Re: [PATCH 3/9 v2] cgroup: implement generic child / descendant walk macros

[Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]

On 2012/11/9 1:59, Tejun Heo wrote:
> Currently, cgroup doesn't provide any generic helper for walking a
> given cgroup's children or descendants.  This patch adds the following
> three macros.
> 
> * cgroup_for_each_child() - walk immediate children of a cgroup.
> 
> * cgroup_for_each_descendant_pre() - visit all descendants of a cgroup
>   in pre-order tree traversal.
> 
> * cgroup_for_each_descendant_post() - visit all descendants of a
>   cgroup in post-order tree traversal.
> 
> All three only require the user to hold RCU read lock during
> traversal.  Verifying that each iterated cgroup is online is the
> responsibility of the user.  When used with proper synchronization,
> cgroup_for_each_descendant_pre() can be used to propagate state
> updates to descendants in reliable way.  See comments for details.
> 
> v2: s/config/state/ in commit message and comments per Michal.  More
>     documentation on synchronization rules.
> 
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu-c2VE3kR2zFovtab9mdV7tw@public.gmane.org>
> Reviewed-by: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>

I don't see anything wrong with the comment on cgroup_next_descendant_pre().

Acked-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>