From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ding Tianhong Subject: [PATCH net v2] vlan: Fix lockdep warning when vlan dev handle notification Date: Thu, 13 Mar 2014 10:22:18 +0800 Message-ID: <5321165A.1000208@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit To: Ben Hutchings , John Fastabend , Patrick McHardy , "David S. Miller" , Netdev , "Florian Fainelli" Return-path: Received: from szxga03-in.huawei.com ([119.145.14.66]:50526 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752715AbaCMCXQ (ORCPT ); Wed, 12 Mar 2014 22:23:16 -0400 Sender: netdev-owner@vger.kernel.org List-ID: When I open the LOCKDEP config and run these steps: modprobe 8021q vconfig add eth2 20 vconfig add eth2.20 30 ifconfig eth2 xx.xx.xx.xx then the Call Trace happened: [32524.386288] ============================================= [32524.386293] [ INFO: possible recursive locking detected ] [32524.386298] 3.14.0-rc2-0.7-default+ #35 Tainted: G O [32524.386302] --------------------------------------------- [32524.386306] ifconfig/3103 is trying to acquire lock: [32524.386310] (&vlan_netdev_addr_lock_key/1){+.....}, at: [] dev_mc_sync+0x64/0xb0 [32524.386326] [32524.386326] but task is already holding lock: [32524.386330] (&vlan_netdev_addr_lock_key/1){+.....}, at: [] dev_set_rx_mode+0x23/0x40 [32524.386341] [32524.386341] other info that might help us debug this: [32524.386345] Possible unsafe locking scenario: [32524.386345] [32524.386350] CPU0 [32524.386352] ---- [32524.386354] lock(&vlan_netdev_addr_lock_key/1); [32524.386359] lock(&vlan_netdev_addr_lock_key/1); [32524.386364] [32524.386364] *** DEADLOCK *** [32524.386364] [32524.386368] May be due to missing lock nesting notation [32524.386368] [32524.386373] 2 locks held by ifconfig/3103: [32524.386376] #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x12/0x20 [32524.386387] #1: (&vlan_netdev_addr_lock_key/1){+.....}, at: [] dev_set_rx_mode+0x23/0x40 [32524.386398] [32524.386398] stack backtrace: [32524.386403] CPU: 1 PID: 3103 Comm: ifconfig Tainted: G O 3.14.0-rc2-0.7-default+ #35 [32524.386409] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007 [32524.386414] ffffffff81ffae40 ffff8800d9625ae8 ffffffff814f68a2 ffff8800d9625bc8 [32524.386421] ffffffff810a35fb ffff8800d8a8d9d0 00000000d9625b28 ffff8800d8a8e5d0 [32524.386428] 000003cc00000000 0000000000000002 ffff8800d8a8e5f8 0000000000000000 [32524.386435] Call Trace: [32524.386441] [] dump_stack+0x6a/0x78 [32524.386448] [] __lock_acquire+0x7ab/0x1940 [32524.386454] [] ? __lock_acquire+0x3ea/0x1940 [32524.386459] [] lock_acquire+0xe4/0x110 [32524.386464] [] ? dev_mc_sync+0x64/0xb0 [32524.386471] [] _raw_spin_lock_nested+0x2a/0x40 [32524.386476] [] ? dev_mc_sync+0x64/0xb0 [32524.386481] [] dev_mc_sync+0x64/0xb0 [32524.386489] [] vlan_dev_set_rx_mode+0x2b/0x50 [8021q] [32524.386495] [] __dev_set_rx_mode+0x5f/0xb0 [32524.386500] [] dev_set_rx_mode+0x2b/0x40 [32524.386506] [] __dev_open+0xef/0x150 [32524.386511] [] __dev_change_flags+0xa7/0x190 [32524.386516] [] dev_change_flags+0x32/0x80 [32524.386524] [] devinet_ioctl+0x7d6/0x830 [32524.386532] [] ? dev_ioctl+0x34b/0x660 [32524.386540] [] inet_ioctl+0x80/0xa0 [32524.386550] [] sock_do_ioctl+0x2d/0x60 [32524.386558] [] sock_ioctl+0x82/0x2a0 [32524.386568] [] do_vfs_ioctl+0x93/0x590 [32524.386578] [] ? rcu_read_lock_held+0x45/0x50 [32524.386586] [] ? __fget_light+0x105/0x110 [32524.386594] [] SyS_ioctl+0x91/0xb0 [32524.386604] [] system_call_fastpath+0x16/0x1b ======================================================================== The reason is that all of the vlan dev have the same class key for dev_lock_list, if we up or down the real dev, the notification will change the state for every vlan dev in the vlan group, then the vlan dev will hold netif_addr_lock and the real dev also hold its own netif_addr_lock together, so the warning happened. The best way to fix the problem is that we should make sure the vlan dev have a new class key which is different with its real dev. v1->v2: Convert the vlan_netdev_addr_lock_key to an array of eight elements, which could support to add 8 vlan id on a same vlan dev, I think it is enough for current scene, because a netdev's name is limited to IFNAMSIZ which could not hold 8 vlan id, and the vlan dev would not meet the same class key with its real dev. The new function vlan_dev_get_lockdep_subkey() will return the subkey and make the vlan dev could get a suitable class key. Signed-off-by: Ding Tianhong --- net/8021q/vlan_dev.c | 30 ++++++++++++++++++++++++++++-- 1 file changed, 28 insertions(+), 2 deletions(-) diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c index 566adbf..4ffa6cc 100644 --- a/net/8021q/vlan_dev.c +++ b/net/8021q/vlan_dev.c @@ -504,8 +504,10 @@ static void vlan_dev_set_rx_mode(struct net_device *vlan_dev) * "super class" of normal network devices; split their locks off into a * separate class since they always nest. */ + +#define MAX_ADDR_LOCK_SUBKEY 8 static struct lock_class_key vlan_netdev_xmit_lock_key; -static struct lock_class_key vlan_netdev_addr_lock_key; +static struct lock_class_key vlan_netdev_addr_lock_key[MAX_ADDR_LOCK_SUBKEY]; static void vlan_dev_set_lockdep_one(struct net_device *dev, struct netdev_queue *txq, @@ -516,10 +518,34 @@ static void vlan_dev_set_lockdep_one(struct net_device *dev, *(int *)_subclass); } +static int vlan_dev_get_lockdep_subkey(struct net_device *dev, int subclass) +{ + int subkey = 0; + struct net_device *real_dev; + + if (!subclass) + return subkey; + + real_dev = vlan_dev_priv(dev)->real_dev; + while(is_vlan_dev(real_dev)) { + subkey ++; + real_dev = vlan_dev_priv(real_dev)->real_dev; + } + + return subkey; +} + static void vlan_dev_set_lockdep_class(struct net_device *dev, int subclass) { + int subkey = vlan_dev_get_lockdep_subkey(dev, subclass); + + if (subkey >= MAX_ADDR_LOCK_SUBKEY) { + pr_err("the addr lock subkey is out of range\n"); + return; + } + lockdep_set_class_and_subclass(&dev->addr_list_lock, - &vlan_netdev_addr_lock_key, + &vlan_netdev_addr_lock_key[subkey], subclass); netdev_for_each_tx_queue(dev, vlan_dev_set_lockdep_one, &subclass); } -- 1.7.12