linux-kernel - [PATCH] locking/rwsem: Remove unnessary check in rwsem_down_read

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Message-Id: <20231108105639.70088-1-haifeng.xu@shopee.com>
Date:   Wed,  8 Nov 2023 10:56:39 +0000
From:   Haifeng Xu <haifeng.xu@...pee.com>
To:     longman@...hat.com
Cc:     peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        boqun.feng@...il.com, linux-kernel@...r.kernel.org,
        Haifeng Xu <haifeng.xu@...pee.com>
Subject: [PATCH] locking/rwsem: Remove unnessary check in rwsem_down_read_slowpath()

When the owner of rw_semaphore is reader, the count can't be
RWSEM_WRITER_LOCKED, so there is no need to check it.

Signed-off-by: Haifeng Xu <haifeng.xu@...pee.com>
---
 kernel/locking/rwsem.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 2340b6d90ec6..7a4d8a9ebd9c 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1005,8 +1005,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, unsigned int stat
 	 * waiter, don't attempt optimistic lock stealing if the lock is
 	 * currently owned by readers.
 	 */
-	if ((atomic_long_read(&sem->owner) & RWSEM_READER_OWNED) &&
-	    (rcnt > 1) && !(count & RWSEM_WRITER_LOCKED))
+	if ((atomic_long_read(&sem->owner) & RWSEM_READER_OWNED) && (rcnt > 1))
 		goto queue;
 
 	/*
-- 
2.25.1