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

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Date:   Tue, 13 Mar 2018 17:25:07 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Grzegorz Jaszczyk <jaz@...ihalf.com>,
        Mark Rutland <mark.rutland@....com>
Cc:     Hoeun Ryu <hoeun.ryu@...il.com>, catalin.marinas@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        Nadav Haklai <nadavh@...vell.com>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
        james.morse@....com, Marcin Wojtas <mw@...ihalf.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64: kdump: fix interrupt handling done during
 machine_crash_shutdown

On 08/03/18 22:06, Grzegorz Jaszczyk wrote:
> 2018-03-02 17:57 GMT+01:00 Mark Rutland <mark.rutland@....com>:
>>>>> Do you see this for a panic() in *any* interrupt handler?
>>>>
>>>> I only test with this two interrupt handlers: watchdog and i2c but I
>>>> think it will behave the same with others - I can try with other if
>>>> you want, any suggestion which? Maybe with some PPI interrupt instead?
> 
> I was able to reproduce it from other interrupts handler (UART, I2C,
> timer and watchdog) no difference if it is PPI or SPI interrupt. I
> also reproduce this issue with GICv3. But again it only happens when
> eoimode = 0.
>>>>>
>>>>> Can you trigger the issue with magic-sysrq c, for example?
>>>>
>>>> There is no problem when I trigger it via 'echo c >
>>>> /proc/sysrq-trigger' - it works well all the time. The problem appears
>>>> only, when the kexec/kdump procedure is triggered from interrupt
>>>> context
>>>
>>> I'd meant that you'd send sysrq + c over serial, rather than writing to
>>> /proc/sysrq-trigger. That way, the panic will be in the context of the
>>> UART IRQ handler.
>>>
>>> If that shows the issue, that's ilikely to be the easiest way for
>>> someone else to reproduce and investigate this.
> 
> Yes it can be triggered by sending sysrq + c and indeed it is the
> easiest way to reproduce it.
>>
>> FWIW, having just given this a go on my Juno R1 with v4.16-rc3
>> defconfig, the UART IRQs work fine in the crash kernel. That crash
>> happened in IRQ context:
> 
> I think that by default Juno uses eoimode = 1, did you try it when
> eoimode was forced to be 0? Only eoimode = 0 triggers the issue.

FWIW, I've now posted fixes to LKML[1]. Feel free to test them and
report whether they fix the issue for you.

Thanks,

	M.

[1] https://lkml.org/lkml/2018/3/13/1088
-- 
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