Re: [PATCH 2/3] drm/i915/execlists: Push the tasklet kick after reset to reset_finish

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

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

> In the unlikely case where we have failed to keep submitting to the GPU,
> we end up with the ELSP queue empty but a pending queue of requests.
> Here, we skip the per-engine reset as there is no guilty request, but in
> doing so we also skip the engine restart leaving ourselves with a
> permanently hung engine. A quick way to recover is by moving the tasklet
> kick to execlists_reset_finish() (from init_hw). We still emit the error
> on hanging, so the error is not lost but we should be able to recover.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Michel Thierry <michel.thierry@intel.com>

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

> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 8d912d0c8fc1..c8d9b5aed94a 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1803,7 +1803,6 @@ static bool unexpected_starting_state(struct intel_engine_cs *engine)
>  
>  static int gen8_init_common_ring(struct intel_engine_cs *engine)
>  {
> -	struct intel_engine_execlists * const execlists = &engine->execlists;
>  	int ret;
>  
>  	ret = intel_mocs_init_engine(engine);
> @@ -1821,10 +1820,6 @@ static int gen8_init_common_ring(struct intel_engine_cs *engine)
>  
>  	enable_execlists(engine);
>  
> -	/* After a GPU reset, we may have requests to replay */
> -	if (execlists->first)
> -		tasklet_schedule(&execlists->tasklet);
> -
>  	return 0;
>  }
>  
> @@ -2006,6 +2001,12 @@ static void execlists_reset(struct intel_engine_cs *engine,
>  
>  static void execlists_reset_finish(struct intel_engine_cs *engine)
>  {
> +	struct intel_engine_execlists * const execlists = &engine->execlists;
> +
> +	/* After a GPU reset, we may have requests to replay */
> +	if (execlists->first)
> +		tasklet_schedule(&execlists->tasklet);
> +
>  	/*
>  	 * Flush the tasklet while we still have the forcewake to be sure
>  	 * that it is not allowed to sleep before we restart and reload a
> @@ -2015,7 +2016,7 @@ static void execlists_reset_finish(struct intel_engine_cs *engine)
>  	 * serialising multiple attempts to reset so that we know that we
>  	 * are the only one manipulating tasklet state.
>  	 */
> -	__tasklet_enable_sync_once(&engine->execlists.tasklet);
> +	__tasklet_enable_sync_once(&execlists->tasklet);
>  
>  	GEM_TRACE("%s\n", engine->name);
>  }
> -- 
> 2.17.1
>
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