Re: [PATCH] kthread: Don't depend on work queues

[Oleg Nesterov <oleg@tv-sign.ru>]

On 04/10, Eric W. Biederman wrote:
> 
> +int kthreadd(void *unused)
> +{
> +	/* Setup a clean context for our children to inherit. */
> +	kthreadd_setup();
> +
> +	current->flags |= PF_NOFREEZE;
> +
> +	for (;;) {
> +		wait_event(kthread_create_work,
> +			   !list_empty(&kthread_create_list));
> +
> +		spin_lock(&kthread_create_lock);
> +		while (!list_empty(&kthread_create_list)) {

Do we need to check the condition under lock? We can miss an event,
but then it will be noticed by wait_event() above.

> +			struct kthread_create_info *create;
> +
> +			create = list_entry(kthread_create_list.next,
> +					    struct kthread_create_info, list);
> +			list_del_init(&create->list);
> +			spin_unlock(&kthread_create_lock);
> +
> +			create_kthread(create);
> +
> +			spin_lock(&kthread_create_lock);
> +		}
> +		spin_unlock(&kthread_create_lock);
> +	}

IOW,

	for (;;) {
		wait_event(kthread_create_work,
			   !list_empty(&kthread_create_list));

		while (!list_empty(&kthread_create_list)) {
			struct kthread_create_info *create;

			spin_lock(&kthread_create_lock);
			create = list_entry(kthread_create_list.next,
					    struct kthread_create_info, list);
			list_del_init(&create->list);
			spin_unlock(&kthread_create_lock);

			create_kthread(create);
		}
	}

Oleg.

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