rcu_sched self-detected stall on CPU

[Zhouyi Zhou]

Hi

I can reproduce it in a ppc virtual cloud server provided by Oregon
State University.  Following is what I do:
1) curl -l https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/snapshot/linux-5.18-rc1.tar.gz
-o linux-5.18-rc1.tar.gz
2) tar zxf linux-5.18-rc1.tar.gz
3) cp config linux-5.18-rc1/.config
4) cd linux-5.18-rc1
5) make vmlinux -j 8
6) qemu-system-ppc64 -kernel vmlinux -nographic -vga none -no-reboot
-smp 2 (QEMU 4.2.1)
7) after 12 rounds, the bug got reproduced:
(http://154.223.142.244/logs/20220406/qemu.log.txt)

Cheers ;-)
Zhouyi

On Wed, Apr 6, 2022 at 3:47 PM Miguel Ojeda
<miguel.ojeda.sandonis at gmail.com> wrote:
>
> Hi PPC/RCU,
>
> While merging v5.18-rc1 changes I noticed our CI PPC runs broke. I
> reproduced the problem in v5.18-rc1 as well as next-20220405, under
> both QEMU 4.2.1 and 6.1.0, with `-smp 2`; but I cannot reproduce it in
> v5.17 from a few tries.
>
> Sadly, the problem is not deterministic although it is not too hard to
> reproduce (1 out of 5?). Please see attached config and QEMU output.
>
> Cheers,
> Miguel