From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: [PATCH] linux-2.6.18: check availibility of
	XS_RESET_WATCHES command
Date: Thu, 05 Jan 2012 21:27:07 +0100
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# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1325795190 -3600
# Node ID 8d1991a7f8a37ec1fc9a660cb48cb40ef42e9ff3
# Parent  821a5b2a10c86f18fbce0907af0db6905b9d540a
linux-2.6.18: check availibility of XS_RESET_WATCHES command

Check platform-feature-xs_reset_watches before sending XS_RESET_WATCHES
command. Buggy xenstored implementations such as EC2 do not ignore unknown
commands properly and cause a guest hang.

Signed-off-by: Olaf Hering <olaf@aepfle.de>

diff -r 821a5b2a10c8 -r 8d1991a7f8a3 drivers/xen/xenbus/xenbus_xs.c
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -630,7 +630,12 @@ static struct xenbus_watch *find_watch(c
 static void xs_reset_watches(void)
 {
 #ifndef CONFIG_XEN
-	int err;
+	int err, supported = 0;
+
+	err = xenbus_scanf(XBT_NIL, "control",
+			"platform-feature-xs_reset_watches", "%d", &supported);
+	if (err != 1 || !supported)
+		return;
 
 	err = xs_error(xs_single(XBT_NIL, XS_RESET_WATCHES, "", NULL));
 	if (err && err != -EEXIST)