[Intel-gfx] [PATCH] drm/i915/gt: Only drop heartbeat.systole if the sole owner

[Chris Wilson]

Mika spotted that only using cancel_delayed_work() could mean that we
attempted to clear the heartbeat.systole while the worker was still
running. Rectify the situation by only touching the systole from outside
the worker if we suceeded in cancelling the worker before it could run.
The worker is expected to clean up by itself upon idling.

Reported-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Fixes: 058179e72e09 ("drm/i915/gt: Replace hangcheck by heartbeats")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
index 5051f304705b..06aa14c7aa8c 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -141,8 +141,8 @@ void intel_engine_unpark_heartbeat(struct intel_engine_cs *engine)
 
 void intel_engine_park_heartbeat(struct intel_engine_cs *engine)
 {
-	cancel_delayed_work(&engine->heartbeat.work);
-	i915_request_put(fetch_and_zero(&engine->heartbeat.systole));
+	if (cancel_delayed_work(&engine->heartbeat.work))
+		i915_request_put(fetch_and_zero(&engine->heartbeat.systole));
 }
 
 void intel_engine_init_heartbeat(struct intel_engine_cs *engine)
-- 
2.24.0