linux-kernel - Re: [PATCH v5 15/18] watchdog/perf: Add a weak function for an arch to detect if perf can use NMIs

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Message-ID: <ZIckscgmirrgxZ75@FVFF77S0Q05N>
Date:   Mon, 12 Jun 2023 14:59:13 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Petr Mladek <pmladek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        kgdb-bugreport@...ts.sourceforge.net,
        Stephane Eranian <eranian@...gle.com>, mpe@...erman.id.au,
        Tzung-Bi Shih <tzungbi@...omium.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        linuxppc-dev@...ts.ozlabs.org, Sumit Garg <sumit.garg@...aro.org>,
        npiggin@...il.com, davem@...emloft.net,
        Marc Zyngier <maz@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>, sparclinux@...r.kernel.org,
        christophe.leroy@...roup.eu,
        Catalin Marinas <catalin.marinas@....com>,
        ravi.v.shankar@...el.com, Randy Dunlap <rdunlap@...radead.org>,
        Pingfan Liu <kernelfans@...il.com>,
        Guenter Roeck <groeck@...omium.org>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        Ian Rogers <irogers@...gle.com>, ito-yuichi@...itsu.com,
        ricardo.neri@...el.com, linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, Will Deacon <will@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, linux-kernel@...r.kernel.org,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v5 15/18] watchdog/perf: Add a weak function for an arch
 to detect if perf can use NMIs

On Mon, Jun 12, 2023 at 06:55:37AM -0700, Doug Anderson wrote:
> Mark,
> 
> On Mon, Jun 12, 2023 at 3:33 AM Mark Rutland <mark.rutland@....com> wrote:
> >
> > On Fri, May 19, 2023 at 10:18:39AM -0700, Douglas Anderson wrote:
> > > On arm64, NMI support needs to be detected at runtime. Add a weak
> > > function to the perf hardlockup detector so that an architecture can
> > > implement it to detect whether NMIs are available.
> > >
> > > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > > ---
> > > While I won't object to this patch landing, I consider it part of the
> > > arm64 perf hardlockup effort. I would be OK with the earlier patches
> > > in the series landing and then not landing ${SUBJECT} patch nor
> > > anything else later.
> >
> > FWIW, everything prior to this looks fine to me, so I reckon it'd be worth
> > splitting the series here and getting the buddy lockup detector in first, to
> > avoid a log-jam on all the subsequent NMI bits.
> 
> I think the whole series has already landed in Andrew's tree,
> including the arm64 "perf" lockup detector bits. I saw all the
> notifications from Andrew go through over the weekend that they were
> moved from an "unstable" branch to a "stable" one and I see them at:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/log/?h=mm-nonmm-stable
> 
> When I first saw Anderw land the arm64 perf lockup detector bits in
> his unstable branch several weeks ago, I sent a private message to the
> arm64 maintainers (yourself included) to make sure you were aware of
> it and that it hadn't been caught in mail filters. I got the
> impression that everything was OK. Is that not the case?

Sorry; I'm slowly catching up with a backlog of email, and I'm just behind.

Feel free to ignore this; sorry for the noise!

If we spot anything going wrong in testing we can look at fixing those up.

Thanks,
Mark.