cgroup/cpuset: Wake up cpuset_attach_wq tasks in cpuset_cancel_attach()

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 3f23b747cc1e38c4f2abdd7a5729e689cd4c064d..4c0c317083d05ed81eeb0baca9e5f8a4ce5ae08d 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2498,11 +2498,15 @@ out_unlock:
 static void cpuset_cancel_attach(struct cgroup_taskset *tset)
 {
        struct cgroup_subsys_state *css;
+       struct cpuset *cs;
 
        cgroup_taskset_first(tset, &css);
+       cs = css_cs(css);
 
        percpu_down_write(&cpuset_rwsem);
-       css_cs(css)->attach_in_progress--;
+       cs->attach_in_progress--;
+       if (!cs->attach_in_progress)
+               wake_up(&cpuset_attach_wq);
        percpu_up_write(&cpuset_rwsem);
 }