Re: [PATCH] drm/i915/pmu: Avoid with_intel_runtime_pm within spinlock

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 20/11/2021 01:42, Umesh Nerlige Ramappa wrote:
> When guc timestamp ping worker runs it takes the spinlock and calls
> with_intel_runtime_pm.  Since with_intel_runtime_pm may sleep, move the
> spinlock inside __update_guc_busyness_stats.
>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
> ---
>   drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 12 +++---------
>   1 file changed, 3 insertions(+), 9 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 77fbcd8730ee..a7108b38973e 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -1251,12 +1251,15 @@ static void __update_guc_busyness_stats(struct intel_guc *guc)
>   	struct intel_gt *gt = guc_to_gt(guc);
>   	struct intel_engine_cs *engine;
>   	enum intel_engine_id id;
> +	unsigned long flags;
>   	ktime_t unused;
>   
> +	spin_lock_irqsave(&guc->timestamp.lock, flags);
>   	for_each_engine(engine, gt, id) {
>   		guc_update_pm_timestamp(guc, engine, &unused);
>   		guc_update_engine_gt_clks(engine);
>   	}
> +	spin_unlock_irqrestore(&guc->timestamp.lock, flags);
>   }
>   
>   static void guc_timestamp_ping(struct work_struct *wrk)
> @@ -1266,7 +1269,6 @@ static void guc_timestamp_ping(struct work_struct *wrk)
>   	struct intel_uc *uc = container_of(guc, typeof(*uc), guc);
>   	struct intel_gt *gt = guc_to_gt(guc);
>   	intel_wakeref_t wakeref;
> -	unsigned long flags;
>   	int srcu, ret;
>   
>   	/*
> @@ -1277,13 +1279,9 @@ static void guc_timestamp_ping(struct work_struct *wrk)
>   	if (ret)
>   		return;
>   
> -	spin_lock_irqsave(&guc->timestamp.lock, flags);
> -
>   	with_intel_runtime_pm(&gt->i915->runtime_pm, wakeref)
>   		__update_guc_busyness_stats(guc);
>   
> -	spin_unlock_irqrestore(&guc->timestamp.lock, flags);
> -
>   	intel_gt_reset_unlock(gt, srcu);
>   
>   	mod_delayed_work(system_highpri_wq, &guc->timestamp.work,
> @@ -1322,16 +1320,12 @@ static void guc_init_engine_stats(struct intel_guc *guc)
>   void intel_guc_busyness_park(struct intel_gt *gt)
>   {
>   	struct intel_guc *guc = &gt->uc.guc;
> -	unsigned long flags;
>   
>   	if (!guc_submission_initialized(guc))
>   		return;
>   
>   	cancel_delayed_work(&guc->timestamp.work);
> -
> -	spin_lock_irqsave(&guc->timestamp.lock, flags);
>   	__update_guc_busyness_stats(guc);
> -	spin_unlock_irqrestore(&guc->timestamp.lock, flags);
>   }
>   
>   void intel_guc_busyness_unpark(struct intel_gt *gt)

Not sure how this sneaked in when I think topic was mentioned. Or if I 
misremembering, are the might_sleep annotations not there in runtime pm get?

Anyway:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

Regards,

Tvrtko