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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Date:   Mon, 12 Jun 2023 06:55:37 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Mark Rutland <mark.rutland@....com>
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

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?


-Doug