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From:   Cong Wang <xiyou.wangcong@gmail.com>
Date:   Wed, 12 May 2021 09:15:06 -0700
Message-ID: <CAM_iQpXbigquRvTF6nBM5732i_dPZ7YZX7egdRqtvydiiP-6vw@mail.gmail.com>
Subject: Re: [PATCH][v3] rtnetlink: add rtnl_lock debug log
To:     "Rocco.Yue" <rocco.yue@mediatek.com>
Cc:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com
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On Wed, May 12, 2021 at 1:38 AM Rocco.Yue <rocco.yue@mediatek.com> wrote:
>
> On Tue, 2021-05-11 at 10:00 -0700, Cong Wang wrote:
> > On Tue, May 11, 2021 at 4:46 AM Rocco yue <rocco.yue@mediatek.com> wrote:
> > >
> > > From: Rocco Yue <rocco.yue@mediatek.com>
> > >
> > > We often encounter system hangs caused by certain process
> > > holding rtnl_lock for a long time. Even if there is a lock
> > > detection mechanism in Linux, it is a bit troublesome and
> > > affects the system performance. We hope to add a lightweight
> > > debugging mechanism for detecting rtnl_lock.
> >
> > Any reason why this is specific to RTNL lock? To me holding
> > a mutex lock for a long time is problematic for any mutex.
> > I have seen some fs mutex being held for a long time caused
> > many hung tasks in the system.
> >
> > Thanks.
>
> Thank you for a good question.
>
> It's a problem to hold rtnl_lock for a long time, and other locks are no
> exception.

Then please try to make it generic so that other mutex locks will
benefit too.

Thanks.