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Commit eaf9ef52 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

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



__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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent b1ea06a9

include/linux/wait.h

+0 −1
Original line number Original line Diff line number Diff line
@@ -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);

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);

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 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);

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 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);

int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);

kernel/sched/wait.c

+21 −43
Original line number Original line Diff line number Diff line
@@ -270,37 +270,6 @@ void finish_wait(wait_queue_head_t *q, wait_queue_t *wait) 
}

}

EXPORT_SYMBOL(finish_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 autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)

{

{

	int ret = default_wake_function(wait, mode, sync, 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_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,

			wait_bit_action_f *action, unsigned mode)

			wait_bit_action_f *action, unsigned mode)

{

{

	do {

	int ret = 0;

		int ret;





	for (;;) {

		prepare_to_wait_exclusive(wq, &q->wait, mode);

		prepare_to_wait_exclusive(wq, &q->wait, mode);

		if (!test_bit(q->key.bit_nr, q->key.flags))

		if (test_bit(q->key.bit_nr, q->key.flags)) {

			continue;

			ret = action(&q->key, mode);

			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)

			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);

				finish_wait(wq, &q->wait);

			return 0;

			return 0;

		} else if (ret) {

			return ret;

		}

	}

}

}

EXPORT_SYMBOL(__wait_on_bit_lock);

EXPORT_SYMBOL(__wait_on_bit_lock);