Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756481Ab0D0QdT (ORCPT ); Tue, 27 Apr 2010 12:33:19 -0400 Received: from mail-bw0-f219.google.com ([209.85.218.219]:41336 "EHLO mail-bw0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756461Ab0D0QdP (ORCPT ); Tue, 27 Apr 2010 12:33:15 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=IFK7625G6ywcEaWopZ537YMFdB589syGTMdlktCBpfk1KMfgKrtwPqQEEjJmVOtP2e tSvvWveglz4rOb2yQAmNsxKmqpxVLZDmvb54Pr6JAvz8VsLK23bmpl/i7ngBdKD6Y5tH MWZCe+Cxd361fXIFJybVUGWwi23Qp7ZI9Djl0= Subject: Re: [PATCH] RCU: don't turn off lockdep when find suspicious rcu_dereference_check() usage From: Eric Dumazet To: paulmck@linux.vnet.ibm.com Cc: "Eric W. Biederman" , Miles Lane , Vivek Goyal , Eric Paris , Lai Jiangshan , Ingo Molnar , Peter Zijlstra , LKML , nauman@google.com, netdev@vger.kernel.org, Jens Axboe , Gui Jianfeng , Li Zefan , Johannes Berg In-Reply-To: <20100427162201.GA5826@linux.vnet.ibm.com> References: <20100422160144.GC2524@linux.vnet.ibm.com> <20100423194255.GE2589@linux.vnet.ibm.com> <20100425023455.GM2440@linux.vnet.ibm.com> <20100426160925.GD2529@linux.vnet.ibm.com> <20100427042744.GD2510@linux.vnet.ibm.com> <20100427162201.GA5826@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 27 Apr 2010 18:33:04 +0200 Message-ID: <1272385984.2295.318.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2791 Lines: 70 Le mardi 27 avril 2010 à 09:22 -0700, Paul E. McKenney a écrit : > 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" 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 > > ------------------------------------------------------------------------ > > commit 85fa42bd568ab99c375f018761ae6345249942cd > Author: Paul E. McKenney > 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 > > 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 > -- Acked-by: Eric Dumazet -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/