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From: David Laight <David.Laight@ACULAB.COM>
To: "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>,
	"'peterz@infradead.org'" <peterz@infradead.org>, "'longman@redhat.com'"
	<longman@redhat.com>
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	<will@kernel.org>, "'boqun.feng@gmail.com'" <boqun.feng@gmail.com>, "'Linus
 Torvalds'" <torvalds@linux-foundation.org>,
	"'virtualization@lists.linux-foundation.org'"
	<virtualization@lists.linux-foundation.org>, 'Zeng Heng'
	<zengheng4@huawei.com>
Subject: [PATCH next v2 1/5] locking/osq_lock: Defer clearing node->locked
 until the slow osq_lock() path.
Thread-Topic: [PATCH next v2 1/5] locking/osq_lock: Defer clearing
 node->locked until the slow osq_lock() path.
Thread-Index: Ado8M4Xvt5eQHXh8TpKpithIgw++9g==
Date: Sun, 31 Dec 2023 21:51:20 +0000
Message-ID: <714ca2e587cf4cd485ae04e5afb8d5bb@AcuMS.aculab.com>
References: <2b4e8a5816a742d2bd23fdbaa8498e80@AcuMS.aculab.com>
In-Reply-To: <2b4e8a5816a742d2bd23fdbaa8498e80@AcuMS.aculab.com>
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Since node->locked cannot be set before the assignment to prev->next
it is save to clear it in the slow path.

Signed-off-by: David Laight <david.laight@aculab.com>
---
 kernel/locking/osq_lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index 75a6f6133866..e0bc74d85a76 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -97,7 +97,6 @@ bool osq_lock(struct optimistic_spin_queue *lock)
 =09int curr =3D encode_cpu(smp_processor_id());
 =09int old;
=20
-=09node->locked =3D 0;
 =09node->next =3D NULL;
 =09node->cpu =3D curr;
=20
@@ -111,6 +110,7 @@ bool osq_lock(struct optimistic_spin_queue *lock)
 =09if (old =3D=3D OSQ_UNLOCKED_VAL)
 =09=09return true;
=20
+=09node->locked =3D 0;
 =09prev =3D decode_cpu(old);
 =09node->prev =3D prev;
=20
--=20
2.17.1

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