xend: destroy stubdoms synchronously

This patch makes the destruction of stubdoms a synchronous event,
therefore it is no longer possible to run out of memory when rebooting
a guest because the stubdom of the old guest is always destroyed
before the creation of the new guest.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

tools/python/xen/xend/XendDomainInfo.py

@@ -855,12 +855,10 @@ class XendDomainInfo:
         dev_config = pci_convert_sxp_to_dict(dev_sxp)
         dev = dev_config['devs'][0]
 
-        dom_list = xstransact.List('/local/domain')
-        for d in dom_list:
-            target = xstransact.Read('/local/domain/' + d + '/target')
-            if target is not None and int(target) is self.domid :
-                from xen.xend import XendDomain
-                XendDomain.instance().domain_lookup(int(d)).pci_device_configure(dev_sxp[:])
+        stubdomid = self.getStubdomDomid()
+        if stubdomid is not None :
+            from xen.xend import XendDomain
+            XendDomain.instance().domain_lookup(stubdomid).pci_device_configure(dev_sxp[:])
 
         # Do HVM specific processing
         if self.info.is_hvm():
@@ -1810,6 +1808,14 @@ class XendDomainInfo:
     def getDomid(self):
         return self.domid
 
+    def getStubdomDomid(self):
+        dom_list = xstransact.List('/local/domain')
+        for d in dom_list:
+            target = xstransact.Read('/local/domain/' + d + '/target')
+            if target is not None and int(target) is self.domid :
+                return int(d)
+        return None
+
     def setName(self, name, to_store = True):
         self._checkName(name)
         self.info['name_label'] = name

tools/python/xen/xend/image.py

@@ -591,7 +591,11 @@ class ImageHandler:
             return
         self.sentinel_lock.acquire()
         try:
-            if self.pid:
+            stubdomid = self.vm.getStubdomDomid()
+            if stubdomid is not None :
+                from xen.xend import XendDomain
+                XendDomain.instance().domain_destroy(stubdomid)
+            elif self.pid:
                 try:
                     os.kill(self.pid, signal.SIGHUP)
                 except OSError, exn: