netdev - Re: 2.6.27.18: bonding: scheduling while atomic

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Date:	Tue, 05 May 2009 12:56:21 -0700
From:	Jay Vosburgh <fubar@...ibm.com>
To:	paul@...-scientist.net
cc:	Netdev <netdev@...r.kernel.org>
Subject: Re: 2.6.27.18: bonding: scheduling while atomic

Paul Smith <paul@...-scientist.net> wrote:

>Hi all;  I got a "scheduling while atomic" error while I was enslaving
>my second interface to my bond (balance-alb / mode 6).  I already have
>the previous fix for a locking error installed here.
[...]
><4> [<ffffffff8046f32c>] packet_notifier+0x8c/0x1f0
><4> [<ffffffffa00ad0a8>] bond_alb_init_slave+0x228/0x250 [bonding]
><4> [<ffffffffa00a766a>] bond_enslave+0x7ca/0x9d0 [bonding]
><4> [<ffffffff804a1981>] _spin_unlock_irq+0x11/0x40
><4> [<ffffffff8041896a>] __dev_get_by_name+0x9a/0xc0
><4> [<ffffffffa00a8af5>] bond_do_ioctl+0x3f5/0x530 [bonding]
><4> [<ffffffff802580f7>] notifier_call_chain+0x37/0x70

	I believe this is happening when the new slave's MAC address is
already in use by the bond somewhere.  You can get that if you set up
and tear down the bond after it's moved things around and you haven't
reset the slaves to their default (hardware) MAC address (by, e.g.,
reloading the drivers).  The alb mode doesn't do that, because that MAC
might still be in use by the bond; if memory serves, you'll see a
message at slave removal about that.

	Anyway, I'm pretty sure the following will make it go away.  I
believe this is safe, as RTNL is held throughout, but I haven't checked
exhaustively.

	This is against 2.6.27.18, and is just for testing.

	-J


diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 4489e58..d199446 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1520,15 +1520,8 @@ int bond_alb_init_slave(struct bonding *bond, struct slave *slave)
 		return res;
 	}
 
-	/* caller must hold the bond lock for write since the mac addresses
-	 * are compared and may be swapped.
-	 */
-	read_lock(&bond->lock);
-
 	res = alb_handle_addr_collision_on_attach(bond, slave);
 
-	read_unlock(&bond->lock);
-
 	if (res) {
 		return res;
 	}


---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com
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