Re: [PATCH 8/8] security/landlock: convert thread iterator to for_each_thread_rcu

["Günther Noack" <gnoack3000@gmail.com>]

On Fri, Sep 04, 2026 at 04:30:00PM +0800, Ye Liu wrote:
> From: Ye Liu <liuye@kylinos.cn>
> 
> Replace guard(rcu)() + for_each_thread() with for_each_thread_rcu(),
> so that the RCU read-side critical section is scoped to the loop body.
> 
> No functional change.
> 
> Signed-off-by: Ye Liu <liuye@kylinos.cn>
> ---
>  security/landlock/tsync.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/security/landlock/tsync.c b/security/landlock/tsync.c
> index 0b71e158c3f5..f1c08aae179b 100644
> --- a/security/landlock/tsync.c
> +++ b/security/landlock/tsync.c
> @@ -335,9 +335,7 @@ static size_t count_additional_threads(const struct tsync_works *works)
>  
>  	caller = current;
>  
> -	guard(rcu)();
> -
> -	for_each_thread(caller, thread) {
> +	for_each_thread_rcu(caller, thread) {
>  		/* Skip current, since it is initiating the sync. */
>  		if (thread == caller)
>  			continue;
> @@ -376,9 +374,7 @@ static bool schedule_task_work(struct tsync_works *works,
>  
>  	caller = current;
>  
> -	guard(rcu)();
> -
> -	for_each_thread(caller, thread) {
> +	for_each_thread_rcu(caller, thread) {
>  		/* Skip current, since it is initiating the sync. */
>  		if (thread == caller)
>  			continue;
> -- 
> 2.25.1
> 

Reviewed-by: Günther Noack <gnoack3000@gmail.com>

Looks good, provided that the for_each_thread_rcu() macro gets
accepted.

Although, I find that in the Landlock case, it does not provide a very
strong advantage over the explicit "guard(rcu)();", and I find it
normally preferrable to use orthogonal APIs.

–Günther