From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>,
Bart Van Assche <bvanassche@acm.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Neil Brown <neilb@suse.de>,
linux-kernel@vger.kernel.org
Subject: [PATCH V3 2/4] sched/wait: avoid abort_exclusive_wait() in ___wait_event()
Date: Thu, 8 Sep 2016 18:48:15 +0200 [thread overview]
Message-ID: <20160908164815.GA18801@redhat.com> (raw)
In-Reply-To: <20160906140050.GA6160@redhat.com>
On 09/06, Oleg Nesterov wrote:
>
> + 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;
Yes, but we should not do set_current_state() in this case, please sere V3.
-------------------------------------------------------------------------------
Subject: [PATCH V3 2/4] 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>
---
include/linux/wait.h | 7 +------
kernel/sched/wait.c | 35 +++++++++++++++++++++++++----------
2 files changed, 26 insertions(+), 16 deletions(-)
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 329f796..5179915 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -280,12 +280,7 @@ wait_queue_head_t *bit_waitqueue(void *, int);
\
if (___wait_is_interruptible(state) && __int) { \
__ret = __int; \
- if (exclusive) { \
- abort_exclusive_wait(&wq, &__wait, \
- NULL); \
- goto __out; \
- } \
- break; \
+ goto __out; \
} \
\
cmd; \
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 2bbba01..2612393 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);
--
2.5.0
next prev parent reply other threads:[~2016-09-08 16:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-06 14:00 [PATCH v2 0/4] sched/wait: fix and then kill abort_exclusive_wait() Oleg Nesterov
2016-09-06 14:00 ` [PATCH V2 1/4] sched/wait: abort_exclusive_wait() should pass TASK_NORMAL to wake_up() Oleg Nesterov
2016-09-30 11:56 ` [tip:sched/core] sched/wait: Fix abort_exclusive_wait(), it " tip-bot for Oleg Nesterov
2016-09-06 14:00 ` [PATCH V2 2/4] sched/wait: avoid abort_exclusive_wait() in ___wait_event() Oleg Nesterov
2016-09-08 16:48 ` Oleg Nesterov [this message]
2016-09-30 11:56 ` [tip:sched/core] sched/wait: Avoid " tip-bot for Oleg Nesterov
2016-09-06 14:00 ` [PATCH V2 3/4] sched/wait: avoid abort_exclusive_wait() in __wait_on_bit_lock() Oleg Nesterov
2016-09-30 11:57 ` [tip:sched/core] sched/wait: Avoid " tip-bot for Oleg Nesterov
2016-09-06 14:00 ` [PATCH V2 4/4] sched/wait: introduce init_wait_entry() Oleg Nesterov
2016-09-30 11:57 ` [tip:sched/core] sched/wait: Introduce init_wait_entry() tip-bot for Oleg Nesterov
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