Re: [PATCH-next v2 2/2] cgroup/cpuset: Remove CS_CPU_EXCLUSIVE handling code from v2

[Ridong Chen <ridong.chen@linux.dev>]

On 9/28/2026 5:53 AM, Waiman Long wrote:
> As the is_cpu_exclusive() function is only used for DEADLINE shrink
> test with v1 there is no need to have the CS_CPU_EXCLUSIVE flag set on
> valid partition root anymore. Remove update_partition_exclusive_flag()
> and other CS_CPU_EXCLUSIVE flag handling code in cpuset.c.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
>   kernel/cgroup/cpuset.c | 52 ++++--------------------------------------
>   1 file changed, 4 insertions(+), 48 deletions(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 104fe10c336d..4a915da37bb3 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1174,25 +1174,6 @@ enum partition_cmd {
>   static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
>   				    struct tmpmasks *tmp);
>   
> -/*
> - * Update partition exclusive flag
> - *
> - * Return: 0 if successful, an error code otherwise
> - */
> -static int update_partition_exclusive_flag(struct cpuset *cs, int new_prs)
> -{
> -	bool exclusive = (new_prs > PRS_MEMBER);
> -
> -	if (exclusive && !is_cpu_exclusive(cs)) {
> -		if (cpuset_update_flag(CS_CPU_EXCLUSIVE, cs, 1))
> -			return PERR_NOTEXCL;
> -	} else if (!exclusive && is_cpu_exclusive(cs)) {
> -		/* Turning off CS_CPU_EXCLUSIVE will not return error */
> -		cpuset_update_flag(CS_CPU_EXCLUSIVE, cs, 0);
> -	}
> -	return 0;
> -}
> -
>   /*
>    * Update partition load balance flag and/or rebuild sched domain
>    *
> @@ -1248,11 +1229,9 @@ static void reset_partition_data(struct cpuset *cs)
>   
>   	lockdep_assert_held(&callback_lock);
>   
> -	if (cpumask_empty(cs->exclusive_cpus)) {
> +	if (cpumask_empty(cs->exclusive_cpus))
>   		cpumask_clear(cs->effective_xcpus);
> -		if (is_cpu_exclusive(cs))
> -			clear_bit(CS_CPU_EXCLUSIVE, &cs->flags);
> -	}
> +
>   	if (!cpumask_and(cs->effective_cpus, parent->effective_cpus, cs->cpus_allowed))
>   		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
>   }
> @@ -2028,19 +2007,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   	if (!adding && !deleting && (new_prs == old_prs))
>   		return 0;
>   
> -	/*
> -	 * Transitioning between invalid to valid or vice versa may require
> -	 * changing CS_CPU_EXCLUSIVE. In the case of partcmd_update,
> -	 * validate_change() has already been successfully called and
> -	 * CPU lists in cs haven't been updated yet. So defer it to later.
> -	 */
> -	if ((old_prs != new_prs) && (cmd != partcmd_update))  {
> -		int err = update_partition_exclusive_flag(cs, new_prs);
> -
> -		if (err)
> -			return err;
> -	}
> -
>   	/*
>   	 * Change the parent's effective_cpus & effective_xcpus (top cpuset
>   	 * only).
> @@ -2063,9 +2029,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   
>   	spin_unlock_irq(&callback_lock);
>   
> -	if ((old_prs != new_prs) && (cmd == partcmd_update))
> -		update_partition_exclusive_flag(cs, new_prs);
> -
>   	if (adding || deleting) {
>   		cpuset_update_tasks_cpumask(parent, tmp->addmask);
>   		update_sibling_cpumasks(parent, cs, tmp);
> @@ -2942,10 +2905,6 @@ static int update_prstate(struct cpuset *cs, int new_prs)
>   	if (alloc_tmpmasks(&tmpmask))
>   		return -ENOMEM;
>   
> -	err = update_partition_exclusive_flag(cs, new_prs);
> -	if (err)
> -		goto out;
> -
>   	if (!old_prs) {
>   		/*
>   		 * cpus_allowed and exclusive_cpus cannot be both empty.
> @@ -3009,13 +2968,10 @@ static int update_prstate(struct cpuset *cs, int new_prs)
>   	}
>   out:
>   	/*
> -	 * Make partition invalid & disable CS_CPU_EXCLUSIVE if an error
> -	 * happens.
> +	 * Make partition invalid if an error happens.
>   	 */
> -	if (err) {
> +	if (err)
>   		new_prs = -new_prs;
> -		update_partition_exclusive_flag(cs, new_prs);
> -	}
>   
>   	spin_lock_irq(&callback_lock);
>   	cs->partition_root_state = new_prs;

Nice.

Reviewed-by: Ridong Chen <ridong.chen@linux.dev>

-- 
Best regards
Ridong