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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Norbert Preining' <norbert@preining.info>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: kernel hard lockups wit 5.9-rc{2,3}
Thread-Topic: kernel hard lockups wit 5.9-rc{2,3}
Thread-Index: AQHWf177xf+hBGUvkEWCmoTo7Rvn6alThq5g
Date:   Tue, 1 Sep 2020 09:36:29 +0000
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From: Norbert Preining
> I am seeing hard lockups with 5.9-rc2 and -rc3, while 5.8.N (1,2,3,4,5)
> work without any problems.
> 
> THe lockups are hard to debug, since not even Sysrq works anymore. The
> screen freezes completely, no reaction. Ports are also dead, ssh into
> the machine is not possible.
> 
> Hangs are repeatable, but not triggerable (at least I didn't find a
> way). Last time I left the screen locked and went shopping to find it
> locked up coming back. In total I got about 10 lock ups.

I've had a random lockup on a pre-rc1 kernel.
But that might be one of our own drivers - OTOH they 'normally'
generate OOPS tracebacks.

Have you tried setting up a serial console?
It might contain some useful messages.

Sysrq is more likely to work with a PS2 keyboard (not USB).
IIRC the 'caps lock' light only needs PS2 keyboard interrupts
to be working - a useful check on how dead a system it.

	David

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