On Thu 08-11-12 09:57:50, Tejun Heo wrote: > Up until now, cgroup_freezer didn't implement hierarchy properly. > cgroups could be arranged in hierarchy but it didn't make any > difference in how each cgroup_freezer behaved. They all operated > separately. > > This patch implements proper hierarchy support. If a cgroup is > frozen, all its descendants are frozen. A cgroup is thawed iff it and > all its ancestors are THAWED. freezer.self_freezing shows the current > freezing state for the cgroup itself. freezer.parent_freezing shows > whether the cgroup is freezing because any of its ancestors is > freezing. > > freezer_post_create() locks the parent and new cgroup and inherits the > parent's state and freezer_change_state() applies new state top-down > using cgroup_for_each_descendant_pre() which guarantees that no child > can escape its parent's state. update_if_frozen() uses > cgroup_for_each_descendant_post() to propagate frozen states > bottom-up. > > Synchronization could be coarser and easier by using a single mutex to > protect all hierarchy operations. Finer grained approach was used > because it wasn't too difficult for cgroup_freezer and I think it's > beneficial to have an example implementation and cgroup_freezer is > rather simple and can serve a good one. > > As this makes cgroup_freezer properly hierarchical, > freezer_subsys.broken_hierarchy marking is removed. > > Note that this patch changes userland visible behavior - freezing a > cgroup now freezes all its descendants too. This behavior change is > intended and has been warned via .broken_hierarchy. > > v2: Michal spotted a bug in freezer_change_state() - descendants were > inheriting from the wrong ancestor. Fixed. > > v3: Documentation/cgroups/freezer-subsystem.txt updated. > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > Reviewed-by: Tejun Heo <tj@xxxxxxxxxx> You probably meant Reviewed-by: Michal Hocko .... ;) -- Michal Hocko SUSE Labs _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
