Re: [PATCH] fs, proc: Introduce the /proc/<pid>/children entry v2

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Fri, Dec 09, 2011 at 05:55:36PM +0100, Oleg Nesterov wrote:
...
> 
> To simplify, let's talk about children_seq_start() your patch adds.
> Suppose that we make ->children/sibling "rcu-safe" (we replace
> __unhash_process()->list_del_init() with list_del_rcu, and so on).
> 
> Now, children_seq_start() does:
> 
> 	rcu_read_lock();
> 
> 	list_for_each(child, task->children)
> 		...;
> 
> Suppose that this task exits and reparents the child we are looking at.
> Once reparent_leader() moves it into another list, list_for_each()
> can never stop.
> 
> In short. forget_original_parent() changes the _head_ of the list,
> in some sense.
> 

Yeah, I missed this, my bad! Thanks for explanation, Oleg. I'll
post updated version once I finish it.

	Cyrill