Re: [PATCH] selftests: cpufreq: stop CPU hotplug loop after cpufreq update test

[Rafael J. Wysocki (Intel)]

On Sat, Oct 10, 2026 at 12:02 PM xiong yining
<xiongyining1480@xxxxxxxxxxxxxx> wrote:
>
> Original test uses a fixed 5000 iteration loop to trigger CPU hotplug
> for verifying cpufreq synchronization between CPU hotplug and sysfs
> writes.
>
> Two issues exist:
> 1. Background hotplug task keeps running after test completes, causing
> redundant CPU on/offline operations.
> 2. When cpufreq frequency setup is slow, the hotplug loop may exit
> before frequency updates finish, which breaks test purpose.
>
> Introduce a file-based stop flag to control the infinite hotplug loop.
> After all cpufreq updates complete, create the stop flag file and
> wait for the hotplug task to exit.
>
> This makes hotplug run only during cpufreq sysfs write test,
> align with test objective.
>
> Signed-off-by: xiong yining <xiongyining1480@xxxxxxxxxxxxxx>
> ---
>  tools/testing/selftests/cpufreq/special-tests.sh | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/cpufreq/special-tests.sh b/tools/testing/selftests/cpufreq/special-tests.sh
> index e87ed7c8e5e5..14530c1b8d25 100755
> --- a/tools/testing/selftests/cpufreq/special-tests.sh
> +++ b/tools/testing/selftests/cpufreq/special-tests.sh
> @@ -97,14 +97,20 @@ governor_race()
>  hotplug_with_updates_cpu()
>  {
>         local filepath="$CPUROOT/$1/cpufreq"
> +       local stop_flag="/tmp/stop_hotplug_$1"
> +       rm -f "$stop_flag"
>
>         # switch to ondemand
>         __switch_governor_for_cpu $1 "ondemand"
>
> -       for i in `seq 1 5000`
> +       while true
>         do
> +               if [ -f "$stop_flag" ]; then
> +                       break
> +               fi
>                 reboot_cpu $1
>         done &
> +       local hotplug_pid=$!
>
>         local freqs=$(cat $filepath/scaling_available_frequencies)
>         local oldfreq=$(cat $filepath/scaling_min_freq)
> @@ -117,6 +123,10 @@ hotplug_with_updates_cpu()
>                 done
>         done
>
> +       touch "$stop_flag"
> +       wait $hotplug_pid
> +       rm -f "$stop_flag"
> +
>         # restore old freq
>         echo $oldfreq > $filepath/scaling_min_freq
>  }
>
> base-commit: 28924df2a08f440c73991b83028032c901de2ae4
> --

Please see Sashiko's feedback on this patch:

https://sashiko.dev/#/patchset/20261010100148.297720-1-xiongyining1480%40phytium.com.cn

and tell me what you think about it.

Thanks!