From d29926fa5f580565a7240c4d6a428795c773fb76 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Wed, 6 Nov 2019 13:31:29 +0000
Subject: drm/i915/gt: Only drop heartbeat.systole if the sole owner
Git-commit: d29926fa5f580565a7240c4d6a428795c773fb76
Patch-mainline: v5.5-rc1
References: bsc#1152489

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@linux.intel.com>
Fixes: 058179e72e09 ("drm/i915/gt: Replace hangcheck by heartbeats")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191106133129.17732-1-chris@chris-wilson.co.uk
(cherry picked from commit 841e86728615baa77b0ea9d8b357e66052c75fe5)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 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)
-- 
2.28.0