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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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include/linux/rwsem.h+0−6
@@ -53,12 +53,6 @@ struct rw_semaphore { · 52 unmodified lines
5353 #endif
5454 };
5555
56−/*
57− * Setting all bits of the owner field except bit 0 will indicate
58− * that the rwsem is writer-owned with an unknown owner.
59− */
60−#define RWSEM_OWNER_UNKNOWN (-2L)
61−
6256 /* In all implementations count != 0 means locked */
6357 static inline int rwsem_is_locked(struct rw_semaphore *sem)
6458 {