[Bug tdep/31442] [gdb/tdep, arm, SIGILL] FAIL: gdb.threads/sigstep-threads.exp: step 92

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31442

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
This could be related to kernel commits:
...
commit 5f41f9198f296091c6a58bc2e86af1e9f019b2a3
Author: Marek Szyprowski <m.szyprowski@samsung.com>
Date:   Tue May 28 09:38:14 2019 +0100

    ARM: 8864/1: Add workaround for I-Cache line size mismatch between CPU
cores
...
and:
...
commit 116c81f427ff6c5380850963e3fb8798cc821d2b
Author: Suzuki K Poulose <suzuki.poulose@arm.com>
Date:   Fri Sep 9 14:07:16 2016 +0100

    arm64: Work around systems with mismatched cache line sizes
...

I'm using 32-bit arm user land on 64-bit kernel on aarch64, so I'm not sure
which commit would apply.  The arm commit first appears in v5.3, the arm64 one
in v4.9.

The kernel used is 4.4.190.

This is because the pinebook came with
https://github.com/mrfixit2001/debian_desktop , and the update script never
work for me, so I hacked the user land to be plain debian, but I got stuck with
the kernel from this (
https://github.com/mrfixit2001/debian_desktop/releases/tag/190905 ) release.

So, it could be that I don't have the necessary fix for this, I'm not sure how
to check.

I confirmed that this is a big.little issue, I ran with taskset -c 0-3 and
taskset -c 4-5 and the issue no longer reproduces.

I looked into upgrading the kernel to 6.1, but it seems that this is difficult
because /boot is read-only due to being flash, so I'm avoiding that for now.

I'm going to work around this by running tests using taskset -c 4-5,
restricting testing to the 2 big cores.

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