linux-kernel - [tip: locking/core] locking/rwsem: Better collate rwsem_read

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Date:   Wed, 09 Dec 2020 18:38:48 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/core] locking/rwsem: Better collate rwsem_read_trylock()

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@...radead.org>
AuthorDate:    Tue, 08 Dec 2020 10:22:16 +01:00
Committer:     Peter Zijlstra <peterz@...radead.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@...radead.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;
 }