Messages in this thread Patch in this message | | | Date | Tue, 27 Apr 2010 09:22:01 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] RCU: don't turn off lockdep when find suspicious rcu_dereference_check() usage |
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On Mon, Apr 26, 2010 at 09:27:44PM -0700, Paul E. McKenney wrote: > On Mon, Apr 26, 2010 at 11:35:10AM -0700, Eric W. Biederman wrote: > > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes: > > > > > Eric Dumazet traced these down to a commit from Eric Biederman. > > > > > > If I don't hear from Eric Biederman in a few days, I will attempt a > > > patch, but it would be more likely to be correct coming from someone > > > with a better understanding of the code. ;-) > > > > I already replied. > > > > http://lkml.org/lkml/2010/4/21/420 > > You did indeed!!! This experience is giving me an even better appreciation > of the maintainers' ability to keep all their patches straight! > > I will put together something based on your suggestion.
How about the following?
Thanx, Paul
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commit 85fa42bd568ab99c375f018761ae6345249942cd Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Date: Mon Apr 26 21:40:05 2010 -0700
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>
diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h index 79f67ea..a066fdd 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
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