Merge branch 'ipc-cleanups'

Merge branch 'ipc-cleanups'

Merge ipc fixes and cleanups from my IPC branch.

The ipc locking has always been pretty ugly, and the scalability fixes
to some degree made it even less readable.  We had two cases of double
unlocks in error paths due to this (one rcu read unlock, one semaphore
unlock), and this fixes the bugs I found while trying to clean things up
a bit so that we are less likely to have more.

* ipc-cleanups:
  ipc: simplify rcu_read_lock() in semctl_nolock()
  ipc: simplify semtimedop/semctl_main() common error path handling
  ipc: move sem_obtain_lock() rcu locking into the only caller
  ipc: fix double sem unlock in semctl error path
  ipc: move the rcu_read_lock() from sem_lock_and_putref() into callers
  ipc: sem_putref() does not need the semaphore lock any more
  ipc: move rcu_read_unlock() out of sem_unlock() and into callers