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drm/i915: Check waiter->seqno carefully in case of preemption 

If preemption occurs at precisely the right moment, we may decide that
the wait is complete even though the wait's request is no longer
executing (having been preempted). We handle this situation by double
checking that request following deciding whether the wait is complete.

Reported-by: Michał Winiarski <michal.winiarski@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170918162734.21294-2-chris@chris-wilson.co.uk
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
This commit is contained in:
Chris Wilson 2017-09-18 17:27:34 +01:00
parent 17b51ad8e5
commit de4d2106f8
1 changed files with 5 additions and 2 deletions
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7
drivers/gpu/drm/i915/i915_irq.c
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@ -1053,10 +1053,13 @@ static void notify_ring(struct intel_engine_cs *engine)
*/
if (i915_seqno_passed(intel_engine_get_seqno(engine),
wait->seqno)) {
struct drm_i915_gem_request *waiter = wait->request;
wakeup = true;
if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
&wait->request->fence.flags))
rq = i915_gem_request_get(wait->request);
&waiter->fence.flags) &&
intel_wait_check_request(wait, waiter))
rq = i915_gem_request_get(waiter);
}
if (wakeup)