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From:   Grzegorz Jaszczyk <jaz@semihalf.com>
Date:   Thu, 8 Mar 2018 23:06:06 +0100
Message-ID: <CAH76GKP5Abx3ty1jVfesd_BjOKaQLaNs0e_W06LBanWDAPS0gQ@mail.gmail.com>
Subject: Re: [PATCH] arm64: kdump: fix interrupt handling done during machine_crash_shutdown
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Hoeun Ryu <hoeun.ryu@gmail.com>,
        Marc Zyngier <marc.zyngier@arm.com>, catalin.marinas@arm.com,
        will.deacon@arm.com, linux-kernel@vger.kernel.org,
        Nadav Haklai <nadavh@marvell.com>,
        "AKASHI, Takahiro" <takahiro.akashi@linaro.org>,
        james.morse@arm.com, Marcin Wojtas <mw@semihalf.com>,
        linux-arm-kernel@lists.infradead.org
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2018-03-02 17:57 GMT+01:00 Mark Rutland <mark.rutland@arm.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.

Thank you,
Grzegorz