From: Peter Zijlstra peterz@infradead.org
commit 285c61aedf6bc5d81b37e4dc48c19012e8ff9836 upstream
One copy of this logic is better than three.
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20201207090243.GE3040@hirez.programming.kicks-ass.... Cc: stable@vger.kernel.org # 5.10 Signed-off-by: Shaoying Xu shaoyi@amazon.com --- 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 7bf45b0a1b1d..6b62654eb0a8 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); }
/*