bnxt_en: Fix NULL ptr dereference crash in bnxt_fw_reset_task()
[linux/fpc-iii.git] / kernel / stop_machine.c
blob998d50ee2d9bbb0856a1a374279dfb170db751a2
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * kernel/stop_machine.c
5 * Copyright (C) 2008, 2005 IBM Corporation.
6 * Copyright (C) 2008, 2005 Rusty Russell rusty@rustcorp.com.au
7 * Copyright (C) 2010 SUSE Linux Products GmbH
8 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
9 */
10 #include <linux/compiler.h>
11 #include <linux/completion.h>
12 #include <linux/cpu.h>
13 #include <linux/init.h>
14 #include <linux/kthread.h>
15 #include <linux/export.h>
16 #include <linux/percpu.h>
17 #include <linux/sched.h>
18 #include <linux/stop_machine.h>
19 #include <linux/interrupt.h>
20 #include <linux/kallsyms.h>
21 #include <linux/smpboot.h>
22 #include <linux/atomic.h>
23 #include <linux/nmi.h>
24 #include <linux/sched/wake_q.h>
27 * Structure to determine completion condition and record errors. May
28 * be shared by works on different cpus.
30 struct cpu_stop_done {
31 atomic_t nr_todo; /* nr left to execute */
32 int ret; /* collected return value */
33 struct completion completion; /* fired if nr_todo reaches 0 */
36 /* the actual stopper, one per every possible cpu, enabled on online cpus */
37 struct cpu_stopper {
38 struct task_struct *thread;
40 raw_spinlock_t lock;
41 bool enabled; /* is this stopper enabled? */
42 struct list_head works; /* list of pending works */
44 struct cpu_stop_work stop_work; /* for stop_cpus */
47 static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
48 static bool stop_machine_initialized = false;
50 /* static data for stop_cpus */
51 static DEFINE_MUTEX(stop_cpus_mutex);
52 static bool stop_cpus_in_progress;
54 static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
56 memset(done, 0, sizeof(*done));
57 atomic_set(&done->nr_todo, nr_todo);
58 init_completion(&done->completion);
61 /* signal completion unless @done is NULL */
62 static void cpu_stop_signal_done(struct cpu_stop_done *done)
64 if (atomic_dec_and_test(&done->nr_todo))
65 complete(&done->completion);
68 static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
69 struct cpu_stop_work *work,
70 struct wake_q_head *wakeq)
72 list_add_tail(&work->list, &stopper->works);
73 wake_q_add(wakeq, stopper->thread);
76 /* queue @work to @stopper. if offline, @work is completed immediately */
77 static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
79 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
80 DEFINE_WAKE_Q(wakeq);
81 unsigned long flags;
82 bool enabled;
84 preempt_disable();
85 raw_spin_lock_irqsave(&stopper->lock, flags);
86 enabled = stopper->enabled;
87 if (enabled)
88 __cpu_stop_queue_work(stopper, work, &wakeq);
89 else if (work->done)
90 cpu_stop_signal_done(work->done);
91 raw_spin_unlock_irqrestore(&stopper->lock, flags);
93 wake_up_q(&wakeq);
94 preempt_enable();
96 return enabled;
99 /**
100 * stop_one_cpu - stop a cpu
101 * @cpu: cpu to stop
102 * @fn: function to execute
103 * @arg: argument to @fn
105 * Execute @fn(@arg) on @cpu. @fn is run in a process context with
106 * the highest priority preempting any task on the cpu and
107 * monopolizing it. This function returns after the execution is
108 * complete.
110 * This function doesn't guarantee @cpu stays online till @fn
111 * completes. If @cpu goes down in the middle, execution may happen
112 * partially or fully on different cpus. @fn should either be ready
113 * for that or the caller should ensure that @cpu stays online until
114 * this function completes.
116 * CONTEXT:
117 * Might sleep.
119 * RETURNS:
120 * -ENOENT if @fn(@arg) was not executed because @cpu was offline;
121 * otherwise, the return value of @fn.
123 int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
125 struct cpu_stop_done done;
126 struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };
128 cpu_stop_init_done(&done, 1);
129 if (!cpu_stop_queue_work(cpu, &work))
130 return -ENOENT;
132 * In case @cpu == smp_proccessor_id() we can avoid a sleep+wakeup
133 * cycle by doing a preemption:
135 cond_resched();
136 wait_for_completion(&done.completion);
137 return done.ret;
140 /* This controls the threads on each CPU. */
141 enum multi_stop_state {
142 /* Dummy starting state for thread. */
143 MULTI_STOP_NONE,
144 /* Awaiting everyone to be scheduled. */
145 MULTI_STOP_PREPARE,
146 /* Disable interrupts. */
147 MULTI_STOP_DISABLE_IRQ,
148 /* Run the function */
149 MULTI_STOP_RUN,
150 /* Exit */
151 MULTI_STOP_EXIT,
154 struct multi_stop_data {
155 cpu_stop_fn_t fn;
156 void *data;
157 /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
158 unsigned int num_threads;
159 const struct cpumask *active_cpus;
161 enum multi_stop_state state;
162 atomic_t thread_ack;
165 static void set_state(struct multi_stop_data *msdata,
166 enum multi_stop_state newstate)
168 /* Reset ack counter. */
169 atomic_set(&msdata->thread_ack, msdata->num_threads);
170 smp_wmb();
171 WRITE_ONCE(msdata->state, newstate);
174 /* Last one to ack a state moves to the next state. */
175 static void ack_state(struct multi_stop_data *msdata)
177 if (atomic_dec_and_test(&msdata->thread_ack))
178 set_state(msdata, msdata->state + 1);
181 void __weak stop_machine_yield(const struct cpumask *cpumask)
183 cpu_relax();
186 /* This is the cpu_stop function which stops the CPU. */
187 static int multi_cpu_stop(void *data)
189 struct multi_stop_data *msdata = data;
190 enum multi_stop_state newstate, curstate = MULTI_STOP_NONE;
191 int cpu = smp_processor_id(), err = 0;
192 const struct cpumask *cpumask;
193 unsigned long flags;
194 bool is_active;
197 * When called from stop_machine_from_inactive_cpu(), irq might
198 * already be disabled. Save the state and restore it on exit.
200 local_save_flags(flags);
202 if (!msdata->active_cpus) {
203 cpumask = cpu_online_mask;
204 is_active = cpu == cpumask_first(cpumask);
205 } else {
206 cpumask = msdata->active_cpus;
207 is_active = cpumask_test_cpu(cpu, cpumask);
210 /* Simple state machine */
211 do {
212 /* Chill out and ensure we re-read multi_stop_state. */
213 stop_machine_yield(cpumask);
214 newstate = READ_ONCE(msdata->state);
215 if (newstate != curstate) {
216 curstate = newstate;
217 switch (curstate) {
218 case MULTI_STOP_DISABLE_IRQ:
219 local_irq_disable();
220 hard_irq_disable();
221 break;
222 case MULTI_STOP_RUN:
223 if (is_active)
224 err = msdata->fn(msdata->data);
225 break;
226 default:
227 break;
229 ack_state(msdata);
230 } else if (curstate > MULTI_STOP_PREPARE) {
232 * At this stage all other CPUs we depend on must spin
233 * in the same loop. Any reason for hard-lockup should
234 * be detected and reported on their side.
236 touch_nmi_watchdog();
238 } while (curstate != MULTI_STOP_EXIT);
240 local_irq_restore(flags);
241 return err;
244 static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1,
245 int cpu2, struct cpu_stop_work *work2)
247 struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1);
248 struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2);
249 DEFINE_WAKE_Q(wakeq);
250 int err;
252 retry:
254 * The waking up of stopper threads has to happen in the same
255 * scheduling context as the queueing. Otherwise, there is a
256 * possibility of one of the above stoppers being woken up by another
257 * CPU, and preempting us. This will cause us to not wake up the other
258 * stopper forever.
260 preempt_disable();
261 raw_spin_lock_irq(&stopper1->lock);
262 raw_spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING);
264 if (!stopper1->enabled || !stopper2->enabled) {
265 err = -ENOENT;
266 goto unlock;
270 * Ensure that if we race with __stop_cpus() the stoppers won't get
271 * queued up in reverse order leading to system deadlock.
273 * We can't miss stop_cpus_in_progress if queue_stop_cpus_work() has
274 * queued a work on cpu1 but not on cpu2, we hold both locks.
276 * It can be falsely true but it is safe to spin until it is cleared,
277 * queue_stop_cpus_work() does everything under preempt_disable().
279 if (unlikely(stop_cpus_in_progress)) {
280 err = -EDEADLK;
281 goto unlock;
284 err = 0;
285 __cpu_stop_queue_work(stopper1, work1, &wakeq);
286 __cpu_stop_queue_work(stopper2, work2, &wakeq);
288 unlock:
289 raw_spin_unlock(&stopper2->lock);
290 raw_spin_unlock_irq(&stopper1->lock);
292 if (unlikely(err == -EDEADLK)) {
293 preempt_enable();
295 while (stop_cpus_in_progress)
296 cpu_relax();
298 goto retry;
301 wake_up_q(&wakeq);
302 preempt_enable();
304 return err;
307 * stop_two_cpus - stops two cpus
308 * @cpu1: the cpu to stop
309 * @cpu2: the other cpu to stop
310 * @fn: function to execute
311 * @arg: argument to @fn
313 * Stops both the current and specified CPU and runs @fn on one of them.
315 * returns when both are completed.
317 int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg)
319 struct cpu_stop_done done;
320 struct cpu_stop_work work1, work2;
321 struct multi_stop_data msdata;
323 msdata = (struct multi_stop_data){
324 .fn = fn,
325 .data = arg,
326 .num_threads = 2,
327 .active_cpus = cpumask_of(cpu1),
330 work1 = work2 = (struct cpu_stop_work){
331 .fn = multi_cpu_stop,
332 .arg = &msdata,
333 .done = &done
336 cpu_stop_init_done(&done, 2);
337 set_state(&msdata, MULTI_STOP_PREPARE);
339 if (cpu1 > cpu2)
340 swap(cpu1, cpu2);
341 if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2))
342 return -ENOENT;
344 wait_for_completion(&done.completion);
345 return done.ret;
349 * stop_one_cpu_nowait - stop a cpu but don't wait for completion
350 * @cpu: cpu to stop
351 * @fn: function to execute
352 * @arg: argument to @fn
353 * @work_buf: pointer to cpu_stop_work structure
355 * Similar to stop_one_cpu() but doesn't wait for completion. The
356 * caller is responsible for ensuring @work_buf is currently unused
357 * and will remain untouched until stopper starts executing @fn.
359 * CONTEXT:
360 * Don't care.
362 * RETURNS:
363 * true if cpu_stop_work was queued successfully and @fn will be called,
364 * false otherwise.
366 bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
367 struct cpu_stop_work *work_buf)
369 *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };
370 return cpu_stop_queue_work(cpu, work_buf);
373 static bool queue_stop_cpus_work(const struct cpumask *cpumask,
374 cpu_stop_fn_t fn, void *arg,
375 struct cpu_stop_done *done)
377 struct cpu_stop_work *work;
378 unsigned int cpu;
379 bool queued = false;
382 * Disable preemption while queueing to avoid getting
383 * preempted by a stopper which might wait for other stoppers
384 * to enter @fn which can lead to deadlock.
386 preempt_disable();
387 stop_cpus_in_progress = true;
388 barrier();
389 for_each_cpu(cpu, cpumask) {
390 work = &per_cpu(cpu_stopper.stop_work, cpu);
391 work->fn = fn;
392 work->arg = arg;
393 work->done = done;
394 if (cpu_stop_queue_work(cpu, work))
395 queued = true;
397 barrier();
398 stop_cpus_in_progress = false;
399 preempt_enable();
401 return queued;
404 static int __stop_cpus(const struct cpumask *cpumask,
405 cpu_stop_fn_t fn, void *arg)
407 struct cpu_stop_done done;
409 cpu_stop_init_done(&done, cpumask_weight(cpumask));
410 if (!queue_stop_cpus_work(cpumask, fn, arg, &done))
411 return -ENOENT;
412 wait_for_completion(&done.completion);
413 return done.ret;
417 * stop_cpus - stop multiple cpus
418 * @cpumask: cpus to stop
419 * @fn: function to execute
420 * @arg: argument to @fn
422 * Execute @fn(@arg) on online cpus in @cpumask. On each target cpu,
423 * @fn is run in a process context with the highest priority
424 * preempting any task on the cpu and monopolizing it. This function
425 * returns after all executions are complete.
427 * This function doesn't guarantee the cpus in @cpumask stay online
428 * till @fn completes. If some cpus go down in the middle, execution
429 * on the cpu may happen partially or fully on different cpus. @fn
430 * should either be ready for that or the caller should ensure that
431 * the cpus stay online until this function completes.
433 * All stop_cpus() calls are serialized making it safe for @fn to wait
434 * for all cpus to start executing it.
436 * CONTEXT:
437 * Might sleep.
439 * RETURNS:
440 * -ENOENT if @fn(@arg) was not executed at all because all cpus in
441 * @cpumask were offline; otherwise, 0 if all executions of @fn
442 * returned 0, any non zero return value if any returned non zero.
444 int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
446 int ret;
448 /* static works are used, process one request at a time */
449 mutex_lock(&stop_cpus_mutex);
450 ret = __stop_cpus(cpumask, fn, arg);
451 mutex_unlock(&stop_cpus_mutex);
452 return ret;
456 * try_stop_cpus - try to stop multiple cpus
457 * @cpumask: cpus to stop
458 * @fn: function to execute
459 * @arg: argument to @fn
461 * Identical to stop_cpus() except that it fails with -EAGAIN if
462 * someone else is already using the facility.
464 * CONTEXT:
465 * Might sleep.
467 * RETURNS:
468 * -EAGAIN if someone else is already stopping cpus, -ENOENT if
469 * @fn(@arg) was not executed at all because all cpus in @cpumask were
470 * offline; otherwise, 0 if all executions of @fn returned 0, any non
471 * zero return value if any returned non zero.
473 int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
475 int ret;
477 /* static works are used, process one request at a time */
478 if (!mutex_trylock(&stop_cpus_mutex))
479 return -EAGAIN;
480 ret = __stop_cpus(cpumask, fn, arg);
481 mutex_unlock(&stop_cpus_mutex);
482 return ret;
485 static int cpu_stop_should_run(unsigned int cpu)
487 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
488 unsigned long flags;
489 int run;
491 raw_spin_lock_irqsave(&stopper->lock, flags);
492 run = !list_empty(&stopper->works);
493 raw_spin_unlock_irqrestore(&stopper->lock, flags);
494 return run;
497 static void cpu_stopper_thread(unsigned int cpu)
499 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
500 struct cpu_stop_work *work;
502 repeat:
503 work = NULL;
504 raw_spin_lock_irq(&stopper->lock);
505 if (!list_empty(&stopper->works)) {
506 work = list_first_entry(&stopper->works,
507 struct cpu_stop_work, list);
508 list_del_init(&work->list);
510 raw_spin_unlock_irq(&stopper->lock);
512 if (work) {
513 cpu_stop_fn_t fn = work->fn;
514 void *arg = work->arg;
515 struct cpu_stop_done *done = work->done;
516 int ret;
518 /* cpu stop callbacks must not sleep, make in_atomic() == T */
519 preempt_count_inc();
520 ret = fn(arg);
521 if (done) {
522 if (ret)
523 done->ret = ret;
524 cpu_stop_signal_done(done);
526 preempt_count_dec();
527 WARN_ONCE(preempt_count(),
528 "cpu_stop: %ps(%p) leaked preempt count\n", fn, arg);
529 goto repeat;
533 void stop_machine_park(int cpu)
535 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
537 * Lockless. cpu_stopper_thread() will take stopper->lock and flush
538 * the pending works before it parks, until then it is fine to queue
539 * the new works.
541 stopper->enabled = false;
542 kthread_park(stopper->thread);
545 extern void sched_set_stop_task(int cpu, struct task_struct *stop);
547 static void cpu_stop_create(unsigned int cpu)
549 sched_set_stop_task(cpu, per_cpu(cpu_stopper.thread, cpu));
552 static void cpu_stop_park(unsigned int cpu)
554 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
556 WARN_ON(!list_empty(&stopper->works));
559 void stop_machine_unpark(int cpu)
561 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
563 stopper->enabled = true;
564 kthread_unpark(stopper->thread);
567 static struct smp_hotplug_thread cpu_stop_threads = {
568 .store = &cpu_stopper.thread,
569 .thread_should_run = cpu_stop_should_run,
570 .thread_fn = cpu_stopper_thread,
571 .thread_comm = "migration/%u",
572 .create = cpu_stop_create,
573 .park = cpu_stop_park,
574 .selfparking = true,
577 static int __init cpu_stop_init(void)
579 unsigned int cpu;
581 for_each_possible_cpu(cpu) {
582 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
584 raw_spin_lock_init(&stopper->lock);
585 INIT_LIST_HEAD(&stopper->works);
588 BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads));
589 stop_machine_unpark(raw_smp_processor_id());
590 stop_machine_initialized = true;
591 return 0;
593 early_initcall(cpu_stop_init);
595 int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
596 const struct cpumask *cpus)
598 struct multi_stop_data msdata = {
599 .fn = fn,
600 .data = data,
601 .num_threads = num_online_cpus(),
602 .active_cpus = cpus,
605 lockdep_assert_cpus_held();
607 if (!stop_machine_initialized) {
609 * Handle the case where stop_machine() is called
610 * early in boot before stop_machine() has been
611 * initialized.
613 unsigned long flags;
614 int ret;
616 WARN_ON_ONCE(msdata.num_threads != 1);
618 local_irq_save(flags);
619 hard_irq_disable();
620 ret = (*fn)(data);
621 local_irq_restore(flags);
623 return ret;
626 /* Set the initial state and stop all online cpus. */
627 set_state(&msdata, MULTI_STOP_PREPARE);
628 return stop_cpus(cpu_online_mask, multi_cpu_stop, &msdata);
631 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
633 int ret;
635 /* No CPUs can come up or down during this. */
636 cpus_read_lock();
637 ret = stop_machine_cpuslocked(fn, data, cpus);
638 cpus_read_unlock();
639 return ret;
641 EXPORT_SYMBOL_GPL(stop_machine);
644 * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU
645 * @fn: the function to run
646 * @data: the data ptr for the @fn()
647 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
649 * This is identical to stop_machine() but can be called from a CPU which
650 * is not active. The local CPU is in the process of hotplug (so no other
651 * CPU hotplug can start) and not marked active and doesn't have enough
652 * context to sleep.
654 * This function provides stop_machine() functionality for such state by
655 * using busy-wait for synchronization and executing @fn directly for local
656 * CPU.
658 * CONTEXT:
659 * Local CPU is inactive. Temporarily stops all active CPUs.
661 * RETURNS:
662 * 0 if all executions of @fn returned 0, any non zero return value if any
663 * returned non zero.
665 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
666 const struct cpumask *cpus)
668 struct multi_stop_data msdata = { .fn = fn, .data = data,
669 .active_cpus = cpus };
670 struct cpu_stop_done done;
671 int ret;
673 /* Local CPU must be inactive and CPU hotplug in progress. */
674 BUG_ON(cpu_active(raw_smp_processor_id()));
675 msdata.num_threads = num_active_cpus() + 1; /* +1 for local */
677 /* No proper task established and can't sleep - busy wait for lock. */
678 while (!mutex_trylock(&stop_cpus_mutex))
679 cpu_relax();
681 /* Schedule work on other CPUs and execute directly for local CPU */
682 set_state(&msdata, MULTI_STOP_PREPARE);
683 cpu_stop_init_done(&done, num_active_cpus());
684 queue_stop_cpus_work(cpu_active_mask, multi_cpu_stop, &msdata,
685 &done);
686 ret = multi_cpu_stop(&msdata);
688 /* Busy wait for completion. */
689 while (!completion_done(&done.completion))
690 cpu_relax();
692 mutex_unlock(&stop_cpus_mutex);
693 return ret ?: done.ret;