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author | Oleg Nesterov <oleg@redhat.com> | 2016-09-08 18:48:15 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2016-09-30 10:53:44 +0200 |
commit | b1ea06a90f528e516929a4da1d9b8838752bceb9 (patch) | |
tree | ca58fca505c7411b393047842c0eaedfe7c4ead0 /kernel/sched/wait.c | |
parent | 38a3e1fc1dac480f3672ab22fc97e1f995c80ed7 (diff) | |
download | linux-b1ea06a90f528e516929a4da1d9b8838752bceb9.tar.gz linux-b1ea06a90f528e516929a4da1d9b8838752bceb9.tar.bz2 linux-b1ea06a90f528e516929a4da1d9b8838752bceb9.zip |
sched/wait: Avoid abort_exclusive_wait() in ___wait_event()
___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(-)
Diffstat (limited to 'kernel/sched/wait.c')
-rw-r--r-- | kernel/sched/wait.c | 35 |
1 files changed, 25 insertions, 10 deletions
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index 2bbba0175ab2..261239392258 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -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) { unsigned long flags; - - if (signal_pending_state(state, current)) - return -ERESTARTSYS; + long ret = 0; wait->private = current; wait->func = autoremove_wake_function; spin_lock_irqsave(&q->lock, flags); - if (list_empty(&wait->task_list)) { - if (wait->flags & WQ_FLAG_EXCLUSIVE) - __add_wait_queue_tail(q, wait); - else - __add_wait_queue(q, wait); + if (unlikely(signal_pending_state(state, current))) { + /* + * Exclusive waiter must not fail if it was selected by wakeup, + * it should "consume" the condition we were waiting for. + * + * 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); - return 0; + return ret; } EXPORT_SYMBOL(prepare_to_wait_event); |