netdev - [PATCH] ipv6: Annotate change of locking mechanism for np->opt

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Message-Id: <1455754833-31567-1-git-send-email-bpoirier@suse.com>
Date:	Wed, 17 Feb 2016 16:20:33 -0800
From:	Benjamin Poirier <bpoirier@...e.com>
To:	netdev@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH] ipv6: Annotate change of locking mechanism for np->opt

follows up commit 45f6fad84cc3 ("ipv6: add complete rcu protection around
np->opt") which added mixed rcu/refcount protection to np->opt.

Given the current implementation of rcu_pointer_handoff(), this has no
effect at runtime.

Signed-off-by: Benjamin Poirier <bpoirier@...e.com>
---
 include/net/ipv6.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 6570f37..f3c9857 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -259,8 +259,12 @@ static inline struct ipv6_txoptions *txopt_get(const struct ipv6_pinfo *np)
 
 	rcu_read_lock();
 	opt = rcu_dereference(np->opt);
-	if (opt && !atomic_inc_not_zero(&opt->refcnt))
-		opt = NULL;
+	if (opt) {
+		if (!atomic_inc_not_zero(&opt->refcnt))
+			opt = NULL;
+		else
+			opt = rcu_pointer_handoff(opt);
+	}
 	rcu_read_unlock();
 	return opt;
 }
-- 
2.7.0