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