cgroup: simplify double-check locking in cgroup_attach_proc

To keep the complexity of the double-check locking in one place, move
the thread_group_leader check up into attach_task_by_pid().  This
allows us to use a goto instead of returning -EAGAIN.

While at it, convert a couple of returns to gotos and use rcu for the
!pid case also in order to simplify the logic.

Changes in V2:
* https://lkml.org/lkml/2011/12/22/86 (Tejun Heo)
  * Use a goto instead of returning -EAGAIN

Signed-off-by: Mandeep Singh Baines <[email protected]>
Acked-by: Li Zefan <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Paul Menage <[email protected]>

0 files changed, 0 insertions, 0 deletions