RE: [PATCH] i2c: busses: Fix a reference count leak.

RE: [PATCH] i2c: busses: Fix a reference count leak.

[Aisheng Dong]

> From: Andy Duan <fugang.duan@nxp.com>
> Sent: Monday, June 15, 2020 10:49 AM
>
> From: wu000273@umn.edu <wu000273@umn.edu> Sent: Sunday, June 14,
> 2020 6:12 AM
> > From: Qiushi Wu <wu000273@umn.edu>
> >
> > pm_runtime_get_sync() increments the runtime PM usage counter even
> > when it returns an error code. Thus call pm_runtime_put_noidle() if
> > pm_runtime_get_sync() fails.
> >
> > Fixes: 13d6eb20fc79 ("i2c: imx-lpi2c: add runtime pm support")
> > Signed-off-by: Qiushi Wu <wu000273@umn.edu>
> 
> Again, which case can trigger the issue ?

It's just error handling improvement because pm_runtime_get_sync() will increase the
reference count even it's failed.

I wonder if such de-reference can be better handled by pm runtime core code.
Copy pm guys to comment.

Regards
Aisheng

> > ---
> >  drivers/i2c/busses/i2c-imx-lpi2c.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > index 9db6ccded5e9..85b9c1fc7681 100644
> > --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > @@ -260,8 +260,10 @@ static int lpi2c_imx_master_enable(struct
> > lpi2c_imx_struct *lpi2c_imx)
> >         int ret;
> >
> >         ret = pm_runtime_get_sync(lpi2c_imx->adapter.dev.parent);
> > -       if (ret < 0)
> > +       if (ret < 0) {
> > +               pm_runtime_put_noidle(lpi2c_imx->adapter.dev.parent);
> >                 return ret;
> > +       }
> >
> >         temp = MCR_RST;
> >         writel(temp, lpi2c_imx->base + LPI2C_MCR);
> > --
> > 2.17.1

Re: [PATCH] i2c: busses: Fix a reference count leak.

[Wolfram Sang]

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On Mon, Jun 15, 2020 at 06:31:28AM +0000, Aisheng Dong wrote:
> > From: Andy Duan <fugang.duan@nxp.com>
> > Sent: Monday, June 15, 2020 10:49 AM
> >
> > From: wu000273@umn.edu <wu000273@umn.edu> Sent: Sunday, June 14,
> > 2020 6:12 AM
> > > From: Qiushi Wu <wu000273@umn.edu>
> > >
> > > pm_runtime_get_sync() increments the runtime PM usage counter even
> > > when it returns an error code. Thus call pm_runtime_put_noidle() if
> > > pm_runtime_get_sync() fails.
> > >
> > > Fixes: 13d6eb20fc79 ("i2c: imx-lpi2c: add runtime pm support")
> > > Signed-off-by: Qiushi Wu <wu000273@umn.edu>
> > 
> > Again, which case can trigger the issue ?
> 
> It's just error handling improvement because pm_runtime_get_sync() will increase the
> reference count even it's failed.
> 
> I wonder if such de-reference can be better handled by pm runtime core code.
> Copy pm guys to comment.

I started a seperate thread:

https://lkml.org/lkml/2020/6/14/76

Still, on-going discussion if the proper fix is to remove the error
check.


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