From: Sumit Garg <sumit.garg@linaro.org>
To: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Lecopzer Chen <lecopzer.chen@mediatek.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
kernel-team@android.com,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] Revert "arm64: Enable perf events based hard lockup detector"
Date: Wed, 13 Jan 2021 19:12:59 +0530 [thread overview]
Message-ID: <CAFA6WYOCxY4U21Rg9d-mh94M9KxUdFDN11QMqo4HjE6paJR-eg@mail.gmail.com> (raw)
In-Reply-To: <20210113102841.GA11503@willie-the-truck>
On Wed, 13 Jan 2021 at 15:58, Will Deacon <will@kernel.org> wrote:
>
> On Wed, Jan 13, 2021 at 12:00:01PM +0530, Sumit Garg wrote:
> > On Wed, 13 Jan 2021 at 03:49, Will Deacon <will@kernel.org> wrote:
> > >
> > > This reverts commit 367c820ef08082e68df8a3bc12e62393af21e4b5.
> > >
> > > lockup_detector_init() makes heavy use of per-cpu variables and must be
> > > called with preemption disabled. Usually, it's handled early during boot
> > > in kernel_ionit_freeable(), before SMP has been initialised.
> > >
> > > Since we do not know whether or not our PMU interrupt can be signalled
> > > as an NMI until considerably later in the boot process, the Arm PMU
> > > driver attempts to re-initialise the lockup detector off the back of a
> > > device_initcall(). Unfortunately, this is called from preemptible
> > > context and results in the following splat:
> >
> > Can we consider the following fix (compile tested only) to bind the
> > call to lockup_detector_init() to a particular CPU instead of
> > reverting the hard lockup detection feature as a whole?
>
> I think the revert is the right approach for 5.11, and you still have time
> to post a new (preferably more than just compile-tested!) version for 5.12.
>
> This is a new feature so we have time to get it right.
>
Okay, fair enough. I will post the new version for 5.12 with this fix included.
-Sumit
> Thanks,
>
> Will
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next prev parent reply other threads:[~2021-01-13 13:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 22:18 [PATCH] Revert "arm64: Enable perf events based hard lockup detector" Will Deacon
2021-01-13 6:30 ` Sumit Garg
2021-01-13 10:28 ` Will Deacon
2021-01-13 13:42 ` Sumit Garg [this message]
2021-01-13 13:02 ` Mark Rutland
2021-01-28 7:05 ` Sumit Garg
2021-01-13 16:07 ` Catalin Marinas
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