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

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Message-ID: <20210330080615.21938-1-lecopzer.chen@mediatek.com>
Date:   Tue, 30 Mar 2021 16:06:15 +0800
From:   Lecopzer Chen <lecopzer.chen@...iatek.com>
To:     <sumit.garg@...aro.org>
CC:     <alexandru.elisei@....com>, <catalin.marinas@....com>,
        <daniel.thompson@...aro.org>, <dianders@...omium.org>,
        <lecopzer.chen@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <mark.rutland@....com>,
        <swboyd@...omium.org>, <will@...nel.org>, <yj.chiang@...iatek.com>,
        <lecopzer@...il.com>
Subject: Re: [PATCH v5] arm64: Enable perf events based hard lockup detector

> 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.
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.


BRs,
Lecopzer