Re: [PATCH v3 1/2] cgroup/cpuset: reset DL migration state on can_attach() failure

[Waiman Long]

On 5/9/26 6:20 AM, Guopeng Zhang wrote:
> cpuset_can_attach() accumulates temporary SCHED_DEADLINE migration
> state in the destination cpuset while walking the taskset.
>
> If a later task_can_attach() or security_task_setscheduler() check
> fails, cgroup_migrate_execute() treats cpuset as the failing subsystem
> and does not call cpuset_cancel_attach() for it. The partially
> accumulated state is then left behind and can be consumed by a later
> attach, corrupting cpuset DL task accounting and pending DL bandwidth
> accounting.
>
> Reset the pending DL migration state from the common error exit when
> ret is non-zero. Successful can_attach() keeps the state for
> cpuset_attach() or cpuset_cancel_attach().
>
> Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
> Signed-off-by: Guopeng Zhang <zhangguopeng@xxxxxxxxxx>
> ---
>   kernel/cgroup/cpuset.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index e3a081a07c6d..b9c839538900 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -3050,16 +3050,13 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
>   		int cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);
>   
>   		if (unlikely(cpu >= nr_cpu_ids)) {
> -			reset_migrate_dl_data(cs);
>   			ret = -EINVAL;
>   			goto out_unlock;
>   		}
>   
>   		ret = dl_bw_alloc(cpu, cs->sum_migrate_dl_bw);
> -		if (ret) {
> -			reset_migrate_dl_data(cs);
> +		if (ret)
>   			goto out_unlock;
> -		}
>   
>   		cs->dl_bw_cpu = cpu;
>   	}
> @@ -3070,7 +3067,10 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
>   	 * changes which zero cpus/mems_allowed.
>   	 */
>   	cs->attach_in_progress++;
> +
>   out_unlock:
> +	if (ret)
> +		reset_migrate_dl_data(cs);
>   	mutex_unlock(&cpuset_mutex);
>   	return ret;
>   }
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>