From: Oleg Nesterov <oleg@redhat.com>
To: Mani Tofigh via B4 Relay <devnull+mt4022.columbia.edu@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Christian Brauner <brauner@kernel.org>,
Michal Nazarewicz <mina86@mina86.com>,
Wen Yang <wen.yang@linux.dev>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
tz2294@columbia.edu, stable@vger.kernel.org,
Mani Tofigh <mt4022@columbia.edu>
Subject: Re: [PATCH] sched/wait: Queue non-exclusive waiters at the head in do_wait_intr*()
Date: Thu, 12 Nov 2026 00:01:35 +0100 [thread overview]
Message-ID: <avTzzxZvE3HqH3KS@redhat.com> (raw)
In-Reply-To: <20261111-b4-sched-wait-intr-head-v1-1-17cf2af5b964@columbia.edu>
On 11/11, Mani Tofigh via B4 Relay wrote:
>
> --- a/kernel/sched/wait.c
> +++ b/kernel/sched/wait.c
> @@ -319,8 +319,12 @@ EXPORT_SYMBOL(prepare_to_wait_event);
> */
> int do_wait_intr(wait_queue_head_t *wq, wait_queue_entry_t *wait)
> {
> - if (likely(list_empty(&wait->entry)))
> - __add_wait_queue_entry_tail(wq, wait);
> + if (likely(list_empty(&wait->entry))) {
> + if (wait->flags & WQ_FLAG_EXCLUSIVE)
> + __add_wait_queue_entry_tail(wq, wait);
> + else
> + __add_wait_queue(wq, wait);
This look right and matches prepare_to_wait_event(). But it seems there is
another problem if WQ_FLAG_EXCLUSIVE, see the
"Exclusive waiter must not fail if it was selected by wakeup" comment in
prepare_to_wait_event().
Perhaps it makes more sense to simply kill __wait_event_interruptible_locked()
and reimplement wait_event_interruptible_locked() on top of
___wait_event(cmd => do_wait_intr) ? This way do_wait_intr() will only need
to do unlock + schedule + lock.
Oleg.
prev parent reply other threads:[~2026-11-11 23:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-11 21:10 Mani Tofigh via B4 Relay
2026-11-11 23:01 ` Oleg Nesterov [this message]
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