[NET] netconsole: Use netif_running() in write_msg()

Based upon initial work by Keiichi Kii <k-keiichi@bx.jp.nec.com>.

Avoid unnecessarily disabling interrupts and calling netpoll_send_udp() if the
corresponding local interface is not up.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Acked-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netconsole.c

@@ -75,16 +75,16 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 	int frag, left;
 	unsigned long flags;
 
-	local_irq_save(flags);
-
-	for (left = len; left;) {
-		frag = min(left, MAX_PRINT_CHUNK);
-		netpoll_send_udp(&np, msg, frag);
-		msg += frag;
-		left -= frag;
+	if (netif_running(np.dev)) {
+		local_irq_save(flags);
+		for (left = len; left;) {
+			frag = min(left, MAX_PRINT_CHUNK);
+			netpoll_send_udp(&np, msg, frag);
+			msg += frag;
+			left -= frag;
+		}
+		local_irq_restore(flags);
 	}
-
-	local_irq_restore(flags);
 }
 
 static struct console netconsole = {