From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933745AbZHEIsF (ORCPT ); Wed, 5 Aug 2009 04:48:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933648AbZHEIsE (ORCPT ); Wed, 5 Aug 2009 04:48:04 -0400 Received: from mx2.redhat.com ([66.187.237.31]:50252 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933365AbZHEIsA (ORCPT ); Wed, 5 Aug 2009 04:48:00 -0400 Date: Wed, 5 Aug 2009 10:47:47 +0200 From: Jiri Pirko To: Ingo Molnar Cc: David Miller , Peter Zijlstra , torvalds@linux-foundation.org, akpm@linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net: Fix spinlock use in alloc_netdev_mq() Message-ID: <20090805084746.GA3897@psychotron.englab.brq.redhat.com> References: <20090804.125742.32009006.davem@davemloft.net> <20090805070205.GA8741@elte.hu> <20090805071411.GA9217@elte.hu> <20090805071658.GA14073@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090805071658.GA14073@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Wed, Aug 05, 2009 at 09:16:58AM CEST, mingo@elte.hu wrote: > >>From 6a0405d0e9b5e15bb81b8278b08fdb931a6e8837 Mon Sep 17 00:00:00 2001 >From: Ingo Molnar >Date: Wed, 5 Aug 2009 09:14:11 +0200 >Subject: [PATCH] net: Fix spinlock use in alloc_netdev_mq() > >-tip testing found this lockdep warning: > >[ 2.272010] calling net_dev_init+0x0/0x164 @ 1 >[ 2.276033] device class 'net': registering >[ 2.280191] INFO: trying to register non-static key. >[ 2.284005] the code is fine but needs lockdep annotation. >[ 2.284005] turning off the locking correctness validator. >[ 2.284005] Pid: 1, comm: swapper Not tainted 2.6.31-rc5-tip #1145 >[ 2.284005] Call Trace: >[ 2.284005] [<7958eb4e>] ? printk+0xf/0x11 >[ 2.284005] [<7904f83c>] __lock_acquire+0x11b/0x622 >[ 2.284005] [<7908c9b7>] ? alloc_debug_processing+0xf9/0x144 >[ 2.284005] [<7904e2be>] ? mark_held_locks+0x3a/0x52 >[ 2.284005] [<7908dbc4>] ? kmem_cache_alloc+0xa8/0x13f >[ 2.284005] [<7904e475>] ? trace_hardirqs_on_caller+0xa2/0xc3 >[ 2.284005] [<7904fdf6>] lock_acquire+0xb3/0xd0 >[ 2.284005] [<79489678>] ? alloc_netdev_mq+0xf5/0x1ad >[ 2.284005] [<79591514>] _spin_lock_bh+0x2d/0x5d >[ 2.284005] [<79489678>] ? alloc_netdev_mq+0xf5/0x1ad >[ 2.284005] [<79489678>] alloc_netdev_mq+0xf5/0x1ad >[ 2.284005] [<793a38f2>] ? loopback_setup+0x0/0x74 >[ 2.284005] [<798eecd0>] loopback_net_init+0x20/0x5d >[ 2.284005] [<79483efb>] register_pernet_device+0x23/0x4b >[ 2.284005] [<798f5c9f>] net_dev_init+0x115/0x164 >[ 2.284005] [<7900104f>] do_one_initcall+0x4a/0x11a >[ 2.284005] [<798f5b8a>] ? net_dev_init+0x0/0x164 >[ 2.284005] [<79066f6d>] ? register_irq_proc+0x8c/0xa8 >[ 2.284005] [<798cc29a>] do_basic_setup+0x42/0x52 >[ 2.284005] [<798cc30a>] kernel_init+0x60/0xa1 >[ 2.284005] [<798cc2aa>] ? kernel_init+0x0/0xa1 >[ 2.284005] [<79003e03>] kernel_thread_helper+0x7/0x10 >[ 2.284078] device: 'lo': device_add >[ 2.288248] initcall net_dev_init+0x0/0x164 returned 0 after 11718 usecs >[ 2.292010] calling neigh_init+0x0/0x66 @ 1 >[ 2.296010] initcall neigh_init+0x0/0x66 returned 0 after 0 usecs > >it's using an zero-initialized spinlock. This is a side-effect of: > > dev_unicast_init(dev); > >in alloc_netdev_mq() making use of dev->addr_list_lock. > >The device has just been allocated freshly, it's not accessible >anywhere yet so no locking is needed at all - in fact it's wrong >to lock it here (the lock isnt initialized yet). Yes this looks like the right approach. Sorry for this bug :( > >This bug was introduced via: > >| commit a6ac65db2329e7685299666f5f7b6093c7b0f3a0 >| Date: Thu Jul 30 01:06:12 2009 +0000 >| >| net: restore the original spinlock to protect unicast list > >Signed-off-by: Ingo Molnar Acked-by: Jiri Pirko >--- > net/core/dev.c | 2 -- > 1 files changed, 0 insertions(+), 2 deletions(-) > >diff --git a/net/core/dev.c b/net/core/dev.c >index 43e61ba..6a94475 100644 >--- a/net/core/dev.c >+++ b/net/core/dev.c >@@ -4007,9 +4007,7 @@ static void dev_unicast_flush(struct net_device *dev) > > static void dev_unicast_init(struct net_device *dev) > { >- netif_addr_lock_bh(dev); > __hw_addr_init(&dev->uc); >- netif_addr_unlock_bh(dev); > } > >