Re: [PATCH] drm/panfrost: fix reference leak in panfrost_job_hw_submit

[Qinglang Miao]

在 2020/11/27 18:06, Steven Price 写道:
> On 27/11/2020 09:44, Qinglang Miao wrote:
> > pm_runtime_get_sync will increment pm usage counter even it
> > failed. Forgetting to putting operation will result in a
> > reference leak here.
> >
> > A new function pm_runtime_resume_and_get is introduced in
> > [0] to keep usage counter balanced. So We fix the reference
> > leak by replacing it with new funtion.
> >
> > [0] dd8088d5a896 ("PM: runtime: Add  pm_runtime_resume_and_get to deal 
> > with usage counter")
> >
> > Fixes: f3ba91228e8e ("drm/panfrost: Add initial panfrost driver")
> > Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> > Signed-off-by: Qinglang Miao <miaoqinglang@xxxxxxxxxx>
> > ---
> >   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 30e7b7196..04cf3bb67 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> > @@ -147,7 +147,7 @@ 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);
>
> Sorry, but in this case this change isn't correct. 
> panfrost_job_hw_submit() is expected to be unbalanced (the PM reference 
> count is expected to be incremented on return).
>
> In the case where pm_runtime_get_sync() fails, the job will eventually 
> timeout, and there's a corresponding pm_runtime_put_noidle() in 
> panfrost_reset().
>
> Potentially this could be handled better (e.g. without waiting for the 
> timeout to occur), but equally this isn't something we expect to happen 
> in normal operation).
>
> Steve
Sorry, I didn't notice the pm_runtime_put_noidle() in 
panfrost_job_timedout() before.

Thanks for your reply.
> >       if (ret < 0)
> >           return;
>
> .