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Date:   Mon, 28 Sep 2020 22:56:23 +0100
From:   Will Deacon <will@kernel.org>
To:     Sumit Garg <sumit.garg@linaro.org>, alexandru.elisei@arm.com
Cc:     linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
        mark.rutland@arm.com, peterz@infradead.org, mingo@redhat.com,
        acme@kernel.org, alexander.shishkin@linux.intel.com,
        jolsa@redhat.com, namhyung@kernel.org, tglx@linutronix.de,
        alexandru.elisei@arm.com, swboyd@chromium.org,
        julien.thierry.kdev@gmail.com, dianders@chromium.org,
        daniel.thompson@linaro.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] arm64: Enable perf events based hard lockup detector
Message-ID: <20200928215622.GA12677@willie-the-truck>
References: <1599204397-17596-1-git-send-email-sumit.garg@linaro.org>
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On Fri, Sep 04, 2020 at 12:56:37PM +0530, Sumit Garg 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@linaro.org>
> ---
> 
> Changes in v3:
> - Rebased to latest pmu NMI patch-set [1].
> - Addressed misc. comments from Stephen.
> 
> [1] https://lkml.org/lkml/2020/8/19/671
> 
> Changes since RFC:
> - Rebased on top of Alex's WIP-pmu-nmi branch.
> - Add comment for safe max. CPU frequency.
> - Misc. cleanup.
> 
>  arch/arm64/Kconfig             |  2 ++
>  arch/arm64/kernel/perf_event.c | 41 +++++++++++++++++++++++++++++++++++++++--
>  drivers/perf/arm_pmu.c         |  9 +++++++++
>  include/linux/perf/arm_pmu.h   |  2 ++
>  4 files changed, 52 insertions(+), 2 deletions(-)

It would be great to have Alexandru's ack on this, since it builds directly
on top of his code.

Will