Pull workqueue updates from Tejun Heo:
 "Only three commits, of which two are trivial.

  The non-trivial chagne is Thomas's patch to switch workqueue from
  sched RCU to regular one. The use of sched RCU is mostly historic and
  doesn't really buy us anything noticeable"

* 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Use normal rcu
  kernel/workqueue: Document wq_worker_last_func() argument
  kernel/workqueue: Use __printf markup to silence compiler in function 'alloc_workqueue'