linux-kernel - Re: [PATCH v5] arm64: Enable perf events based hard lockup detector

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Date:   Tue, 30 Mar 2021 18:00:39 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Lecopzer Chen <lecopzer.chen@...iatek.com>
Cc:     Alexandru Elisei <alexandru.elisei@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Lecopzer Chen <lecopzer@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Stephen Boyd <swboyd@...omium.org>,
        Will Deacon <will@...nel.org>, yj.chiang@...iatek.com
Subject: Re: [PATCH v5] arm64: Enable perf events based hard lockup detector

On Tue, 30 Mar 2021 at 14:07, Lecopzer Chen <lecopzer.chen@...iatek.com> wrote:
>
> > > Hi Will, Mark,
> > >
> > > On Fri, 15 Jan 2021 at 17:32, Sumit Garg <sumit.garg@...aro.org> wrote:
> > > >
> > > > With the recent feature added to enable perf events to use pseudo NMIs
> > > > as interrupts on platforms which support GICv3 or later, its now been
> > > > possible to enable hard lockup detector (or NMI watchdog) on arm64
> > > > platforms. So enable corresponding support.
> > > >
> > > > One thing to note here is that normally lockup detector is initialized
> > > > just after the early initcalls but PMU on arm64 comes up much later as
> > > > device_initcall(). So we need to re-initialize lockup detection once
> > > > PMU has been initialized.
> > > >
> > > > Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
> > > > ---
> > > >
> > > > Changes in v5:
> > > > - Fix lockup_detector_init() invocation to be rather invoked from CPU
> > > >   binded context as it makes heavy use of per-cpu variables and shouldn't
> > > >   be invoked from preemptible context.
> > > >
> > >
> > > Do you have any further comments on this?
> > >
> > > Lecopzer,
> > >
> > > Does this feature work fine for you now?
> >
> > This really fixes the warning, I have a real hardware for testing this now.

Thanks for the testing. I assume it as an implicit Tested-by.

> > but do we need to call lockup_detector_init() for each cpu?
> >
> > In init/main.c, it's only called by cpu 0 for once.
>
> Oh sorry, I just misread the code, please ignore previous mail.
>

No worries.

-Sumit

>
> BRs,
> Lecopzer