From cb3d870a1a0e686e6f8b972cd7aba1b48d31a02f Mon Sep 17 00:00:00 2001
From: "emellor@leeni.uk.xensource.com" <emellor@leeni.uk.xensource.com>
Date: Mon, 31 Oct 2005 17:10:57 +0100
Subject: [PATCH] From Murillo Fernandes Bernardes <mfb@br.ibm.com>:

The problem is: There is no mechanism to detect block device setup failure

Network devices have the same problem, and are fixed with this too.

I handling this problem in the way suggested by aliguori:
- hotplug scripts write a "hotplug-status" node on store
- Xend DevController.createDevice() check verify this node and return success
or throw an exception on failure.
- If no changes in "hotplug-status" node after DEVICE_CREATE_TIMEOUT seconds
Xend throw an exception showing the problem with hotplug scripts.

Signed-off-by: Ewan Mellor <ewan@xensource.com>
---
 tools/examples/block-common.sh                |  9 +++-
 tools/examples/vif-bridge                     |  1 +
 tools/examples/vif-nat                        |  2 +
 tools/examples/vif-route                      |  2 +
 tools/examples/xen-hotplug-common.sh          |  6 +++
 tools/python/xen/xend/server/DevController.py | 41 +++++++++++++++++++
 6 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/tools/examples/block-common.sh b/tools/examples/block-common.sh
index 1d20550a9d..397f588c71 100644
--- a/tools/examples/block-common.sh
+++ b/tools/examples/block-common.sh
@@ -42,10 +42,17 @@ write_dev() {
   local major
   local minor
   local pdev
-	
+  
   major=$(stat -L -c %t "$1")
   minor=$(stat -L -c %T "$1")
+ 
+  if [ -z $major  -o -z $minor ]; then
+    fatal "Backend device does not exist"
+  fi
+ 
   pdev=$(printf "0x%02x%02x" "0x$major" "0x$minor")
   xenstore_write "$XENBUS_PATH"/physical-device "$pdev" \
                  "$XENBUS_PATH"/node "$1"
+
+  success
 }
diff --git a/tools/examples/vif-bridge b/tools/examples/vif-bridge
index 4ba683c25c..d95d8ecef5 100755
--- a/tools/examples/vif-bridge
+++ b/tools/examples/vif-bridge
@@ -58,6 +58,7 @@ case "$command" in
           fatal "brctl addif $bridge $vif failed"
 
         ifconfig "$vif" up || fatal "ifconfig $vif up failed"
+        success
         ;;
     down)
         # vifs are auto-removed from bridge.
diff --git a/tools/examples/vif-nat b/tools/examples/vif-nat
index bf9f40a7b9..2d751edc60 100644
--- a/tools/examples/vif-nat
+++ b/tools/examples/vif-nat
@@ -54,3 +54,5 @@ esac
 ip r ${ipcmd} ${ip} dev ${vif} src ${main_ip}
 
 handle_iptable()
+
+success
diff --git a/tools/examples/vif-route b/tools/examples/vif-route
index beb8e43ef2..c804a01840 100755
--- a/tools/examples/vif-route
+++ b/tools/examples/vif-route
@@ -46,3 +46,5 @@ if [ "${ip}" ] ; then
 fi
 
 handle_iptable()
+
+success
diff --git a/tools/examples/xen-hotplug-common.sh b/tools/examples/xen-hotplug-common.sh
index cc5af864a2..9cce5175a2 100644
--- a/tools/examples/xen-hotplug-common.sh
+++ b/tools/examples/xen-hotplug-common.sh
@@ -30,10 +30,16 @@ log() {
 }
 
 fatal() {
+  xenstore_write "$XENBUS_PATH"/hotplug-status error
   log err "$@"
   exit 1
 }
 
+success() {
+  # Tell DevController that backend is "connected"
+  xenstore_write "$XENBUS_PATH"/hotplug-status connected
+}
+
 ##
 # xenstore_read <path>+
 #
diff --git a/tools/python/xen/xend/server/DevController.py b/tools/python/xen/xend/server/DevController.py
index fdc0404235..83363f9281 100644
--- a/tools/python/xen/xend/server/DevController.py
+++ b/tools/python/xen/xend/server/DevController.py
@@ -16,12 +16,18 @@
 # Copyright (C) 2005 XenSource Ltd
 #============================================================================
 
+from threading import Event
 
 from xen.xend import sxp
 from xen.xend.XendError import VmError
 from xen.xend.XendLogging import log
+
 from xen.xend.xenstore.xstransact import xstransact
+from xen.xend.xenstore.xswatch import xswatch
 
+DEVICE_CREATE_TIMEOUT = 120
+HOTPLUG_STATUS_NODE = "hotplug-status"
+HOTPLUG_STATUS_ERROR = "error"
 
 class DevController:
     """Abstract base class for a device controller.  Device controllers create
@@ -54,6 +60,18 @@ class DevController:
 
         self.writeDetails(config, devid, back, front)
 
+        status, fn_ret = self.waitForBackend(devid)
+        if status:
+            self.destroyDevice(devid)
+            raise VmError( ("Device %s (%s) could not be connected. "
+                            "Hotplug scripts not working") 
+                            % (devid, self.deviceClass))
+
+        elif fn_ret == HOTPLUG_STATUS_ERROR:
+            self.destroyDevice(devid)
+            raise VmError( ("Device %s (%s) could not be connected. "
+                            "Backend device not found!") 
+                            % (devid, self.deviceClass))
         return devid
 
 
@@ -242,6 +260,29 @@ class DevController:
         xstransact.Write(frontpath, frontDetails)
         xstransact.Write(backpath, backDetails)
 
+    def waitForBackend(self,devid):
+        ev = Event()
+
+        def hotplugStatus():
+            status = self.readBackend(devid, HOTPLUG_STATUS_NODE)
+            if status is not None:
+                watch.xs.unwatch(backpath, watch)
+                hotplugStatus.value = status
+                ev.set()
+
+        hotplugStatus.value = None
+        frontpath = self.frontendPath(devid)
+        backpath = xstransact.Read(frontpath, "backend")
+
+        watch = xswatch(backpath, hotplugStatus)
+
+        ev.wait(DEVICE_CREATE_TIMEOUT)
+        if ev.isSet():
+            return (0, hotplugStatus.value)
+        else:
+            return (-1, hotplugStatus.value)
+
+
 
     def backendPath(self, backdom, devid):
         """@param backdom [XendDomainInfo] The backend domain info."""
-- 
2.30.2