Bug 35819

Summary:	[SNB] compiz crashed with segfault in gen6_vs_state.c:upload_vs_state()
Product:	Mesa	Reporter:	Christopher James Halse Rogers <chalserogers>
Component:	Drivers/DRI/i965	Assignee:	Chris Wilson <chris>
Status:	RESOLVED WONTFIX	QA Contact:
Severity:	major
Priority:	medium
Version:	git
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:

Description Christopher James Halse Rogers 2011-03-30 22:27:36 UTC

Forwarded from https://bugs.launchpad.net/ubuntu/+source/mesa/+bug/733192

It seems that there's a segfault condition in upload_vs_state() which at least one person has managed to hit in the linked Ubuntu bug.

When setting up the contstant buffer upload_vs_state() does
      drm_intel_gem_bo_map_gtt(constant_bo);
      param = constant_bo->virtual;
and then proceeds to memcpy to param.  However, there are a number of possible failure paths in gem_bo_map_gtt that will result in constant_bo->virtual being NULL, resulting in a segfault.

Since this seems like it'll occur part-way through emitting 3D state I'm not sure how to gracefully handle this, or even if it's possible.

Original stacktrace is here: https://bugs.launchpad.net/ubuntu/+source/mesa/+bug/733192/+attachment/1900771/+files/Stacktrace.txt

Comment 1 Chris Wilson 2011-03-31 02:12:35 UTC

We can do better, but the root cause is whatever caused the map failure is likely to be system-wide.

Comment 2 Ian Romanick 2011-04-06 09:54:11 UTC

This looks similar to some of the failure cases seen in bug #33046.  What Mesa bits are being used?  It looks like 7.10, so it's probably something different.  It's worth checking, though.

Comment 3 Eric Anholt 2011-05-14 12:16:02 UTC

The dmesg in the linked bug report doesn't sound like one from when the crash had happened.  This is probably fallout from a GPU hang, and the thing to do is to fix the GPU hang.

Comment 4 Eric Anholt 2011-07-09 07:58:15 UTC

OK, the original bug report confirms that this is just fallout from a GPU hang.  Let's see a bug report for the hang if you can get details, instead.

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