Re: [PATCH] cgroup: fix a race condition in manipulatingtsk->cg_list

[Andrew Morton]

On Thu, 17 Apr 2008 13:10:33 +0800 Li Zefan <lizf@xxxxxxxxxxxxxx> wrote:

> Andrew Morton wrote:
> > On Wed, 16 Apr 2008 21:17:34 -0700 "Paul Menage" <menage@xxxxxxxxxx> wrote:
> > 
> >> On Wed, Apr 16, 2008 at 9:11 PM, Andrew Morton
> >> <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> >>>  I don't fully understand the race.  Both paths hold css_set_lock.
> >>>
> >>>  Can you describe it in more detail please?
> >> Task A starts exiting, passes the check for unlinking current->cg_list.
> > 
> > So cgroup_exit() sees !list_empty(tsk->cg_list)
> > 
> 
> cgroup_exit() sees list_empty(tsk->cg_list), then cgroup_enable_task_cg_list()
> links the task to the list, and then the task exited, so the list entry won't
> get deleted.

OK.
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