linux-kernel - Re: [PATCH] wait: fix false timeouts when using wait_event

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Message-ID: <20130502123517.GL7800@kernel.dk>
Date:	Thu, 2 May 2013 14:35:17 +0200
From:	Jens Axboe <axboe@...nel.dk>
To:	David Howells <dhowells@...hat.com>
Cc:	Imre Deak <imre.deak@...el.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Dave Jones <davej@...hat.com>,
	Lukas Czerner <lczerner@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] wait: fix false timeouts when using wait_event_timeout()

On Thu, May 02 2013, David Howells wrote:
> Imre Deak <imre.deak@...el.com> wrote:
> 
> > Many callers of the wait_event_timeout() and
> > wait_event_interruptible_timeout() expect that the return value will be
> > positive if the specified condition becomes true before the timeout
> > elapses. However, at the moment this isn't guaranteed. If the wake-up
> > handler is delayed enough, the time remaining until timeout will be
> > calculated as 0 - and passed back as a return value - even if the
> > condition became true before the timeout has passed.
> > 
> > Fix this by returning at least 1 if the condition becomes true. This
> > semantic is in line with what wait_for_condition_timeout() does; see
> > commit bb10ed09 - "sched: fix wait_for_completion_timeout() spurious
> > failure under heavy load".
> > 
> > Signed-off-by: Imre Deak <imre.deak@...el.com>
> 
> Acked-by: David Howells <dhowells@...hat.com>

You can add mine, too:

Acked-by: Jens Axboe <axboe@...nel.dk>

-- 
Jens Axboe

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