linux-kernel - Re: Regression with mainline kernel on rpi4

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Date:   Wed, 22 Sep 2021 08:22:40 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:     Maxime Ripard <maxime@...no.tech>, Emma Anholt <emma@...olt.net>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Regression with mainline kernel on rpi4

On Wed, Sep 22, 2021 at 3:11 AM Sudip Mukherjee
<sudipm.mukherjee@...il.com> wrote:
>
> That test script is triggering the openqa job, but its running only
> after lava is able to login. The trace is appearing before the login
> prompt even, so test_mainline.sh should not matter here.

Side note: the traces might be more legible if you have debug info in
the kernel, and run the dmesg through the script in

  scripts/decode_stacktrace.sh

which should give line numbers and inlining information.

That often makes it much easier to see which access it is that hits a
NULL pointer dereference.

On x86-64, generally just decode the instruction stream, and look at
the instruction patterns and try to figure out where an oops is coming
from, but that's much less useful on arm64 (partly because I'm not as
used to it, but because the arm64 oopses don't print out much of the
instructions so there's often little to go by).

         Linus