Re: [PATCH] Fix for ptrace breakage

[OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>]

Ingo Molnar <mingo@elte.hu> writes:

> > This patch fixes the following,
> >
> >    - race condition of ptrace flag
> >    - sent odd signal to the tracer
> >    - broken before behavior
> 
> (looks good to me). I'm wondering about the following:
> 
> -	while (!list_empty(&current->children))
> -		zap_thread(list_entry(current->children.next,struct task_struct,sibling), current, 0);
> -	while (!list_empty(&current->ptrace_children))
> -		zap_thread(list_entry(current->ptrace_children.next,struct task_struct,ptrace_list), current, 1);
> +	while ((p = eldest_child(current)) != NULL)
> +		zap_thread(p, current);
>  	BUG_ON(!list_empty(&current->children));
> 
> is it guaranteed that at this point current->ptrace_children is empty?

Yes, I think so.

	list_for_each(_p, &father->ptrace_children) {
		p = list_entry(_p,struct task_struct,ptrace_list);
		list_del_init(&p->ptrace_list);
		reparent_thread(p, reaper, child_reaper);
		if (p->parent != p->real_parent)
			list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
	}

current->ptrace_children should be empty after this reparent.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>