Merge branch 'for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - Oleg's pids controller accounting update which gets rid of rcu delay
   in pids accounting updates

 - rstat (cgroup hierarchical stat collection mechanism) optimization

 - Doc updates

* 'for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cpuset: remove unused task_has_mempolicy()
  cgroup, rstat: Don't flush subtree root unless necessary
  cgroup: add documentation for pids.events file
  Documentation: cgroup-v2: eliminate markup warnings
  MAINTAINERS: Update cgroup entry
  cgroup/pids: turn cgroup_subsys->free() into cgroup_subsys->release() to fix the accounting

Documentation/cgroup-v1/pids.txt

@@ -33,6 +33,9 @@ limit in the hierarchy is followed).
 pids.current tracks all child cgroup hierarchies, so parent/pids.current is a
 superset of parent/child/pids.current.
 
+The pids.events file contains event counters:
+  - max: Number of times fork failed because limit was hit.
+
 Example
 -------