Re: [PATCH] drm: bridge: cdns-mhdp8546: Fix PM reference leak in cdns_mhdp_probe()

[yukuai (C)]

ping ...

On 2021/05/18 20:58, Robert Foss wrote:
> On Tue, 18 May 2021 at 09:42, Johan Hovold <johan@xxxxxxxxxx> wrote:
> > On Mon, May 17, 2021 at 11:27:38AM +0200, Robert Foss wrote:
> > > Hey Yu,
> > >
> > > On Mon, 17 May 2021 at 10:08, Yu Kuai <yukuai3@xxxxxxxxxx> 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: Yu Kuai <yukuai3@xxxxxxxxxx>
> > > > ---
> > > >   drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 2 +-
> > > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> > > > index 0cd8f40fb690..305489d48c16 100644
> > > > --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> > > > +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> > > > @@ -2478,7 +2478,7 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
> > > >          clk_prepare_enable(clk);
> > > >
> > > >          pm_runtime_enable(dev);
> > > > -       ret = pm_runtime_get_sync(dev);
> > > > +       ret = pm_runtime_resume_and_get(dev);
> > > >          if (ret < 0) {
> > > >                  dev_err(dev, "pm_runtime_get_sync failed\n");
>
> This error message is a bit confusing now, could you update it.
>
> > > >                  pm_runtime_disable(dev);
> > >
> > > The code is correct as it is. If pm_runtime_get_sync() fails and
> > > increments[1] the pm.usage_count variable, that isn't a problem since
> > > pm_runtime_disable() disables pm, and resets pm.usage_count variable
> > > to zero[2].
> >
> > No it doesn't; pm_runtime_disable() does not reset the counter and you
> > still need to decrement the usage count when pm_runtime_get_sync()
> > fails.
>
> Thanks for chiming in Johan, you're absolutely right and I must have
> misread something.
>
> With the above fix, feel free to add my r-b.
>
> Reviewed-by: Robert Foss <robert.foss@xxxxxxxxxx>
> .