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drm/i915: Assert mutex_is_locked on context lookup

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Because our context refcounting doesn't grab a ref at lookup time, it is
unsafe to do so without the lock.

NOTE: We don't have an easy way to put the assertion in the lookup
function which is where this really belongs. Context switching is good
enough because it actually asserts even more correctness by protecting
the default_context.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[danvet: s/BUG/WARN/]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Ben Widawsky 2013-04-23 23:15:29 -07:00 committed by Daniel Vetter
parent a1520318a5
commit 186507e9e8
1 changed files with 2 additions and 0 deletions
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2
drivers/gpu/drm/i915/i915_gem_context.c
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@ -463,6 +463,8 @@ int i915_switch_context(struct intel_ring_buffer *ring,
if (dev_priv->hw_contexts_disabled)
return 0;
WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
if (ring != &dev_priv->ring[RCS])
return 0;