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

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Message-ID: <d76da5a6-d4fa-405b-8fec-7b87cb776e71@paulmck-laptop>
Date:   Tue, 17 Oct 2023 07:11:13 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
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 Tue, Oct 17, 2023 at 08:49:46AM +0200, Thomas Gleixner wrote:
> 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.

OK, good.  And again, agreed.

							Thanx, Paul