exit: reparent: cleanup the usage of reparent_leader()
exit: reparent: cleanup the usage of reparent_leader()

1. Now that reparent_leader() doesn't abuse ->sibling we can shift
   list_move_tail() from reparent_leader() to forget_original_parent()
   and turn it into a single list_splice_tail_init(). This also makes
   BUG_ON(!list_empty()) and list_for_each_entry_safe() unnecessary.

2. This also allows to shift the same_thread_group() check, it looks
   a bit more clear in the caller.

Signed-off-by: Oleg Nesterov <20b70f0af00562e63758b9ee42012ecc96c58590@redhat.com>
Cc: Aaron Tomlin <4ed61b0b61ab8b39dcdee4eca4730f0b305b3047@redhat.com>
Cc: Alexey Dobriyan <b99bff5923d24d2fb8e844db9dac7cd59203da1d@gmail.com>
Cc: "Eric W. Biederman" <8a741aa8cbd77ebc4a56ddb528ce9fd15d42f034@xmission.com>,
Cc: Sterling Alexander <9eb90039aece32f9874377e394d636d5e7a331fe@redhat.com>
Cc: Peter Zijlstra <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Cc: Roland McGrath <0d270388f2f92757a5de0f4bd891d3b392c44c4f@hack.frob.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs