sched: introduce this_rq_lock_irq()

do_sched_yield() disables IRQs, looks up this_rq() and locks it.  The next
patch is adding another site with the same pattern, so provide a
convenience function for it.

Link: http://lkml.kernel.org/r/20180828172258.3185-8-hannes@cmpxchg.org


Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Tested-by: Daniel Drake <drake@endlessm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: I06a20fdb7386c7837f3c1c593f7ad6fc70022c4b
Git-commit: 246b3b3342c9b0a2e24cda2178be87bc36e1c874
Git-repo: https://source.codeaurora.org/quic/la/kernel/msm-4.19


Signed-off-by: Patrick Daly <pdaly@codeaurora.org>