linux-kernel - [PATCH 2/2] locking/rwsem: Use rcu_read_lock

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Date:   Sun, 26 Sep 2021 18:16:24 +0800
From:   Yanfei Xu <yanfei.xu@...driver.com>
To:     peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        longman@...hat.com, boqun.feng@...il.com
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] locking/rwsem: Use rcu_read_lock_sched to simplify codes

Use rcu_read_lock_sched to simplify the codes, and it also saves
some cycles of handling rcu nesting counter.

Signed-off-by: Yanfei Xu <yanfei.xu@...driver.com>
---
 kernel/locking/rwsem.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 000e8d5a2884..7afadfe02286 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -616,8 +616,7 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
 		return false;
 	}
 
-	preempt_disable();
-	rcu_read_lock();
+	rcu_read_lock_sched();
 	owner = rwsem_owner_flags(sem, &flags);
 	/*
 	 * Don't check the read-owner as the entry may be stale.
@@ -625,8 +624,7 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
 	if ((flags & RWSEM_NONSPINNABLE) ||
 	    (owner && !(flags & RWSEM_READER_OWNED) && !owner_on_cpu(owner)))
 		ret = false;
-	rcu_read_unlock();
-	preempt_enable();
+	rcu_read_unlock_sched();
 
 	lockevent_cond_inc(rwsem_opt_fail, !ret);
 	return ret;
-- 
2.27.0