Re: [PATCH] media: vsp1: Fix runtime PM imbalance in vsp1_probe

Laurent Pinchart
2020-06-08T01:58:18Z

On Mon, Jun 08, 2020 at 04:54:57AM +0300, Laurent Pinchart wrote:
> Hi Dinghao,
>
> Thank you for the patch.
>
> On Sat, May 23, 2020 at 07:54:26PM +0800, Dinghao Liu wrote:
> > pm_runtime_get_sync() increments the runtime PM usage counter even
> > when it returns an error code. Thus a pairing decrement is needed on
> > the error handling path to keep the counter balanced.
>
> I wonder how many bugs we have today, and how many bugs will keep
> appearing in the future, due to this historical design mistake :-(
>
> > Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
> > ---
> > drivers/media/platform/vsp1/vsp1_drv.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/vsp1/vsp1_drv.c b/drivers/media/platform/vsp1/vsp1_drv.c
> > index c650e45bb0ad..017a54f2fdd8 100644
> > --- a/drivers/media/platform/vsp1/vsp1_drv.c
> > +++ b/drivers/media/platform/vsp1/vsp1_drv.c
> > @@ -846,8 +846,10 @@ static int vsp1_probe(struct platform_device *pdev)
> > pm_runtime_enable(&pdev->dev);
> >
> > ret = pm_runtime_get_sync(&pdev->dev);
> > - if (ret < 0)
> > + if (ret < 0) {
> > + pm_runtime_put_sync(&pdev->dev);
> > goto done;
> > + }
>
> This change looks good to me, but we also need a similar change in the
> vsp1_device_get() function if I'm not mistaken. Could you combine both
> in the same patch ?

And actually, after fixing vsp1_device_get(), we should replace the
pm_runtime_get_sync() call here with vsp1_device_get(), and the
pm_runtime_put_sync() below with vsp1_device_put(), so there would be no
need to call pm_runtime_put_sync() manually in the error path here.

> >
> > vsp1->version = vsp1_read(vsp1, VI6_IP_VERSION);
> > pm_runtime_put_sync(&pdev->dev);