On Fri, Nov 04, 2022 at 08:59:02PM -0400, Waiman Long wrote: > As noted by Michal, the blkg_iostat_set's in the lockless list > hold reference to blkg's to protect against their removal. Those > blkg's hold reference to blkcg. When a cgroup is being destroyed, > cgroup_rstat_flush() is only called at css_release_work_fn() which is > called when the blkcg reference count reaches 0. This circular dependency > will prevent blkcg from being freed until some other events cause > cgroup_rstat_flush() to be called to flush out the pending blkcg stats. > > To prevent this delayed blkcg removal, add a new cgroup_rstat_css_flush() > function to flush stats for a given css and cpu and call it at the blkgs > destruction path, blkcg_destroy_blkgs(), whenever there are still some > pending stats to be flushed. This will ensure that blkcg reference > count can reach 0 ASAP. > > Signed-off-by: Waiman Long <longman@xxxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun
