[PATCH 10/17] futex: Pull rt_mutex_futex_unlock() out from under hb->lock

From: Peter Zijlstra commit 16ffa12d742534d4ff73e8b3a4e81c1de39196f0 upstream. There's a number of 'interesting' problems, all caused by holding hb->lock while doing the rt_mutex_unlock() equivalient. Notably: - a PI inversion on hb->lock; and, - a SCHED_DEADLINE crash because of pointer

[PATCH 10/17] futex: Pull rt_mutex_futex_unlock() out from under hb->lock

From: Peter Zijlstra commit 16ffa12d742534d4ff73e8b3a4e81c1de39196f0 upstream. There's a number of 'interesting' problems, all caused by holding hb->lock while doing the rt_mutex_unlock() equivalient. Notably: - a PI inversion on hb->lock; and, - a SCHED_DEADLINE crash because of pointer