Hello,
As far as i knew, the GDBusProxy object initialization flow have two mainly
actions:
(1). Listen for properties change signal to update property cache in GDBusProxy.
(2). Called the GetAll metod call to get the default value of an object
properties.
I've encountered a race condition with GDBusProxy object initialization. if the
signal of properties_change occurred while the GDBusProxy was already in a
GetAll reply handler flow, the properties_change signal will be immediately
discarded. This causes the GDBusProxy object has not yet initialized when the
callback function on_properties_changed() called.
The ascii figure below shows the possible execution of this isseus: (Y axis is
a time axis)
[GDBus Worker thread] {Default GLib main context}
[Main thread]
| |
|
+-------------------------+ push the idle GSource |
|
| | <async_init_get_all_cb()> | pop the idle
GSource |
| receiving GetAll method | to the mainloop |
<async_init_get_all_cb()> |
| reply message +--------------------------->> | from the mainloop
+------------------------------------+
| |
+--------------------------->> | |
+-------------------------+ |
| running <async_init_get_all_cb()> |
| |
| callback function, and adding the |
+-------------------------+ push the idle GSource |
| idle GSource user-defined |
| | <on_properties_changed()> | push the idle
GSource | GDBusProxy ready callback function |
| ((unexpected signal!)) | to the mainloop | <on_proxy_ready()>
| to the mainloop (such as |
| receiving the signal of +--------------------------->> | to the mainloop
| <on_proxy_ready()> ...) |
| properties change | |
<<---------------------------+ |
| | |
+------------------------------------+
+-------------------------+ |
|
| |
|
| |
+------------------------------------+
| | pop the idle
GSource | |
| |
<on_properties_changed()> | running <on_properties_changed()> |
| | from the mainloop
| callback function, but the |
|
+--------------------------->> | GDBusProxy object has not yet been |
| |
| initialized, so the signal will be |
| |
| DISCARDED! |
| |
+------------------------------------+
| |
|
| |
+------------------------------------+
| | pop the idle
GSource | |
| | <on_proxy_ready()>
| running <on_proxy_ready()> |
| | from the mainloop
| callback function, and call the |
|
+--------------------------->> | function => |
| |
| <async_initable_init_finish()> |
| |
| to set GDBusProxy object |
| |
| initialization compiled, but some |
| |
| cache results of properties was |
| |
| incorrect! |
| |
| |
| |
+------------------------------------+
| |
|
| |
|
... ...
...
I think an easy way to fix this problem is to raising idle GSources priority in
whole GetAll reply handler flow, to makesure the on_properties_changed() have
been executed after async_init_get_all_cb() and on_proxy_ready(). However this
occurs rarely, and in any case the signal of properties changed should not be
discarded.
There is proposed patch corrects this.
1. add new API <g_simple_async_result_complete_in_idle_full()> in order to
raising idle GSources priority.
2. Change idle GSources priority to HIGH in whole GetAll reply handler flow, to
avoid the properties_change signal will be discarded when it's fallowing
recevie GetAll reply message.
diff --git a/gio/gdbusconnection.c b/gio/gdbusconnection.c
index fc9acbe..6b2a434 100644
--- a/gio/gdbusconnection.c
+++ b/gio/gdbusconnection.c
@@ -1832,7 +1832,7 @@ send_message_with_reply_deliver (SendMessageData *data,
gboolean remove)
data->delivered = TRUE;
- g_simple_async_result_complete_in_idle (data->simple);
+ g_simple_async_result_complete_in_idle_full (data->simple, G_PRIORITY_HIGH);
g_object_unref (data->simple);
data->simple = NULL;
diff --git a/gio/gdbusproxy.c b/gio/gdbusproxy.c
index 33492b7..c7ace07 100644
--- a/gio/gdbusproxy.c
+++ b/gio/gdbusproxy.c
@@ -1463,7 +1463,7 @@ async_init_get_all_cb (GDBusConnection *connection,
(GDestroyNotify)
g_variant_unref);
}
- g_simple_async_result_complete_in_idle (data->simple);
+ g_simple_async_result_complete_in_idle_full (data->simple, G_PRIORITY_HIGH);
async_init_data_free (data);
}
diff --git a/gio/gsimpleasyncresult.c b/gio/gsimpleasyncresult.c
index ee30da2..7e9caf3 100644
--- a/gio/gsimpleasyncresult.c
+++ b/gio/gsimpleasyncresult.c
@@ -778,19 +778,16 @@ complete_in_idle_cb (gpointer data)
}
/**
- * g_simple_async_result_complete_in_idle:
+ * g_simple_async_result_complete_in_idle_full:
* @simple: a #GSimpleAsyncResult.
*
- * Completes an asynchronous function in an idle handler in the
- * [thread-default main context][g-main-context-push-thread-default]
- * of the thread that @simple was initially created in
- * (and re-pushes that context around the invocation of the callback).
+ * This function is the same as g_simple_async_result_complete_in_idle()
except that it lets you specify the priority.
*
* Calling this function takes a reference to @simple for as long as
* is needed to complete the call.
*/
void
-g_simple_async_result_complete_in_idle (GSimpleAsyncResult *simple)
+g_simple_async_result_complete_in_idle_full (GSimpleAsyncResult *simple, gint
priority)
{
GSource *source;
@@ -799,13 +796,31 @@ g_simple_async_result_complete_in_idle
(GSimpleAsyncResult *simple)
g_object_ref (simple);
source = g_idle_source_new ();
- g_source_set_priority (source, G_PRIORITY_DEFAULT);
+ g_source_set_priority (source, priority);
g_source_set_callback (source, complete_in_idle_cb, simple, g_object_unref);
g_source_attach (source, simple->context);
g_source_unref (source);
}
+/**
+ * g_simple_async_result_complete_in_idle:
+ * @simple: a #GSimpleAsyncResult.
+ *
+ * Completes an asynchronous function in an idle handler in the
+ * [thread-default main context][g-main-context-push-thread-default]
+ * of the thread that @simple was initially created in
+ * (and re-pushes that context around the invocation of the callback).
+ *
+ * Calling this function takes a reference to @simple for as long as
+ * is needed to complete the call.
+ */
+void
+g_simple_async_result_complete_in_idle (GSimpleAsyncResult *simple)
+{
+ g_simple_async_result_complete_in_idle_full (simple, G_PRIORITY_DEFAULT);
+}
+
typedef struct {
GSimpleAsyncResult *simple;
GCancellable *cancellable;
diff --git a/gio/gsimpleasyncresult.h b/gio/gsimpleasyncresult.h
index 94412f4..52b1039 100644
--- a/gio/gsimpleasyncresult.h
+++ b/gio/gsimpleasyncresult.h
@@ -103,6 +103,8 @@ void
g_simple_async_result_set_handle_cancellation (GSimpleAsyncR
GLIB_AVAILABLE_IN_ALL
void g_simple_async_result_complete (GSimpleAsyncResult
*simple);
GLIB_AVAILABLE_IN_ALL
+void g_simple_async_result_complete_in_idle_full
(GSimpleAsyncResult *simple, gint priority);
+GLIB_AVAILABLE_IN_ALL
void g_simple_async_result_complete_in_idle (GSimpleAsyncResult
*simple);
GLIB_AVAILABLE_IN_ALL
void g_simple_async_result_run_in_thread (GSimpleAsyncResult
*simple,
--
Regards,
Brant Li
glib_gdbusproxy_race_condition.patch
Description: glib_gdbusproxy_race_condition.patch
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