Messages in this thread | | | Subject | Re: [PATCH] wait: fix false timeouts when using wait_event_timeout() | From | Imre Deak <> | Date | Wed, 08 May 2013 12:49:48 +0300 |
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On Tue, 2013-05-07 at 16:12 -0700, Andrew Morton wrote: > On Thu, 2 May 2013 11:36:56 +0200 Daniel Vetter <daniel.vetter@ffwll.ch> wrote: > > > On Thu, May 2, 2013 at 10:58 AM, 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> > > > > We have 3 instances of this bug in drm/i915. One case even where we > > switch between the interruptible and not interruptible > > wait_event_timeout variants, foolishly presuming they have the same > > semantics. I very much like this. > > Let's think about scheduling this fix. > > Are any of the bugs which we expect this patch fixes serious enough to > warrant merging it into 3.10? And -stable?
There is at least [1], but I'm sure there is more similar reports about i915. I'd vote for -stable at least.
--Imre
[1] https://bugs.freedesktop.org/show_bug.cgi?id=64133
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