On Fri 14-06-13 18:15:12, Glauber Costa wrote: > On Fri, Jun 14, 2013 at 02:55:39PM +0200, Michal Hocko wrote: > > On Wed 12-06-13 21:04:58, Tejun Heo wrote: > > [...] > > > +/** > > > + * cgroup_destroy_locked - the first stage of cgroup destruction > > > + * @cgrp: cgroup to be destroyed > > > + * > > > + * css's make use of percpu refcnts whose killing latency shouldn't be > > > + * exposed to userland and are RCU protected. Also, cgroup core needs to > > > + * guarantee that css_tryget() won't succeed by the time ->css_offline() is > > > + * invoked. To satisfy all the requirements, destruction is implemented in > > > + * the following two steps. > > > + * > > > + * s1. Verify @cgrp can be destroyed and mark it dying. Remove all > > > + * userland visible parts and start killing the percpu refcnts of > > > + * css's. Set up so that the next stage will be kicked off once all > > > + * the percpu refcnts are confirmed to be killed. > > > + * > > > + * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the > > > + * rest of destruction. Once all cgroup references are gone, the > > > + * cgroup is RCU-freed. > > > + * > > > + * This function implements s1. After this step, @cgrp is gone as far as > > > + * the userland is concerned and a new cgroup with the same name may be > > > + * created. As cgroup doesn't care about the names internally, this > > > + * doesn't cause any problem. > > > > Glauber is this asumption correct for kmem caches naming scheme? > > I guess it should, but I would rather be sure this won't blow up later > > specially when caches might live longer than css_offline. > > > > We append names to caches, but never the name alone, always (kmemcg_id:name) > So you can reuse the same name as many times as you want (from the kmemcg > perspective), provided you use different kmemcg_ids. Because kmemcg_ids are > dissociated from css_ids (partly because I was already seeing people talking > about wanting to free the css_ids earlier), we should not have any problems > with this. Thanks for double checking, Glauber! -- Michal Hocko SUSE Labs _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
