cgroup_freezer: fix freezing groups with stopped tasks
authorMichal Hocko <mhocko@suse.cz>
Tue, 22 Nov 2011 15:44:47 +0000 (07:44 -0800)
committerGreg Kroah-Hartman <gregkh@suse.de>
Fri, 9 Dec 2011 16:54:23 +0000 (08:54 -0800)
commitc1d98cbbfc393f166b8a675b3acbdfab320adadc
tree282d99595890cb6a5352b5acb452c8557ae2cea4
parentffdb8ca9bea2170b97edb9372bb365fd387a1ff9
cgroup_freezer: fix freezing groups with stopped tasks

commit 884a45d964dd395eda945842afff5e16bcaedf56 upstream.

2d3cbf8b (cgroup_freezer: update_freezer_state() does incorrect state
transitions) removed is_task_frozen_enough and replaced it with a simple
frozen call. This, however, breaks freezing for a group with stopped tasks
because those cannot be frozen and so the group remains in CGROUP_FREEZING
state (update_if_frozen doesn't count stopped tasks) and never reaches
CGROUP_FROZEN.

Let's add is_task_frozen_enough back and use it at the original locations
(update_if_frozen and try_to_freeze_cgroup). Semantically we consider
stopped tasks as frozen enough so we should consider both cases when
testing frozen tasks.

Testcase:
mkdir /dev/freezer
mount -t cgroup -o freezer none /dev/freezer
mkdir /dev/freezer/foo
sleep 1h &
pid=$!
kill -STOP $pid
echo $pid > /dev/freezer/foo/tasks
echo FROZEN > /dev/freezer/foo/freezer.state
while true
do
cat /dev/freezer/foo/freezer.state
[ "`cat /dev/freezer/foo/freezer.state`" = "FROZEN" ] && break
sleep 1
done
echo OK

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Tomasz Buchert <tomasz.buchert@inria.fr>
Cc: Paul Menage <paul@paulmenage.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
kernel/cgroup_freezer.c