[PATCH] bonding: Fix lockdep warning after bond_vlan_rx_register()

[Jarek Poplawski <jarkao2@gmail.com>]

On Wed, Oct 27, 2010 at 03:00:16PM +0200, Eric Dumazet wrote:
> 
> Indeed this is the right fix, I wonder why I did not catch it before ?
> 
> Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Thanks,
Jarek P.
------------------------>

Fix lockdep warning:
[   52.991402] ======================================================
[   52.991511] [ INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected ]
[   52.991569] 2.6.36-04573-g4b60626-dirty #65
[   52.991622] ------------------------------------------------------
[   52.991696] ip/4842 [HC0[0]:SC0[4]:HE1:SE0] is trying to acquire:
[   52.991758]  (&bond->lock){++++..}, at: [<efe4d300>] bond_set_multicast_list+0x60/0x2c0 [bonding]
[   52.991966] 
[   52.991967] and this task is already holding:
[   52.992008]  (&bonding_netdev_addr_lock_key){+.....}, at: [<c04e5530>] dev_mc_sync+0x50/0xa0
[   52.992008] which would create a new lock dependency:
[   52.992008]  (&bonding_netdev_addr_lock_key){+.....} -> (&bond->lock){++++..}
[   52.992008] 
[   52.992008] but this new dependency connects a SOFTIRQ-irq-safe lock:
[   52.992008]  (&(&mc->mca_lock)->rlock){+.-...}
[   52.992008] ... which became SOFTIRQ-irq-safe at:
[   52.992008]   [<c0272beb>] __lock_acquire+0x96b/0x1960
[   52.992008]   [<c027415e>] lock_acquire+0x7e/0xf0
[   52.992008]   [<c05f356d>] _raw_spin_lock_bh+0x3d/0x50
[   52.992008]   [<c0584e40>] mld_ifc_timer_expire+0xf0/0x280
[   52.992008]   [<c024cee6>] run_timer_softirq+0x146/0x310
[   52.992008]   [<c024591d>] __do_softirq+0xad/0x1c0
[   52.992008] 
[   52.992008] to a SOFTIRQ-irq-unsafe lock:
[   52.992008]  (&bond->lock){++++..}
[   52.992008] ... which became SOFTIRQ-irq-unsafe at:
[   52.992008] ...  [<c0272c3b>] __lock_acquire+0x9bb/0x1960
[   52.992008]   [<c027415e>] lock_acquire+0x7e/0xf0
[   52.992008]   [<c05f36b8>] _raw_write_lock+0x38/0x50
[   52.992008]   [<efe4cbe4>] bond_vlan_rx_register+0x24/0x70 [bonding]
[   52.992008]   [<c0598010>] register_vlan_dev+0xc0/0x280
[   52.992008]   [<c0599f3a>] vlan_newlink+0xaa/0xd0
[   52.992008]   [<c04ed4b4>] rtnl_newlink+0x404/0x490
[   52.992008]   [<c04ece35>] rtnetlink_rcv_msg+0x1e5/0x220
[   52.992008]   [<c050424e>] netlink_rcv_skb+0x8e/0xb0
[   52.992008]   [<c04ecbac>] rtnetlink_rcv+0x1c/0x30
[   52.992008]   [<c0503bfb>] netlink_unicast+0x24b/0x290
[   52.992008]   [<c0503e37>] netlink_sendmsg+0x1f7/0x310
[   52.992008]   [<c04cd41c>] sock_sendmsg+0xac/0xe0
[   52.992008]   [<c04ceb80>] sys_sendmsg+0x130/0x230
[   52.992008]   [<c04cf04e>] sys_socketcall+0xde/0x280
[   52.992008]   [<c0202d10>] sysenter_do_call+0x12/0x36
[   52.992008] 
[   52.992008] other info that might help us debug this:
...
[ Full info at netdev: Wed, 27 Oct 2010 12:24:30 +0200
  Subject: [BUG net-2.6 vlan/bonding] lockdep splats ]

Use BH variant of write_lock(&bond->lock) (as elsewhere in bond_main)
to prevent this dependency.

Fixes commit f35188faa0fbabefac476536994f4b6f3677380f [v2.6.36]

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Jay Vosburgh <fubar@us.ibm.com>
---

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index beb3b7c..bdb68a6 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -493,9 +493,9 @@ static void bond_vlan_rx_register(struct net_device *bond_dev,
 	struct slave *slave;
 	int i;
 
-	write_lock(&bond->lock);
+	write_lock_bh(&bond->lock);
 	bond->vlgrp = grp;
-	write_unlock(&bond->lock);
+	write_unlock_bh(&bond->lock);
 
 	bond_for_each_slave(bond, slave, i) {
 		struct net_device *slave_dev = slave->dev;