1 files changed, 56 insertions, 17 deletions

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 96772a15bd..fc4daa36fa 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -51,6 +51,12 @@ const VMStateDescription *qdev_get_vmsd(DeviceState *dev)
     return dc->vmsd;
 }
 
+static void bus_free_bus_child(BusChild *kid)
+{
+    object_unref(OBJECT(kid->child));
+    g_free(kid);
+}
+
 static void bus_remove_child(BusState *bus, DeviceState *child)
 {
     BusChild *kid;
@@ -60,15 +66,16 @@ static void bus_remove_child(BusState *bus, DeviceState *child)
             char name[32];
 
             snprintf(name, sizeof(name), "child[%d]", kid->index);
-            QTAILQ_REMOVE(&bus->children, kid, sibling);
+            QTAILQ_REMOVE_RCU(&bus->children, kid, sibling);
 
             bus->num_children--;
 
             /* This gives back ownership of kid->child back to us.  */
             object_property_del(OBJECT(bus), name);
-            object_unref(OBJECT(kid->child));
-            g_free(kid);
-            return;
+
+            /* free the bus kid, when it is safe to do so*/
+            call_rcu(kid, bus_free_bus_child, rcu);
+            break;
         }
     }
 }
@@ -83,7 +90,7 @@ static void bus_add_child(BusState *bus, DeviceState *child)
     kid->child = child;
     object_ref(OBJECT(kid->child));
 
-    QTAILQ_INSERT_HEAD(&bus->children, kid, sibling);
+    QTAILQ_INSERT_HEAD_RCU(&bus->children, kid, sibling);
 
     /* This transfers ownership of kid->child to the property.  */
     snprintf(name, sizeof(name), "child[%d]", kid->index);
@@ -94,13 +101,23 @@ static void bus_add_child(BusState *bus, DeviceState *child)
                              0);
 }
 
-void qdev_set_parent_bus(DeviceState *dev, BusState *bus)
+static bool bus_check_address(BusState *bus, DeviceState *child, Error **errp)
+{
+    BusClass *bc = BUS_GET_CLASS(bus);
+    return !bc->check_address || bc->check_address(bus, child, errp);
+}
+
+bool qdev_set_parent_bus(DeviceState *dev, BusState *bus, Error **errp)
 {
     BusState *old_parent_bus = dev->parent_bus;
     DeviceClass *dc = DEVICE_GET_CLASS(dev);
 
     assert(dc->bus_type && object_dynamic_cast(OBJECT(bus), dc->bus_type));
 
+    if (!bus_check_address(bus, dev, errp)) {
+        return false;
+    }
+
     if (old_parent_bus) {
         trace_qdev_update_parent_bus(dev, object_get_typename(OBJECT(dev)),
             old_parent_bus, object_get_typename(OBJECT(old_parent_bus)),
@@ -126,6 +143,7 @@ void qdev_set_parent_bus(DeviceState *dev, BusState *bus)
         object_unref(OBJECT(old_parent_bus));
         object_unref(OBJECT(dev));
     }
+    return true;
 }
 
 DeviceState *qdev_new(const char *name)
@@ -371,7 +389,9 @@ bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp)
     assert(!dev->realized && !dev->parent_bus);
 
     if (bus) {
-        qdev_set_parent_bus(dev, bus);
+        if (!qdev_set_parent_bus(dev, bus, errp)) {
+            return false;
+        }
     } else {
         assert(!DEVICE_GET_CLASS(dev)->bus_type);
     }
@@ -659,17 +679,19 @@ DeviceState *qdev_find_recursive(BusState *bus, const char *id)
     DeviceState *ret;
     BusState *child;
 
-    QTAILQ_FOREACH(kid, &bus->children, sibling) {
-        DeviceState *dev = kid->child;
+    WITH_RCU_READ_LOCK_GUARD() {
+        QTAILQ_FOREACH_RCU(kid, &bus->children, sibling) {
+            DeviceState *dev = kid->child;
 
-        if (dev->id && strcmp(dev->id, id) == 0) {
-            return dev;
-        }
+            if (dev->id && strcmp(dev->id, id) == 0) {
+                return dev;
+            }
 
-        QLIST_FOREACH(child, &dev->child_bus, sibling) {
-            ret = qdev_find_recursive(child, id);
-            if (ret) {
-                return ret;
+            QLIST_FOREACH(child, &dev->child_bus, sibling) {
+                ret = qdev_find_recursive(child, id);
+                if (ret) {
+                    return ret;
+                }
             }
         }
     }
@@ -924,7 +946,25 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
             }
        }
 
+       qatomic_store_release(&dev->realized, value);
+
     } else if (!value && dev->realized) {
+
+        /*
+         * Change the value so that any concurrent users are aware
+         * that the device is going to be unrealized
+         *
+         * TODO: change .realized property to enum that states
+         * each phase of the device realization/unrealization
+         */
+
+        qatomic_set(&dev->realized, value);
+        /*
+         * Ensure that concurrent users see this update prior to
+         * any other changes done by unrealize.
+         */
+        smp_wmb();
+
         QLIST_FOREACH(bus, &dev->child_bus, sibling) {
             qbus_unrealize(bus);
         }
@@ -939,7 +979,6 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
     }
 
     assert(local_err == NULL);
-    dev->realized = value;
     return;
 
 child_realize_fail: