From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: 2.6.34-rc1: rcu lockdep bug? Date: Sat, 13 Mar 2010 13:58:38 -0800 Message-ID: <20100313215838.GB6805@linux.vnet.ibm.com> References: <20100311134556.GA6344@linux.vnet.ibm.com> <20100311161751.GA3804@hack> <2375c9f91003112356g1b4164e4pb5f63f0e0e2f310a@mail.gmail.com> <20100312.000705.225033546.davem@davemloft.net> <2375c9f91003120059g771d162fxefc21beb2ab17b4d@mail.gmail.com> <1268392276.3141.4.camel@edumazet-laptop> <2375c9f91003120511j6f33592cl12cb2617a27351ec@mail.gmail.com> <1268401058.3141.9.camel@edumazet-laptop> <20100313053356.GC3704@hack> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Eric Dumazet , David Miller , peterz@infradead.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: =?iso-8859-1?Q?Am=E9rico?= Wang Return-path: Content-Disposition: inline In-Reply-To: <20100313053356.GC3704@hack> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Sat, Mar 13, 2010 at 01:33:56PM +0800, Am=E9rico Wang wrote: > On Fri, Mar 12, 2010 at 02:37:38PM +0100, Eric Dumazet wrote: > >Le vendredi 12 mars 2010 =E0 21:11 +0800, Am=E9rico Wang a =E9crit : > > > >> Oh, but lockdep complains about rcu_read_lock(), it said > >> rcu_read_lock() can't be used in softirq context. > >>=20 > >> Am I missing something? > > > >Well, lockdep might be dumb, I dont know... > > > >I suggest you read rcu_read_lock_bh kernel doc : > > > >/** > > * rcu_read_lock_bh - mark the beginning of a softirq-only RCU criti= cal > >section > > * > > * This is equivalent of rcu_read_lock(), but to be used when update= s > > * are being done using call_rcu_bh(). Since call_rcu_bh() callbacks > > * consider completion of a softirq handler to be a quiescent state, > > * a process in RCU read-side critical section must be protected by > > * disabling softirqs. Read-side critical sections in interrupt cont= ext > > * can use just rcu_read_lock(). > > * > > */ > > > > > >Last sentence being perfect : > > > >Read-side critical sections in interrupt context > >can use just rcu_read_lock(). > > >=20 > Yeah, right, then it is more likely to be a bug of rcu lockdep. > Paul is looking at it. Except that it seems to be working correctly for me... Thanx, Paul