linux-kernel - Re: [PATCH AUTOSEL for 3.18 36/40] powerpc/xmon: Avoid tripping SMP hardlockup watchdog

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Message-ID: <87h8r47yl1.fsf@concordia.ellerman.id.au>
Date:   Tue, 30 Jan 2018 15:35:54 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     alexander.levin@...izon.com
Cc:     "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable\@vger.kernel.org" <stable@...r.kernel.org>,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH AUTOSEL for 3.18 36/40] powerpc/xmon: Avoid tripping SMP hardlockup watchdog

alexander.levin@...izon.com writes:

> On Thu, Dec 14, 2017 at 12:10:39AM +1100, Michael Ellerman wrote:
>>alexander.levin@...izon.com writes:
>>
>>> From: Nicholas Piggin <npiggin@...il.com>
>>>
>>> [ Upstream commit 064996d62a33ffe10264b5af5dca92d54f60f806 ]
>>>
>>> The SMP hardlockup watchdog cross-checks other CPUs for lockups, which
>>> causes xmon headaches because it's assuming interrupts hard disabled
>>> means no watchdog troubles. Try to improve that by calling
>>> touch_nmi_watchdog() in obvious places where secondaries are spinning.
>>>
>>> Also annotate these spin loops with spin_begin/end calls.
>>
>>These macros didn't exist until 4.13, and haven't been backported AFAIK.
>
> But the touch_nmi_watchdog() bits are something we want in stable, right?

I don't think you need them unless you've also back ported
arch/powerpc/kernel/watchdog.c, which I don't think you have.

Maybe Nick can confirm?


Also, I thought 3.18 was EOL?

cheers