From patchwork Mon Nov 26 16:57:59 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [189/270] cgroup: notify_on_release may not be triggered in some cases Date: Mon, 26 Nov 2012 06:57:59 -0000 From: Herton Ronaldo Krzesinski X-Patchwork-Id: 201921 Message-Id: <1353949160-26803-190-git-send-email-herton.krzesinski@canonical.com> To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Ben Blum , Tejun Heo , Daisuke Nishimura 3.5.7u1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Daisuke Nishimura 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. Cc: Ben Blum Acked-by: Li Zefan Signed-off-by: Daisuke Nishimura Signed-off-by: Tejun Heo Signed-off-by: Herton Ronaldo Krzesinski --- kernel/cgroup.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 15462a0..63c9596 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1927,9 +1927,8 @@ 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); } /**