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

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Date:   Mon, 15 Jun 2020 09:06:47 +0200
From:   Wolfram Sang <wsa@...nel.org>
To:     Aisheng Dong <aisheng.dong@....com>
Cc:     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>,
        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>,
        "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.

On Mon, Jun 15, 2020 at 06:31:28AM +0000, Aisheng Dong wrote:
> > 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.

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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