linux-kernel - Re: [External] Re: [PATCH 1/2] watchdog: refactor watchdog

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Message-ID: <CAEEQ3wn2FfgzKq-vwt5m=Xy5NThrGkZaY4=U45QmN4JzJG8Rng@mail.gmail.com>
Date: Mon, 15 Sep 2025 09:56:22 +0800
From: yunhui cui <cuiyunhui@...edance.com>
To: Ian Rogers <irogers@...gle.com>
Cc: Doug Anderson <dianders@...omium.org>, paul.walmsley@...ive.com, palmer@...belt.com, 
	aou@...s.berkeley.edu, alex@...ti.fr, atish.patra@...ux.dev, 
	anup@...infault.org, will@...nel.org, mark.rutland@....com, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org, 
	catalin.marinas@....com, masahiroy@...nel.org, suzuki.poulose@....com, 
	maz@...nel.org, zhanjie9@...ilicon.com, yangyicong@...ilicon.com, 
	mingo@...nel.org, lihuafei1@...wei.com, akpm@...ux-foundation.org, 
	jpoimboe@...nel.org, rppt@...nel.org, kees@...nel.org, 
	thomas.weissschuh@...utronix.de
Subject: Re: [External] Re: [PATCH 1/2] watchdog: refactor watchdog_hld functionality

Hi,

On Mon, Sep 8, 2025 at 7:15 AM Ian Rogers <irogers@...gle.com> wrote:
>
> On Fri, Sep 5, 2025 at 4:57 PM Doug Anderson <dianders@...omium.org> wrote:
> >
> > Hi,
> >
> > On Wed, Sep 3, 2025 at 4:56 AM yunhui cui <cuiyunhui@...edance.com> wrote:
> > > I’ve read your linked content, which details the pros and cons of perf
> > > watchdog and buddy watchdog.
> > > I think everyone will agree on choosing one as the default.
> > > It seems there’s no kernel/watchdog entry in MAINTAINERS—what’s next
> > > for these two approaches?
> >
> > I guess to start, someone (you?) should send some patches to the list.
> > Maybe one patch to make buddy the default and one to change the
> > description of the "perf" lockup detector say that its usage is
> > discouraged, that it might be removed, that people should use the
> > "buddy" detector instead, and that if there's a reason someone needs
> > the "perf" detector instead of the buddy one then they should make
> > some loud noises.
> >
> > You'd want to CC folks who were involved in recent watchdog changes
> > and make sure to CC Andrew (akpm). If folks react positive and Andrew
> > agrees then he'll likely land the the patches and we'll have made
> > forward progress. :-)
>
> +1

Okay, I intend to directly send a patch that removes
HARDLOCKUP_DETECTOR_PERF, and then we can discuss on that patch.

>
> There are also things like /proc/sys/kernel/nmi_watchdog being used to
> enable/disable the hard lookup detector. If we could move that to a
> unique file so that perf is less confused in places like:
> https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/util/util.c#n70
> ie. perf shouldn't warn about the NMI watchdog being enabled and
> taking a perf event when it doesn't.

Okay, let's first take a look at the status of the discussion on the
patch for removing HARDLOCKUP_DETECTOR_PERF, and then we'll modify
this part.

>
> Thanks,
> Ian

Thanks,
Yunhui