[Intel-gfx] [PATCH 4/4] drm/i915: Emit dma-fence (and execlists submit) first from signaler

[Chris Wilson]

When introduced, I thought that reducing client latency from the
signaler was the priority. Since its inception the signaler has become
responsible for keeping the execlists full, via the dma-fence. As this
is very important to minimise overall execution time, signal the
dma-fence first and then signal any waiting clients.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/intel_breadcrumbs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index fcfa423d08bd..c1f3bd2e053b 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -459,16 +459,16 @@ static int intel_breadcrumbs_signaler(void *arg)
 		 */
 		request = READ_ONCE(b->first_signal);
 		if (signal_complete(request)) {
+			local_bh_disable();
+			dma_fence_signal(&request->fence);
+			local_bh_enable(); /* kick start the tasklets */
+
 			/* Wake up all other completed waiters and select the
 			 * next bottom-half for the next user interrupt.
 			 */
 			intel_engine_remove_wait(engine,
 						 &request->signaling.wait);
 
-			local_bh_disable();
-			dma_fence_signal(&request->fence);
-			local_bh_enable(); /* kick start the tasklets */
-
 			/* Find the next oldest signal. Note that as we have
 			 * not been holding the lock, another client may
 			 * have installed an even older signal than the one
-- 
2.11.0