Re: [PATCH 3/4] kthreads: rework kthread_stop()

[Andrew Morton]

On Fri, 30 Jan 2009 13:33:58 +0100
Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

>  int kthread_stop(struct task_struct *k)
>  {
> +	struct kthread *kthread;
>  	int ret;
>  
> -	mutex_lock(&kthread_stop_lock);
> -
> -	/* It could exit after stop_info.k set, but before wake_up_process. */
> -	get_task_struct(k);
> -
>  	trace_sched_kthread_stop(k);
> +	get_task_struct(k);
>  
> -	/* Must init completion *before* thread sees kthread_stop_info.k */
> -	init_completion(&kthread_stop_info.done);
> -	smp_wmb();
> +	kthread = to_kthread(k);
> +	barrier(); /* it might have exited */

Why the change from smp_wmb() to plain old barrier()?
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