[Intel-gfx] [PATCH] drm/i915: Prevent signals from interrupting close()

[Chris Wilson]

On Wed, Apr 09, 2014 at 04:49:02PM +0200, Daniel Vetter wrote:
> On Wed, Apr 09, 2014 at 08:03:39AM +0100, Chris Wilson wrote:
> > We neither report any unfinished operations during releasing GEM objects
> > associated with the file, and even if we did, it is bad form to report
> > -EINTR from a close().
> > 
> > The root cause of the bug that first showed itself during close is that
> > we do not do proper live tracking of vma and contexts under full-ppgtt,
> > but this is useful piece of defensive programming enforcing our
> > userspace API contract.
> > 
> > Cc: Ben Widawsky <benjamin.widawsky at intel.com>
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> 
> I'd really prefer something annoying and loud like we've done when nuking
> the deferred free list in
> 
> commit 1488fc08c1706288616c602416654fd38c773deb
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Tue Apr 24 15:47:31 2012 +0100
> 
>     drm/i915: Remove the deferred-free list
> 
> where we've added a WARN_ON in gem_free_object if any unbind was failing
> due to interrupts. This patch here disables that imo useful safety check.

It doesn't classify as a safety check if kernel/userspace explodes. The
trick would be to somehow get the error code back. And in this case we
cannot accept any error anyway. So yes, I would like a nice big warning
to catch bugs, but that is icing on the cake compared to preventing bugs
from destroying data.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre