From 9a55fef20afb3d7362b0c9d19ba1e78dfe482d3d Mon Sep 17 00:00:00 2001 From: Daisuke Nishimura Date: Thu, 4 Oct 2012 16:37:16 +0900 Subject: cgroup: notify_on_release may not be triggered in some cases commit 1f5320d5972aa50d3e8d2b227b636b370e608359 upstream. notify_on_release must be triggered when the last process in a cgroup is move to another. But if the first(and only) process in a cgroup is moved to another, notify_on_release is not triggered. # mkdir /cgroup/cpu/SRC # mkdir /cgroup/cpu/DST # # echo 1 >/cgroup/cpu/SRC/notify_on_release # echo 1 >/cgroup/cpu/DST/notify_on_release # # sleep 300 & [1] 8629 # # echo 8629 >/cgroup/cpu/SRC/tasks # echo 8629 >/cgroup/cpu/DST/tasks -> notify_on_release for /SRC must be triggered at this point, but it isn't. This is because put_css_set() is called before setting CGRP_RELEASABLE in cgroup_task_migrate(), and is a regression introduce by the commit:74a1166d(cgroups: make procs file writable), which was merged into v3.0. Acked-by: Li Zefan Cc: Ben Blum Signed-off-by: Daisuke Nishimura Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- kernel/cgroup.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index ed64ccac67c9..b76dd5862a8c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1868,9 +1868,8 @@ static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, * trading it for newcg is protected by cgroup_mutex, we're safe to drop * it here; it will be freed under RCU. */ - put_css_set(oldcg); - set_bit(CGRP_RELEASABLE, &oldcgrp->flags); + put_css_set(oldcg); } /** -- cgit v1.2.3