On 2012/11/1 3:44, Tejun Heo wrote: > CSS_REMOVED is one of the several contortions which were necessary to > support css reference draining on cgroup removal. All css->refcnts > which need draining should be deactivated and verified to equal zero > atomically w.r.t. css_tryget(). If any one isn't zero, all refcnts > needed to be re-activated and css_tryget() shouldn't fail in the > process. > > This was achieved by letting css_tryget() busy-loop until either the > refcnt is reactivated (failed removal attempt) or CSS_REMOVED is set > (committing to removal). > > Now that css refcnt draining is no longer used, there's no need for > atomic rollback mechanism. css_tryget() simply can look at the > reference count and fail if it's deactivated - it's never getting > re-activated. > > This patch removes CSS_REMOVED and updates __css_tryget() to fail if > the refcnt is deactivated. As deactivation and removal are a single > step now, they no longer need to be protected against css_tryget() > happening from irq context. Remove local_irq_disable/enable() from > cgroup_rmdir(). > > Note that this removes css_is_removed() whose only user is VM_BUG_ON() > in memcontrol.c. We can replace it with a check on the refcnt but > given that the only use case is a debug assert, I think it's better to > simply unexport it. > > v2: Comment updated and explanation on local_irq_disable/enable() > added per Michal Hocko. > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > Reviewed-by: Michal Hocko <mhocko@xxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Balbir Singh <bsingharora@xxxxxxxxx> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Acked-by: Li Zefan <lizefan@xxxxxxxxxx> _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
