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

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___wait_event() doesn't really need abort_exclusive_wait(), we can simply
change prepare_to_wait_event() to remove the waiter from q->task_list if
it was interrupted.

This simplifies the code/logic, and this way prepare_to_wait_event() can
have more users, see the next change.

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/20160908164815.GA18801@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
--
 include/linux/wait.h |    7 +------
 kernel/sched/wait.c  |   35 +++++++++++++++++++++++++----------
 2 files changed, 26 insertions(+), 16 deletions(-)
This commit is contained in:
Oleg Nesterov 2016-09-08 18:48:15 +02:00 • committed by Ingo Molnar
parent 38a3e1fc1d
commit b1ea06a90f
2 changed files with 26 additions and 16 deletions
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7
include/linux/wait.h
View file

@ -280,12 +280,7 @@ wait_queue_head_t *bit_waitqueue(void *, int);
\ \
if (___wait_is_interruptible(state) && __int) { \ if (___wait_is_interruptible(state) && __int) { \
__ret = __int; \ __ret = __int; \
if (exclusive) { \ goto __out; \
abort_exclusive_wait(&wq, &__wait, \
NULL); \
goto __out; \
} \
break; \
} \ } \
\ \
cmd; \ cmd; \

35
kernel/sched/wait.c
View file

@ -199,24 +199,39 @@ EXPORT_SYMBOL(prepare_to_wait_exclusive);
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)
{ {
unsigned long flags; unsigned long flags;
long ret = 0;
if (signal_pending_state(state, current))
return -ERESTARTSYS;
wait->private = current; wait->private = current;
wait->func = autoremove_wake_function; wait->func = autoremove_wake_function;
spin_lock_irqsave(&q->lock, flags); spin_lock_irqsave(&q->lock, flags);
if (list_empty(&wait->task_list)) { if (unlikely(signal_pending_state(state, current))) {
if (wait->flags & WQ_FLAG_EXCLUSIVE) /*
__add_wait_queue_tail(q, wait); * Exclusive waiter must not fail if it was selected by wakeup,
else * it should "consume" the condition we were waiting for.
__add_wait_queue(q, wait); *
* The caller will recheck the condition and return success if
* we were already woken up, we can not miss the event because
* wakeup locks/unlocks the same q->lock.
*
* But we need to ensure that set-condition + wakeup after that
* can't see us, it should wake up another exclusive waiter if
* we fail.
*/
list_del_init(&wait->task_list);
ret = -ERESTARTSYS;
} else {
if (list_empty(&wait->task_list)) {
if (wait->flags & WQ_FLAG_EXCLUSIVE)
__add_wait_queue_tail(q, wait);
else
__add_wait_queue(q, wait);
}
set_current_state(state);
} }
set_current_state(state);
spin_unlock_irqrestore(&q->lock, flags); spin_unlock_irqrestore(&q->lock, flags);
return 0; return ret;
} }
EXPORT_SYMBOL(prepare_to_wait_event); EXPORT_SYMBOL(prepare_to_wait_event);