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

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

[wu000273]

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>
---
 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


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

[Andy Duan]

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 ?
> ---
>  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


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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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