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Re: [libvirt] [libvirt-glib 2/2] Remove transient domain reference on shutdown



On Tue, Nov 29, 2011 at 11:51:38PM +0100, Christophe Fergeau wrote:
> On Tue, Nov 29, 2011 at 05:00:54PM +0200, Zeeshan Ali (Khattak) wrote:
> > From: "Zeeshan Ali (Khattak)" <zeeshanak gnome org>
> > 
> > This patch doesn't work cause virDomainIsPersistent() is returning '1'
> > on transient domain for some reason. Send it to list to get some help.
> > ---
> >  libvirt-gobject/libvirt-gobject-connection.c |    9 +++++++++
> >  1 files changed, 9 insertions(+), 0 deletions(-)
> > 
> > diff --git a/libvirt-gobject/libvirt-gobject-connection.c b/libvirt-gobject/libvirt-gobject-connection.c
> > index b647bfa..1b0259e 100644
> > --- a/libvirt-gobject/libvirt-gobject-connection.c
> > +++ b/libvirt-gobject/libvirt-gobject-connection.c
> > @@ -362,6 +362,15 @@ static int domain_event_cb(virConnectPtr conn G_GNUC_UNUSED,
> >                  g_signal_emit_by_name(gdom, "stopped::from-snapshot");
> >              else
> >                  g_warn_if_reached();
> > +
> > +            if (!virDomainIsPersistent(dom)) {
> > +                g_mutex_lock(priv->lock);
> > +                g_hash_table_steal(priv->domains, uuid);
> > +                g_mutex_unlock(priv->lock);
> > +
> > +                g_signal_emit(gconn, signals[VIR_DOMAIN_REMOVED], 0, gdom);
> > +                g_object_unref(gdom);
> > +            }
> >              break;
> 
> Not directly related to this patch since the same pattern is already
> present in domain_event_cb, but this can race with gvir_connection_close,
> ie gdom is looked up in domain_event_cb, gvir_connection_close frees
> priv->domains and its content, domain_event_cb resumes and happily uses
> gdom which it hasn't reffed and priv->domains. Something similar can also
> happen between domain_event_cb and gvir_connection_fetch_domains.

What about something like the patch below? I'll make a proper patch and
make sure it does not conflict with Zeeshan's patch if that looks like the
way to go.

Christophe


diff --git a/libvirt-gobject/libvirt-gobject-connection.c b/libvirt-gobject/libvirt-gobject-connection.c
index c9985b2..e00c5bf 100644
--- a/libvirt-gobject/libvirt-gobject-connection.c
+++ b/libvirt-gobject/libvirt-gobject-connection.c
@@ -261,6 +261,7 @@ static int domain_event_cb(virConnectPtr conn G_GNUC_UNUSED,
     GVirDomain *gdom;
     GVirConnectionPrivate *priv = gconn->priv;
     gboolean was_unknown = FALSE;
+    GHashTable *doms;
 
     if (virDomainGetUUIDString(dom, uuid) < 0) {
         g_warning("Failed to get domain UUID on %p", dom);
@@ -270,14 +271,17 @@ static int domain_event_cb(virConnectPtr conn G_GNUC_UNUSED,
     g_debug("%s: %s event:%d, detail:%d", G_STRFUNC, uuid, event, detail);
 
     g_mutex_lock(priv->lock);
-    gdom = g_hash_table_lookup(priv->domains, uuid);
+    doms = g_hash_table_ref(priv->domains);
+    gdom = g_hash_table_lookup(doms, uuid);
+    if (gdom != NULL)
+        g_object_ref(G_OBJECT(gdom));
     g_mutex_unlock(priv->lock);
 
     if (gdom == NULL) {
         gdom = GVIR_DOMAIN(g_object_new(GVIR_TYPE_DOMAIN, "handle", dom, NULL));
 
         g_mutex_lock(priv->lock);
-        g_hash_table_insert(priv->domains, (gpointer)gvir_domain_get_uuid(gdom), gdom);
+        g_hash_table_insert(doms, (gpointer)gvir_domain_get_uuid(gdom), gdom);
         g_mutex_unlock(priv->lock);
 
         was_unknown = TRUE;
@@ -296,11 +300,10 @@ static int domain_event_cb(virConnectPtr conn G_GNUC_UNUSED,
         case VIR_DOMAIN_EVENT_UNDEFINED:
             if (detail == VIR_DOMAIN_EVENT_UNDEFINED_REMOVED) {
                 g_mutex_lock(priv->lock);
-                g_hash_table_steal(priv->domains, uuid);
+                g_hash_table_remove(doms, uuid);
                 g_mutex_unlock(priv->lock);
 
                 g_signal_emit(gconn, signals[VIR_DOMAIN_REMOVED], 0, gdom);
-                g_object_unref(gdom);
             } else
                 g_warn_if_reached();
             break;
@@ -372,6 +375,8 @@ static int domain_event_cb(virConnectPtr conn G_GNUC_UNUSED,
             g_warn_if_reached();
     }
 
+    g_object_unref(G_OBJECT(gdom));
+    g_hash_table_unref(doms);
     return 0;
 }
 

Christophe

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