linux-kernel - Re: [PATCH v11 4/6] arm64: smp: Add arch support for backtrace using pseudo-NMI

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Message-ID: <CAD=FV=UZeHicVLn3GAxdFrtUbwHnb8GEvsfe9BM7cfBrTrK=Fg@mail.gmail.com>
Date:   Tue, 29 Aug 2023 09:03:04 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     "Tomohiro Misono (Fujitsu)" <misono.tomohiro@...itsu.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Marc Zyngier <maz@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "kgdb-bugreport@...ts.sourceforge.net" 
        <kgdb-bugreport@...ts.sourceforge.net>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        Chen-Yu Tsai <wens@...e.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "Yuichi Ito (Fujitsu)" <ito-yuichi@...itsu.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        D Scott Phillips <scott@...amperecomputing.com>,
        Ingo Molnar <mingo@...nel.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Valentin Schneider <vschneid@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 4/6] arm64: smp: Add arch support for backtrace using pseudo-NMI

Hi,

On Mon, Aug 28, 2023 at 10:23 PM Tomohiro Misono (Fujitsu)
<misono.tomohiro@...itsu.com> wrote:
>
> > -----Original Message-----
> > Subject: [PATCH v11 4/6] arm64: smp: Add arch support for backtrace using
> > pseudo-NMI
> >
> > Enable arch_trigger_cpumask_backtrace() support on arm64. This enables
> > things much like they are enabled on arm32 (including some of the
> > funky logic around NR_IPI, nr_ipi, and MAX_IPI) but with the
> > difference that, unlike arm32, we'll try to enable the backtrace to
> > use pseudo-NMI.
> >
> > NOTE: this patch is a squash of the little bit of code adding the
> > ability to mark an IPI to try to use pseudo-NMI plus the little bit of
> > code to hook things up for kgdb. This approach was decided upon in the
> > discussion of v9 [1].
> >
> > This patch depends on commit 36759e343ff9 ("nmi_backtrace: allow
>
> Hi,
> Is this commit ID valid? I believe this commit is not included in the
> mainline yet. Other than this,
>  Reviewed-by: Misono Tomohiro <misono.tomohiro@...itsu.com>

Ah, good call. I must have grabbed that git hash before the commit
moved from Andrew Morton's unstable branch to his stable branch. As
far as I can tell, it should be commit 8d539b84f1e3 ("nmi_backtrace:
allow excluding an arbitrary CPU"). ...at least that's what's in
linuxnext today. That also appears to match the commit hash in the
pull request that Andrew just sent to Linus [1].

I'll update the git hash and add your tag in v12, which I'm currently
aiming to send out tomorrow.

[1] https://lore.kernel.org/r/20230828225431.354d3d2d3b80ee5b88e65eb5@linux-foundation.org