[tip: locking/core] locking/rwsem: Better collate rwsem_read_trylock()

tip-bot2 for Peter Zijlstra
2020-12-09T18:40:25Z

The following commit has been merged into the locking/core branch of tip:

Commit-ID: 3379116a0ca965b00e6522c7ea3f16c9dbd8f9f9
Gitweb: https://git.kernel.org/tip/3379116a0ca965b00e6522c7ea3f16c9dbd8f9f9
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue, 08 Dec 2020 10:22:16 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 09 Dec 2020 17:08:47 +01:00

locking/rwsem: Better collate rwsem_read_trylock()

All users of rwsem_read_trylock() do rwsem_set_reader_owned(sem) on
success, move it into rwsem_read_trylock() proper.

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 | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index a163542..5c0dc7e 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -273,9 +273,16 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem)
static inline bool rwsem_read_trylock(struct rw_semaphore *sem)
{
long cnt = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
+
if (WARN_ON_ONCE(cnt < 0))
rwsem_set_nonspinnable(sem);
- return !(cnt & RWSEM_READ_FAILED_MASK);
+
+ if (!(cnt & RWSEM_READ_FAILED_MASK)) {
+ rwsem_set_reader_owned(sem);
+ return true;
+ }
+
+ return false;
}

/*
@@ -1340,8 +1347,6 @@ static inline void __down_read(struct rw_semaphore *sem)
if (!rwsem_read_trylock(sem)) {
rwsem_down_read_slowpath(sem, TASK_UNINTERRUPTIBLE);
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
- } else {
- rwsem_set_reader_owned(sem);
}
}

@@ -1351,8 +1356,6 @@ static inline int __down_read_interruptible(struct rw_semaphore *sem)
if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE)))
return -EINTR;
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
- } else {
- rwsem_set_reader_owned(sem);
}
return 0;
}
@@ -1363,8 +1366,6 @@ static inline int __down_read_killable(struct rw_semaphore *sem)
if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_KILLABLE)))
return -EINTR;
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
- } else {
- rwsem_set_reader_owned(sem);
}
return 0;
}