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

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> 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.

succeeded

> 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>
> ---
>  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));

We don't arm in park path so this should do the trick.

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

>  }
>  
>  void intel_engine_init_heartbeat(struct intel_engine_cs *engine)
> -- 
> 2.24.0
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