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

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Message-ID: <CAD=FV=XYGmayve1ujv9oqRrJaq-D6g7pRygvQf31WfEMsT3g8Q@mail.gmail.com>
Date: Wed, 24 Sep 2025 08:22:21 -0700
From: Doug Anderson <dianders@...omium.org>
To: yunhui cui <cuiyunhui@...edance.com>
Cc: 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 Tue, Sep 23, 2025 at 7:41 PM yunhui cui <cuiyunhui@...edance.com> wrote:
>
> Hi Doug,
>
> On Sat, Aug 30, 2025 at 5:34 AM Doug Anderson <dianders@...omium.org> wrote:
> >
> > Hi,
> >
> > On Wed, Aug 27, 2025 at 3:10 AM Yunhui Cui <cuiyunhui@...edance.com> wrote:
> > >
> > > Move watchdog_hld.c to kernel/, and rename arm_pmu_irq_is_nmi()
> > > to arch_pmu_irq_is_nmi() for cross-arch reusability.
> > >
> > > Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> > > ---
> > >  arch/arm64/kernel/Makefile                   | 1 -
> > >  drivers/perf/arm_pmu.c                       | 2 +-
> > >  include/linux/nmi.h                          | 1 +
> > >  include/linux/perf/arm_pmu.h                 | 2 --
> > >  kernel/Makefile                              | 2 +-
> > >  {arch/arm64/kernel => kernel}/watchdog_hld.c | 8 ++++++--
> > >  6 files changed, 9 insertions(+), 7 deletions(-)
> > >  rename {arch/arm64/kernel => kernel}/watchdog_hld.c (97%)
> >
> > I'm not a huge fan of the perf hardlockup detector and IMO we should
> > maybe just delete it. Thus spreading it to support a new architecture
> > isn't my favorite thing to do. Can't you use the buddy hardlockup
> > detector?
> >
> > That being said, I did a quick look at your patch. I'm pretty sure you
> > can't just move the arm64 "watchdog_hld.c" to be generic. Won't
> > hw_nmi_get_sample_period() conflict with everyone else's (x86 and
> > powerpc)?
>
> After discussing whether to remove watchdog perf, it still seems
> necessary to keep advancing with it. For the code, we just need to
> decorate hw_nmi_get_sample_period() with __weak, right?

That would probably work, but IMO you should make sure you can figure
out how to at least compile the x86/powerpc kernels to confirm.

-Doug