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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Fri, 22 May 2020 18:22:51 +0300
Message-ID: <CAHp75VexCBc6iCrd_VLj5jXE8cxxdzUUf6pMG6O8LjtNj0J1Aw@mail.gmail.com>
Subject: Re: Re: [PATCH] spi: tegra20-slink: Fix runtime PM imbalance on error
To:     Dinghao Liu <dinghao.liu@zju.edu.cn>
Cc:     Kangjie Lu <kjlu@umn.edu>, Laxman Dewangan <ldewangan@nvidia.com>,
        Mark Brown <broonie@kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        linux-spi <linux-spi@vger.kernel.org>,
        linux-tegra@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Fri, May 22, 2020 at 6:20 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Fri, May 22, 2020 at 10:46 AM <dinghao.liu@zju.edu.cn> wrote:

...

> Moreover, consider below case
>
> CPU1: ...somewhere in the code...
> pm_runtime_get() // with success!
> ...see below...
> pm_runtime_put()
>
> CPU2: ...on parallel thread...
> ret = pm_runtime_get_sync() // failed!
> if (ret)
>   pm_runtime_put() // oi vei, we put device into sleep
>
> So, there is a potential issue.

...and even if it's impossible (no bugs in runtime PM core, etc) the
code with put() looks suspicious.

-- 
With Best Regards,
Andy Shevchenko