[PATCH 02/27] drm/i915/gt: Add a safety submission flush in the heartbeat

[Chris Wilson]

Just in case everything fails (like for example "missed interrupt
syndrome" on Sandybridge), always flush the submission tasklet from the
heartbeat. This papers over such issues, but will still appear as a
second long glitch, and prevents us from detecting it unless we happen
to be performing a timed test.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c     | 19 +++++++------------
 .../gpu/drm/i915/gt/intel_engine_heartbeat.c  |  3 +++
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index d613cf31970c..81884303bf6d 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1094,19 +1094,14 @@ void intel_engine_flush_submission(struct intel_engine_cs *engine)
 {
 	struct tasklet_struct *t = &engine->execlists.tasklet;
 
-	if (__tasklet_is_scheduled(t)) {
-		local_bh_disable();
-		if (tasklet_trylock(t)) {
-			/* Must wait for any GPU reset in progress. */
-			if (__tasklet_is_enabled(t))
-				t->func(t->data);
-			tasklet_unlock(t);
-		}
-		local_bh_enable();
+	local_bh_disable();
+	if (tasklet_trylock(t)) {
+		/* Must wait for any GPU reset in progress. */
+		if (__tasklet_is_enabled(t))
+			t->func(t->data);
+		tasklet_unlock(t);
 	}
-
-	/* Otherwise flush the tasklet if it was running on another cpu */
-	tasklet_unlock_wait(t);
+	local_bh_enable();
 }
 
 /**
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
index f67ad937eefb..cd20fb549b38 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -65,6 +65,9 @@ static void heartbeat(struct work_struct *wrk)
 	struct intel_context *ce = engine->kernel_context;
 	struct i915_request *rq;
 
+	/* Just in case everything has gone horribly wrong, give it a kick */
+	intel_engine_flush_submission(engine);
+
 	rq = engine->heartbeat.systole;
 	if (rq && i915_request_completed(rq)) {
 		i915_request_put(rq);
-- 
2.20.1