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

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Message-ID: <CAE-0n514xGWz1yaF84zL=QBCQcMwct+pu8nLBgRHPq6+DE3g5g@mail.gmail.com>
Date:   Fri, 25 Aug 2023 18:23:18 -0500
From:   Stephen Boyd <swboyd@...omium.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sumit Garg <sumit.garg@...aro.org>,
        Will Deacon <will@...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,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        linux-perf-users@...r.kernel.org,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        Chen-Yu Tsai <wens@...e.org>,
        linux-arm-kernel@...ts.infradead.org, ito-yuichi@...itsu.com,
        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
Subject: Re: [PATCH v11 4/6] arm64: smp: Add arch support for backtrace using pseudo-NMI

Quoting Doug Anderson (2023-08-25 16:02:46)
> On Fri, Aug 25, 2023 at 3:27 PM Stephen Boyd <swboyd@...omium.org> wrote:
> >
> > Quoting Douglas Anderson (2023-08-24 08:30:30)
> > > diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
> > >
> > >  static int ipi_irq_base __read_mostly;
> > >  static int nr_ipi __read_mostly = NR_IPI;
> > > -static struct irq_desc *ipi_desc[NR_IPI] __read_mostly;
> > > +static struct irq_desc *ipi_desc[MAX_IPI] __read_mostly;
> >
> > Side note: it would be nice to mark ipi_desc as __ro_after_init. Same
> > for nr_ipi and ipi_irq_base.
>
> I'd rather not change it in this patch since it's a pre-existing and
> separate issue, but I can add a patch to the end of the series for
> that if I end up spinning it. Otherwise I can send a follow-up patch
> for it.

Of course. Don't change it in this patch.

>
>
> > >  static void ipi_setup(int cpu);
> > >
> > > @@ -845,6 +852,22 @@ static void __noreturn ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs
> > >  #endif
> > >  }
> > >
> > > +static void arm64_backtrace_ipi(cpumask_t *mask)
> > > +{
> > > +       __ipi_send_mask(ipi_desc[IPI_CPU_BACKTRACE], mask);
> > > +}
> > > +
> > > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
> >
> > Can this be 'bool exclude_self' instead of int? That matches all other
> > implementations from what I can tell.
>
> Nope. See the part of the commit message that says:
>
> This patch depends on commit 36759e343ff9 ("nmi_backtrace: allow
> excluding an arbitrary CPU") since that commit changed the prototype
> of arch_trigger_cpumask_backtrace(), which this patch implements.

Ah, ok. Sounds fine then.