The Xen console intercepts ^O and prevents it from propagating

through to the guest.  However, ^O is a useful key in bash and in
Emacs.  This patch changes the console to pass a single ^O
through to the guest when it is pressed twice.

Signed-off-by: Ben Pfaff <blp@cs.stanford.edu>

linux-2.6-xen-sparse/drivers/xen/console/console.c

@@ -348,8 +348,11 @@ void xencons_rx(char *buf, unsigned len, struct pt_regs *regs)
 #ifdef CONFIG_MAGIC_SYSRQ
 		if (sysrq_enabled) {
 			if (buf[i] == '\x0f') { /* ^O */
-				sysrq_requested = jiffies;
-				continue; /* don't print the sysrq key */
+				if (!sysrq_requested) {
+					sysrq_requested = jiffies;
+					continue; /* don't print sysrq key */
+				}
+				sysrq_requested = 0;
 			} else if (sysrq_requested) {
 				unsigned long sysrq_timeout =
 					sysrq_requested + HZ*2;