drm/i915/gt: Fix up missing error propagation for heartbeat pulses

Just missed setting err along an interruptible error path for the
intel_engine_pulse().
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200218162150.1300405-4-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c

@@ -180,7 +180,7 @@ int intel_engine_pulse(struct intel_engine_cs *engine)
 	struct i915_sched_attr attr = { .priority = I915_PRIORITY_BARRIER };
 	struct intel_context *ce = engine->kernel_context;
 	struct i915_request *rq;
-	int err = 0;
+	int err;
 
 	if (!intel_engine_has_preemption(engine))
 		return -ENODEV;
@@ -188,8 +188,10 @@ int intel_engine_pulse(struct intel_engine_cs *engine)
 	if (!intel_engine_pm_get_if_awake(engine))
 		return 0;
 
-	if (mutex_lock_interruptible(&ce->timeline->mutex))
+	if (mutex_lock_interruptible(&ce->timeline->mutex)) {
+		err = -EINTR;
 		goto out_rpm;
+	}
 
 	intel_context_enter(ce);
 	rq = __i915_request_create(ce, GFP_NOWAIT | __GFP_NOWARN);
@@ -204,6 +206,8 @@ int intel_engine_pulse(struct intel_engine_cs *engine)
 
 	__i915_request_commit(rq);
 	__i915_request_queue(rq, &attr);
+	GEM_BUG_ON(rq->sched.attr.priority < I915_PRIORITY_BARRIER);
+	err = 0;
 
 out_unlock:
 	mutex_unlock(&ce->timeline->mutex);