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

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Message-ID: <AM6PR04MB496688E213BDF2B104E5FCE1809C0@AM6PR04MB4966.eurprd04.prod.outlook.com>
Date:   Mon, 15 Jun 2020 06:31:28 +0000
From:   Aisheng Dong <aisheng.dong@....com>
To:     Andy Duan <fugang.duan@....com>,
        "wu000273@....edu" <wu000273@....edu>,
        "kjlu@....edu" <kjlu@....edu>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "khilman@...nel.org" <khilman@...nel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
CC:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>, Wolfram Sang <wsa@...nel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] i2c: busses: Fix a reference count leak.

> From: Andy Duan <fugang.duan@....com>
> Sent: Monday, June 15, 2020 10:49 AM
>
> From: wu000273@....edu <wu000273@....edu> Sent: Sunday, June 14,
> 2020 6:12 AM
> > From: Qiushi Wu <wu000273@....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@....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