The following commit has been merged into the locking/core branch of tip: Commit-ID: 285c61aedf6bc5d81b37e4dc48c19012e8ff9836 Gitweb: https://git.kernel.org/tip/285c61aedf6bc5d81b37e4dc48c19012e8ff9836 Author: Peter Zijlstra <[email protected]> AuthorDate: Tue, 08 Dec 2020 10:25:06 +01:00 Committer: Peter Zijlstra <[email protected]> CommitterDate: Wed, 09 Dec 2020 17:08:47 +01:00
locking/rwsem: Introduce rwsem_write_trylock() One copy of this logic is better than three. Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- kernel/locking/rwsem.c | 38 ++++++++++++++++---------------------- 1 file changed, 16 insertions(+), 22 deletions(-) diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 5c0dc7e..7915456 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -285,6 +285,18 @@ static inline bool rwsem_read_trylock(struct rw_semaphore *sem) return false; } +static inline bool rwsem_write_trylock(struct rw_semaphore *sem) +{ + long tmp = RWSEM_UNLOCKED_VALUE; + + if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, RWSEM_WRITER_LOCKED)) { + rwsem_set_owner(sem); + return true; + } + + return false; +} + /* * Return just the real task structure pointer of the owner */ @@ -1395,42 +1407,24 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) */ static inline void __down_write(struct rw_semaphore *sem) { - long tmp = RWSEM_UNLOCKED_VALUE; - - if (unlikely(!atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, - RWSEM_WRITER_LOCKED))) + if (unlikely(!rwsem_write_trylock(sem))) rwsem_down_write_slowpath(sem, TASK_UNINTERRUPTIBLE); - else - rwsem_set_owner(sem); } static inline int __down_write_killable(struct rw_semaphore *sem) { - long tmp = RWSEM_UNLOCKED_VALUE; - - if (unlikely(!atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, - RWSEM_WRITER_LOCKED))) { + if (unlikely(!rwsem_write_trylock(sem))) { if (IS_ERR(rwsem_down_write_slowpath(sem, TASK_KILLABLE))) return -EINTR; - } else { - rwsem_set_owner(sem); } + return 0; } static inline int __down_write_trylock(struct rw_semaphore *sem) { - long tmp; - DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem); - - tmp = RWSEM_UNLOCKED_VALUE; - if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, - RWSEM_WRITER_LOCKED)) { - rwsem_set_owner(sem); - return true; - } - return false; + return rwsem_write_trylock(sem); } /*
