[Intel-gfx] [PATCH 2/2] drm/i915: Reset hangcheck timeouts upon idling

[Chris Wilson]

If we have a long period of idleness, we turn off the hangcheck timer
and stop polling the hardware. Before we restart the hangcheck, we
should clear the previous timestamps to prevent us thinking that the
engine was stalled for a long time, if the seqno were manipulated
carefully (such as the repeating patterns in gem_exec_whisper).

It should have no impact upon normal use.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_hangcheck.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_hangcheck.c b/drivers/gpu/drm/i915/intel_hangcheck.c
index b0ca0c4c70d9..a74decca5109 100644
--- a/drivers/gpu/drm/i915/intel_hangcheck.c
+++ b/drivers/gpu/drm/i915/intel_hangcheck.c
@@ -409,13 +409,13 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
 	int busy_count = 0;
 
 	if (!i915.enable_hangcheck)
-		return;
+		goto disarm_hangcheck;
 
 	if (!READ_ONCE(dev_priv->gt.awake))
-		return;
+		goto disarm_hangcheck;
 
 	if (i915_terminally_wedged(&dev_priv->gpu_error))
-		return;
+		goto disarm_hangcheck;
 
 	/* As enabling the GPU requires fairly extensive mmio access,
 	 * periodically arm the mmio checker to see if we are triggering
@@ -446,8 +446,14 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
 		hangcheck_declare_hang(dev_priv, hung, stuck);
 
 	/* Reset timer in case GPU hangs without another request being added */
-	if (busy_count)
+	if (busy_count) {
 		i915_queue_hangcheck(dev_priv);
+		return;
+	}
+
+disarm_hangcheck:
+	for_each_engine(engine, dev_priv, id)
+		intel_engine_init_hangcheck(engine);
 }
 
 void intel_engine_init_hangcheck(struct intel_engine_cs *engine)
-- 
2.11.0