linux-kernel - Re: [PATCH] clocksource: disable irq when holding watchdog

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Date:   Tue, 17 Oct 2023 08:49:46 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     paulmck@...nel.org
Cc:     John Stultz <jstultz@...gle.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Stephen Boyd <sboyd@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        x86@...nel.org
Subject: Re: [PATCH] clocksource: disable irq when holding watchdog_lock.

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