Merge branch 'for-3.11-cpuset' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cpuset changes from Tejun Heo:
 "cpuset has always been rather odd about its configurations - a cgroup
  right after creation didn't allow any task executions before
  configuration, changing configuration in the parent modifies the
  descendants irreversibly and so on.  These behaviors are inherently
  nasty and almost hostile against sharing the hierarchy with other
  controllers making it very difficult to use in unified hierarchy.

  Li is currently in the process of updating the behaviors for
  __DEVEL__sane_behavior which is the bulk of changes in this pull
  request.  It isn't complete yet and the behaviors will change further
  but all changes are gated behind sane_behavior.  In the process, the
  rather hairy work-item punting which was used to work around the
  limitations of cgroup descendant iterator was simplified."

* 'for-3.11-cpuset' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cpuset: rename @cont to @cgrp
  cpuset: fix to migrate mm correctly in a corner case
  cpuset: allow to move tasks to empty cpusets
  cpuset: allow to keep tasks in empty cpusets
  cpuset: introduce effective_{cpumask|nodemask}_cpuset()
  cpuset: record old_mems_allowed in struct cpuset
  cpuset: remove async hotplug propagation work
  cpuset: let hotplug propagation work wait for task attaching
  cpuset: re-structure update_cpumask() a bit
  cpuset: remove cpuset_test_cpumask()
  cpuset: remove unnecessary variable in cpuset_attach()
  cpuset: cleanup guarantee_online_{cpus|mems}()
  cpuset: remove redundant check in cpuset_cpus_allowed_fallback()

include/linux/cgroup.h

@@ -261,13 +261,20 @@ enum {
 	 *
 	 * - Remount is disallowed.
 	 *
+	 * - rename(2) is disallowed.
+	 *
 	 * - "tasks" is removed.  Everything should be at process
 	 *   granularity.  Use "cgroup.procs" instead.
 	 *
 	 * - "release_agent" and "notify_on_release" are removed.
 	 *   Replacement notification mechanism will be implemented.
 	 *
-	 * - rename(2) is disallowed.
+	 * - cpuset: tasks will be kept in empty cpusets when hotplug happens
+	 *   and take masks of ancestors with non-empty cpus/mems, instead of
+	 *   being moved to an ancestor.
+	 *
+	 * - cpuset: a task can be moved into an empty cpuset, and again it
+	 *   takes masks of ancestors.
 	 *
 	 * - memcg: use_hierarchy is on by default and the cgroup file for
 	 *   the flag is not created.