The following commit has been merged into the locking/core branch of tip: Commit-ID: bcba67cd806800fa8e973ac49dbc7d2d8fb3e55e Gitweb: https://git.kernel.org/tip/bcba67cd806800fa8e973ac49dbc7d2d8fb3e55e Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Tue, 04 Feb 2020 09:34:37 +01:00 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Tue, 11 Feb 2020 13:10:57 +01:00 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. Requested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Reviewed-by: Davidlohr Bueso <dbueso@xxxxxxx> Acked-by: Will Deacon <will@xxxxxxxxxx> Acked-by: Waiman Long <longman@xxxxxxxxxx> Tested-by: Juri Lelli <juri.lelli@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200204092228.GP14946@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx --- include/linux/rwsem.h | 6 ------ kernel/locking/rwsem.c | 2 -- 2 files changed, 8 deletions(-) diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 00d6054..8a418d9 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -53,12 +53,6 @@ struct rw_semaphore { #endif }; -/* - * Setting all bits of the owner field except bit 0 will indicate - * that the rwsem is writer-owned with an unknown owner. - */ -#define RWSEM_OWNER_UNKNOWN (-2L) - /* In all implementations count != 0 means locked */ static inline int rwsem_is_locked(struct rw_semaphore *sem) { diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 81c0d75..e6f437b 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -659,8 +659,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem, unsigned long flags; bool ret = true; - BUILD_BUG_ON(!(RWSEM_OWNER_UNKNOWN & RWSEM_NONSPINNABLE)); - if (need_resched()) { lockevent_inc(rwsem_opt_fail); return false;
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