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Commit 38a3e1fc authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
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sched/wait: Fix abort_exclusive_wait(), it should pass TASK_NORMAL to wake_up() 



Otherwise this logic only works if mode is "compatible" with another
exclusive waiter.

If some wq has both TASK_INTERRUPTIBLE and TASK_UNINTERRUPTIBLE waiters,
abort_exclusive_wait() won't wait an uninterruptible waiter.

The main user is __wait_on_bit_lock() and currently it is fine but only
because TASK_KILLABLE includes TASK_UNINTERRUPTIBLE and we do not have
lock_page_interruptible() yet.

Just use TASK_NORMAL and remove the "mode" arg from abort_exclusive_wait().
Yes, this means that (say) wake_up_interruptible() can wake up the non-
interruptible waiter(s), but I think this is fine. And in fact I think
that abort_exclusive_wait() must die, see the next change.

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/20160906140047.GA6157@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ab522e33

include/linux/wait.h

+3 −3
Original line number Diff line number Diff line
@@ -282,7 +282,7 @@ wait_queue_head_t *bit_waitqueue(void *, int); 
			__ret = __int;					\

			if (exclusive) {				\

				abort_exclusive_wait(&wq, &__wait, 	\

						     state, NULL);	\

						     NULL);		\

				goto __out;				\

			}						\

			break;						\
@@ -989,7 +989,7 @@ 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, unsigned int mode, void *key);

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);

kernel/sched/wait.c

+3 −5
Original line number Diff line number Diff line
@@ -259,7 +259,6 @@ EXPORT_SYMBOL(finish_wait); 
 * abort_exclusive_wait - abort exclusive waiting in a queue

 * @q: waitqueue waited on

 * @wait: wait descriptor

 * @mode: runstate of the waiter to be woken

 * @key: key to identify a wait bit queue or %NULL

 *

 * Sets current thread back to running state and removes
@@ -273,8 +272,7 @@ EXPORT_SYMBOL(finish_wait); 
 * 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,

			unsigned int mode, void *key)

void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, void *key)

{

	unsigned long flags;
@@ -283,7 +281,7 @@ void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, 
	if (!list_empty(&wait->task_list))

		list_del_init(&wait->task_list);

	else if (waitqueue_active(q))

		__wake_up_locked_key(q, mode, key);

		__wake_up_locked_key(q, TASK_NORMAL, key);

	spin_unlock_irqrestore(&q->lock, flags);

}

EXPORT_SYMBOL(abort_exclusive_wait);
@@ -434,7 +432,7 @@ __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q, 
		ret = action(&q->key, mode);

		if (!ret)

			continue;

		abort_exclusive_wait(wq, &q->wait, mode, &q->key);

		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);