linux-kernel - Re: RFC: a failing pm_runtime

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Date:   Sun, 14 Jun 2020 12:42:58 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Wolfram Sang <wsa@...nel.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-i2c <linux-i2c@...r.kernel.org>
Subject: Re: RFC: a failing pm_runtime_get increases the refcnt?

On Sun, Jun 14, 2020 at 12:34 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Sun, Jun 14, 2020 at 12:10 PM Wolfram Sang <wsa@...nel.org> wrote:
> > both in the I2C subsystem and also for Renesas drivers I maintain, I am
> > starting to get boilerplate patches doing some pm_runtime_put_* variant
> > because a failing pm_runtime_get is supposed to increase the ref
> > counters? Really? This feels wrong and unintuitive to me.
>
> Yeah, that is a well known issue with PM (I even have for a long time
> a coccinelle script, when I realized myself that there are a lot of
> cases like this, but someone else discovered this recently, like
> opening a can of worms).
>
> > I expect there
> > has been a discussion around it but I couldn't find it.
>
> Rafael explained (again) recently this. I can't find it quickly, unfortunately.

I _think_ this discussion, but may be it's simple another tentacle of
the same octopus.
https://patchwork.ozlabs.org/project/linux-tegra/patch/20200520095148.10995-1-dinghao.liu@zju.edu.cn/

>
> > I wonder why we
> > don't fix the code where the incremented refcount is expected for some
> > reason.
>
> The main idea behind API that a lot of drivers do *not* check error
> codes from runtime PM, so, we need to keep balance in case of
>
> pm_runtime_get(...);
> ...
> pm_runtime_put(...);
>
> > Can I have some pointers please?
>
> --
> With Best Regards,
> Andy Shevchenko



-- 
With Best Regards,
Andy Shevchenko