Hello, Michal. On Tue, Dec 04, 2012 at 04:14:20PM +0100, Michal Hocko wrote: > OK, I read this as "generic helper doesn't make much sense". Then I > would just ask. Does cgroup core really care whether we do > list_empty test? Is this something that we have to care about in memcg > and should fix? If yes then just try to do it as simple as possible. The thing is, what does the test mean when it doesn't have proper synchronization? list_empty(&cgroup->children) doesn't really have a precise meaning if you're not synchronized. There could be cases where such correct-most-of-the-time results are okay but depending on stuff like that is a sure-fire way to subtle bugs. So, my recommendation would be to bite the bullet and implement properly synchronized on/offline state and teach the memcg iterator about it so that memcg can definitively tell what's online and what's not while holding memcg_mutex, and use such knowledge consistently. Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>