[Intel-gfx] [PATCH] drm/i915: Skip barriers inside waits

[Chris Wilson]

Attaching to the i915_active barrier is a two stage process, and a flush
is only effective when the barrier is activation. Thus it is possible
for us to see a barrier, and attempt to flush, only for our flush to
have no effect. As such, before attempting to activate signaling on the
fence we need to double check it is a fence!

Fixes: d13a31770077 ("drm/i915: Flush idle barriers when waiting")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/i915_active.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index 0b12d5023800..7b3d6c12ad61 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -453,6 +453,9 @@ static void enable_signaling(struct i915_active_fence *active)
 {
 	struct dma_fence *fence;
 
+	if (unlikely(is_barrier(active)))
+		return;
+
 	fence = i915_active_fence_get(active);
 	if (!fence)
 		return;
-- 
2.25.1