Re: [PATCH v4 09/15] rcu: convert process/thread iterator to for_each_process_thread_rculock

[Paul E. McKenney]

On Mon, Sep 21, 2026 at 05:20:55PM +0800, Ye Liu wrote:
> From: Ye Liu <liuye@xxxxxxxxxx>
> 
> Replace the manual rcu_read_lock()/rcu_read_unlock() pair combined
> with for_each_process_thread() loop in kernel/rcu/update.c with
> for_each_process_thread_rculock(), which scopes the RCU read lock
> to the loop body via scoped_guard(rcu).
> 
> No functional change.
> 
> Signed-off-by: Ye Liu <liuye@xxxxxxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Reviewed-by: SJ Park <sj@xxxxxxxxxx>
> Reviewed-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx>

Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

> ---
>  kernel/rcu/update.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index 2a778b8ab4ad..d8e0b5896db9 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -548,15 +548,13 @@ void synchronize_rcu_trivial_preempt(void)
>  	struct task_struct *t;
>  
>  	smp_mb(); // Order prior accesses before grace-period start.
> -	rcu_read_lock(); // Protect task list.
> -	for_each_process_thread(g, t) {
> +	for_each_process_thread_rculock(g, t) {
>  		if (t == current)
>  			continue;  // Don't deadlock on ourselves!
>  		// Order later rcu_read_lock() on other tasks after QS.
>  		while (smp_load_acquire(&t->rcu_trivial_preempt_nesting))
>  			continue;
>  	}
> -	rcu_read_unlock();
>  }
>  EXPORT_SYMBOL_GPL(synchronize_rcu_trivial_preempt);
>  #endif // #if IS_ENABLED(CONFIG_TRIVIAL_PREEMPT_RCU)
> -- 
> 2.25.1
>