[Xen-devel] [PATCH]xend: fix dual destroy

["Cui, Dexuan" <dexuan.cui@xxxxxxxxx>]

After changeset 18030 and 18064 were checked in, I found some issues
when creating HVM domains with devices assigned:

In XendDomainInfo.py, we have the call trace: the global function
create() => vm.start()  => _constructDomain().
In _constructDomain(), we invoke xc.test_assign_device() and when the
function fails (maybe because iommu=1 is not specified in grub entry
since iommu is 0 by defaut now; maybe because the device doesn't exist;
maybe because the device has been assigned, or something) we raise
VmError;
Then start() will invoke self.destroy() and re-raise the exception;
Next, the global create() will invoke vm.destroy() again; finally,
_cleanupVm()  and "self.metrics.destroy()" will be invoked again. Here
when we execute metrics.destroy() for the second time, the deregister()
in XendAPIStore.py will complain: there is no such an element in the
dict __classes and a KeyError exception is raised!

We can avoid the dual destroy by adding a check as follows.

Signed-off-by: Dexuan Cui <dexuan.cui@xxxxxxxxx>

diff -r f0cd9df566ec tools/python/xen/xend/XendDomainInfo.py
--- a/tools/python/xen/xend/XendDomainInfo.py   Thu Jul 24 17:36:27 2008
+0100
+++ b/tools/python/xen/xend/XendDomainInfo.py   Fri Jul 25 18:00:29 2008
+0800
@@ -2374,6 +2374,9 @@ class XendDomainInfo:
     def destroy(self):
         """Cleanup VM and destroy domain.  Nothrow guarantee."""

+        if self.domid is None:
+            return
+
         log.debug("XendDomainInfo.destroy: domid=%s", str(self.domid))

         paths = self._prepare_phantom_paths()

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