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sched/wait: Avoid abort_exclusive_wait() in __wait_on_bit_lock()

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__wait_on_bit_lock() doesn't need abort_exclusive_wait() too. Right
now it can't use prepare_to_wait_event() (see the next change), but
it can do the additional finish_wait() if action() fails.

abort_exclusive_wait() no longer has callers, remove it.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160906140053.GA6164@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Oleg Nesterov 2016-09-06 16:00:53 +02:00 committed by Ingo Molnar
parent b1ea06a90f
commit eaf9ef5224
2 changed files with 21 additions and 44 deletions
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1
include/linux/wait.h
View file

@ -984,7 +984,6 @@ void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state);
void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state);
long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state);
void finish_wait(wait_queue_head_t *q, wait_queue_t *wait);
void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, void *key);
long wait_woken(wait_queue_t *wait, unsigned mode, long timeout);
int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);

64
kernel/sched/wait.c
View file

@ -270,37 +270,6 @@ void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
}
EXPORT_SYMBOL(finish_wait);
/**
* abort_exclusive_wait - abort exclusive waiting in a queue
* @q: waitqueue waited on
* @wait: wait descriptor
* @key: key to identify a wait bit queue or %NULL
*
* Sets current thread back to running state and removes
* the wait descriptor from the given waitqueue if still
* queued.
*
* Wakes up the next waiter if the caller is concurrently
* woken up through the queue.
*
* This prevents waiter starvation where an exclusive waiter
* aborts and is woken up concurrently and no one wakes up
* the next waiter.
*/
void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, void *key)
{
unsigned long flags;
__set_current_state(TASK_RUNNING);
spin_lock_irqsave(&q->lock, flags);
if (!list_empty(&wait->task_list))
list_del_init(&wait->task_list);
else if (waitqueue_active(q))
__wake_up_locked_key(q, TASK_NORMAL, key);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(abort_exclusive_wait);
int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
{
int ret = default_wake_function(wait, mode, sync, key);
@ -438,20 +407,29 @@ int __sched
__wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
wait_bit_action_f *action, unsigned mode)
{
do {
int ret;
int ret = 0;
for (;;) {
prepare_to_wait_exclusive(wq, &q->wait, mode);
if (!test_bit(q->key.bit_nr, q->key.flags))
continue;
ret = action(&q->key, mode);
if (!ret)
continue;
abort_exclusive_wait(wq, &q->wait, &q->key);
return ret;
} while (test_and_set_bit(q->key.bit_nr, q->key.flags));
finish_wait(wq, &q->wait);
return 0;
if (test_bit(q->key.bit_nr, q->key.flags)) {
ret = action(&q->key, mode);
/*
* See the comment in prepare_to_wait_event().
* finish_wait() does not necessarily takes wq->lock,
* but test_and_set_bit() implies mb() which pairs with
* smp_mb__after_atomic() before wake_up_page().
*/
if (ret)
finish_wait(wq, &q->wait);
}
if (!test_and_set_bit(q->key.bit_nr, q->key.flags)) {
if (!ret)
finish_wait(wq, &q->wait);
return 0;
} else if (ret) {
return ret;
}
}
}
EXPORT_SYMBOL(__wait_on_bit_lock);