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

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Message-ID: <CAFA6WYPXu8biPPim5EoQ1pi+w3APKm65tzfOvH4OSORZdJ6+8Q@mail.gmail.com>
Date:   Mon, 12 Apr 2021 17:31:13 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Will Deacon <will@...nel.org>
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>,
        Lecopzer Chen <lecopzer.chen@...iatek.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>, yj.chiang@...iatek.com
Subject: Re: [PATCH v5] arm64: Enable perf events based hard lockup detector

Hi Will,

On Tue, 30 Mar 2021 at 18:00, Sumit Garg <sumit.garg@...aro.org> wrote:
>
> 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?
> > > >

Since there aren't any further comments, can you re-pick this feature for 5.13?

-Sumit

> > > > 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