Re: [PATCH] drm/i915/pmu: Fix wakeref leak in PMU busyness during reset

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>]

On Mon, Dec 06, 2021 at 05:30:43PM -0800, Dixit, Ashutosh wrote:
> On Mon, 06 Dec 2021 16:45:42 -0800, Umesh Nerlige Ramappa wrote:
> > GuC PMU busyness gets gt wakeref if awake, but fails to release the
> > wakeref if a reset is in progress. Release the wakeref if it was
> > acquried successfully.
> >
> > Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
> > ---
> >  drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 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 1f9d4fde421f..a243304a2db1 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -1181,6 +1181,7 @@ static ktime_t guc_engine_busyness(struct intel_engine_cs *engine, ktime_t *now)
> > 	struct intel_gt *gt = engine->gt;
> > 	struct intel_guc *guc = &gt->uc.guc;
> > 	u64 total, gt_stamp_saved;
> > +	intel_wakeref_t wakeref;
>
> Should be bool.
>
> > 	unsigned long flags;
> > 	u32 reset_count;
> > 	bool in_reset;
> > @@ -1206,18 +1207,21 @@ static ktime_t guc_engine_busyness(struct intel_engine_cs *engine, ktime_t *now)
> > 	 * start_gt_clk is derived from GuC state. To get a consistent
> > 	 * view of activity, we query the GuC state only if gt is awake.
> > 	 */
> > -	if (intel_gt_pm_get_if_awake(gt) && !in_reset) {
>
> Also how about just switch them around:
>
> 	if (!in_reset && intel_gt_pm_get_if_awake(gt))
>
> Then you don't need any other changes I think.

:) that looks much simpler, I posted this in v2.

Thanks
Umesh
> > +	wakeref = intel_gt_pm_get_if_awake(gt);
> > +	if (wakeref && !in_reset) {
> > 		stats_saved = *stats;
> > 		gt_stamp_saved = guc->timestamp.gt_stamp;
> > 		guc_update_engine_gt_clks(engine);
> > 		guc_update_pm_timestamp(guc, engine, now);
> > -		intel_gt_pm_put_async(gt);
> > 		if (i915_reset_count(gpu_error) != reset_count) {
> > 			*stats = stats_saved;
> > 			guc->timestamp.gt_stamp = gt_stamp_saved;
> > 		}
> > 	}
> >
> > +	if (wakeref)
> > +		intel_gt_pm_put_async(gt);
> > +
> > 	total = intel_gt_clock_interval_to_ns(gt, stats->total_gt_clks);
> > 	if (stats->running) {
> > 		u64 clk = guc->timestamp.gt_stamp - stats->start_gt_clk;
> > --
> > 2.20.1