Re: [PATCH 1/2] drm/i915/guc: Improve clean up of busyness stats worker

["Ceraolo Spurio, Daniele" <daniele.ceraolospurio@xxxxxxxxx>]

On 1/11/2023 5:54 PM, John.C.Harrison@xxxxxxxxx wrote:
> From: John Harrison <John.C.Harrison@xxxxxxxxx>
>
> The stats worker thread management was mis-matched between
> enable/disable call sites. Fix those up. Also, abstract the cancel
> code into a helper function rather than replicating in multiple places.
>
> Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
> ---
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 22 ++++++++++++-------
>   1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index b436dd7f12e42..982364777d0c6 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -1435,19 +1435,25 @@ static void guc_init_engine_stats(struct intel_guc *guc)
>   {
>   	struct intel_gt *gt = guc_to_gt(guc);
>   	intel_wakeref_t wakeref;
> +	int ret;
>   
>   	mod_delayed_work(system_highpri_wq, &guc->timestamp.work,
>   			 guc->timestamp.ping_delay);
>   
> -	with_intel_runtime_pm(&gt->i915->runtime_pm, wakeref) {
> -		int ret = guc_action_enable_usage_stats(guc);
> +	with_intel_runtime_pm(&gt->i915->runtime_pm, wakeref)
> +		ret = guc_action_enable_usage_stats(guc);
>   
> -		if (ret)
> -			drm_err(&gt->i915->drm,
> -				"Failed to enable usage stats: %d!\n", ret);
> +	if (ret) {
> +		cancel_delayed_work_sync(&guc->timestamp.work);

Wouldn't it be easier to just call mod_delayed_work after the H2G if 
ret==0, instead of having it before and cancelling if we get a failure?

> +		drm_err(&gt->i915->drm, "Failed to enable usage stats: %d!\n", ret);
>   	}
>   }
>   
> +static void guc_park_engine_stats(struct intel_guc *guc)
> +{
> +	cancel_delayed_work_sync(&guc->timestamp.work);
> +}
> +

Now you're asymmetric with the park/unpark, because on the park side you 
have this wrapper, while on the unpark side you directly call 
mod_delayed_work.

Daniele

>   void intel_guc_busyness_park(struct intel_gt *gt)
>   {
>   	struct intel_guc *guc = &gt->uc.guc;
> @@ -1460,7 +1466,7 @@ void intel_guc_busyness_park(struct intel_gt *gt)
>   	 * and causes an unclaimed register access warning. Cancel the worker
>   	 * synchronously here.
>   	 */
> -	cancel_delayed_work_sync(&guc->timestamp.work);
> +	guc_park_engine_stats(guc);
>   
>   	/*
>   	 * Before parking, we should sample engine busyness stats if we need to.
> @@ -4409,11 +4415,11 @@ void intel_guc_submission_enable(struct intel_guc *guc)
>   	guc_init_global_schedule_policy(guc);
>   }
>   
> +/* Note: By the time we're here, GuC may have already been reset */
>   void intel_guc_submission_disable(struct intel_guc *guc)
>   {
>   	struct intel_gt *gt = guc_to_gt(guc);
> -
> -	/* Note: By the time we're here, GuC may have already been reset */
> +	guc_park_engine_stats(guc);
>   
>   	/* Disable and route to host */
>   	if (GRAPHICS_VER(gt->i915) >= 12)