netdev - [PATCH net-next RFC 09/20] net: introduce rcu_replace_pointer

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Date:   Tue, 24 Jan 2023 12:04:59 -0500
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     netdev@...r.kernel.org
Cc:     kernel@...atatu.com, deb.chatterjee@...el.com,
        anjali.singhai@...el.com, namrata.limaye@...el.com,
        khalidm@...dia.com, tom@...anda.io, pratyush@...anda.io,
        jiri@...nulli.us, xiyou.wangcong@...il.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        vladbu@...dia.com, simon.horman@...igine.com
Subject: [PATCH net-next RFC 09/20] 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 92ad75549..56a1e80fe 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -71,6 +71,18 @@ static inline bool lockdep_rtnl_is_held(void)
 #define rcu_dereference_bh_rtnl(p)				\
 	rcu_dereference_bh_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