diff options
author | Oleg Nesterov <oleg@redhat.com> | 2016-09-06 16:00:53 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2016-09-30 10:54:03 +0200 |
commit | eaf9ef52241b545fe63621266bfc6fd8b06559ff (patch) | |
tree | 7cc771e86505f117bcdfabccf13048fc9dc78451 /kernel/sched | |
parent | b1ea06a90f528e516929a4da1d9b8838752bceb9 (diff) |
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: 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>
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/wait.c | 64 |
1 files changed, 21 insertions, 43 deletions
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index 261239392258..0cb615d69013 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -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); |