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From:   Thomas Gleixner <tglx@linutronix.de>
To:     paulmck@kernel.org
Cc:     John Stultz <jstultz@google.com>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Stephen Boyd <sboyd@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        x86@kernel.org
Subject: Re: [PATCH] clocksource: disable irq when holding watchdog_lock.
In-Reply-To: <ae4e5836-bc42-42fa-bd41-2a2fd483acb5@paulmck-laptop>
References: <80ff5036-8449-44a6-ba2f-0130d3be6b57@I-love.SAKURA.ne.jp>
 <CANDhNCpw+hEHNbtdAZR01HsHW_L1C0BXjZq21eXouQGNnYuUNQ@mail.gmail.com>
 <878r826xys.ffs@tglx>
 <ae4e5836-bc42-42fa-bd41-2a2fd483acb5@paulmck-laptop>
Date:   Tue, 17 Oct 2023 08:49:46 +0200
Message-ID: <8734y97ng5.ffs@tglx>
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On Mon, Oct 16 2023 at 16:03, Paul E. McKenney wrote:
> On Mon, Oct 16, 2023 at 11:47:55PM +0200, Thomas Gleixner wrote:
>> That said, this whole clocksource watchdog mess wants a proper
>> overhaul. It has become a pile of warts and duct tape by now and after
>> staring at it long enough there is no real reason to run it in a timer
>> callback anymore. It just can move into delayed work and the whole
>> locking problem can be reduced to the clocksource_mutex and some well
>> thought out atomic operations to handle the mark unstable case. But
>> that's a different story and not relevant for curing the problem at
>> hand.
>
> Moving the code to delayed work seems quite reasonable.
>
> But Thomas, you do understand that the way things have been going for
> the clocksource watchdog, pushing it out to delayed work will no doubt
> add yet more hair on large busy systems, right?  Yeah, yeah, I know,
> delayed work shouldn't be any worse than ksoftirqd.  The key word of
> course being "shouldn't".  ;-)

Yes, I'm aware of that. I still think it's worth at least to try it.

Thanks,

        tglx