[PATCH 3.14 080/140] vlan: Fix lockdep warning when vlan dev handle notification

Greg Kroah-Hartman
2014-05-29T05:21:33Z

From: dingtianhong <dingtianhong@huawei.com>

[ Upstream commit dc8eaaa006350d24030502a4521542e74b5cb39f ]

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: [<ffffffff814275f4>] dev_mc_sync+0x64/0xb0
[32524.386326]
[32524.386326] but task is already holding lock:
[32524.386330] (&vlan_netdev_addr_lock_key/1){+.....}, at: [<ffffffff8141af83>] 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: [<ffffffff81431d42>] rtnl_lock+0x12/0x20
[32524.386387] #1: (&vlan_netdev_addr_lock_key/1){+.....}, at: [<ffffffff8141af83>] 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] [<ffffffff814f68a2>] dump_stack+0x6a/0x78
[32524.386448] [<ffffffff810a35fb>] __lock_acquire+0x7ab/0x1940
[32524.386454] [<ffffffff810a323a>] ? __lock_acquire+0x3ea/0x1940
[32524.386459] [<ffffffff810a4874>] lock_acquire+0xe4/0x110
[32524.386464] [<ffffffff814275f4>] ? dev_mc_sync+0x64/0xb0
[32524.386471] [<ffffffff814fc07a>] _raw_spin_lock_nested+0x2a/0x40
[32524.386476] [<ffffffff814275f4>] ? dev_mc_sync+0x64/0xb0
[32524.386481] [<ffffffff814275f4>] dev_mc_sync+0x64/0xb0
[32524.386489] [<ffffffffa0500cab>] vlan_dev_set_rx_mode+0x2b/0x50 [8021q]
[32524.386495] [<ffffffff8141addf>] __dev_set_rx_mode+0x5f/0xb0
[32524.386500] [<ffffffff8141af8b>] dev_set_rx_mode+0x2b/0x40
[32524.386506] [<ffffffff8141b3cf>] __dev_open+0xef/0x150
[32524.386511] [<ffffffff8141b177>] __dev_change_flags+0xa7/0x190
[32524.386516] [<ffffffff8141b292>] dev_change_flags+0x32/0x80
[32524.386524] [<ffffffff8149ca56>] devinet_ioctl+0x7d6/0x830
[32524.386532] [<ffffffff81437b0b>] ? dev_ioctl+0x34b/0x660
[32524.386540] [<ffffffff814a05b0>] inet_ioctl+0x80/0xa0
[32524.386550] [<ffffffff8140199d>] sock_do_ioctl+0x2d/0x60
[32524.386558] [<ffffffff81401a52>] sock_ioctl+0x82/0x2a0
[32524.386568] [<ffffffff811a7123>] do_vfs_ioctl+0x93/0x590
[32524.386578] [<ffffffff811b2705>] ? rcu_read_lock_held+0x45/0x50
[32524.386586] [<ffffffff811b39e5>] ? __fget_light+0x105/0x110
[32524.386594] [<ffffffff811a76b1>] SyS_ioctl+0x91/0xb0
[32524.386604] [<ffffffff815057e2>] system_call_fastpath+0x16/0x1b

========================================================================

The reason is that all of the addr_lock_key for vlan dev have the same class,
so if we change the status for vlan dev, the vlan dev and its real dev will
hold the same class of addr_lock_key together, so the warning happened.

we should distinguish the lock depth for vlan dev and 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.

v2->v3: According David's suggestion, I use the subclass to distinguish the lock key for vlan dev
and its real dev, but it make no sense, because the difference for subclass in the
lock_class_key doesn't mean that the difference class for lock_key, so I use lock_depth
to distinguish the different depth for every vlan dev, the same depth of the vlan dev
could have the same lock_class_key, I import the MAX_LOCK_DEPTH from the include/linux/sched.h,
I think it is enough here, the lockdep should never exceed that value.

v3->v4: Add a huge array of locking keys will waste static kernel memory and is not a appropriate method,
we could use _nested() variants to fix the problem, calculate the depth for every vlan dev,
and use the depth as the subclass for addr_lock_key.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/8021q/vlan_dev.c | 46 +++++++++++++++++++++++++++++++++++++++++-----
net/core/dev.c | 1 +
2 files changed, 42 insertions(+), 5 deletions(-)

--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -493,10 +493,48 @@ static void vlan_dev_change_rx_flags(str
}
}

+static int vlan_calculate_locking_subclass(struct net_device *real_dev)
+{
+ int subclass = 0;
+
+ while (is_vlan_dev(real_dev)) {
+ subclass++;
+ real_dev = vlan_dev_priv(real_dev)->real_dev;
+ }
+
+ return subclass;
+}
+
+static void vlan_dev_mc_sync(struct net_device *to, struct net_device *from)
+{
+ int err = 0, subclass;
+
+ subclass = vlan_calculate_locking_subclass(to);
+
+ spin_lock_nested(&to->addr_list_lock, subclass);
+ err = __hw_addr_sync(&to->mc, &from->mc, to->addr_len);
+ if (!err)
+ __dev_set_rx_mode(to);
+ spin_unlock(&to->addr_list_lock);
+}
+
+static void vlan_dev_uc_sync(struct net_device *to, struct net_device *from)
+{
+ int err = 0, subclass;
+
+ subclass = vlan_calculate_locking_subclass(to);
+
+ spin_lock_nested(&to->addr_list_lock, subclass);
+ err = __hw_addr_sync(&to->uc, &from->uc, to->addr_len);
+ if (!err)
+ __dev_set_rx_mode(to);
+ spin_unlock(&to->addr_list_lock);
+}
+
static void vlan_dev_set_rx_mode(struct net_device *vlan_dev)
{
- dev_mc_sync(vlan_dev_priv(vlan_dev)->real_dev, vlan_dev);
- dev_uc_sync(vlan_dev_priv(vlan_dev)->real_dev, vlan_dev);
+ vlan_dev_mc_sync(vlan_dev_priv(vlan_dev)->real_dev, vlan_dev);
+ vlan_dev_uc_sync(vlan_dev_priv(vlan_dev)->real_dev, vlan_dev);
}

/*
@@ -608,9 +646,7 @@ static int vlan_dev_init(struct net_devi

SET_NETDEV_DEVTYPE(dev, &vlan_type);

- if (is_vlan_dev(real_dev))
- subclass = 1;
-
+ subclass = vlan_calculate_locking_subclass(dev);
vlan_dev_set_lockdep_class(dev, subclass);

vlan_dev_priv(dev)->vlan_pcpu_stats = alloc_percpu(struct vlan_pcpu_stats);
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5219,6 +5219,7 @@ void __dev_set_rx_mode(struct net_device
if (ops->ndo_set_rx_mode)
ops->ndo_set_rx_mode(dev);
}
+EXPORT_SYMBOL(__dev_set_rx_mode);

void dev_set_rx_mode(struct net_device *dev)
{