[Spice-devel] [spice-gtk v2] vmcstream, gtask: Do idle ourself as GTask's return gets messed up

[Fabiano Fidêncio]

Seems that our coroutines can mess up with GTask's return, ending up
in an early return from g_task_return_now() instead of doing a return
in idle.
As I still don't know if the bug is on spice-gtk or on GTask itself,
I've opened a bug[0] in spice-gtk's bugzilla and also made a reference
to the very same bug in the code.

[0]: https://bugs.freedesktop.org/show_bug.cgi?id=94662

Signed-off-by: Fabiano Fidêncio <fidencio at redhat.com>
---
Changes since v1, as per Marc-André review:
- Use g_idle_add() instead of GSource ... which worries me a bit about the
  context used when using g_idle_add(), as previously the context used was
  the one from the GTask.
---
 src/vmcstream.c | 41 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/src/vmcstream.c b/src/vmcstream.c
index 5ebf15a..54bf4d9 100644
--- a/src/vmcstream.c
+++ b/src/vmcstream.c
@@ -97,6 +97,32 @@ spice_vmc_input_stream_new(void)
     return self;
 }
 
+typedef struct _complete_in_idle_cb_data {
+    GTask *task;
+    gssize pos;
+} complete_in_idle_cb_data;
+
+static void
+complete_in_idle_cb_data_free (gpointer user_data)
+{
+    complete_in_idle_cb_data *data = user_data;
+
+    g_object_unref (data->task);
+    g_free (data);
+}
+
+static gboolean
+complete_in_idle_cb(gpointer user_data)
+{
+    complete_in_idle_cb_data *data = user_data;
+
+    g_task_return_int(data->task, data->pos);
+
+    complete_in_idle_cb_data_free(data);
+
+    return FALSE;
+}
+
 /* coroutine */
 /**
  * Feed a SpiceVmc stream with new data from a coroutine
@@ -116,6 +142,8 @@ spice_vmc_input_stream_co_data(SpiceVmcInputStream *self,
     self->coroutine = coroutine_self();
 
     while (size > 0) {
+        complete_in_idle_cb_data *cb_data;
+
         SPICE_DEBUG("spicevmc co_data %p", self->task);
         if (!self->task)
             coroutine_yield(NULL);
@@ -137,10 +165,19 @@ spice_vmc_input_stream_co_data(SpiceVmcInputStream *self,
         if (self->all && min > 0 && self->pos != self->count)
             continue;
 
-        g_task_return_int(self->task, self->pos);
+        /* Somehow we are messing up with GTask return. As it's not known
+         * for now if it's a spice-gtk issue due to the coroutine usage or
+         * a GTask issue itself, let's do the idle ourself.
+         *
+         * For a future reference, see:
+         * https://bugs.freedesktop.org/show_bug.cgi?id=94662
+         */
+        cb_data = g_new(complete_in_idle_cb_data , 1);
+        cb_data->task = g_object_ref(self->task);
+        cb_data->pos = self->pos;
+        g_idle_add(complete_in_idle_cb, cb_data);
 
         g_cancellable_disconnect(g_task_get_cancellable(self->task), self->cancel_id);
-
         g_clear_object(&self->task);
     }
 
-- 
2.5.0