[Intel-gfx] [PATCH v3] drm/i915: Always normalize return timeout for wait_timeout_ioctl

[Ben Widawsky]

On Fri, Apr 26, 2013 at 04:22:46PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Chris Wilson <chris at chris-wilson.co.uk>
> 
> As we recompute the remaining timeout after waiting, there is a
> potential for that timeout to be less than zero and so need sanitizing.
> The timeout is always returned to userspace and validated, so we should
> always perform the sanitation.
> 
> v2 [vsyrjala]: Only normalize the timespec if it's invalid
> v3: Add a comment to clarify the situation and remove the now
>     useless WARN_ON() (ickle)
> 
> Cc: Ben Widawsky <ben at bwidawsk.net>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

This does an excellent job of removing the warnings I'd sometimes see.

Unfortunately I've confirmed I can still reproduce the hang, and now
with no errors to leave any clues. I can't promise, but I'm 75%ish
certain I'd not always see a WARN before too (in fact I think that was
the case when Chris wrote the original patch)

The frequency with which I see the hangs seem to be increasing as well.
Does nobody else see this? I will have to take a shot at getting more
info.

[snip]

-- 
Ben Widawsky, Intel Open Source Technology Center