• Michal Hocko's avatar
    cgroup_freezer: fix freezing groups with stopped tasks · 884a45d9
    Michal Hocko authored
    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: default avatarMichal Hocko <mhocko@suse.cz>
    Acked-by: default avatarLi 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>
    Cc: stable@kernel.org
    Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
    884a45d9
cgroup_freezer.c 9.6 KB