From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: [PATCH 08/11] xen/hvm kexec: unregister the watch of
	the "backend" node during reboot
Date: Thu, 28 Jul 2011 15:23:08 +0200
Message-ID: <20110728132302.745855909@aepfle.de>
References: <20110728132300.248098023@aepfle.de>
Return-path: <xen-devel-bounces@lists.xensource.com>
Content-Disposition: inline;
	filename=xen.syscore_ops.unregister_watch.xenbus_backend.patch
List-Unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: xen-devel@lists.xensource.com
List-Id: xen-devel@lists.xenproject.org

The watch of the xenstore "backend" node has to be unregistered during a
kexec reboot. Otherwise the kexec kernel will crash due to a memory
corruption because more than one watch is registered on that node.

v2:
 use kexec_is_loaded() function

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

---
 drivers/xen/xenbus/xenbus_probe_backend.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

Index: linux-3.0/drivers/xen/xenbus/xenbus_probe_backend.c
===================================================================
--- linux-3.0.orig/drivers/xen/xenbus/xenbus_probe_backend.c
+++ linux-3.0/drivers/xen/xenbus/xenbus_probe_backend.c
@@ -42,6 +42,8 @@
 #include <linux/fcntl.h>
 #include <linux/mm.h>
 #include <linux/notifier.h>
+#include <linux/kexec.h>
+#include <linux/syscore_ops.h>
 
 #include <asm/page.h>
 #include <asm/pgtable.h>
@@ -255,6 +257,18 @@ static int backend_probe_and_watch(struc
 	return NOTIFY_DONE;
 }
 
+static void xenbus_backend_shutdown_watcher(void)
+{
+	if (!kexec_is_loaded())
+		return;
+
+	unregister_xenbus_watch(&be_watch);
+}
+
+static struct syscore_ops xenbus_backend_watcher_syscore_ops = {
+	.shutdown = xenbus_backend_shutdown_watcher,
+};
+
 static int __init xenbus_probe_backend_init(void)
 {
 	static struct notifier_block xenstore_notifier = {
@@ -270,6 +284,7 @@ static int __init xenbus_probe_backend_i
 		return err;
 
 	register_xenstore_notifier(&xenstore_notifier);
+	register_syscore_ops(&xenbus_backend_watcher_syscore_ops);
 
 	return 0;
 }