netdev - [PATCH net-next 1/3] sock: fix lockdep annotation in release

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Message-Id: <1459869016-13896-2-git-send-email-hannes@stressinduktion.org>
Date:	Tue,  5 Apr 2016 17:10:14 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	netdev@...r.kernel.org
Cc:	daniel@...earbox.net, Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 1/3] sock: fix lockdep annotation in release_sock

During release_sock we use callbacks to finish the processing
of outstanding skbs on the socket. We actually are still locked,
sk_locked.owned == 1, but we already told lockdep that the mutex
is released. This could lead to false positives in lockdep for
lockdep_sock_is_held (we don't hold the slock spinlock during processing
the outstanding skbs).

I took over this patch from Eric Dumazet and tested it.

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
 include/net/sock.h | 7 ++++++-
 net/core/sock.c    | 5 -----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 310c4367ea83f6..4654ad45e84e7f 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1329,7 +1329,12 @@ static inline void sk_wmem_free_skb(struct sock *sk, struct sk_buff *skb)
 
 static inline void sock_release_ownership(struct sock *sk)
 {
-	sk->sk_lock.owned = 0;
+	if (sk->sk_lock.owned) {
+		sk->sk_lock.owned = 0;
+
+		/* The sk_lock has mutex_unlock() semantics: */
+		mutex_release(&sk->sk_lock.dep_map, 1, _RET_IP_);
+	}
 }
 
 /*
diff --git a/net/core/sock.c b/net/core/sock.c
index 2f517ea5678612..f5923e9c92bb0d 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2467,11 +2467,6 @@ EXPORT_SYMBOL(lock_sock_nested);
 
 void release_sock(struct sock *sk)
 {
-	/*
-	 * The sk_lock has mutex_unlock() semantics:
-	 */
-	mutex_release(&sk->sk_lock.dep_map, 1, _RET_IP_);
-
 	spin_lock_bh(&sk->sk_lock.slock);
 	if (sk->sk_backlog.tail)
 		__release_sock(sk);
-- 
2.5.5