On Thu, Dec 05, 2013 at 06:07:27PM +0200, Mika Kuoppala wrote:
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
>
> > As the rings may be processed and their requests deallocated in a
> > different order to the natural retirement during a reset,
> >
> > /* Whilst this request exists, batch_obj will be on the
> > * active_list, and so will hold the active reference. Only when this
> > * request is retired will the the batch_obj be moved onto the
> > * inactive_list and lose its active reference. Hence we do not need
> > * to explicitly hold another reference here.
> > */
> >
> > is violated, and the batch_obj may be dereferenced after it had been
> > freed on another ring. This can be simply avoided by processing the
> > status update prior to deallocating any requests.
> >
> > Fixes regression (a possible OOPS following a GPU hang) from
> > commit aa60c664e6df502578454621c3a9b1f087ff8d25
> > Author: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> > Date: Wed Jun 12 15:13:20 2013 +0300
> >
> > drm/i915: find guilty batch buffer on ring resets
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
>
> Passes the igt/gem_reset_stats/close-pending-fork and
> doesn't affect the fast path.
>
> Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
For reference, this is the comment I added upon request:
@@ -2502,8 +2508,15 @@ void i915_gem_reset(struct drm_device *dev)
struct intel_ring_buffer *ring;
int i;
+ /* Before we free the objects from the requests, we need to inspect
+ * them for finding the guilty party. As the requests only borrow
+ * their reference to the objects, the inspection must be done first.
+ */
+ for_each_ring(ring, dev_priv, i)
+ i915_gem_reset_ring_status(dev_priv, ring);
+
for_each_ring(ring, dev_priv, i)
- i915_gem_reset_ring_lists(dev_priv, ring);
+ i915_gem_reset_ring_cleanup(dev_priv, ring);
i915_gem_cleanup_ringbuffer(dev);
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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