// SPDX-License-Identifier: GPL-2.0 /* * Generic wait-for-completion handler; * * It differs from semaphores in that their default case is the opposite, * wait_for_completion default blocks whereas semaphore default non-block. The * interface also makes it easy to 'complete' multiple waiting threads, * something which isn't entirely natural for semaphores. * * But more importantly, the primitive documents the usage. Semaphores would * typically be used for exclusion which gives rise to priority inversion. * Waiting for completion is a typically sync point, but not an exclusion point. */ #include <linux/linkage.h> #include <linux/sched/debug.h> #include <linux/completion.h> #include "sched.h" static void complete_with_flags(struct completion *x, int wake_flags) { unsigned long flags; raw_spin_lock_irqsave(&x->wait.lock, flags); if (x->done != UINT_MAX) x->done++; swake_up_locked(&x->wait, wake_flags); raw_spin_unlock_irqrestore(&x->wait.lock, flags); } void complete_on_current_cpu(struct completion *x) { return complete_with_flags(x, WF_CURRENT_CPU); } /** * complete: - signals a single thread waiting on this completion * @x: holds the state of this particular completion * * This will wake up a single thread waiting on this completion. Threads will be * awakened in the same order in which they were queued. * * See also complete_all(), wait_for_completion() and related routines. * * If this function wakes up a task, it executes a full memory barrier before * accessing the task state. */ void complete(struct completion *x) { complete_with_flags(x, 0); } EXPORT_SYMBOL(complete); /** * complete_all: - signals all threads waiting on this completion * @x: holds the state of this particular completion * * This will wake up all threads waiting on this particular completion event. * * If this function wakes up a task, it executes a full memory barrier before * accessing the task state. * * Since complete_all() sets the completion of @x permanently to done * to allow multiple waiters to finish, a call to reinit_completion() * must be used on @x if @x is to be used again. The code must make * sure that all waiters have woken and finished before reinitializing * @x. Also note that the function completion_done() can not be used * to know if there are still waiters after complete_all() has been called. */ void complete_all(struct completion *x) { unsigned long flags; lockdep_assert_RT_in_threaded_ctx(); raw_spin_lock_irqsave(&x->wait.lock, flags); x->done = UINT_MAX; swake_up_all_locked(&x->wait); raw_spin_unlock_irqrestore(&x->wait.lock, flags); } EXPORT_SYMBOL(complete_all); static inline long __sched do_wait_for_common(struct completion *x, long (*action)(long), long timeout, int state) { if (!x->done) { DECLARE_SWAITQUEUE(wait); do { if (signal_pending_state(state, current)) { timeout = -ERESTARTSYS; break; } __prepare_to_swait(&x->wait, &wait); __set_current_state(state); raw_spin_unlock_irq(&x->wait.lock); timeout = action(timeout); raw_spin_lock_irq(&x->wait.lock); } while (!x->done && timeout); __finish_swait(&x->wait, &wait); if (!x->done) return timeout; } if (x->done != UINT_MAX) x->done--; return timeout ?: 1; } static inline long __sched __wait_for_common(struct completion *x, long (*action)(long), long timeout, int state) { might_sleep(); complete_acquire(x); raw_spin_lock_irq(&x->wait.lock); timeout = do_wait_for_common(x, action, timeout, state); raw_spin_unlock_irq(&x->wait.lock); complete_release(x); return timeout; } static long __sched wait_for_common(struct completion *x, long timeout, int state) { return __wait_for_common(x, schedule_timeout, timeout, state); } static long __sched wait_for_common_io(struct completion *x, long timeout, int state) { return __wait_for_common(x, io_schedule_timeout, timeout, state); } /** * wait_for_completion: - waits for completion of a task * @x: holds the state of this particular completion * * This waits to be signaled for completion of a specific task. It is NOT * interruptible and there is no timeout. * * See also similar routines (i.e. wait_for_completion_timeout()) with timeout * and interrupt capability. Also see complete(). */ void __sched wait_for_completion(struct completion *x) { wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE); } EXPORT_SYMBOL(wait_for_completion); /** * wait_for_completion_timeout: - waits for completion of a task (w/timeout) * @x: holds the state of this particular completion * @timeout: timeout value in jiffies * * This waits for either a completion of a specific task to be signaled or for a * specified timeout to expire. The timeout is in jiffies. It is not * interruptible. * * Return: 0 if timed out, and positive (at least 1, or number of jiffies left * till timeout) if completed. */ unsigned long __sched wait_for_completion_timeout(struct completion *x, unsigned long timeout) { return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE); } EXPORT_SYMBOL(wait_for_completion_timeout); /** * wait_for_completion_io: - waits for completion of a task * @x: holds the state of this particular completion * * This waits to be signaled for completion of a specific task. It is NOT * interruptible and there is no timeout. The caller is accounted as waiting * for IO (which traditionally means blkio only). */ void __sched wait_for_completion_io(struct completion *x) { wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE); } EXPORT_SYMBOL(wait_for_completion_io); /** * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout) * @x: holds the state of this particular completion * @timeout: timeout value in jiffies * * This waits for either a completion of a specific task to be signaled or for a * specified timeout to expire. The timeout is in jiffies. It is not * interruptible. The caller is accounted as waiting for IO (which traditionally * means blkio only). * * Return: 0 if timed out, and positive (at least 1, or number of jiffies left * till timeout) if completed. */ unsigned long __sched wait_for_completion_io_timeout(struct completion *x, unsigned long timeout) { return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE); } EXPORT_SYMBOL(wait_for_completion_io_timeout); /** * wait_for_completion_interruptible: - waits for completion of a task (w/intr) * @x: holds the state of this particular completion * * This waits for completion of a specific task to be signaled. It is * interruptible. * * Return: -ERESTARTSYS if interrupted, 0 if completed. */ int __sched wait_for_completion_interruptible(struct completion *x) { long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE); if (t == -ERESTARTSYS) return t; return 0; } EXPORT_SYMBOL(wait_for_completion_interruptible); /** * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr)) * @x: holds the state of this particular completion * @timeout: timeout value in jiffies * * This waits for either a completion of a specific task to be signaled or for a * specified timeout to expire. It is interruptible. The timeout is in jiffies. * * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, * or number of jiffies left till timeout) if completed. */ long __sched wait_for_completion_interruptible_timeout(struct completion *x, unsigned long timeout) { return wait_for_common(x, timeout, TASK_INTERRUPTIBLE); } EXPORT_SYMBOL(wait_for_completion_interruptible_timeout); /** * wait_for_completion_killable: - waits for completion of a task (killable) * @x: holds the state of this particular completion * * This waits to be signaled for completion of a specific task. It can be * interrupted by a kill signal. * * Return: -ERESTARTSYS if interrupted, 0 if completed. */ int __sched wait_for_completion_killable(struct completion *x) { long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE); if (t == -ERESTARTSYS) return t; return 0; } EXPORT_SYMBOL(wait_for_completion_killable); int __sched wait_for_completion_state(struct completion *x, unsigned int state) { long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, state); if (t == -ERESTARTSYS) return t; return 0; } EXPORT_SYMBOL(wait_for_completion_state); /** * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable)) * @x: holds the state of this particular completion * @timeout: timeout value in jiffies * * This waits for either a completion of a specific task to be * signaled or for a specified timeout to expire. It can be * interrupted by a kill signal. The timeout is in jiffies. * * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, * or number of jiffies left till timeout) if completed. */ long __sched wait_for_completion_killable_timeout(struct completion *x, unsigned long timeout) { return wait_for_common(x, timeout, TASK_KILLABLE); } EXPORT_SYMBOL(wait_for_completion_killable_timeout); /** * try_wait_for_completion - try to decrement a completion without blocking * @x: completion structure * * Return: 0 if a decrement cannot be done without blocking * 1 if a decrement succeeded. * * If a completion is being used as a counting completion, * attempt to decrement the counter without blocking. This * enables us to avoid waiting if the resource the completion * is protecting is not available. */ bool try_wait_for_completion(struct completion *x) { unsigned long flags; bool ret = true; /* * Since x->done will need to be locked only * in the non-blocking case, we check x->done * first without taking the lock so we can * return early in the blocking case. */ if (!READ_ONCE(x->done)) return false; raw_spin_lock_irqsave(&x->wait.lock, flags); if (!x->done) ret = false; else if (x->done != UINT_MAX) x->done--; raw_spin_unlock_irqrestore(&x->wait.lock, flags); return ret; } EXPORT_SYMBOL(try_wait_for_completion); /** * completion_done - Test to see if a completion has any waiters * @x: completion structure * * Return: 0 if there are waiters (wait_for_completion() in progress) * 1 if there are no waiters. * * Note, this will always return true if complete_all() was called on @X. */ bool completion_done(struct completion *x) { unsigned long flags; if (!READ_ONCE(x->done)) return false; /* * If ->done, we need to wait for complete() to release ->wait.lock * otherwise we can end up freeing the completion before complete() * is done referencing it. */ raw_spin_lock_irqsave(&x->wait.lock, flags); raw_spin_unlock_irqrestore(&x->wait.lock, flags); return true; } EXPORT_SYMBOL(completion_done);
