[tip: locking/core] locking/rwsem: Introduce rwsem_write_trylock()

tip-bot2 for Peter Zijlstra
2020-12-09T18:40:04Z

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 <peterz@infradead.org>
AuthorDate: Tue, 08 Dec 2020 10:25:06 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
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) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201207090243.GE3040@hirez.programming.kicks-ass.net
---
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);
}

/*