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 <[email protected]> Cc: Tvrtko Ursulin <[email protected]> --- 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 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
