io: add ability to set a name for IO channels

The GSource object has ability to have a name, which is useful
when debugging performance problems with the mainloop event
callbacks that take too long. By associating a name with a
QIOChannel object, we can then set the name on any GSource
associated with the channel.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

include/glib-compat.h

@@ -304,4 +304,11 @@ static inline void g_slist_free_full(GSList *list, GDestroyNotify free_func)
 }
 #endif
 
+#if !GLIB_CHECK_VERSION(2, 26, 0)
+static inline void g_source_set_name(GSource *source, const char *name)
+{
+    /* This is just a debugging aid, so leaving it a no-op */
+}
+#endif
+
 #endif

include/io/channel.h

@@ -79,6 +79,7 @@ typedef gboolean (*QIOChannelFunc)(QIOChannel *ioc,
 struct QIOChannel {
     Object parent;
     unsigned int features; /* bitmask of QIOChannelFeatures */
+    char *name;
 #ifdef _WIN32
     HANDLE event; /* For use with GSource on Win32 */
 #endif
@@ -158,6 +159,18 @@ bool qio_channel_has_feature(QIOChannel *ioc,
 void qio_channel_set_feature(QIOChannel *ioc,
                              QIOChannelFeature feature);
 
+/**
+ * qio_channel_set_name:
+ * @ioc: the channel object
+ * @name: the name of the channel
+ *
+ * Sets the name of the channel, which serves as an aid
+ * to debugging. The name is used when creating GSource
+ * watches for this channel.
+ */
+void qio_channel_set_name(QIOChannel *ioc,
+                          const char *name);
+
 /**
  * qio_channel_readv_full:
  * @ioc: the channel object

io/channel.c

@@ -37,6 +37,14 @@ void qio_channel_set_feature(QIOChannel *ioc,
 }
 
 
+void qio_channel_set_name(QIOChannel *ioc,
+                          const char *name)
+{
+    g_free(ioc->name);
+    ioc->name = g_strdup(name);
+}
+
+
 ssize_t qio_channel_readv_full(QIOChannel *ioc,
                                const struct iovec *iov,
                                size_t niov,
@@ -136,7 +144,13 @@ GSource *qio_channel_create_watch(QIOChannel *ioc,
                                   GIOCondition condition)
 {
     QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);
-    return klass->io_create_watch(ioc, condition);
+    GSource *ret = klass->io_create_watch(ioc, condition);
+
+    if (ioc->name) {
+        g_source_set_name(ret, ioc->name);
+    }
+
+    return ret;
 }
 
 
@@ -282,24 +296,24 @@ void qio_channel_wait(QIOChannel *ioc,
 }
 
 
-#ifdef _WIN32
 static void qio_channel_finalize(Object *obj)
 {
     QIOChannel *ioc = QIO_CHANNEL(obj);
 
+    g_free(ioc->name);
+
+#ifdef _WIN32
     if (ioc->event) {
         CloseHandle(ioc->event);
     }
-}
 #endif
+}
 
 static const TypeInfo qio_channel_info = {
     .parent = TYPE_OBJECT,
     .name = TYPE_QIO_CHANNEL,
     .instance_size = sizeof(QIOChannel),
-#ifdef _WIN32
     .instance_finalize = qio_channel_finalize,
-#endif
     .abstract = true,
     .class_size = sizeof(QIOChannelClass),
 };