locking/rwsem: Remove RWSEM_OWNER_UNKNOWN

Remove the now unused RWSEM_OWNER_UNKNOWN hack. This hack breaks PREEMPT_RT and getting rid of it was the entire motivation for re-writing the percpu rwsem. The biggest problem is that it is fundamentally incompatible with any form of Priority Inheritance, any exclusively held lock must have a distinct owner.

Peter Zijlstra committed 6 years ago

Commit bcba67c1 parent 7f264822 files · +0 −8Browse files

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kernel/locking/rwsem.c+0−2

@@ -659,8 +659,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem, · 658 unmodified lines
659	659	unsigned long flags;
660	660	bool ret = true;
661	661
662		− BUILD_BUG_ON(!(RWSEM_OWNER_UNKNOWN & RWSEM_NONSPINNABLE));
663		−
664	662	if (need_resched()) {
665	663	lockevent_inc(rwsem_opt_fail);
666	664	return false;