IPv6: addrconf dad timer unnecessary bh_disable

Timer code runs in bottom half, so there is no need for
using _bh form of locking.  Also check if device is not ready
to avoid race with address that is no longer active.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -2850,9 +2850,9 @@ static void addrconf_dad_timer(unsigned long data)
 	struct inet6_dev *idev = ifp->idev;
 	struct in6_addr mcaddr;
 
-	read_lock_bh(&idev->lock);
-	if (idev->dead) {
-		read_unlock_bh(&idev->lock);
+	read_lock(&idev->lock);
+	if (idev->dead || !(idev->if_flags & IF_READY)) {
+		read_unlock(&idev->lock);
 		goto out;
 	}
 
@@ -2864,7 +2864,7 @@ static void addrconf_dad_timer(unsigned long data)
 
 		ifp->flags &= ~(IFA_F_TENTATIVE|IFA_F_OPTIMISTIC|IFA_F_DADFAILED);
 		spin_unlock(&ifp->lock);
-		read_unlock_bh(&idev->lock);
+		read_unlock(&idev->lock);
 
 		addrconf_dad_completed(ifp);
 
@@ -2874,7 +2874,7 @@ static void addrconf_dad_timer(unsigned long data)
 	ifp->probes--;
 	addrconf_mod_timer(ifp, AC_DAD, ifp->idev->nd_parms->retrans_time);
 	spin_unlock(&ifp->lock);
-	read_unlock_bh(&idev->lock);
+	read_unlock(&idev->lock);
 
 	/* send a neighbour solicitation for our addr */
 	addrconf_addr_solict_mult(&ifp->addr, &mcaddr);