iothread: provide helpers for internal use

IOThread is a general framework that contains IO loop environment and a
real thread behind.  It's also good to be used internally inside qemu.
Provide some helpers for it to create iothreads to be used internally.

Put all the internal used iothreads into the internal object container.
Reviewed-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-id: 20170928025958.1420-3-peterx@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

include/sysemu/iothread.h

@@ -46,4 +46,12 @@ AioContext *iothread_get_aio_context(IOThread *iothread);
 void iothread_stop_all(void);
 GMainContext *iothread_get_g_main_context(IOThread *iothread);
 
+/*
+ * Helpers used to allocate iothreads for internal use.  These
+ * iothreads will not be seen by monitor clients when query using
+ * "query-iothreads".
+ */
+IOThread *iothread_create(const char *id, Error **errp);
+void iothread_destroy(IOThread *iothread);
+
 #endif /* IOTHREAD_H */

iothread.c

@@ -354,3 +354,19 @@ GMainContext *iothread_get_g_main_context(IOThread *iothread)
 
     return iothread->worker_context;
 }
+
+IOThread *iothread_create(const char *id, Error **errp)
+{
+    Object *obj;
+
+    obj = object_new_with_props(TYPE_IOTHREAD,
+                                object_get_internal_root(),
+                                id, errp, NULL);
+
+    return IOTHREAD(obj);
+}
+
+void iothread_destroy(IOThread *iothread)
+{
+    object_unparent(OBJECT(iothread));
+}