Daniel P. Berrange wrote:
On Mon, Jul 23, 2007 at 05:11:09PM +0100, Richard W.M. Jones wrote:This is my test case: ------------------------------------------ #!/usr/bin/python import libvirt def get_dom(): conn = libvirt.open ("xen"); dom = conn.lookupByName ("debian32fv"); return dom dom = get_dom() print "name = %s\n" % dom.name() ------------------------------------------ I would say that it's working as intended.In this case yes, but if you add one further line at the end of this example conn2 = dom.get_connection() And then have python garbage collect 'dom' and the original 'conn' you're not safe because 'conn2' didn't increment the reference count:
I finally managed to reproduce this. For reference, the reproduction code is below:
--------------------
#!/usr/bin/python
import libvirt
import libvirtmod
def get_dom():
conn = libvirt.open ("xen");
dom = conn.lookupByName ("debian32fv");
return dom
dom = get_dom()
print "name = %s" % dom.name()
conn2 =
libvirt.virConnect (_obj = libvirtmod.virDomainGetConnect (dom._o))
dom2 = conn2.lookupByName ("debian32fv")
--------------------
This crashes at the last line because virConnectClose was called in the
destructor of conn.
It doesn't seem like changing virDomainGetConnect to play with reference counts will fix this. The damage was done when virConnectClose was called, which happened much earlier. The only solution is to keep the relation that domain contains a connection explicit in the Python code. Same probably applies to OCaml bindings too.
/* * virDomainGetConnect: * @dom: pointer to a domain * * Provides the connection pointer associated with a domain. The * reference counter on the connection is not increased by this * call. */
For this reason also I suggest that we remove virDomainGetConnect and virNetworkGetConnect calls entirely, to prevent anyone from thinking they can use them in a safe way. Patch is attached, and yes I know in this case it breaks strict ABI compatibility.
Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903
Index: include/libvirt/libvirt.h.in
===================================================================
RCS file: /data/cvs/libvirt/include/libvirt/libvirt.h.in,v
retrieving revision 1.31
diff -u -p -r1.31 libvirt.h.in
--- include/libvirt/libvirt.h.in 18 Jul 2007 10:11:10 -0000 1.31
+++ include/libvirt/libvirt.h.in 24 Jul 2007 14:14:48 -0000
@@ -288,11 +288,6 @@ int virConnectNumOfDomains (virConnect
/*
- * Get connection from domain.
- */
-virConnectPtr virDomainGetConnect (virDomainPtr domain);
-
-/*
* Domain creation and destruction
*/
virDomainPtr virDomainCreateLinux (virConnectPtr conn,
@@ -521,11 +516,6 @@ typedef struct _virNetwork virNetwork;
typedef virNetwork *virNetworkPtr;
/*
- * Get connection from network.
- */
-virConnectPtr virNetworkGetConnect (virNetworkPtr network);
-
-/*
* List active networks
*/
int virConnectNumOfNetworks (virConnectPtr conn);
Index: src/libvirt.c
===================================================================
RCS file: /data/cvs/libvirt/src/libvirt.c,v
retrieving revision 1.90
diff -u -p -r1.90 libvirt.c
--- src/libvirt.c 17 Jul 2007 14:40:26 -0000 1.90
+++ src/libvirt.c 24 Jul 2007 14:14:50 -0000
@@ -743,28 +743,6 @@ virConnectNumOfDomains(virConnectPtr con
}
/**
- * virDomainGetConnect:
- * @dom: pointer to a domain
- *
- * Provides the connection pointer associated with a domain. The
- * reference counter on the connection is not increased by this
- * call.
- *
- * Returns the virConnectPtr or NULL in case of failure.
- */
-virConnectPtr
-virDomainGetConnect (virDomainPtr dom)
-{
- DEBUG("dom=%p", dom);
-
- if (!VIR_IS_DOMAIN (dom)) {
- virLibDomainError (dom, VIR_ERR_INVALID_DOMAIN, __FUNCTION__);
- return NULL;
- }
- return dom->conn;
-}
-
-/**
* virDomainCreateLinux:
* @conn: pointer to the hypervisor connection
* @xmlDesc: an XML description of the domain
@@ -2317,28 +2295,6 @@ virDomainDetachDevice(virDomainPtr domai
}
/**
- * virNetworkGetConnect:
- * @net: pointer to a network
- *
- * Provides the connection pointer associated with a network. The
- * reference counter on the connection is not increased by this
- * call.
- *
- * Returns the virConnectPtr or NULL in case of failure.
- */
-virConnectPtr
-virNetworkGetConnect (virNetworkPtr net)
-{
- DEBUG("net=%p", net);
-
- if (!VIR_IS_NETWORK (net)) {
- virLibNetworkError (net, VIR_ERR_INVALID_NETWORK, __FUNCTION__);
- return NULL;
- }
- return net->conn;
-}
-
-/**
* virConnectNumOfNetworks:
* @conn: pointer to the hypervisor connection
*
Index: docs/libvir.html
===================================================================
RCS file: /data/cvs/libvirt/docs/libvir.html,v
retrieving revision 1.73
diff -u -p -r1.73 libvir.html
--- docs/libvir.html 16 Jul 2007 21:37:08 -0000 1.73
+++ docs/libvir.html 24 Jul 2007 14:14:52 -0000
@@ -2837,11 +2837,6 @@ updated on <i>2007-06-29</i>.
<td> ≥ 0.3.0 </td>
</tr>
<tr>
- <td> virDomainGetConnect </td>
- <td> 0.3.0 </td>
- <td colspan="4"> not a HV function </td>
-</tr>
-<tr>
<td> virDomainGetID </td>
<td> All </td>
<td> All </td>
@@ -3140,9 +3135,6 @@ first appeared in libvirt 0.2.0.
<td> virNetworkGetAutostart </td> <td> 0.2.1 </td>
</tr>
<tr>
- <td> virNetworkGetConnect </td> <td> 0.3.0 </td>
-</tr>
-<tr>
<td> virNetworkGetBridgeName </td> <td> 0.2.0 </td>
</tr>
<tr>
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