1 files changed, 16 insertions, 15 deletions

diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index a2391ac135c8..7628c3fc37ca 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -246,19 +246,22 @@ struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
 
 	return sem;
 }
+EXPORT_SYMBOL(rwsem_down_read_failed);
 
 static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem)
 {
-	if (!(count & RWSEM_ACTIVE_MASK)) {
-		/* try acquiring the write lock */
-		if (sem->count == RWSEM_WAITING_BIAS &&
-		    cmpxchg(&sem->count, RWSEM_WAITING_BIAS,
-			    RWSEM_ACTIVE_WRITE_BIAS) == RWSEM_WAITING_BIAS) {
-			if (!list_is_singular(&sem->wait_list))
-				rwsem_atomic_update(RWSEM_WAITING_BIAS, sem);
-			return true;
-		}
+	/*
+	 * Try acquiring the write lock. Check count first in order
+	 * to reduce unnecessary expensive cmpxchg() operations.
+	 */
+	if (count == RWSEM_WAITING_BIAS &&
+	    cmpxchg(&sem->count, RWSEM_WAITING_BIAS,
+		    RWSEM_ACTIVE_WRITE_BIAS) == RWSEM_WAITING_BIAS) {
+		if (!list_is_singular(&sem->wait_list))
+			rwsem_atomic_update(RWSEM_WAITING_BIAS, sem);
+		return true;
 	}
+
 	return false;
 }
 
@@ -329,7 +332,7 @@ bool rwsem_spin_on_owner(struct rw_semaphore *sem, struct task_struct *owner)
 		if (need_resched())
 			break;
 
-		arch_mutex_cpu_relax();
+		cpu_relax_lowlatency();
 	}
 	rcu_read_unlock();
 
@@ -381,7 +384,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
 		 * memory barriers as we'll eventually observe the right
 		 * values at the cost of a few extra spins.
 		 */
-		arch_mutex_cpu_relax();
+		cpu_relax_lowlatency();
 	}
 	osq_unlock(&sem->osq);
 done:
@@ -465,6 +468,7 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
 
 	return sem;
 }
+EXPORT_SYMBOL(rwsem_down_write_failed);
 
 /*
  * handle waking up a waiter on the semaphore
@@ -485,6 +489,7 @@ struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem)
 
 	return sem;
 }
+EXPORT_SYMBOL(rwsem_wake);
 
 /*
  * downgrade a write lock into a read lock
@@ -506,8 +511,4 @@ struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
 
 	return sem;
 }
-
-EXPORT_SYMBOL(rwsem_down_read_failed);
-EXPORT_SYMBOL(rwsem_down_write_failed);
-EXPORT_SYMBOL(rwsem_wake);
 EXPORT_SYMBOL(rwsem_downgrade_wake);