// SPDX-License-Identifier: GPL-2.0-or-later/* * kernel/stop_machine.c * * Copyright (C) 2008, 2005 IBM Corporation. * Copyright (C) 2008, 2005 Rusty Russell rusty@rustcorp.com.au * Copyright (C) 2010 SUSE Linux Products GmbH * Copyright (C) 2010 Tejun Heo <tj@kernel.org> */#include <linux/compiler.h>#include <linux/completion.h>#include <linux/cpu.h>#include <linux/init.h>#include <linux/kthread.h>#include <linux/export.h>#include <linux/percpu.h>#include <linux/sched.h>#include <linux/stop_machine.h>#include <linux/interrupt.h>#include <linux/kallsyms.h>#include <linux/smpboot.h>#include <linux/atomic.h>#include <linux/nmi.h>#include <linux/sched/wake_q.h> /* * Structure to determine completion condition and record errors. May * be shared by works on different cpus. */struct cpu_stop_done { atomic_t nr_todo; /* nr left to execute */ int ret; /* collected return value */ struct completion completion; /* fired if nr_todo reaches 0 */}; /* the actual stopper, one per every possible cpu, enabled on online cpus */struct cpu_stopper { struct task_struct *thread; raw_spinlock_t lock; bool enabled; /* is this stopper enabled? */ struct list_head works; /* list of pending works */ struct cpu_stop_work stop_work; /* for stop_cpus */ unsigned long caller; cpu_stop_fn_t fn;}; static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);static bool stop_machine_initialized = false; void print_stop_info(const char *log_lvl, struct task_struct *task){ /* * If @task is a stopper task, it cannot migrate and task_cpu() is * stable. */ struct cpu_stopper *stopper = per_cpu_ptr(&cpu_stopper, task_cpu(task)); if (task != stopper->thread) return; printk("%sStopper: %pS <- %pS\n", log_lvl, stopper->fn, (void *)stopper->caller);} /* static data for stop_cpus */static DEFINE_MUTEX(stop_cpus_mutex);static bool stop_cpus_in_progress; static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo){ memset(done, 0, sizeof(*done)); atomic_set(&done->nr_todo, nr_todo); init_completion(&done->completion);} /* signal completion unless @done is NULL */static void cpu_stop_signal_done(struct cpu_stop_done *done){ if (atomic_dec_and_test(&done->nr_todo)) complete(&done->completion);} static void __cpu_stop_queue_work(struct cpu_stopper *stopper, struct cpu_stop_work *work, struct wake_q_head *wakeq){ list_add_tail(&work->list, &stopper->works); wake_q_add(wakeq, stopper->thread);} /* queue @work to @stopper. if offline, @work is completed immediately */static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work){ struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); DEFINE_WAKE_Q(wakeq); unsigned long flags; bool enabled; preempt_disable(); raw_spin_lock_irqsave(&stopper->lock, flags); enabled = stopper->enabled; if (enabled) __cpu_stop_queue_work(stopper, work, &wakeq); else if (work->done) cpu_stop_signal_done(work->done); raw_spin_unlock_irqrestore(&stopper->lock, flags); wake_up_q(&wakeq); preempt_enable(); return enabled;} /** * stop_one_cpu - stop a cpu * @cpu: cpu to stop * @fn: function to execute * @arg: argument to @fn * * Execute @fn(@arg) on @cpu. @fn is run in a process context with * the highest priority preempting any task on the cpu and * monopolizing it. This function returns after the execution is * complete. * * This function doesn't guarantee @cpu stays online till @fn * completes. If @cpu goes down in the middle, execution may happen * partially or fully on different cpus. @fn should either be ready * for that or the caller should ensure that @cpu stays online until * this function completes. * * CONTEXT: * Might sleep. * * RETURNS: * -ENOENT if @fn(@arg) was not executed because @cpu was offline; * otherwise, the return value of @fn. */int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg){ struct cpu_stop_done done; struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done, .caller = _RET_IP_ }; cpu_stop_init_done(&done, 1); if (!cpu_stop_queue_work(cpu, &work)) return -ENOENT; /* * In case @cpu == smp_proccessor_id() we can avoid a sleep+wakeup * cycle by doing a preemption: */ cond_resched(); wait_for_completion(&done.completion); return done.ret;} /* This controls the threads on each CPU. */enum multi_stop_state { /* Dummy starting state for thread. */ MULTI_STOP_NONE, /* Awaiting everyone to be scheduled. */ MULTI_STOP_PREPARE, /* Disable interrupts. */ MULTI_STOP_DISABLE_IRQ, /* Run the function */ MULTI_STOP_RUN, /* Exit */ MULTI_STOP_EXIT,}; struct multi_stop_data { cpu_stop_fn_t fn; void *data; /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */ unsigned int num_threads; const struct cpumask *active_cpus; enum multi_stop_state state; atomic_t thread_ack;}; static void set_state(struct multi_stop_data *msdata, enum multi_stop_state newstate){ /* Reset ack counter. */ atomic_set(&msdata->thread_ack, msdata->num_threads); smp_wmb(); WRITE_ONCE(msdata->state, newstate);} /* Last one to ack a state moves to the next state. */static void ack_state(struct multi_stop_data *msdata){ if (atomic_dec_and_test(&msdata->thread_ack)) set_state(msdata, msdata->state + 1);} notrace void __weak stop_machine_yield(const struct cpumask *cpumask){ cpu_relax();} /* This is the cpu_stop function which stops the CPU. */static int multi_cpu_stop(void *data){ struct multi_stop_data *msdata = data; enum multi_stop_state newstate, curstate = MULTI_STOP_NONE; int cpu = smp_processor_id(), err = 0; const struct cpumask *cpumask; unsigned long flags; bool is_active; /* * When called from stop_machine_from_inactive_cpu(), irq might * already be disabled. Save the state and restore it on exit. */ local_save_flags(flags); if (!msdata->active_cpus) { cpumask = cpu_online_mask; is_active = cpu == cpumask_first(cpumask); } else { cpumask = msdata->active_cpus; is_active = cpumask_test_cpu(cpu, cpumask); } /* Simple state machine */ do { /* Chill out and ensure we re-read multi_stop_state. */ stop_machine_yield(cpumask); newstate = READ_ONCE(msdata->state); if (newstate != curstate) { curstate = newstate; switch (curstate) { case MULTI_STOP_DISABLE_IRQ: local_irq_disable(); hard_irq_disable(); break; case MULTI_STOP_RUN: if (is_active) err = msdata->fn(msdata->data); break; default: break; } ack_state(msdata); } else if (curstate > MULTI_STOP_PREPARE) { /* * At this stage all other CPUs we depend on must spin * in the same loop. Any reason for hard-lockup should * be detected and reported on their side. */ touch_nmi_watchdog(); } rcu_momentary_dyntick_idle(); } while (curstate != MULTI_STOP_EXIT); local_irq_restore(flags); return err;} static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1, int cpu2, struct cpu_stop_work *work2){ struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1); struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2); DEFINE_WAKE_Q(wakeq); int err; retry: /* * The waking up of stopper threads has to happen in the same * scheduling context as the queueing. Otherwise, there is a * possibility of one of the above stoppers being woken up by another * CPU, and preempting us. This will cause us to not wake up the other * stopper forever. */ preempt_disable(); raw_spin_lock_irq(&stopper1->lock); raw_spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING); if (!stopper1->enabled || !stopper2->enabled) { err = -ENOENT; goto unlock; } /* * Ensure that if we race with __stop_cpus() the stoppers won't get * queued up in reverse order leading to system deadlock. * * We can't miss stop_cpus_in_progress if queue_stop_cpus_work() has * queued a work on cpu1 but not on cpu2, we hold both locks. * * It can be falsely true but it is safe to spin until it is cleared, * queue_stop_cpus_work() does everything under preempt_disable(). */ if (unlikely(stop_cpus_in_progress)) { err = -EDEADLK; goto unlock; } err = 0; __cpu_stop_queue_work(stopper1, work1, &wakeq); __cpu_stop_queue_work(stopper2, work2, &wakeq); unlock: raw_spin_unlock(&stopper2->lock); raw_spin_unlock_irq(&stopper1->lock); if (unlikely(err == -EDEADLK)) { preempt_enable(); while (stop_cpus_in_progress) cpu_relax(); goto retry; } wake_up_q(&wakeq); preempt_enable(); return err;}/** * stop_two_cpus - stops two cpus * @cpu1: the cpu to stop * @cpu2: the other cpu to stop * @fn: function to execute * @arg: argument to @fn * * Stops both the current and specified CPU and runs @fn on one of them. * * returns when both are completed. */int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg){ struct cpu_stop_done done; struct cpu_stop_work work1, work2; struct multi_stop_data msdata; msdata = (struct multi_stop_data){ .fn = fn, .data = arg, .num_threads = 2, .active_cpus = cpumask_of(cpu1), }; work1 = work2 = (struct cpu_stop_work){ .fn = multi_cpu_stop, .arg = &msdata, .done = &done, .caller = _RET_IP_, }; cpu_stop_init_done(&done, 2); set_state(&msdata, MULTI_STOP_PREPARE); if (cpu1 > cpu2) swap(cpu1, cpu2); if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2)) return -ENOENT; wait_for_completion(&done.completion); return done.ret;} /** * stop_one_cpu_nowait - stop a cpu but don't wait for completion * @cpu: cpu to stop * @fn: function to execute * @arg: argument to @fn * @work_buf: pointer to cpu_stop_work structure * * Similar to stop_one_cpu() but doesn't wait for completion. The * caller is responsible for ensuring @work_buf is currently unused * and will remain untouched until stopper starts executing @fn. * * CONTEXT: * Don't care. * * RETURNS: * true if cpu_stop_work was queued successfully and @fn will be called, * false otherwise. */bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, struct cpu_stop_work *work_buf){ *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, .caller = _RET_IP_, }; return cpu_stop_queue_work(cpu, work_buf);} static bool queue_stop_cpus_work(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg, struct cpu_stop_done *done){ struct cpu_stop_work *work; unsigned int cpu; bool queued = false; /* * Disable preemption while queueing to avoid getting * preempted by a stopper which might wait for other stoppers * to enter @fn which can lead to deadlock. */ preempt_disable(); stop_cpus_in_progress = true; barrier(); for_each_cpu(cpu, cpumask) { work = &per_cpu(cpu_stopper.stop_work, cpu); work->fn = fn; work->arg = arg; work->done = done; if (cpu_stop_queue_work(cpu, work)) queued = true; } barrier(); stop_cpus_in_progress = false; preempt_enable(); return queued;} static int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg){ struct cpu_stop_done done; cpu_stop_init_done(&done, cpumask_weight(cpumask)); if (!queue_stop_cpus_work(cpumask, fn, arg, &done)) return -ENOENT; wait_for_completion(&done.completion); return done.ret;} /** * stop_cpus - stop multiple cpus * @cpumask: cpus to stop * @fn: function to execute * @arg: argument to @fn * * Execute @fn(@arg) on online cpus in @cpumask. On each target cpu, * @fn is run in a process context with the highest priority * preempting any task on the cpu and monopolizing it. This function * returns after all executions are complete. * * This function doesn't guarantee the cpus in @cpumask stay online * till @fn completes. If some cpus go down in the middle, execution * on the cpu may happen partially or fully on different cpus. @fn * should either be ready for that or the caller should ensure that * the cpus stay online until this function completes. * * All stop_cpus() calls are serialized making it safe for @fn to wait * for all cpus to start executing it. * * CONTEXT: * Might sleep. * * RETURNS: * -ENOENT if @fn(@arg) was not executed at all because all cpus in * @cpumask were offline; otherwise, 0 if all executions of @fn * returned 0, any non zero return value if any returned non zero. */static int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg){ int ret; /* static works are used, process one request at a time */ mutex_lock(&stop_cpus_mutex); ret = __stop_cpus(cpumask, fn, arg); mutex_unlock(&stop_cpus_mutex); return ret;} static int cpu_stop_should_run(unsigned int cpu){ struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); unsigned long flags; int run; raw_spin_lock_irqsave(&stopper->lock, flags); run = !list_empty(&stopper->works); raw_spin_unlock_irqrestore(&stopper->lock, flags); return run;} static void cpu_stopper_thread(unsigned int cpu){ struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); struct cpu_stop_work *work; repeat: work = NULL; raw_spin_lock_irq(&stopper->lock); if (!list_empty(&stopper->works)) { work = list_first_entry(&stopper->works, struct cpu_stop_work, list); list_del_init(&work->list); } raw_spin_unlock_irq(&stopper->lock); if (work) {Lines 1–500 of 686. 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// SPDX-License-Identifier: GPL-2.0-or-later /* * kernel/stop_machine.c * * Copyright (C) 2008, 2005 IBM Corporation. * Copyright (C) 2008, 2005 Rusty Russell rusty@rustcorp.com.au * Copyright (C) 2010 SUSE Linux Products GmbH * Copyright (C) 2010 Tejun Heo <tj@kernel.org> */ #include <linux/compiler.h> #include <linux/completion.h> #include <linux/cpu.h> #include <linux/init.h> #include <linux/kthread.h> #include <linux/export.h> #include <linux/percpu.h> #include <linux/sched.h> #include <linux/stop_machine.h> #include <linux/interrupt.h> #include <linux/kallsyms.h> #include <linux/smpboot.h> #include <linux/atomic.h> #include <linux/nmi.h> #include <linux/sched/wake_q.h> /* * Structure to determine completion condition and record errors. May * be shared by works on different cpus. */ struct cpu_stop_done { atomic_t nr_todo; /* nr left to execute */ int ret; /* collected return value */ struct completion completion; /* fired if nr_todo reaches 0 */ }; /* the actual stopper, one per every possible cpu, enabled on online cpus */ struct cpu_stopper { struct task_struct *thread; raw_spinlock_t lock; bool enabled; /* is this stopper enabled? */ struct list_head works; /* list of pending works */ struct cpu_stop_work stop_work; /* for stop_cpus */ unsigned long caller; cpu_stop_fn_t fn; }; static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper); static bool stop_machine_initialized = false; void print_stop_info(const char *log_lvl, struct task_struct *task) { /* * If @task is a stopper task, it cannot migrate and task_cpu() is * stable. */ struct cpu_stopper *stopper = per_cpu_ptr(&cpu_stopper, task_cpu(task)); if (task != stopper->thread) return; printk("%sStopper: %pS <- %pS\n", log_lvl, stopper->fn, (void *)stopper->caller); } /* static data for stop_cpus */ static DEFINE_MUTEX(stop_cpus_mutex); static bool stop_cpus_in_progress; static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo) { memset(done, 0, sizeof(*done)); atomic_set(&done->nr_todo, nr_todo); init_completion(&done->completion); } /* signal completion unless @done is NULL */ static void cpu_stop_signal_done(struct cpu_stop_done *done) { if (atomic_dec_and_test(&done->nr_todo)) complete(&done->completion); } static void __cpu_stop_queue_work(struct cpu_stopper *stopper, struct cpu_stop_work *work, struct wake_q_head *wakeq) { list_add_tail(&work->list, &stopper->works); wake_q_add(wakeq, stopper->thread); } /* queue @work to @stopper. if offline, @work is completed immediately */ static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work) { struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); DEFINE_WAKE_Q(wakeq); unsigned long flags; bool enabled; preempt_disable(); raw_spin_lock_irqsave(&stopper->lock, flags); enabled = stopper->enabled; if (enabled) __cpu_stop_queue_work(stopper, work, &wakeq); else if (work->done) cpu_stop_signal_done(work->done); raw_spin_unlock_irqrestore(&stopper->lock, flags); wake_up_q(&wakeq); preempt_enable(); return enabled; } /** * stop_one_cpu - stop a cpu * @cpu: cpu to stop * @fn: function to execute * @arg: argument to @fn * * Execute @fn(@arg) on @cpu. @fn is run in a process context with * the highest priority preempting any task on the cpu and * monopolizing it. This function returns after the execution is * complete. * * This function doesn't guarantee @cpu stays online till @fn * completes. If @cpu goes down in the middle, execution may happen * partially or fully on different cpus. @fn should either be ready * for that or the caller should ensure that @cpu stays online until * this function completes. * * CONTEXT: * Might sleep. * * RETURNS: * -ENOENT if @fn(@arg) was not executed because @cpu was offline; * otherwise, the return value of @fn. */ int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg) { struct cpu_stop_done done; struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done, .caller = _RET_IP_ }; cpu_stop_init_done(&done, 1); if (!cpu_stop_queue_work(cpu, &work)) return -ENOENT; /* * In case @cpu == smp_proccessor_id() we can avoid a sleep+wakeup * cycle by doing a preemption: */ cond_resched(); wait_for_completion(&done.completion); return done.ret; } /* This controls the threads on each CPU. */ enum multi_stop_state { /* Dummy starting state for thread. */ MULTI_STOP_NONE, /* Awaiting everyone to be scheduled. */ MULTI_STOP_PREPARE, /* Disable interrupts. */ MULTI_STOP_DISABLE_IRQ, /* Run the function */ MULTI_STOP_RUN, /* Exit */ MULTI_STOP_EXIT, }; struct multi_stop_data { cpu_stop_fn_t fn; void *data; /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */ unsigned int num_threads; const struct cpumask *active_cpus; enum multi_stop_state state; atomic_t thread_ack; }; static void set_state(struct multi_stop_data *msdata, enum multi_stop_state newstate) { /* Reset ack counter. */ atomic_set(&msdata->thread_ack, msdata->num_threads); smp_wmb(); WRITE_ONCE(msdata->state, newstate); } /* Last one to ack a state moves to the next state. */ static void ack_state(struct multi_stop_data *msdata) { if (atomic_dec_and_test(&msdata->thread_ack)) set_state(msdata, msdata->state + 1); } notrace void __weak stop_machine_yield(const struct cpumask *cpumask) { cpu_relax(); } /* This is the cpu_stop function which stops the CPU. */ static int multi_cpu_stop(void *data) { struct multi_stop_data *msdata = data; enum multi_stop_state newstate, curstate = MULTI_STOP_NONE; int cpu = smp_processor_id(), err = 0; const struct cpumask *cpumask; unsigned long flags; bool is_active; /* * When called from stop_machine_from_inactive_cpu(), irq might * already be disabled. Save the state and restore it on exit. */ local_save_flags(flags); if (!msdata->active_cpus) { cpumask = cpu_online_mask; is_active = cpu == cpumask_first(cpumask); } else { cpumask = msdata->active_cpus; is_active = cpumask_test_cpu(cpu, cpumask); } /* Simple state machine */ do { /* Chill out and ensure we re-read multi_stop_state. */ stop_machine_yield(cpumask); newstate = READ_ONCE(msdata->state); if (newstate != curstate) { curstate = newstate; switch (curstate) { case MULTI_STOP_DISABLE_IRQ: local_irq_disable(); hard_irq_disable(); break; case MULTI_STOP_RUN: if (is_active) err = msdata->fn(msdata->data); break; default: break; } ack_state(msdata); } else if (curstate > MULTI_STOP_PREPARE) { /* * At this stage all other CPUs we depend on must spin * in the same loop. Any reason for hard-lockup should * be detected and reported on their side. */ touch_nmi_watchdog(); } rcu_momentary_dyntick_idle(); } while (curstate != MULTI_STOP_EXIT); local_irq_restore(flags); return err; } static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1, int cpu2, struct cpu_stop_work *work2) { struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1); struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2); DEFINE_WAKE_Q(wakeq); int err; retry: /* * The waking up of stopper threads has to happen in the same * scheduling context as the queueing. Otherwise, there is a * possibility of one of the above stoppers being woken up by another * CPU, and preempting us. This will cause us to not wake up the other * stopper forever. */ preempt_disable(); raw_spin_lock_irq(&stopper1->lock); raw_spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING); if (!stopper1->enabled || !stopper2->enabled) { err = -ENOENT; goto unlock; } /* * Ensure that if we race with __stop_cpus() the stoppers won't get * queued up in reverse order leading to system deadlock. * * We can't miss stop_cpus_in_progress if queue_stop_cpus_work() has * queued a work on cpu1 but not on cpu2, we hold both locks. * * It can be falsely true but it is safe to spin until it is cleared, * queue_stop_cpus_work() does everything under preempt_disable(). */ if (unlikely(stop_cpus_in_progress)) { err = -EDEADLK; goto unlock; } err = 0; __cpu_stop_queue_work(stopper1, work1, &wakeq); __cpu_stop_queue_work(stopper2, work2, &wakeq); unlock: raw_spin_unlock(&stopper2->lock); raw_spin_unlock_irq(&stopper1->lock); if (unlikely(err == -EDEADLK)) { preempt_enable(); while (stop_cpus_in_progress) cpu_relax(); goto retry; } wake_up_q(&wakeq); preempt_enable(); return err; } /** * stop_two_cpus - stops two cpus * @cpu1: the cpu to stop * @cpu2: the other cpu to stop * @fn: function to execute * @arg: argument to @fn * * Stops both the current and specified CPU and runs @fn on one of them. * * returns when both are completed. */ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg) { struct cpu_stop_done done; struct cpu_stop_work work1, work2; struct multi_stop_data msdata; msdata = (struct multi_stop_data){ .fn = fn, .data = arg, .num_threads = 2, .active_cpus = cpumask_of(cpu1), }; work1 = work2 = (struct cpu_stop_work){ .fn = multi_cpu_stop, .arg = &msdata, .done = &done, .caller = _RET_IP_, }; cpu_stop_init_done(&done, 2); set_state(&msdata, MULTI_STOP_PREPARE); if (cpu1 > cpu2) swap(cpu1, cpu2); if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2)) return -ENOENT; wait_for_completion(&done.completion); return done.ret; } /** * stop_one_cpu_nowait - stop a cpu but don't wait for completion * @cpu: cpu to stop * @fn: function to execute * @arg: argument to @fn * @work_buf: pointer to cpu_stop_work structure * * Similar to stop_one_cpu() but doesn't wait for completion. The * caller is responsible for ensuring @work_buf is currently unused * and will remain untouched until stopper starts executing @fn. * * CONTEXT: * Don't care. * * RETURNS: * true if cpu_stop_work was queued successfully and @fn will be called, * false otherwise. */ bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, struct cpu_stop_work *work_buf) { *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, .caller = _RET_IP_, }; return cpu_stop_queue_work(cpu, work_buf); } static bool queue_stop_cpus_work(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg, struct cpu_stop_done *done) { struct cpu_stop_work *work; unsigned int cpu; bool queued = false; /* * Disable preemption while queueing to avoid getting * preempted by a stopper which might wait for other stoppers * to enter @fn which can lead to deadlock. */ preempt_disable(); stop_cpus_in_progress = true; barrier(); for_each_cpu(cpu, cpumask) { work = &per_cpu(cpu_stopper.stop_work, cpu); work->fn = fn; work->arg = arg; work->done = done; if (cpu_stop_queue_work(cpu, work)) queued = true; } barrier(); stop_cpus_in_progress = false; preempt_enable(); return queued; } static int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) { struct cpu_stop_done done; cpu_stop_init_done(&done, cpumask_weight(cpumask)); if (!queue_stop_cpus_work(cpumask, fn, arg, &done)) return -ENOENT; wait_for_completion(&done.completion); return done.ret; } /** * stop_cpus - stop multiple cpus * @cpumask: cpus to stop * @fn: function to execute * @arg: argument to @fn * * Execute @fn(@arg) on online cpus in @cpumask. On each target cpu, * @fn is run in a process context with the highest priority * preempting any task on the cpu and monopolizing it. This function * returns after all executions are complete. * * This function doesn't guarantee the cpus in @cpumask stay online * till @fn completes. If some cpus go down in the middle, execution * on the cpu may happen partially or fully on different cpus. @fn * should either be ready for that or the caller should ensure that * the cpus stay online until this function completes. * * All stop_cpus() calls are serialized making it safe for @fn to wait * for all cpus to start executing it. * * CONTEXT: * Might sleep. * * RETURNS: * -ENOENT if @fn(@arg) was not executed at all because all cpus in * @cpumask were offline; otherwise, 0 if all executions of @fn * returned 0, any non zero return value if any returned non zero. */ static int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) { int ret; /* static works are used, process one request at a time */ mutex_lock(&stop_cpus_mutex); ret = __stop_cpus(cpumask, fn, arg); mutex_unlock(&stop_cpus_mutex); return ret; } static int cpu_stop_should_run(unsigned int cpu) { struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); unsigned long flags; int run; raw_spin_lock_irqsave(&stopper->lock, flags); run = !list_empty(&stopper->works); raw_spin_unlock_irqrestore(&stopper->lock, flags); return run; } static void cpu_stopper_thread(unsigned int cpu) { struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); struct cpu_stop_work *work; repeat: work = NULL; raw_spin_lock_irq(&stopper->lock); if (!list_empty(&stopper->works)) { work = list_first_entry(&stopper->works, struct cpu_stop_work, list); list_del_init(&work->list); } raw_spin_unlock_irq(&stopper->lock); if (work) {