Re: [PATCH v2] selftests/cgroup: Preserve CPU hotplug write errors

[Waiman Long]

On 8/13/26 9:28 AM, Rui Qi wrote:
> The cpuset partition root state selftest checks several CPU hotplug
> transitions. If writing to a CPU online file fails, the helper still
> runs pause afterwards and returns the status of pause instead of the
> failed write.
>
> This hides the real hotplug failure and can make later checks run
> against expectations for a transition that never happened. Move the
> write before the bookkeeping and return when it fails, so callers can
> observe the hotplug error and the test does not record a CPU as offline
> unless the offline operation actually succeeded.
>
> Also change the O* command handler in set_ctrl_state() to use
> "eval $COMM $REDIRECT" like all other handlers. The previous version
> set COMM but still called write_cpu_online directly, bypassing the
> redirect that captures stderr for error reporting.
>
> Changes since v1:
>   - Use eval $COMM $REDIRECT in the O* handler instead of calling
>     write_cpu_online directly (Waiman Long)
>
> Fixes: a8c52eba880a ("kselftest/cgroup: Add cpuset v2 partition root state test")
> Signed-off-by: Rui Qi <qirui.001@xxxxxxxxxxxxx>
> ---
>   tools/testing/selftests/cgroup/test_cpuset_prs.sh | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
> index 8380fd9d76bd..da8f7b920178 100755
> --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
> +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
> @@ -526,6 +526,7 @@ write_cpu_online()
>   	CPU=${1%=*}
>   	VAL=${1#*=}
>   	CPUFILE=//sys/devices/system/cpu/cpu${CPU}/online
> +	echo $VAL > $CPUFILE || return 1
>   	if [[ $VAL -eq 0 ]]
>   	then
>   		OFFLINE_CPUS="$OFFLINE_CPUS $CPU"
> @@ -535,7 +536,6 @@ write_cpu_online()
>   					sort | uniq -u)
>   		}
>   	fi
> -	echo $VAL > $CPUFILE
>   	pause 0.05
>   }
>   
> @@ -603,7 +603,8 @@ set_ctrl_state()
>   			eval $COMM $REDIRECT
>   			;;
>   		    O*) VAL=${CMD#?}
> -			write_cpu_online $VAL
> +			COMM="write_cpu_online $VAL"
> +			eval $COMM $REDIRECT
>   			;;
>   		    T*) COMM="echo 0 > $TFILE"
>   			eval $COMM $REDIRECT
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>