
203 new.u.cnt = old.u.cnt + 1;
204 } while (cmpxchg(&cfd_seq, old.val, new.val) != old.val);
205
206 return old.val;
207}
208
209#define cfd_seq_store(var, src, dst, type) \
210 do { \
211 if (static_branch_unlikely(&csdlock_debug_extended)) \
212 var = cfd_seq_inc(src, dst, type); \
213 } while (0)
214
215/* Record current CSD work for current CPU, NULL to erase. */
216static void __csd_lock_record(struct __call_single_data *csd)
217{
218 if (!csd) {
219 smp_mb(); /* NULL cur_csd after unlock. */
220 __this_cpu_write(cur_csd, NULL);
221 return;
222 }
223 __this_cpu_write(cur_csd_func, csd->func);
224 __this_cpu_write(cur_csd_info, csd->info);
225 smp_wmb(); /* func and info before csd. */
226 __this_cpu_write(cur_csd, csd);
227 smp_mb(); /* Update cur_csd before function call. */
228 /* Or before unlock, as the case may be. */
229}
230
231static __always_inline void csd_lock_record(struct __call_single_data *csd)
232{
233 if (static_branch_unlikely(&csdlock_debug_enabled))
234 __csd_lock_record(csd);
235}
236
237static int csd_lock_wait_getcpu(struct __call_single_data *csd)
238{
239 unsigned int csd_type;
240
241 csd_type = CSD_TYPE(csd);
242 if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC)
243 return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */
244 return -1;
245}
246
247static void cfd_seq_data_add(u64 val, unsigned int src, unsigned int dst,
248 unsigned int type, union cfd_seq_cnt *data,
249 unsigned int *n_data, unsigned int now)
250{
251 union cfd_seq_cnt new[2];
252 unsigned int i, j, k;
253
254 new[0].val = val;
255 new[1] = CFD_SEQ(src, dst, type, new[0].u.cnt + 1);
256
257 for (i = 0; i < 2; i++) {
258 if (new[i].u.cnt <= now)
259 new[i].u.cnt |= 0x80000000U;
260 for (j = 0; j < *n_data; j++) {
261 if (new[i].u.cnt == data[j].u.cnt) {
262 /* Direct read value trumps generated one. */
263 if (i == 0)
264 data[j].val = new[i].val;
265 break;
266 }
267 if (new[i].u.cnt < data[j].u.cnt) {
268 for (k = *n_data; k > j; k--)
269 data[k].val = data[k - 1].val;
270 data[j].val = new[i].val;
271 (*n_data)++;
272 break;
273 }
274 }
275 if (j == *n_data) {
276 data[j].val = new[i].val;
277 (*n_data)++;
278 }
279 }
280}
281
282static const char *csd_lock_get_type(unsigned int type)
283{
284 return (type >= ARRAY_SIZE(seq_type)) ? "?" : seq_type[type];
285}
286
287static void csd_lock_print_extended(struct __call_single_data *csd, int cpu)
288{
289 struct cfd_seq_local *seq = &per_cpu(cfd_seq_local, cpu);
290 unsigned int srccpu = csd->node.src;
291 struct call_function_data *cfd = per_cpu_ptr(&cfd_data, srccpu);
292 struct cfd_percpu *pcpu = per_cpu_ptr(cfd->pcpu, cpu);
293 unsigned int now;
294 union cfd_seq_cnt data[2 * ARRAY_SIZE(seq_type)];
295 unsigned int n_data = 0, i;
296
297 data[0].val = READ_ONCE(cfd_seq);
298 now = data[0].u.cnt;
299
300 cfd_seq_data_add(pcpu->seq_queue, srccpu, cpu, CFD_SEQ_QUEUE, data, &n_data, now);
301 cfd_seq_data_add(pcpu->seq_ipi, srccpu, cpu, CFD_SEQ_IPI, data, &n_data, now);
302 cfd_seq_data_add(pcpu->seq_noipi, srccpu, cpu, CFD_SEQ_NOIPI, data, &n_data, now);
303
304 cfd_seq_data_add(per_cpu(cfd_seq_local.ping, srccpu), srccpu, CFD_SEQ_NOCPU, CFD_SEQ_PING, data, &n_data, now);
305 cfd_seq_data_add(per_cpu(cfd_seq_local.pinged, srccpu), srccpu, CFD_SEQ_NOCPU, CFD_SEQ_PINGED, data, &n_data, now);
306
307 cfd_seq_data_add(seq->idle, CFD_SEQ_NOCPU, cpu, CFD_SEQ_IDLE, data, &n_data, now);
308 cfd_seq_data_add(seq->gotipi, CFD_SEQ_NOCPU, cpu, CFD_SEQ_GOTIPI, data, &n_data, now);
309 cfd_seq_data_add(seq->handle, CFD_SEQ_NOCPU, cpu, CFD_SEQ_HANDLE, data, &n_data, now);
310 cfd_seq_data_add(seq->dequeue, CFD_SEQ_NOCPU, cpu, CFD_SEQ_DEQUEUE, data, &n_data, now);
311 cfd_seq_data_add(seq->hdlend, CFD_SEQ_NOCPU, cpu, CFD_SEQ_HDLEND, data, &n_data, now);
312
313 for (i = 0; i < n_data; i++) {
314 pr_alert("\tcsd: cnt(%07x): %04x->%04x %s\n",
315 data[i].u.cnt & ~0x80000000U, data[i].u.src,
316 data[i].u.dst, csd_lock_get_type(data[i].u.type));
317 }
318 pr_alert("\tcsd: cnt now: %07x\n", now);
319}
320
321/*
322 * Complain if too much time spent waiting. Note that only
323 * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU,
324 * so waiting on other types gets much less information.
325 */
326static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 *ts1, int *bug_id)
327{
328 int cpu = -1;
329 int cpux;
330 bool firsttime;
331 u64 ts2, ts_delta;
332 call_single_data_t *cpu_cur_csd;
333 unsigned int flags = READ_ONCE(csd->node.u_flags);
334 unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC;
335
336 if (!(flags & CSD_FLAG_LOCK)) {
337 if (!unlikely(*bug_id))
338 return true;
339 cpu = csd_lock_wait_getcpu(csd);
340 pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n",
341 *bug_id, raw_smp_processor_id(), cpu);
342 return true;
343 }
344
345 ts2 = sched_clock();
346 ts_delta = ts2 - *ts1;
347 if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0))
348 return false;
349
350 firsttime = !*bug_id;
351 if (firsttime)
352 *bug_id = atomic_inc_return(&csd_bug_count);
353 cpu = csd_lock_wait_getcpu(csd);
354 if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
355 cpux = 0;
356 else
357 cpux = cpu;
358 cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */
359 pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n",
360 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts2 - ts0,
361 cpu, csd->func, csd->info);
362 if (cpu_cur_csd && csd != cpu_cur_csd) {
363 pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n",
364 *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),
365 READ_ONCE(per_cpu(cur_csd_info, cpux)));
366 } else {
367 pr_alert("\tcsd: CSD lock (#%d) %s.\n",
368 *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request");
369 }
370 if (cpu >= 0) {
371 if (static_branch_unlikely(&csdlock_debug_extended))
372 csd_lock_print_extended(csd, cpu);
373 dump_cpu_task(cpu);
374 if (!cpu_cur_csd) {
375 pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu);
376 arch_send_call_function_single_ipi(cpu);
377 }
378 }
379 dump_stack();
380 *ts1 = ts2;
381
382 return false;
383}
384
385/*
386 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
387 *
388 * For non-synchronous ipi calls the csd can still be in use by the
389 * previous function call. For multi-cpu calls its even more interesting
390 * as we'll have to ensure no other cpu is observing our csd.
391 */
392static void __csd_lock_wait(struct __call_single_data *csd)
393{
394 int bug_id = 0;
395 u64 ts0, ts1;
396
397 ts1 = ts0 = sched_clock();
398 for (;;) {
399 if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id))
400 break;
401 cpu_relax();
402 }
403 smp_acquire__after_ctrl_dep();
404}
405
406static __always_inline void csd_lock_wait(struct __call_single_data *csd)
407{
408 if (static_branch_unlikely(&csdlock_debug_enabled)) {
409 __csd_lock_wait(csd);
410 return;
411 }
412
413 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));
414}
415
416static void __smp_call_single_queue_debug(int cpu, struct llist_node *node)
417{
418 unsigned int this_cpu = smp_processor_id();
419 struct cfd_seq_local *seq = this_cpu_ptr(&cfd_seq_local);
420 struct call_function_data *cfd = this_cpu_ptr(&cfd_data);
421 struct cfd_percpu *pcpu = per_cpu_ptr(cfd->pcpu, cpu);
422
423 cfd_seq_store(pcpu->seq_queue, this_cpu, cpu, CFD_SEQ_QUEUE);
424 if (llist_add(node, &per_cpu(call_single_queue, cpu))) {
425 cfd_seq_store(pcpu->seq_ipi, this_cpu, cpu, CFD_SEQ_IPI);
426 cfd_seq_store(seq->ping, this_cpu, cpu, CFD_SEQ_PING);
427 send_call_function_single_ipi(cpu);
428 cfd_seq_store(seq->pinged, this_cpu, cpu, CFD_SEQ_PINGED);
429 } else {
430 cfd_seq_store(pcpu->seq_noipi, this_cpu, cpu, CFD_SEQ_NOIPI);
431 }
432}
433#else
434#define cfd_seq_store(var, src, dst, type)
435
436static void csd_lock_record(struct __call_single_data *csd)
437{
438}
439
440static __always_inline void csd_lock_wait(struct __call_single_data *csd)
441{
442 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));
443}
444#endif
445
446static __always_inline void csd_lock(struct __call_single_data *csd)
447{
448 csd_lock_wait(csd);
449 csd->node.u_flags |= CSD_FLAG_LOCK;
450
451 /*
452 * prevent CPU from reordering the above assignment
453 * to ->flags with any subsequent assignments to other
454 * fields of the specified call_single_data_t structure:
455 */
456 smp_wmb();
457}
458
459static __always_inline void csd_unlock(struct __call_single_data *csd)
460{
461 WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK));
462
463 /*
464 * ensure we're all done before releasing data:
465 */
466 smp_store_release(&csd->node.u_flags, 0);
467}
468
469static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data);
470
471void __smp_call_single_queue(int cpu, struct llist_node *node)
472{
473#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
474 if (static_branch_unlikely(&csdlock_debug_extended)) {
475 unsigned int type;
476
477 type = CSD_TYPE(container_of(node, call_single_data_t,
478 node.llist));
479 if (type == CSD_TYPE_SYNC || type == CSD_TYPE_ASYNC) {
480 __smp_call_single_queue_debug(cpu, node);
481 return;
482 }
483 }
484#endif
485
486 /*
487 * The list addition should be visible before sending the IPI
488 * handler locks the list to pull the entry off it because of
489 * normal cache coherency rules implied by spinlocks.
490 *
491 * If IPIs can go out of order to the cache coherency protocol
492 * in an architecture, sufficient synchronisation should be added
493 * to arch code to make it appear to obey cache coherency WRT
494 * locking and barrier primitives. Generic code isn't really
495 * equipped to do the right thing...
496 */
497 if (llist_add(node, &per_cpu(call_single_queue, cpu)))
498 send_call_function_single_ipi(cpu);
499}
500
501/*
502 * Insert a previously allocated call_single_data_t element
503 * for execution on the given CPU. data must already have
504 * ->func, ->info, and ->flags set.
505 */
506static int generic_exec_single(int cpu, struct __call_single_data *csd)
507{
508 if (cpu == smp_processor_id()) {
509 smp_call_func_t func = csd->func;
510 void *info = csd->info;
511 unsigned long flags;
512
513 /*
514 * We can unlock early even for the synchronous on-stack case,
515 * since we're doing this from the same CPU..
516 */
517 csd_lock_record(csd);
518 csd_unlock(csd);
519 local_irq_save(flags);
520 func(info);
521 csd_lock_record(NULL);
522 local_irq_restore(flags);
523 return 0;
524 }
525
526 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
527 csd_unlock(csd);
528 return -ENXIO;
529 }
530
531 __smp_call_single_queue(cpu, &csd->node.llist);
532
533 return 0;
534}
535
536/**
537 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
538 *
539 * Invoked by arch to handle an IPI for call function single.
540 * Must be called with interrupts disabled.
541 */
542void generic_smp_call_function_single_interrupt(void)
543{
544 cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->gotipi, CFD_SEQ_NOCPU,
545 smp_processor_id(), CFD_SEQ_GOTIPI);
546 __flush_smp_call_function_queue(true);
547}
548
549/**
550 * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks
551 *
552 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
553 * offline CPU. Skip this check if set to 'false'.
554 *
555 * Flush any pending smp-call-function callbacks queued on this CPU. This is
556 * invoked by the generic IPI handler, as well as by a CPU about to go offline,
557 * to ensure that all pending IPI callbacks are run before it goes completely
558 * offline.
559 *
560 * Loop through the call_single_queue and run all the queued callbacks.
561 * Must be called with interrupts disabled.
562 */
563static void __flush_smp_call_function_queue(bool warn_cpu_offline)
564{
565 call_single_data_t *csd, *csd_next;
566 struct llist_node *entry, *prev;
567 struct llist_head *head;
568 static bool warned;
569
570 lockdep_assert_irqs_disabled();
571
572 head = this_cpu_ptr(&call_single_queue);
573 cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->handle, CFD_SEQ_NOCPU,
574 smp_processor_id(), CFD_SEQ_HANDLE);
575 entry = llist_del_all(head);
576 cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->dequeue,
577 /* Special meaning of source cpu: 0 == queue empty */
578 entry ? CFD_SEQ_NOCPU : 0,
579 smp_processor_id(), CFD_SEQ_DEQUEUE);
580 entry = llist_reverse_order(entry);
581
582 /* There shouldn't be any pending callbacks on an offline CPU. */
583 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
584 !warned && entry != NULL)) {
585 warned = true;
586 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
587
588 /*
589 * We don't have to use the _safe() variant here
590 * because we are not invoking the IPI handlers yet.
591 */
592 llist_for_each_entry(csd, entry, node.llist) {
593 switch (CSD_TYPE(csd)) {
594 case CSD_TYPE_ASYNC:
595 case CSD_TYPE_SYNC:
596 case CSD_TYPE_IRQ_WORK:
597 pr_warn("IPI callback %pS sent to offline CPU\n",
598 csd->func);
599 break;
600
601 case CSD_TYPE_TTWU:
602 pr_warn("IPI task-wakeup sent to offline CPU\n");
603 break;
604
605 default:
606 pr_warn("IPI callback, unknown type %d, sent to offline CPU\n",
607 CSD_TYPE(csd));
608 break;
609 }
610 }
611 }
612
613 /*
614 * First; run all SYNC callbacks, people are waiting for us.
615 */
616 prev = NULL;
617 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) {
618 /* Do we wait until *after* callback? */
619 if (CSD_TYPE(csd) == CSD_TYPE_SYNC) {
620 smp_call_func_t func = csd->func;
621 void *info = csd->info;
622
623 if (prev) {
624 prev->next = &csd_next->node.llist;
625 } else {
626 entry = &csd_next->node.llist;
627 }
628
629 csd_lock_record(csd);
630 func(info);
631 csd_unlock(csd);
632 csd_lock_record(NULL);
633 } else {
634 prev = &csd->node.llist;
635 }
636 }
637
638 if (!entry) {
639 cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->hdlend,
640 0, smp_processor_id(),
641 CFD_SEQ_HDLEND);
642 return;
643 }
644
645 /*
646 * Second; run all !SYNC callbacks.
647 */
648 prev = NULL;
649 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) {
650 int type = CSD_TYPE(csd);
651
652 if (type != CSD_TYPE_TTWU) {
653 if (prev) {
654 prev->next = &csd_next->node.llist;
655 } else {
656 entry = &csd_next->node.llist;
657 }
658
659 if (type == CSD_TYPE_ASYNC) {
660 smp_call_func_t func = csd->func;
661 void *info = csd->info;
662
663 csd_lock_record(csd);
664 csd_unlock(csd);
665 func(info);
666 csd_lock_record(NULL);
667 } else if (type == CSD_TYPE_IRQ_WORK) {
668 irq_work_single(csd);
669 }
670
671 } else {
672 prev = &csd->node.llist;
673 }
674 }
675
676 /*
677 * Third; only CSD_TYPE_TTWU is left, issue those.
678 */
679 if (entry)
680 sched_ttwu_pending(entry);
681
682 cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->hdlend, CFD_SEQ_NOCPU,
683 smp_processor_id(), CFD_SEQ_HDLEND);
684}
685
686
687/**
688 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
689 * from task context (idle, migration thread)
690 *
691 * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it
692 * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by
693 * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to
694 * handle queued SMP function calls before scheduling.
695 *
696 * The migration thread has to ensure that an eventually pending wakeup has
697 * been handled before it migrates a task.
698 */
699void flush_smp_call_function_queue(void)
700{
701 unsigned int was_pending;
702 unsigned long flags;
703
704 if (llist_empty(this_cpu_ptr(&call_single_queue)))
705 return;
706
707 cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->idle, CFD_SEQ_NOCPU,
708 smp_processor_id(), CFD_SEQ_IDLE);
709 local_irq_save(flags);
710 /* Get the already pending soft interrupts for RT enabled kernels */
711 was_pending = local_softirq_pending();
712 __flush_smp_call_function_queue(true);
713 if (local_softirq_pending())
714 do_softirq_post_smp_call_flush(was_pending);
715
716 local_irq_restore(flags);
717}
718
719/*
720 * smp_call_function_single - Run a function on a specific CPU
721 * @func: The function to run. This must be fast and non-blocking.
722 * @info: An arbitrary pointer to pass to the function.
723 * @wait: If true, wait until function has completed on other CPUs.
724 *
725 * Returns 0 on success, else a negative status code.
726 */
727int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
728 int wait)
729{
730 call_single_data_t *csd;
731 call_single_data_t csd_stack = {
732 .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, },
733 };
734 int this_cpu;
735 int err;
736
737 /*
738 * prevent preemption and reschedule on another processor,
739 * as well as CPU removal
740 */
741 this_cpu = get_cpu();
742
743 /*
744 * Can deadlock when called with interrupts disabled.
745 * We allow cpu's that are not yet online though, as no one else can
746 * send smp call function interrupt to this cpu and as such deadlocks
747 * can't happen.
748 */
749 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
750 && !oops_in_progress);
751
752 /*
753 * When @wait we can deadlock when we interrupt between llist_add() and
754 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
755 * csd_lock() on because the interrupt context uses the same csd
756 * storage.
757 */
758 WARN_ON_ONCE(!in_task());
759
760 csd = &csd_stack;
761 if (!wait) {
762 csd = this_cpu_ptr(&csd_data);
763 csd_lock(csd);
764 }
765
766 csd->func = func;
767 csd->info = info;
768#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
769 csd->node.src = smp_processor_id();
770 csd->node.dst = cpu;
771#endif
772
773 err = generic_exec_single(cpu, csd);
774
775 if (wait)
776 csd_lock_wait(csd);
777
778 put_cpu();
779
780 return err;
781}
782EXPORT_SYMBOL(smp_call_function_single);
783
784/**
785 * smp_call_function_single_async() - Run an asynchronous function on a
786 * specific CPU.
787 * @cpu: The CPU to run on.
788 * @csd: Pre-allocated and setup data structure
789 *
790 * Like smp_call_function_single(), but the call is asynchonous and
791 * can thus be done from contexts with disabled interrupts.
792 *
793 * The caller passes his own pre-allocated data structure
794 * (ie: embedded in an object) and is responsible for synchronizing it
795 * such that the IPIs performed on the @csd are strictly serialized.
796 *
797 * If the function is called with one csd which has not yet been
798 * processed by previous call to smp_call_function_single_async(), the
799 * function will return immediately with -EBUSY showing that the csd
800 * object is still in progress.
801 *
802 * NOTE: Be careful, there is unfortunately no current debugging facility to
803 * validate the correctness of this serialization.
804 *
805 * Return: %0 on success or negative errno value on error
806 */
807int smp_call_function_single_async(int cpu, struct __call_single_data *csd)
808{
809 int err = 0;
810
811 preempt_disable();
812
813 if (csd->node.u_flags & CSD_FLAG_LOCK) {
814 err = -EBUSY;
815 goto out;
816 }
817
818 csd->node.u_flags = CSD_FLAG_LOCK;
819 smp_wmb();
820
821 err = generic_exec_single(cpu, csd);
822
823out:
824 preempt_enable();
825
826 return err;
827}
828EXPORT_SYMBOL_GPL(smp_call_function_single_async);
829
830/*
831 * smp_call_function_any - Run a function on any of the given cpus
832 * @mask: The mask of cpus it can run on.
833 * @func: The function to run. This must be fast and non-blocking.
834 * @info: An arbitrary pointer to pass to the function.
835 * @wait: If true, wait until function has completed.
836 *
837 * Returns 0 on success, else a negative status code (if no cpus were online).
838 *
839 * Selection preference:
840 * 1) current cpu if in @mask
841 * 2) any cpu of current node if in @mask
842 * 3) any other online cpu in @mask
843 */
844int smp_call_function_any(const struct cpumask *mask,
845 smp_call_func_t func, void *info, int wait)
846{
847 unsigned int cpu;
848 const struct cpumask *nodemask;
849 int ret;
850
851 /* Try for same CPU (cheapest) */
852 cpu = get_cpu();
853 if (cpumask_test_cpu(cpu, mask))
854 goto call;
855
856 /* Try for same node. */
857 nodemask = cpumask_of_node(cpu_to_node(cpu));
858 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
859 cpu = cpumask_next_and(cpu, nodemask, mask)) {
860 if (cpu_online(cpu))
861 goto call;
862 }
863
864 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
865 cpu = cpumask_any_and(mask, cpu_online_mask);
866call:
867 ret = smp_call_function_single(cpu, func, info, wait);
868 put_cpu();
869 return ret;
870}
871EXPORT_SYMBOL_GPL(smp_call_function_any);
872
873/*
874 * Flags to be used as scf_flags argument of smp_call_function_many_cond().
875 *
876 * %SCF_WAIT: Wait until function execution is completed
877 * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask
878 */
879#define SCF_WAIT (1U << 0)
880#define SCF_RUN_LOCAL (1U << 1)
881
882static void smp_call_function_many_cond(const struct cpumask *mask,
883 smp_call_func_t func, void *info,
884 unsigned int scf_flags,
885 smp_cond_func_t cond_func)
886{
887 int cpu, last_cpu, this_cpu = smp_processor_id();
888 struct call_function_data *cfd;
889 bool wait = scf_flags & SCF_WAIT;
890 bool run_remote = false;
891 bool run_local = false;
892 int nr_cpus = 0;
893
894 lockdep_assert_preemption_disabled();
895
896 /*
897 * Can deadlock when called with interrupts disabled.
898 * We allow cpu's that are not yet online though, as no one else can
899 * send smp call function interrupt to this cpu and as such deadlocks
900 * can't happen.
901 */
902 if (cpu_online(this_cpu) && !oops_in_progress &&
903 !early_boot_irqs_disabled)
904 lockdep_assert_irqs_enabled();
905
906 /*
907 * When @wait we can deadlock when we interrupt between llist_add() and
908 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
909 * csd_lock() on because the interrupt context uses the same csd
910 * storage.
911 */
912 WARN_ON_ONCE(!in_task());
913
914 /* Check if we need local execution. */
915 if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask))
916 run_local = true;
917
918 /* Check if we need remote execution, i.e., any CPU excluding this one. */
919 cpu = cpumask_first_and(mask, cpu_online_mask);
920 if (cpu == this_cpu)
921 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
922 if (cpu < nr_cpu_ids)
923 run_remote = true;
924
925 if (run_remote) {
926 cfd = this_cpu_ptr(&cfd_data);
927 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
928 __cpumask_clear_cpu(this_cpu, cfd->cpumask);
929
930 cpumask_clear(cfd->cpumask_ipi);
931 for_each_cpu(cpu, cfd->cpumask) {
932 struct cfd_percpu *pcpu = per_cpu_ptr(cfd->pcpu, cpu);
933 call_single_data_t *csd = &pcpu->csd;
934
935 if (cond_func && !cond_func(cpu, info))
936 continue;
937
938 csd_lock(csd);
939 if (wait)
940 csd->node.u_flags |= CSD_TYPE_SYNC;
941 csd->func = func;
942 csd->info = info;
943#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
944 csd->node.src = smp_processor_id();
945 csd->node.dst = cpu;
946#endif
947 cfd_seq_store(pcpu->seq_queue, this_cpu, cpu, CFD_SEQ_QUEUE);
948 if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) {
949 __cpumask_set_cpu(cpu, cfd->cpumask_ipi);
950 nr_cpus++;
951 last_cpu = cpu;
952
953 cfd_seq_store(pcpu->seq_ipi, this_cpu, cpu, CFD_SEQ_IPI);
954 } else {
955 cfd_seq_store(pcpu->seq_noipi, this_cpu, cpu, CFD_SEQ_NOIPI);
956 }
957 }
958
959 cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->ping, this_cpu, CFD_SEQ_NOCPU, CFD_SEQ_PING);
960
961 /*
962 * Choose the most efficient way to send an IPI. Note that the
963 * number of CPUs might be zero due to concurrent changes to the
964 * provided mask.
965 */
966 if (nr_cpus == 1)
967 send_call_function_single_ipi(last_cpu);
968 else if (likely(nr_cpus > 1))
969 arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
970
971 cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->pinged, this_cpu, CFD_SEQ_NOCPU, CFD_SEQ_PINGED);
972 }
973
974 if (run_local && (!cond_func || cond_func(this_cpu, info))) {
975 unsigned long flags;
976
977 local_irq_save(flags);
978 func(info);
979 local_irq_restore(flags);
980 }
981
982 if (run_remote && wait) {
983 for_each_cpu(cpu, cfd->cpumask) {
984 call_single_data_t *csd;
985
986 csd = &per_cpu_ptr(cfd->pcpu, cpu)->csd;
987 csd_lock_wait(csd);
988 }
989 }
990}
991
992/**
993 * smp_call_function_many(): Run a function on a set of CPUs.
994 * @mask: The set of cpus to run on (only runs on online subset).
995 * @func: The function to run. This must be fast and non-blocking.
996 * @info: An arbitrary pointer to pass to the function.
997 * @wait: Bitmask that controls the operation. If %SCF_WAIT is set, wait
998 * (atomically) until function has completed on other CPUs. If
999 * %SCF_RUN_LOCAL is set, the function will also be run locally
1000 * if the local CPU is set in the @cpumask.
1001 *
1002 * If @wait is true, then returns once @func has returned.
1003 *
1004 * You must not call this function with disabled interrupts or from a
1005 * hardware interrupt handler or from a bottom half handler. Preemption
1006 * must be disabled when calling this function.
1007 */
1008void smp_call_function_many(const struct cpumask *mask,
1009 smp_call_func_t func, void *info, bool wait)
1010{
1011 smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL);
1012}
1013EXPORT_SYMBOL(smp_call_function_many);
1014
1015/**
1016 * smp_call_function(): Run a function on all other CPUs.
1017 * @func: The function to run. This must be fast and non-blocking.
1018 * @info: An arbitrary pointer to pass to the function.
1019 * @wait: If true, wait (atomically) until function has completed
1020 * on other CPUs.
1021 *
1022 * Returns 0.
1023 *
1024 * If @wait is true, then returns once @func has returned; otherwise
1025 * it returns just before the target cpu calls @func.
1026 *
1027 * You must not call this function with disabled interrupts or from a
1028 * hardware interrupt handler or from a bottom half handler.
1029 */
1030void smp_call_function(smp_call_func_t func, void *info, int wait)
1031{
1032 preempt_disable();
1033 smp_call_function_many(cpu_online_mask, func, info, wait);
1034 preempt_enable();
1035}
1036EXPORT_SYMBOL(smp_call_function);
1037
1038/* Setup configured maximum number of CPUs to activate */
1039unsigned int setup_max_cpus = NR_CPUS;
1040EXPORT_SYMBOL(setup_max_cpus);
1041
1042
1043/*
1044 * Setup routine for controlling SMP activation
1045 *
1046 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
1047 * activation entirely (the MPS table probe still happens, though).
1048 *
1049 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
1050 * greater than 0, limits the maximum number of CPUs activated in
1051 * SMP mode to <NUM>.
1052 */
1053
1054void __weak arch_disable_smp_support(void) { }
1055
1056static int __init nosmp(char *str)
1057{
1058 setup_max_cpus = 0;
1059 arch_disable_smp_support();
1060
1061 return 0;
1062}
1063
1064early_param("nosmp", nosmp);
1065
1066/* this is hard limit */
1067static int __init nrcpus(char *str)
1068{
1069 int nr_cpus;
1070
1071 if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids)
1072 set_nr_cpu_ids(nr_cpus);
1073
1074 return 0;
1075}
1076
1077early_param("nr_cpus", nrcpus);
1078
1079static int __init maxcpus(char *str)
1080{
1081 get_option(&str, &setup_max_cpus);
1082 if (setup_max_cpus == 0)
1083 arch_disable_smp_support();
1084
1085 return 0;
1086}
1087
1088early_param("maxcpus", maxcpus);
1089
1090#if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS)
1091/* Setup number of possible processor ids */
1092unsigned int nr_cpu_ids __read_mostly = NR_CPUS;
1093EXPORT_SYMBOL(nr_cpu_ids);
1094#endif
1095
1096/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
1097void __init setup_nr_cpu_ids(void)
1098{
1099 set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1);
1100}
1101
1102/* Called by boot processor to activate the rest. */
1103void __init smp_init(void)
1104{
1105 int num_nodes, num_cpus;
1106
1107 idle_threads_init();
1108 cpuhp_threads_init();
1109
1110 pr_info("Bringing up secondary CPUs ...\n");
1111
1112 bringup_nonboot_cpus(setup_max_cpus);
1113
1114 num_nodes = num_online_nodes();
1115 num_cpus = num_online_cpus();
1116 pr_info("Brought up %d node%s, %d CPU%s\n",
1117 num_nodes, (num_nodes > 1 ? "s" : ""),
1118 num_cpus, (num_cpus > 1 ? "s" : ""));
1119
1120 /* Any cleanup work */
1121 smp_cpus_done(setup_max_cpus);
1122}
1123
1124/*
1125 * on_each_cpu_cond(): Call a function on each processor for which
1126 * the supplied function cond_func returns true, optionally waiting
1127 * for all the required CPUs to finish. This may include the local
1128 * processor.
1129 * @cond_func: A callback function that is passed a cpu id and
1130 * the info parameter. The function is called
1131 * with preemption disabled. The function should
1132 * return a blooean value indicating whether to IPI
1133 * the specified CPU.
1134 * @func: The function to run on all applicable CPUs.
1135 * This must be fast and non-blocking.
1136 * @info: An arbitrary pointer to pass to both functions.
1137 * @wait: If true, wait (atomically) until function has
1138 * completed on other CPUs.
1139 *
1140 * Preemption is disabled to protect against CPUs going offline but not online.
1141 * CPUs going online during the call will not be seen or sent an IPI.
1142 *
1143 * You must not call this function with disabled interrupts or
1144 * from a hardware interrupt handler or from a bottom half handler.
1145 */
1146void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
1147 void *info, bool wait, const struct cpumask *mask)
1148{
1149 unsigned int scf_flags = SCF_RUN_LOCAL;
1150
1151 if (wait)
1152 scf_flags |= SCF_WAIT;
1153
1154 preempt_disable();
1155 smp_call_function_many_cond(mask, func, info, scf_flags, cond_func);
1156 preempt_enable();
1157}
1158EXPORT_SYMBOL(on_each_cpu_cond_mask);
1159
1160static void do_nothing(void *unused)
1161{
1162}
1163
1164/**
1165 * kick_all_cpus_sync - Force all cpus out of idle
1166 *
1167 * Used to synchronize the update of pm_idle function pointer. It's
1168 * called after the pointer is updated and returns after the dummy
1169 * callback function has been executed on all cpus. The execution of
1170 * the function can only happen on the remote cpus after they have
1171 * left the idle function which had been called via pm_idle function
1172 * pointer. So it's guaranteed that nothing uses the previous pointer
1173 * anymore.
1174 */
1175void kick_all_cpus_sync(void)
1176{
1177 /* Make sure the change is visible before we kick the cpus */
1178 smp_mb();
1179 smp_call_function(do_nothing, NULL, 1);
1180}
1181EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
1182
1183/**
1184 * wake_up_all_idle_cpus - break all cpus out of idle
1185 * wake_up_all_idle_cpus try to break all cpus which is in idle state even
1186 * including idle polling cpus, for non-idle cpus, we will do nothing
1187 * for them.
1188 */
1189void wake_up_all_idle_cpus(void)
1190{
1191 int cpu;
1192
1193 for_each_possible_cpu(cpu) {
1194 preempt_disable();
1195 if (cpu != smp_processor_id() && cpu_online(cpu))
1196 wake_up_if_idle(cpu);
1197 preempt_enable();
1198 }
1199}
1200EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
1201
1202/**
1203 * struct smp_call_on_cpu_struct - Call a function on a specific CPU
1204 * @work: &work_struct
1205 * @done: &completion to signal
1206 * @func: function to call
1207 * @data: function's data argument
1208 * @ret: return value from @func
1209 * @cpu: target CPU (%-1 for any CPU)
1210 *
1211 * Used to call a function on a specific cpu and wait for it to return.
1212 * Optionally make sure the call is done on a specified physical cpu via vcpu
1213 * pinning in order to support virtualized environments.
1214 */
1215struct smp_call_on_cpu_struct {
1216 struct work_struct work;
1217 struct completion done;
1218 int (*func)(void *);
1219 void *data;
1220 int ret;
1221 int cpu;
1222};
1223
1224static void smp_call_on_cpu_callback(struct work_struct *work)
1225{
1226 struct smp_call_on_cpu_struct *sscs;
1227
1228 sscs = container_of(work, struct smp_call_on_cpu_struct, work);
1229 if (sscs->cpu >= 0)
1230 hypervisor_pin_vcpu(sscs->cpu);
1231 sscs->ret = sscs->func(sscs->data);
1232 if (sscs->cpu >= 0)
1233 hypervisor_pin_vcpu(-1);
1234
1235 complete(&sscs->done);
1236}
1237
1238int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
1239{
1240 struct smp_call_on_cpu_struct sscs = {
1241 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done),
1242 .func = func,
1243 .data = par,
1244 .cpu = phys ? cpu : -1,
1245 };
1246
1247 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
1248
1249 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
1250 return -ENXIO;
1251
1252 queue_work_on(cpu, system_wq, &sscs.work);
1253 wait_for_completion(&sscs.done);
1254
1255 return sscs.ret;
1256}
1257EXPORT_SYMBOL_GPL(smp_call_on_cpu);
1/*
2 * Generic helpers for smp ipi calls
3 *
4 * (C) Jens Axboe <jens.axboe@oracle.com> 2008
5 */
6
7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8
9#include <linux/irq_work.h>
10#include <linux/rcupdate.h>
11#include <linux/rculist.h>
12#include <linux/kernel.h>
13#include <linux/export.h>
14#include <linux/percpu.h>
15#include <linux/init.h>
16#include <linux/gfp.h>
17#include <linux/smp.h>
18#include <linux/cpu.h>
19#include <linux/sched.h>
20#include <linux/hypervisor.h>
21
22#include "smpboot.h"
23
24enum {
25 CSD_FLAG_LOCK = 0x01,
26 CSD_FLAG_SYNCHRONOUS = 0x02,
27};
28
29struct call_function_data {
30 struct call_single_data __percpu *csd;
31 cpumask_var_t cpumask;
32};
33
34static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
35
36static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
37
38static void flush_smp_call_function_queue(bool warn_cpu_offline);
39
40int smpcfd_prepare_cpu(unsigned int cpu)
41{
42 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
43
44 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
45 cpu_to_node(cpu)))
46 return -ENOMEM;
47 cfd->csd = alloc_percpu(struct call_single_data);
48 if (!cfd->csd) {
49 free_cpumask_var(cfd->cpumask);
50 return -ENOMEM;
51 }
52
53 return 0;
54}
55
56int smpcfd_dead_cpu(unsigned int cpu)
57{
58 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
59
60 free_cpumask_var(cfd->cpumask);
61 free_percpu(cfd->csd);
62 return 0;
63}
64
65int smpcfd_dying_cpu(unsigned int cpu)
66{
67 /*
68 * The IPIs for the smp-call-function callbacks queued by other
69 * CPUs might arrive late, either due to hardware latencies or
70 * because this CPU disabled interrupts (inside stop-machine)
71 * before the IPIs were sent. So flush out any pending callbacks
72 * explicitly (without waiting for the IPIs to arrive), to
73 * ensure that the outgoing CPU doesn't go offline with work
74 * still pending.
75 */
76 flush_smp_call_function_queue(false);
77 return 0;
78}
79
80void __init call_function_init(void)
81{
82 int i;
83
84 for_each_possible_cpu(i)
85 init_llist_head(&per_cpu(call_single_queue, i));
86
87 smpcfd_prepare_cpu(smp_processor_id());
88}
89
90/*
91 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
92 *
93 * For non-synchronous ipi calls the csd can still be in use by the
94 * previous function call. For multi-cpu calls its even more interesting
95 * as we'll have to ensure no other cpu is observing our csd.
96 */
97static __always_inline void csd_lock_wait(struct call_single_data *csd)
98{
99 smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK));
100}
101
102static __always_inline void csd_lock(struct call_single_data *csd)
103{
104 csd_lock_wait(csd);
105 csd->flags |= CSD_FLAG_LOCK;
106
107 /*
108 * prevent CPU from reordering the above assignment
109 * to ->flags with any subsequent assignments to other
110 * fields of the specified call_single_data structure:
111 */
112 smp_wmb();
113}
114
115static __always_inline void csd_unlock(struct call_single_data *csd)
116{
117 WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
118
119 /*
120 * ensure we're all done before releasing data:
121 */
122 smp_store_release(&csd->flags, 0);
123}
124
125static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
126
127/*
128 * Insert a previously allocated call_single_data element
129 * for execution on the given CPU. data must already have
130 * ->func, ->info, and ->flags set.
131 */
132static int generic_exec_single(int cpu, struct call_single_data *csd,
133 smp_call_func_t func, void *info)
134{
135 if (cpu == smp_processor_id()) {
136 unsigned long flags;
137
138 /*
139 * We can unlock early even for the synchronous on-stack case,
140 * since we're doing this from the same CPU..
141 */
142 csd_unlock(csd);
143 local_irq_save(flags);
144 func(info);
145 local_irq_restore(flags);
146 return 0;
147 }
148
149
150 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
151 csd_unlock(csd);
152 return -ENXIO;
153 }
154
155 csd->func = func;
156 csd->info = info;
157
158 /*
159 * The list addition should be visible before sending the IPI
160 * handler locks the list to pull the entry off it because of
161 * normal cache coherency rules implied by spinlocks.
162 *
163 * If IPIs can go out of order to the cache coherency protocol
164 * in an architecture, sufficient synchronisation should be added
165 * to arch code to make it appear to obey cache coherency WRT
166 * locking and barrier primitives. Generic code isn't really
167 * equipped to do the right thing...
168 */
169 if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
170 arch_send_call_function_single_ipi(cpu);
171
172 return 0;
173}
174
175/**
176 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
177 *
178 * Invoked by arch to handle an IPI for call function single.
179 * Must be called with interrupts disabled.
180 */
181void generic_smp_call_function_single_interrupt(void)
182{
183 flush_smp_call_function_queue(true);
184}
185
186/**
187 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
188 *
189 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
190 * offline CPU. Skip this check if set to 'false'.
191 *
192 * Flush any pending smp-call-function callbacks queued on this CPU. This is
193 * invoked by the generic IPI handler, as well as by a CPU about to go offline,
194 * to ensure that all pending IPI callbacks are run before it goes completely
195 * offline.
196 *
197 * Loop through the call_single_queue and run all the queued callbacks.
198 * Must be called with interrupts disabled.
199 */
200static void flush_smp_call_function_queue(bool warn_cpu_offline)
201{
202 struct llist_head *head;
203 struct llist_node *entry;
204 struct call_single_data *csd, *csd_next;
205 static bool warned;
206
207 WARN_ON(!irqs_disabled());
208
209 head = this_cpu_ptr(&call_single_queue);
210 entry = llist_del_all(head);
211 entry = llist_reverse_order(entry);
212
213 /* There shouldn't be any pending callbacks on an offline CPU. */
214 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
215 !warned && !llist_empty(head))) {
216 warned = true;
217 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
218
219 /*
220 * We don't have to use the _safe() variant here
221 * because we are not invoking the IPI handlers yet.
222 */
223 llist_for_each_entry(csd, entry, llist)
224 pr_warn("IPI callback %pS sent to offline CPU\n",
225 csd->func);
226 }
227
228 llist_for_each_entry_safe(csd, csd_next, entry, llist) {
229 smp_call_func_t func = csd->func;
230 void *info = csd->info;
231
232 /* Do we wait until *after* callback? */
233 if (csd->flags & CSD_FLAG_SYNCHRONOUS) {
234 func(info);
235 csd_unlock(csd);
236 } else {
237 csd_unlock(csd);
238 func(info);
239 }
240 }
241
242 /*
243 * Handle irq works queued remotely by irq_work_queue_on().
244 * Smp functions above are typically synchronous so they
245 * better run first since some other CPUs may be busy waiting
246 * for them.
247 */
248 irq_work_run();
249}
250
251/*
252 * smp_call_function_single - Run a function on a specific CPU
253 * @func: The function to run. This must be fast and non-blocking.
254 * @info: An arbitrary pointer to pass to the function.
255 * @wait: If true, wait until function has completed on other CPUs.
256 *
257 * Returns 0 on success, else a negative status code.
258 */
259int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
260 int wait)
261{
262 struct call_single_data *csd;
263 struct call_single_data csd_stack = { .flags = CSD_FLAG_LOCK | CSD_FLAG_SYNCHRONOUS };
264 int this_cpu;
265 int err;
266
267 /*
268 * prevent preemption and reschedule on another processor,
269 * as well as CPU removal
270 */
271 this_cpu = get_cpu();
272
273 /*
274 * Can deadlock when called with interrupts disabled.
275 * We allow cpu's that are not yet online though, as no one else can
276 * send smp call function interrupt to this cpu and as such deadlocks
277 * can't happen.
278 */
279 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
280 && !oops_in_progress);
281
282 csd = &csd_stack;
283 if (!wait) {
284 csd = this_cpu_ptr(&csd_data);
285 csd_lock(csd);
286 }
287
288 err = generic_exec_single(cpu, csd, func, info);
289
290 if (wait)
291 csd_lock_wait(csd);
292
293 put_cpu();
294
295 return err;
296}
297EXPORT_SYMBOL(smp_call_function_single);
298
299/**
300 * smp_call_function_single_async(): Run an asynchronous function on a
301 * specific CPU.
302 * @cpu: The CPU to run on.
303 * @csd: Pre-allocated and setup data structure
304 *
305 * Like smp_call_function_single(), but the call is asynchonous and
306 * can thus be done from contexts with disabled interrupts.
307 *
308 * The caller passes his own pre-allocated data structure
309 * (ie: embedded in an object) and is responsible for synchronizing it
310 * such that the IPIs performed on the @csd are strictly serialized.
311 *
312 * NOTE: Be careful, there is unfortunately no current debugging facility to
313 * validate the correctness of this serialization.
314 */
315int smp_call_function_single_async(int cpu, struct call_single_data *csd)
316{
317 int err = 0;
318
319 preempt_disable();
320
321 /* We could deadlock if we have to wait here with interrupts disabled! */
322 if (WARN_ON_ONCE(csd->flags & CSD_FLAG_LOCK))
323 csd_lock_wait(csd);
324
325 csd->flags = CSD_FLAG_LOCK;
326 smp_wmb();
327
328 err = generic_exec_single(cpu, csd, csd->func, csd->info);
329 preempt_enable();
330
331 return err;
332}
333EXPORT_SYMBOL_GPL(smp_call_function_single_async);
334
335/*
336 * smp_call_function_any - Run a function on any of the given cpus
337 * @mask: The mask of cpus it can run on.
338 * @func: The function to run. This must be fast and non-blocking.
339 * @info: An arbitrary pointer to pass to the function.
340 * @wait: If true, wait until function has completed.
341 *
342 * Returns 0 on success, else a negative status code (if no cpus were online).
343 *
344 * Selection preference:
345 * 1) current cpu if in @mask
346 * 2) any cpu of current node if in @mask
347 * 3) any other online cpu in @mask
348 */
349int smp_call_function_any(const struct cpumask *mask,
350 smp_call_func_t func, void *info, int wait)
351{
352 unsigned int cpu;
353 const struct cpumask *nodemask;
354 int ret;
355
356 /* Try for same CPU (cheapest) */
357 cpu = get_cpu();
358 if (cpumask_test_cpu(cpu, mask))
359 goto call;
360
361 /* Try for same node. */
362 nodemask = cpumask_of_node(cpu_to_node(cpu));
363 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
364 cpu = cpumask_next_and(cpu, nodemask, mask)) {
365 if (cpu_online(cpu))
366 goto call;
367 }
368
369 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
370 cpu = cpumask_any_and(mask, cpu_online_mask);
371call:
372 ret = smp_call_function_single(cpu, func, info, wait);
373 put_cpu();
374 return ret;
375}
376EXPORT_SYMBOL_GPL(smp_call_function_any);
377
378/**
379 * smp_call_function_many(): Run a function on a set of other CPUs.
380 * @mask: The set of cpus to run on (only runs on online subset).
381 * @func: The function to run. This must be fast and non-blocking.
382 * @info: An arbitrary pointer to pass to the function.
383 * @wait: If true, wait (atomically) until function has completed
384 * on other CPUs.
385 *
386 * If @wait is true, then returns once @func has returned.
387 *
388 * You must not call this function with disabled interrupts or from a
389 * hardware interrupt handler or from a bottom half handler. Preemption
390 * must be disabled when calling this function.
391 */
392void smp_call_function_many(const struct cpumask *mask,
393 smp_call_func_t func, void *info, bool wait)
394{
395 struct call_function_data *cfd;
396 int cpu, next_cpu, this_cpu = smp_processor_id();
397
398 /*
399 * Can deadlock when called with interrupts disabled.
400 * We allow cpu's that are not yet online though, as no one else can
401 * send smp call function interrupt to this cpu and as such deadlocks
402 * can't happen.
403 */
404 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
405 && !oops_in_progress && !early_boot_irqs_disabled);
406
407 /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
408 cpu = cpumask_first_and(mask, cpu_online_mask);
409 if (cpu == this_cpu)
410 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
411
412 /* No online cpus? We're done. */
413 if (cpu >= nr_cpu_ids)
414 return;
415
416 /* Do we have another CPU which isn't us? */
417 next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
418 if (next_cpu == this_cpu)
419 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
420
421 /* Fastpath: do that cpu by itself. */
422 if (next_cpu >= nr_cpu_ids) {
423 smp_call_function_single(cpu, func, info, wait);
424 return;
425 }
426
427 cfd = this_cpu_ptr(&cfd_data);
428
429 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
430 cpumask_clear_cpu(this_cpu, cfd->cpumask);
431
432 /* Some callers race with other cpus changing the passed mask */
433 if (unlikely(!cpumask_weight(cfd->cpumask)))
434 return;
435
436 for_each_cpu(cpu, cfd->cpumask) {
437 struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
438
439 csd_lock(csd);
440 if (wait)
441 csd->flags |= CSD_FLAG_SYNCHRONOUS;
442 csd->func = func;
443 csd->info = info;
444 llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
445 }
446
447 /* Send a message to all CPUs in the map */
448 arch_send_call_function_ipi_mask(cfd->cpumask);
449
450 if (wait) {
451 for_each_cpu(cpu, cfd->cpumask) {
452 struct call_single_data *csd;
453
454 csd = per_cpu_ptr(cfd->csd, cpu);
455 csd_lock_wait(csd);
456 }
457 }
458}
459EXPORT_SYMBOL(smp_call_function_many);
460
461/**
462 * smp_call_function(): Run a function on all other CPUs.
463 * @func: The function to run. This must be fast and non-blocking.
464 * @info: An arbitrary pointer to pass to the function.
465 * @wait: If true, wait (atomically) until function has completed
466 * on other CPUs.
467 *
468 * Returns 0.
469 *
470 * If @wait is true, then returns once @func has returned; otherwise
471 * it returns just before the target cpu calls @func.
472 *
473 * You must not call this function with disabled interrupts or from a
474 * hardware interrupt handler or from a bottom half handler.
475 */
476int smp_call_function(smp_call_func_t func, void *info, int wait)
477{
478 preempt_disable();
479 smp_call_function_many(cpu_online_mask, func, info, wait);
480 preempt_enable();
481
482 return 0;
483}
484EXPORT_SYMBOL(smp_call_function);
485
486/* Setup configured maximum number of CPUs to activate */
487unsigned int setup_max_cpus = NR_CPUS;
488EXPORT_SYMBOL(setup_max_cpus);
489
490
491/*
492 * Setup routine for controlling SMP activation
493 *
494 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
495 * activation entirely (the MPS table probe still happens, though).
496 *
497 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
498 * greater than 0, limits the maximum number of CPUs activated in
499 * SMP mode to <NUM>.
500 */
501
502void __weak arch_disable_smp_support(void) { }
503
504static int __init nosmp(char *str)
505{
506 setup_max_cpus = 0;
507 arch_disable_smp_support();
508
509 return 0;
510}
511
512early_param("nosmp", nosmp);
513
514/* this is hard limit */
515static int __init nrcpus(char *str)
516{
517 int nr_cpus;
518
519 get_option(&str, &nr_cpus);
520 if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
521 nr_cpu_ids = nr_cpus;
522
523 return 0;
524}
525
526early_param("nr_cpus", nrcpus);
527
528static int __init maxcpus(char *str)
529{
530 get_option(&str, &setup_max_cpus);
531 if (setup_max_cpus == 0)
532 arch_disable_smp_support();
533
534 return 0;
535}
536
537early_param("maxcpus", maxcpus);
538
539/* Setup number of possible processor ids */
540int nr_cpu_ids __read_mostly = NR_CPUS;
541EXPORT_SYMBOL(nr_cpu_ids);
542
543/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
544void __init setup_nr_cpu_ids(void)
545{
546 nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
547}
548
549/* Called by boot processor to activate the rest. */
550void __init smp_init(void)
551{
552 int num_nodes, num_cpus;
553 unsigned int cpu;
554
555 idle_threads_init();
556 cpuhp_threads_init();
557
558 pr_info("Bringing up secondary CPUs ...\n");
559
560 /* FIXME: This should be done in userspace --RR */
561 for_each_present_cpu(cpu) {
562 if (num_online_cpus() >= setup_max_cpus)
563 break;
564 if (!cpu_online(cpu))
565 cpu_up(cpu);
566 }
567
568 num_nodes = num_online_nodes();
569 num_cpus = num_online_cpus();
570 pr_info("Brought up %d node%s, %d CPU%s\n",
571 num_nodes, (num_nodes > 1 ? "s" : ""),
572 num_cpus, (num_cpus > 1 ? "s" : ""));
573
574 /* Any cleanup work */
575 smp_cpus_done(setup_max_cpus);
576}
577
578/*
579 * Call a function on all processors. May be used during early boot while
580 * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
581 * of local_irq_disable/enable().
582 */
583int on_each_cpu(void (*func) (void *info), void *info, int wait)
584{
585 unsigned long flags;
586 int ret = 0;
587
588 preempt_disable();
589 ret = smp_call_function(func, info, wait);
590 local_irq_save(flags);
591 func(info);
592 local_irq_restore(flags);
593 preempt_enable();
594 return ret;
595}
596EXPORT_SYMBOL(on_each_cpu);
597
598/**
599 * on_each_cpu_mask(): Run a function on processors specified by
600 * cpumask, which may include the local processor.
601 * @mask: The set of cpus to run on (only runs on online subset).
602 * @func: The function to run. This must be fast and non-blocking.
603 * @info: An arbitrary pointer to pass to the function.
604 * @wait: If true, wait (atomically) until function has completed
605 * on other CPUs.
606 *
607 * If @wait is true, then returns once @func has returned.
608 *
609 * You must not call this function with disabled interrupts or from a
610 * hardware interrupt handler or from a bottom half handler. The
611 * exception is that it may be used during early boot while
612 * early_boot_irqs_disabled is set.
613 */
614void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
615 void *info, bool wait)
616{
617 int cpu = get_cpu();
618
619 smp_call_function_many(mask, func, info, wait);
620 if (cpumask_test_cpu(cpu, mask)) {
621 unsigned long flags;
622 local_irq_save(flags);
623 func(info);
624 local_irq_restore(flags);
625 }
626 put_cpu();
627}
628EXPORT_SYMBOL(on_each_cpu_mask);
629
630/*
631 * on_each_cpu_cond(): Call a function on each processor for which
632 * the supplied function cond_func returns true, optionally waiting
633 * for all the required CPUs to finish. This may include the local
634 * processor.
635 * @cond_func: A callback function that is passed a cpu id and
636 * the the info parameter. The function is called
637 * with preemption disabled. The function should
638 * return a blooean value indicating whether to IPI
639 * the specified CPU.
640 * @func: The function to run on all applicable CPUs.
641 * This must be fast and non-blocking.
642 * @info: An arbitrary pointer to pass to both functions.
643 * @wait: If true, wait (atomically) until function has
644 * completed on other CPUs.
645 * @gfp_flags: GFP flags to use when allocating the cpumask
646 * used internally by the function.
647 *
648 * The function might sleep if the GFP flags indicates a non
649 * atomic allocation is allowed.
650 *
651 * Preemption is disabled to protect against CPUs going offline but not online.
652 * CPUs going online during the call will not be seen or sent an IPI.
653 *
654 * You must not call this function with disabled interrupts or
655 * from a hardware interrupt handler or from a bottom half handler.
656 */
657void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
658 smp_call_func_t func, void *info, bool wait,
659 gfp_t gfp_flags)
660{
661 cpumask_var_t cpus;
662 int cpu, ret;
663
664 might_sleep_if(gfpflags_allow_blocking(gfp_flags));
665
666 if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
667 preempt_disable();
668 for_each_online_cpu(cpu)
669 if (cond_func(cpu, info))
670 cpumask_set_cpu(cpu, cpus);
671 on_each_cpu_mask(cpus, func, info, wait);
672 preempt_enable();
673 free_cpumask_var(cpus);
674 } else {
675 /*
676 * No free cpumask, bother. No matter, we'll
677 * just have to IPI them one by one.
678 */
679 preempt_disable();
680 for_each_online_cpu(cpu)
681 if (cond_func(cpu, info)) {
682 ret = smp_call_function_single(cpu, func,
683 info, wait);
684 WARN_ON_ONCE(ret);
685 }
686 preempt_enable();
687 }
688}
689EXPORT_SYMBOL(on_each_cpu_cond);
690
691static void do_nothing(void *unused)
692{
693}
694
695/**
696 * kick_all_cpus_sync - Force all cpus out of idle
697 *
698 * Used to synchronize the update of pm_idle function pointer. It's
699 * called after the pointer is updated and returns after the dummy
700 * callback function has been executed on all cpus. The execution of
701 * the function can only happen on the remote cpus after they have
702 * left the idle function which had been called via pm_idle function
703 * pointer. So it's guaranteed that nothing uses the previous pointer
704 * anymore.
705 */
706void kick_all_cpus_sync(void)
707{
708 /* Make sure the change is visible before we kick the cpus */
709 smp_mb();
710 smp_call_function(do_nothing, NULL, 1);
711}
712EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
713
714/**
715 * wake_up_all_idle_cpus - break all cpus out of idle
716 * wake_up_all_idle_cpus try to break all cpus which is in idle state even
717 * including idle polling cpus, for non-idle cpus, we will do nothing
718 * for them.
719 */
720void wake_up_all_idle_cpus(void)
721{
722 int cpu;
723
724 preempt_disable();
725 for_each_online_cpu(cpu) {
726 if (cpu == smp_processor_id())
727 continue;
728
729 wake_up_if_idle(cpu);
730 }
731 preempt_enable();
732}
733EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
734
735/**
736 * smp_call_on_cpu - Call a function on a specific cpu
737 *
738 * Used to call a function on a specific cpu and wait for it to return.
739 * Optionally make sure the call is done on a specified physical cpu via vcpu
740 * pinning in order to support virtualized environments.
741 */
742struct smp_call_on_cpu_struct {
743 struct work_struct work;
744 struct completion done;
745 int (*func)(void *);
746 void *data;
747 int ret;
748 int cpu;
749};
750
751static void smp_call_on_cpu_callback(struct work_struct *work)
752{
753 struct smp_call_on_cpu_struct *sscs;
754
755 sscs = container_of(work, struct smp_call_on_cpu_struct, work);
756 if (sscs->cpu >= 0)
757 hypervisor_pin_vcpu(sscs->cpu);
758 sscs->ret = sscs->func(sscs->data);
759 if (sscs->cpu >= 0)
760 hypervisor_pin_vcpu(-1);
761
762 complete(&sscs->done);
763}
764
765int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
766{
767 struct smp_call_on_cpu_struct sscs = {
768 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done),
769 .func = func,
770 .data = par,
771 .cpu = phys ? cpu : -1,
772 };
773
774 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
775
776 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
777 return -ENXIO;
778
779 queue_work_on(cpu, system_wq, &sscs.work);
780 wait_for_completion(&sscs.done);
781
782 return sscs.ret;
783}
784EXPORT_SYMBOL_GPL(smp_call_on_cpu);