linux-kernel - Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting

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Message-ID: <87mu3ho48v.fsf@kurt>
Date:   Thu, 30 Jul 2020 09:23:44 +0200
From:   Kurt Kanzenbach <kurt.kanzenbach@...utronix.de>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Alison Wang <alison.wang@....com>, catalin.marinas@....com,
        will@...nel.org, paulmck@...nel.org, mw@...ihalf.com,
        leoyang.li@....com, vladimir.oltean@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>
Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting

Hi Vladimir,

On Wed Jul 29 2020, Vladimir Oltean wrote:
> For more context, here is my original report of the issue:
> https://lkml.org/lkml/2020/6/4/1062
>
> Just like you, I could not reproduce the RCU stalls and system hang on a
> 5.6-rt kernel, just on mainline and derivatives, using the plain
> defconfig.
>
> The issue is not specific to Layerscape or i.MX8, but rather I was able
> to see the same behavior on Marvell Armada 37xx as well as Qualcomm
> MSM8976.
>
> So, while of course I agree that disabling IRQ time accounting for arm64
> isn't a real solution, it isn't by far an exaggerated proposal either.
> Nonetheless, the patch is just a RFC and should be treated as such. We
> are at a loss when it comes to debugging this any further and we would
> appreciate some pointers.

Yeah, sure. I'll try to reproduce this issue first. So it triggers with:

 * arm64
 * mainline, not -rt kernel
 * opened serial console
 * irq accounting enabled

Anything else?

Thanks,
Kurt

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