[Intel-gfx] Patch for crashing intel server

Chris Wilson chris at chris-wilson.co.uk
Sun Oct 13 11:43:49 CEST 2013

On Sun, Oct 13, 2013 at 05:49:04AM +0200, Bas Wijnen wrote:
> On Sat, Oct 12, 2013 at 09:46:14PM +0100, Chris Wilson wrote:
> > On Fri, Oct 11, 2013 at 09:24:54PM +0200, Bas Wijnen wrote:
> > > Hello,
> > > 
> > > My X server was crashing when playing video, and I wrote a patch to fix
> > > it.  Please find the background and the patch at
> > > http://bugs.debian.org/724944 .
> > 
> > The patch is a shotgun solution, putting NULL pointer checks where the
> > pointer is explicitly not allowed to be NULL. I need an actual
> > stacktrace to find the root cause.
> > -Chris
> Sure thing; you can find it attached.  Of course it shows when the
> segfault is triggered, not when the data became NULL.  And that should
> be fixed, because even though the server doesn't crash with the patch,
> it also doesn't play video.

Ok, I can see the allocation failure that leads to the crash:

commit f9a18c9f38d09c145eb513ca989966dc135c1e9b
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Sun Oct 13 10:36:35 2013 +0100

    uxa: Check for allocation failure in i915 video
    For a large screen, we have to create a temporary surface for rendering
    the textured video. If this pixmap creation fails we may be left with a
    system memory only pixmap leading to a segfault.
    Reported-by: Bas Wijnen <wijnen at debian.org>
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

However, that still leaveas the question as to how you ended up being
unable to allocate bo...

You can watch /sys/kernel/debug/dri/0/i915_gem_objects (or just use
intel-gpu-overlay) and see if there is an object leak.

Chris Wilson, Intel Open Source Technology Centre

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