[PATCH] ipvs: fix dst_lock locking on dest update

[Julian Anastasov <ja@xxxxxx>]

        Fix dst_lock usage in __ip_vs_update_dest. We need
_bh locking because destination is updated in user context.
Can cause lockups on frequent destination updates.
Problem reported by Simon Kirby. Bug was introduced
in 2.6.37 from the "ipvs: changes for local real server"
change.

Signed-off-by: Julian Anastasov <ja@xxxxxx>
---

        Dave, please apply to net-2.6.
Patch is for 2.6.37+ and applies to 2.6.38-rc6. There is
little fuzz when applying to net-next, let me know if
I should provide patch for other trees.

--- linux-2.6.37/net/netfilter/ipvs/ip_vs_ctl.c 2011-01-06 00:01:23.600069161 
+0200
+++ linux/net/netfilter/ipvs/ip_vs_ctl.c        2011-02-19 23:14:44.463250743 
+0200
@@ -810,9 +810,9 @@ __ip_vs_update_dest(struct ip_vs_service
        dest->u_threshold = udest->u_threshold;
        dest->l_threshold = udest->l_threshold;

-       spin_lock(&dest->dst_lock);
+       spin_lock_bh(&dest->dst_lock);
        ip_vs_dst_reset(dest);
-       spin_unlock(&dest->dst_lock);
+       spin_unlock_bh(&dest->dst_lock);

        if (add)
                ip_vs_new_estimator(&dest->stats);
--
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