From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Tue, 27 Apr 2010 06:22:01 +0000 (+0000)
Subject: net: suppress RCU lockdep false positive in twsk_net()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=7ec75c582e639d956ce3afd499f67febe6f902a4;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

net: suppress RCU lockdep false positive in twsk_net()

Calls to twsk_net() are in some cases protected by reference counting
as an alternative to RCU protection.  Cases covered by reference counts
include __inet_twsk_kill(), inet_twsk_free(), inet_twdr_do_twkill_work(),
inet_twdr_twcal_tick(), and tcp_timewait_state_process().  RCU is used
by inet_twsk_purge().  Locking is used by established_get_first()
and established_get_next().  Finally, __inet_twsk_hashdance() is an
initialization case.

It appears to be non-trivial to locate the appropriate locks and
reference counts from within twsk_net(), so used rcu_dereference_raw().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index 79f67eae8a7e..a066fdd50da6 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -224,7 +224,9 @@ static inline
 struct net *twsk_net(const struct inet_timewait_sock *twsk)
 {
 #ifdef CONFIG_NET_NS
-	return rcu_dereference(twsk->tw_net);
+	return rcu_dereference_raw(twsk->tw_net); /* protected by locking, */
+						  /* reference counting, */
+						  /* initialization, or RCU. */
 #else
 	return &init_net;
 #endif