On 27/02/2020 08:57, Chris Wilson wrote:
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@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
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;
So that smp_rmb() is not really effective, I mean the race is wider than
that. I was worried about that.. now I need to figure out where it
starts and where it ends (the race).
Regards,
Tvrtko
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