Re: [PATCH] wait: fix false timeouts when using wait_event_timeout()

[Imre Deak <imre.deak@intel.com>]

On Thu, 2013-05-02 at 14:35 +0200, Jens Axboe wrote:
> On Thu, May 02 2013, David Howells wrote:
> > Imre Deak <imre.deak@intel.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@intel.com>
> > 
> > Acked-by: David Howells <dhowells@redhat.com>
> 
> You can add mine, too:
> 
> Acked-by: Jens Axboe <axboe@kernel.dk>

Ok, I think we agree that the +1 thing in schedule_timeout() discussed
in this thread should be handled separately, so if there is no other
objection I'd be happy if this patch was merged through someone's tree
as-is.

--Imre