linux-kernel - Re: [RFC PATCH v3 00/12] Unify SMP stop generic logic to common code

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Date:   Mon, 13 Jan 2020 17:05:43 +0000
From:   Cristian Marussi <cristian.marussi@....com>
To:     Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        mark.rutland@....com, peterz@...radead.org,
        catalin.marinas@....com, takahiro.akashi@...aro.org,
        james.morse@....com, hidehiro.kawai.ez@...achi.com,
        tglx@...utronix.de, linux-arm-kernel@...ts.infradead.org,
        mingo@...hat.com, x86@...nel.org, dzickus@...hat.com,
        ehabkost@...hat.com, linux@...linux.org.uk, davem@...emloft.net,
        sparclinux@...r.kernel.org, hch@...radead.org
Subject: Re: [RFC PATCH v3 00/12] Unify SMP stop generic logic to common code

Hi Will

On 13/01/2020 16:40, Will Deacon wrote:
> On Thu, Dec 19, 2019 at 12:18:53PM +0000, Cristian Marussi wrote:
>> the logic underlying SMP stop and kexec crash procedures, beside containing
>> some arch-specific bits, is mostly generic and common across all archs:
>> despite this fact, such logic is now scattered across all architectures and
>> on some of them is flawed, in such a way that, under some specific
>> conditions, you can end up with a CPU left still running after a panic and
>> possibly lost across a subsequent kexec crash reboot. [1]
> 
> Is this still the case even after 20bb759a66be ("panic: ensure preemption is
> disabled during panic()")?
> 

v3 is based on 5.5-rc2 which seems to include 20bb759a66be, and when I tested before
re-posting a few weeks ago it was still failing as usual, i.e. kernel still alive after panic.
[but please be aware that to reproduce it, you need to have only one core online and another one
 panicing while starting up (while still marked offline)]

Thanks

Cristian