From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Nick Piggin <npiggin@suse.de>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH]: wait: don't resched in prepare_to_wait()
Date: Fri, 6 Mar 2009 16:41:44 +0100 [thread overview]
Message-ID: <20090306154144.GA7841@redhat.com> (raw)
In-Reply-To: <1236350377.6326.389.camel@laptop>
On 03/06, Peter Zijlstra wrote:
>
> After prepare to wait, we either call schedule() or find !cond in which
> case we'll call finish_wait() which contains another preemption check.
>
> @@ -73,7 +73,9 @@ prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
> if (list_empty(&wait->task_list))
> __add_wait_queue(q, wait);
> set_current_state(state);
> + preempt_disable();
> spin_unlock_irqrestore(&q->lock, flags);
> + preempt_enable_no_resched();
But this only helps if the task gets TIF_NEED_RESCHED while it was in
spin_lock_irqsave() section, right? This window should be very small
unless we have the contention.
Or do you have something else in mind?
Oleg.
next prev parent reply other threads:[~2009-03-06 15:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-06 14:39 [RFC][PATCH]: wait: don't resched in prepare_to_wait() Peter Zijlstra
2009-03-06 15:41 ` Oleg Nesterov [this message]
2009-03-06 15:47 ` Peter Zijlstra
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