Re: [PATCH -next] drm/panfrost: Fix PM reference leak in panfrost_job_hw_submit()

[Samuel Zou]

Hi Steven,

Thanks for your review and also answer my doubts. Looking forward to 
your patch.

On 2021/5/12 23:23, Steven Price wrote:
> On 11/05/2021 07:29, Zou Wei wrote:
> > pm_runtime_get_sync will increment pm usage counter even it failed.
> > Forgetting to putting operation will result in reference leak here.
> > Fix it by replacing it with pm_runtime_resume_and_get to keep usage
> > counter balanced.
> >
> > Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> > Signed-off-by: Zou Wei <zou_wei@xxxxxxxxxx>
>
> Thanks for the patch, but this is actually incorrect. 
> panfrost_job_hw_submit() is expected to unconditionally increment the pm 
> usage counter. This is because panfrost_job_hw_submit() can (currently) 
> never fail, so in this case the job is considered "submitted" (even 
> though it never reaches the hardware) and it's handled by the job timeout.
>
> However this is at least the second time[1] this phantom "reference 
> leak" has been raised, so perhaps it's time to handle this better. I'll 
> post a patch reworking panfrost_job_hw_submit() so it can fail.
>
> Thanks,
>
> Steve
>
> [1] 
> https://lore.kernel.org/r/20200520110504.24388-1-dinghao.liu%40zju.edu.cn
>
> > ---
> >   drivers/gpu/drm/panfrost/panfrost_job.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c 
> > b/drivers/gpu/drm/panfrost/panfrost_job.c
> > index 6003cfe..42d8dbc 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> > @@ -157,7 +157,7 @@ static void panfrost_job_hw_submit(struct 
> > panfrost_job *job, int js)
> >       panfrost_devfreq_record_busy(&pfdev->pfdevfreq);
> > -    ret = pm_runtime_get_sync(pfdev->dev);
> > +    ret = pm_runtime_resume_and_get(pfdev->dev);
> >       if (ret < 0)
> >           return;
>
> .