netdev - [PATCH net-next 1/2] net: rtnl: introduce rcu_replace_pointer

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Date: Fri, 15 Dec 2023 14:57:10 -0300
From: Pedro Tammela <pctammela@...atatu.com>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	horms@...nel.org,
	jiri@...nulli.us,
	jhs@...atatu.com,
	victor@...atatu.com,
	martin@...ongswan.org,
	idosch@...dia.com,
	razor@...ckwall.org,
	lucien.xin@...il.com,
	edwin.peer@...adcom.com,
	amcohen@...dia.com,
	Pedro Tammela <pctammela@...atatu.com>
Subject: [PATCH net-next 1/2] net: rtnl: introduce rcu_replace_pointer_rtnl

From: Jamal Hadi Salim <jhs@...atatu.com>

Introduce the rcu_replace_pointer_rtnl helper to lockdep check rtnl lock
rcu replacements, alongside the already existing helpers.

This is a quality of life helper so instead of using:
   rcu_replace_pointer(rp, p, lockdep_rtnl_is_held())
   .. or the open coded..
   rtnl_dereference() / rcu_assign_pointer()
   .. or the lazy check version ..
   rcu_replace_pointer(rp, p, 1)
Use:
   rcu_replace_pointer_rtnl(rp, p)

Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
Signed-off-by: Victor Nogueira <victor@...atatu.com>
Signed-off-by: Pedro Tammela <pctammela@...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 6a8543b34e2c..410529fca18b 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -79,6 +79,18 @@ static inline bool lockdep_rtnl_is_held(void)
 #define rtnl_dereference(p)					\
 	rcu_dereference_protected(p, lockdep_rtnl_is_held())
 
+/**
+ * rcu_replace_pointer_rtnl - replace an RCU pointer under rtnl_lock, returning
+ * its old value
+ * @rp: RCU pointer, whose value is returned
+ * @p: regular pointer
+ *
+ * Perform a replacement under rtnl_lock, where @rp is an RCU-annotated
+ * pointer. The old value of @rp is returned, and @rp is set to @p
+ */
+#define rcu_replace_pointer_rtnl(rp, p)			\
+	rcu_replace_pointer(rp, p, lockdep_rtnl_is_held())
+
 static inline struct netdev_queue *dev_ingress_queue(struct net_device *dev)
 {
 	return rtnl_dereference(dev->ingress_queue);
-- 
2.40.1