netdev - [PATCH RFC v6 net-next 06/17] net: introduce rcu_replace_pointer

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Date: Sat, 30 Sep 2023 10:35:31 -0400
From: Jamal Hadi Salim <jhs@...atatu.com>
To: netdev@...r.kernel.org
Cc: deb.chatterjee@...el.com,
	anjali.singhai@...el.com,
	namrata.limaye@...el.com,
	tom@...anda.io,
	mleitner@...hat.com,
	Mahesh.Shirshyad@....com,
	tomasz.osinski@...el.com,
	jiri@...nulli.us,
	xiyou.wangcong@...il.com,
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	edumazet@...gle.com,
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	horms@...nel.org,
	kernel@...atatu.com,
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	toke@...hat.com,
	mattyk@...dia.com
Subject: [PATCH RFC v6 net-next 06/17] net: introduce rcu_replace_pointer_rtnl

We use rcu_replace_pointer(rcu_ptr, ptr, lockdep_rtnl_is_held()) throughout
the P4TC infrastructure code.

It may be useful for other use cases, so we create a helper.

Co-developed-by: Victor Nogueira <victor@...atatu.com>
Signed-off-by: Victor Nogueira <victor@...atatu.com>
Co-developed-by: Pedro Tammela <pctammela@...atatu.com>
Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
---
 include/linux/rtnetlink.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 3d6cf306c..971055e66 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -62,6 +62,18 @@ static inline bool lockdep_rtnl_is_held(void)
 #define rcu_dereference_rtnl(p)					\
 	rcu_dereference_check(p, lockdep_rtnl_is_held())
 
+/**
+ * rcu_replace_pointer_rtnl - replace an RCU pointer under rtnl_lock, returning
+ * its old value
+ * @rcu_ptr: RCU pointer, whose old value is returned
+ * @ptr: regular pointer
+ *
+ * Perform a replacement under rtnl_lock, where @rcu_ptr is an RCU-annotated
+ * pointer. The old value of @rcu_ptr is returned, and @rcu_ptr is set to @ptr
+ */
+#define rcu_replace_pointer_rtnl(rcu_ptr, ptr)			\
+	rcu_replace_pointer(rcu_ptr, ptr, lockdep_rtnl_is_held())
+
 /**
  * rtnl_dereference - fetch RCU pointer when updates are prevented by RTNL
  * @p: The pointer to read, prior to dereferencing
-- 
2.34.1