Changes in v3:
- Expend commit log and comments.
- Put argument @tsk at end in cgroup_attach_lock/unlock.
- down_write global cgroup_thread_rwsem when flipping favordynmods to
synchronize with task between cgroup_threadgroup_change_begin and end.
- Rename group_rwsem to cgroup_threadgroup_rwsem.
- Fix bug causing abnormal cgroup migration due to threadgroup leader changes。

Changes in v2:
- Use favordynmods as the enabling switch.
- Determine whether to use the per-thread-group rwsem based on whether
the task is NULL.
- Fix system hang caused by acquiring cgroup_threadgroup_rwsem inside
rcu_read_lock.

Yi Tao (1):
  cgroup: replace global percpu_rwsem with per threadgroup resem when
    writing to cgroup.procs

 include/linux/cgroup-defs.h     |  12 +++-
 include/linux/sched/signal.h    |   4 ++
 init/init_task.c                |   3 +
 kernel/cgroup/cgroup-internal.h |   4 +-
 kernel/cgroup/cgroup-v1.c       |   8 +--
 kernel/cgroup/cgroup.c          | 105 ++++++++++++++++++++++----------
 kernel/fork.c                   |   4 ++
 7 files changed, 101 insertions(+), 39 deletions(-)

-- 
2.32.0.3.g01195cf9f