From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755306Ab0FHQZh (ORCPT ); Tue, 8 Jun 2010 12:25:37 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:42179 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754041Ab0FHQZf (ORCPT ); Tue, 8 Jun 2010 12:25:35 -0400 Date: Tue, 8 Jun 2010 09:25:32 -0700 From: "Paul E. McKenney" To: Miles Lane Cc: Vivek Goyal , Eric Paris , David Woodhouse , Lai Jiangshan , Ingo Molnar , Peter Zijlstra , LKML , nauman@google.com, eric.dumazet@gmail.com, netdev@vger.kernel.org, Jens Axboe , Gui Jianfeng , Li Zefan , Johannes Berg Subject: Re: 2.6.35-rc2-git1 - lib/idr.c:605 invoked rcu_dereference_check() without protection! Message-ID: <20100608162532.GB2397@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20100608001234.GE2387@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 08, 2010 at 12:28:15AM -0400, Miles Lane wrote: > On Mon, Jun 7, 2010 at 8:12 PM, Paul E. McKenney > wrote: > > On Mon, Jun 07, 2010 at 02:23:17PM -0400, Miles Lane wrote: > >> [    2.677955] [ INFO: suspicious rcu_dereference_check() usage. ] > >> [    2.679089] --------------------------------------------------- > >> [    2.680276] lib/idr.c:605 invoked rcu_dereference_check() without protection! > >> [    2.681499] > >> [    2.681500] other info that might help us debug this: > >> [    2.681501] > >> [    2.685509] > >> [    2.685510] rcu_scheduler_active = 1, debug_locks = 1 > >> [    2.688221] 1 lock held by swapper/1: > >> [    2.689587]  #0:  (mtd_table_mutex){+.+...}, at: > >> [] register_mtd_user+0x1a/0x69 > >> [    2.691096] > >> [    2.691098] stack backtrace: > >> [    2.694059] Pid: 1, comm: swapper Not tainted 2.6.35-rc2-git1 #8 > >> [    2.695601] Call Trace: > >> [    2.697243]  [] lockdep_rcu_dereference+0x9d/0xa5 > >> [    2.698868]  [] idr_get_next+0x60/0x124 > >> [    2.700556]  [] __mtd_next_device+0x1b/0x1d > >> [    2.702238]  [] register_mtd_user+0x51/0x69 > >> [    2.703964]  [] init_mtdchar+0xb3/0xd3 > >> [    2.705686]  [] ? init_mtdchar+0x0/0xd3 > >> [    2.707470]  [] do_one_initcall+0x59/0x14e > >> [    2.709255]  [] kernel_init+0x144/0x1ce > >> [    2.711082]  [] kernel_thread_helper+0x4/0x10 > >> [    2.712862]  [] ? restore_args+0x0/0x30 > >> [    2.714647]  [] ? kernel_init+0x0/0x1ce > >> [    2.716415]  [] ? kernel_thread_helper+0x0/0x10 > > > > This looks like a new one!  Does the following patch take care of it? > > > >                                                        Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit 2d54a6c31b72c902b09d365e9c66205a5c07e549 > > Author: Paul E. McKenney > > Date:   Mon Jun 7 17:09:45 2010 -0700 > > > >    idr: fix RCU lockdep splat in idr_get_next() > > > >    Convert to rcu_dereference_raw() given that many callers may have many > >    different locking models. > > > >    Located-by: Miles Lane > >    Signed-off-by: Paul E. McKenney > > > > diff --git a/lib/idr.c b/lib/idr.c > > index 2eb1dca..f099f25 100644 > > --- a/lib/idr.c > > +++ b/lib/idr.c > > @@ -599,7 +599,7 @@ void *idr_get_next(struct idr *idp, int *nextidp) > >        /* find first ent */ > >        n = idp->layers * IDR_BITS; > >        max = 1 << n; > > -       p = rcu_dereference(idp->top); > > +       p = rcu_dereference_raw(idp->top); > >        if (!p) > >                return NULL; > > > > @@ -607,7 +607,7 @@ void *idr_get_next(struct idr *idp, int *nextidp) > >                while (n > 0 && p) { > >                        n -= IDR_BITS; > >                        *paa++ = p; > > -                       p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]); > > +                       p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]); > >                } > > > >                if (p) { > > > > Tested. Looks good! Thank you very much for both locating this one and for testing the fix! I have added your Tested-by. Thanx, Paul