cgroup_freezer: fix freezing groups with stopped tasks

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 <[email protected]>
Acked-by: Li Zefan <[email protected]>
Cc: Tomasz Buchert <[email protected]>
Cc: Paul Menage <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: [email protected]
Signed-off-by: Tejun Heo <[email protected]>

0 files changed, 0 insertions, 0 deletions