drm/i915: Flush execution tasklets before checking request status

Rather than flushing the submission tasklets just before we sleep, flush
before we check the request status. Ideally this gives us a moment to
process the tasklets after sleeping just before we timeout.

v2: Compromise by pushing the flush prior to the timeout, but after the
check on completion so that we do not further delay the ready client.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200205095441.1769599-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_request.c

@@ -1571,6 +1571,8 @@ long i915_request_wait(struct i915_request *rq,
 			break;
 		}
 
+		intel_engine_flush_submission(rq->engine);
+
 		if (signal_pending_state(state, current)) {
 			timeout = -ERESTARTSYS;
 			break;
@@ -1581,7 +1583,6 @@ long i915_request_wait(struct i915_request *rq,
 			break;
 		}
 
-		intel_engine_flush_submission(rq->engine);
 		timeout = io_schedule_timeout(timeout);
 	}
 	__set_current_state(TASK_RUNNING);