commit ba9182a89626d5f83c2ee4594f55cb9c1e60f0e2 upstream.

After a successful cpuset_can_attach() call which increments the attach_in_progress flag, either cpuset_cancel_attach() or cpuset_attach() will be called later. In cpuset_attach(), tasks in cpuset_attach_wq, if present, will be woken up at the end. That is not the case in cpuset_cancel_attach(). So missed wakeup is possible if the attach operation is somehow cancelled. Fix that by doing the wakeup in cpuset_cancel_attach() as well.

Fixes: e44193d39e8d ("cpuset: let hotplug propagation work wait for task attaching") Signed-off-by: Waiman Long longman@redhat.com Reviewed-by: Michal Koutný mkoutny@suse.com Cc: stable@vger.kernel.org # v3.11+ Signed-off-by: Tejun Heo tj@kernel.org --- kernel/cgroup/cpuset.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 0b82e3857d33..20c1ccc6a0bb 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1508,7 +1508,9 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset) cs = css_cs(css);

mutex_lock(&cpuset_mutex); - css_cs(css)->attach_in_progress--; + cs->attach_in_progress--; + if (!cs->attach_in_progress) + wake_up(&cpuset_attach_wq); mutex_unlock(&cpuset_mutex); }