Revert "genetlink: fix family dump race"

This reverts commit 58ad436f.

It turns out that the change introduced a potential deadlock
by causing a locking dependency with netlink's cb_mutex. I
can't seem to find a way to resolve this without doing major
changes to the locking, so revert this.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Acked-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netlink/genetlink.c

@@ -789,10 +789,6 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 	struct net *net = sock_net(skb->sk);
 	int chains_to_skip = cb->args[0];
 	int fams_to_skip = cb->args[1];
-	bool need_locking = chains_to_skip || fams_to_skip;
-
-	if (need_locking)
-		genl_lock();
 
 	for (i = chains_to_skip; i < GENL_FAM_TAB_SIZE; i++) {
 		n = 0;
@@ -814,9 +810,6 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 	cb->args[0] = i;
 	cb->args[1] = n;
 
-	if (need_locking)
-		genl_unlock();
-
 	return skb->len;
 }