linux-kernel - Re: Re: [PATCH] spi: tegra20-slink: Fix runtime PM imbalance on error

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5a8a6e7b.bef25.1723b588c7f.Coremail.dinghao.liu@zju.edu.cn>
Date:   Fri, 22 May 2020 15:45:58 +0800 (GMT+08:00)
From:   dinghao.liu@....edu.cn
To:     "Andy Shevchenko" <andy.shevchenko@...il.com>
Cc:     "Kangjie Lu" <kjlu@....edu>,
        "Laxman Dewangan" <ldewangan@...dia.com>,
        "Mark Brown" <broonie@...nel.org>,
        "Thierry Reding" <thierry.reding@...il.com>,
        "Jonathan Hunter" <jonathanh@...dia.com>,
        linux-spi <linux-spi@...r.kernel.org>,
        linux-tegra@...r.kernel.org,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH] spi: tegra20-slink: Fix runtime PM imbalance on
 error

Hi Andy,

Thank you for your advice!

Your suggestion is to use pm_runtime_put_noidle(), right? 
The only difference between pm_runtime_put() and this function
is that pm_runtime_put() will run an extra pm_request_idle().

I checked this patched function again and found there is a
pm_runtime_put() in the normal branch of pm_runtime_get_sync().
Does this mean the original program logic need to execute idle
callback?

According to runtime PM's doc, the pm_runtime_get_sync() call
paired with a pm_runtime_put() call will be appropriate to ensure
that the device is not put back to sleep during the probe. Therefore
I think pm_runtime_put() is more appropriate here. Do you have 
more detailed suggestion for why we should use _put_noidle()?

Regards,
Dinghao 
> On Thu, May 21, 2020 at 10:50 AM Dinghao Liu <dinghao.liu@....edu.cn> wrote:
> >
> > pm_runtime_get_sync() increments the runtime PM usage counter even
> > when it returns an error code. Thus a pairing decrement is needed on
> > the error handling path to keep the counter balanced.
> 
> ...
> 
> >         ret = pm_runtime_get_sync(&pdev->dev);
> >         if (ret < 0) {
> >                 dev_err(&pdev->dev, "pm runtime get failed, e = %d\n", ret);
> 
> > +               pm_runtime_put(&pdev->dev);
> 
> For all your patches, please, double check what you are proposing.
> 
> Here, I believe, the correct one will be _put_noidle().
> 
> AFAIU you are not supposed to actually suspend the device in case of error.
> But I might be mistaken, thus see above.
> 
> >                 goto exit_pm_disable;
> >         }
> 
> -- 
> With Best Regards,
> Andy Shevchenko