locking/rwsem: Introduce rwsem_write_trylock()

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.net

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 5c0dc7e..7915456 100644 (file)
--- 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);
 }
 
 /*