IB/ipath: NMI cpu lockup if local loopback used

If a post send is done in loopback and there is no receive queue
entry, the sending QP is put on a timeout list for a while so the
receiver has a chance to post a receive buffer. If the another post
send is done, the code incorrectly tried to put the QP on the timeout
list again an corrupted the timeout list. This eventually leads to a
spin lock deadlock NMI due to the timer function looping forever with
the lock held.
Signed-off-by: Bryan O'Sullivan <bryan.osullivan@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_ruc.c

@@ -265,7 +265,8 @@ static void ipath_ruc_loopback(struct ipath_qp *sqp)
 again:
 	spin_lock_irqsave(&sqp->s_lock, flags);
 
-	if (!(ib_ipath_state_ops[sqp->state] & IPATH_PROCESS_SEND_OK)) {
+	if (!(ib_ipath_state_ops[sqp->state] & IPATH_PROCESS_SEND_OK) ||
+	    qp->s_rnr_timeout) {
 		spin_unlock_irqrestore(&sqp->s_lock, flags);
 		goto done;
 	}