Re: test_x86_64_hotplug_cpu.py times out frequently in CI

[Peter Maydell <peter.maydell@linaro.org>]

On Mon, 6 Jan 2025 at 16:45, Stefan Hajnoczi <stefanha@gmail.com> wrote:
>
> Hi Thomas,
> test_x86_64_hotplug_cpu.py times out frequently in CI runs. Here is an example:
> https://gitlab.com/qemu-project/qemu/-/jobs/8777540230#L1151
>
> The detailed test logs are here:
> https://gitlab.com/qemu-project/qemu/-/jobs/8777540230/artifacts/browse/build/tests/functional/x86_64/test_x86_64_hotplug_cpu.HotPlugCPU.test_hotplug/
>
> I looked at this failure with Dan and Peter on IRC. It was pointed out
> that the final command assumes that device_del takes effect
> immediately. The console log shows that the CPU was still visible to
> the guest when the final command executed.
>
> Could be a bug in QEMU, the test, or both?
>
> 2025-01-06 15:45:29,308: :/#
> 2025-01-06 15:45:29,313: cd /sys/devices/system/cpu/cpu0
> 2025-01-06 15:45:29,315: :/sys/devices/system/cpu/cpu0#
> 2025-01-06 15:45:29,320: cd /sys/devices/system/cpu/cpu1
> 2025-01-06 15:45:29,322: sh: cd: /sys/devices/system/cpu/cpu1: No such
> file or directory
> 2025-01-06 15:45:29,325:
> 2025-01-06 15:45:29,330: :/sys/devices/system/cpu/cpu0# [    7.337146]
> CPU1 has been hot-added
> 2025-01-06 15:45:29,330:
> 2025-01-06 15:45:29,335: cd /sys/devices/system/cpu/cpu1
> 2025-01-06 15:45:29,337: :/sys/devices/system/cpu/cpu1#
> 2025-01-06 15:45:29,342: cd /sys/devices/system/cpu/cpu1

Though the fact that there is no final shell prompt after
the last 'cd' command is perhaps evidence against this being
a simple race where the guest execution of the "cd" command
beat the guest handling of the hot-unplug event.

-- PMM