3c59x: Fix deadlock in vortex_error()

This fixes a bug introduced in commit
de847272149365363a6043a963a6f42fb91566e2
"3c59x: Use fine-grained locks for MII and windowed register access".

vortex_interrupt() holds vp->window_lock over multiple register
accesses to reduce locking overhead.  However it also needs to call
vortex_error() sometimes, and that uses the regular functions for
access to windowed registers, which will try to acquire window_lock
again.

Therefore, drop window_lock around the call to vortex_error() and set
the window afterward reacquiring the lock.  Since vortex_error() may
call vortex_rx(), which *does* require its caller to hold window_lock,
lift that call up into vortex_interrupt().  This also removes the
potential for calling vortex_rx() on a later-generation NIC.

Reported-and-tested-by: Jens Schüßler <jgs@trash.net> [in Debian's 2.6.32]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/3c59x.c

@@ -1994,10 +1994,9 @@ vortex_error(struct net_device *dev, int status)
 		}
 	}
 
-	if (status & RxEarly) {				/* Rx early is unused. */
-		vortex_rx(dev);
+	if (status & RxEarly)				/* Rx early is unused. */
 		iowrite16(AckIntr | RxEarly, ioaddr + EL3_CMD);
-	}
+
 	if (status & StatsFull) {			/* Empty statistics. */
 		static int DoneDidThat;
 		if (vortex_debug > 4)
@@ -2298,7 +2297,12 @@ vortex_interrupt(int irq, void *dev_id)
 		if (status & (HostError | RxEarly | StatsFull | TxComplete | IntReq)) {
 			if (status == 0xffff)
 				break;
+			if (status & RxEarly)
+				vortex_rx(dev);
+			spin_unlock(&vp->window_lock);
 			vortex_error(dev, status);
+			spin_lock(&vp->window_lock);
+			window_set(vp, 7);
 		}
 
 		if (--work_done < 0) {