linux-kernel - Re: [PATCH] arm64: kdump: fix interrupt handling done during machine_crash

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Date:   Fri, 2 Mar 2018 13:15:46 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Grzegorz Jaszczyk <jaz@...ihalf.com>
Cc:     Marc Zyngier <marc.zyngier@....com>, catalin.marinas@....com,
        will.deacon@....com, james.morse@....com,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
        Hoeun Ryu <hoeun.ryu@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Nadav Haklai <nadavh@...vell.com>,
        Marcin Wojtas <mw@...ihalf.com>
Subject: Re: [PATCH] arm64: kdump: fix interrupt handling done during
 machine_crash_shutdown

On Fri, Mar 02, 2018 at 01:59:27PM +0100, Grzegorz Jaszczyk wrote:
> 2018-03-02 13:05 GMT+01:00 Mark Rutland <mark.rutland@....com>:
> > Do you have a way to reproduce the problem?
> >
> > Is there an easy way to cause the watchdog to trigger a kdump as above,
> > e.g. via LKDTM?
> 
> You can reproduce this problem by:
> - enabling CONFIG_ARM_SBSA_WATCHDOG in your kernel
> - passing via command-line: sbsa_gwdt.action=1 sbsa_gwdt.timeout=170
> - then load/prepare crasdump kernel (I am doing it via kexec tool)
> - echo 1 > /dev/watchdog
> 
> and after 170s the watchdog interrupt will hit triggering panic and
> the whole kexec machinery will run. The sbsa_gwdt.timeout can't be too
> small since it is also used for reset:
> |----timeout-----(panic)----timeout-----reset.
> If it is too small the crasdump kernel will not have enough time to start.
> 
> It is also reproducible with different interrupts, e.g. for test I put
> the panic to i2c interrupt handler and it was behaving the same.

Do you see this for a panic() in *any* interrupt handler?

Can you trigger the issue with magic-sysrq c, for example?

> > I think you just mean GICv2 here. GICv2m is an MSI controller, and
> > shouldn't interact with the SBSA watchdog's SPI.
> 
> Yes of course, I just wanted to mention that it has MSI controller.

Can you please tell us which platform you're seeing this on?

Thanks,
Mark.