After a css finishes offlining, offline_css() mistakenly performs RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css) which just sets the cgroup->subsys[] pointer to the current value. The intention was to clear it after offline is complete, not reassign the same value. Update it to assign NULL instead of the current value. This makes cgroup_css() to return NULL once offline is complete. All the existing users of the function either can handle NULL return already or guarantee that the css doesn't get offlined. While this is a bugfix, as css lifetime is currently tied to the cgroup it belongs to, this bug doesn't cause any actual problems. Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Acked-by: Li Zefan <lizefan@xxxxxxxxxx> --- kernel/cgroup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 0318bfc..3de3951 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3714,7 +3714,7 @@ static void offline_css(struct cgroup_subsys_state *css) css->flags &= ~CSS_ONLINE; css->cgroup->nr_css--; - RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css); + RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL); } /** -- 1.9.0 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
