[evolution-data-server/gnome-3-16] Bug 746276 - Add thread-safety into EAsyncClosure

[Milan Crha <mcrha src gnome org>]

commit 7473c395dfbfff0ac315da56655fdfb18d2971a1
Author: Milan Crha <mcrha redhat com>
Date:   Tue Apr 14 17:14:14 2015 +0200

    Bug 746276 - Add thread-safety into EAsyncClosure
    
    It could happen that the e_async_closure_callback() was called before
    the e_async_closure_wait() was called, more precisely before
    the closure's loop was run, which could eventually cause indefinite
    waiting for the closure's loop to quit.

 libedataserver/e-data-server-util.c |   44 ++++++++++++++++++++++++++++++++--
 1 files changed, 41 insertions(+), 3 deletions(-)
---
diff --git a/libedataserver/e-data-server-util.c b/libedataserver/e-data-server-util.c
index 709016b..7fccb96 100644
--- a/libedataserver/e-data-server-util.c
+++ b/libedataserver/e-data-server-util.c
@@ -1608,6 +1608,8 @@ struct _EAsyncClosure {
        GMainLoop *loop;
        GMainContext *context;
        GAsyncResult *result;
+       gboolean finished;
+       GMutex lock;
 };
 
 /**
@@ -1627,12 +1629,26 @@ e_async_closure_new (void)
        closure = g_slice_new0 (EAsyncClosure);
        closure->context = g_main_context_new ();
        closure->loop = g_main_loop_new (closure->context, FALSE);
+       closure->finished = FALSE;
+       g_mutex_init (&closure->lock);
 
        g_main_context_push_thread_default (closure->context);
 
        return closure;
 }
 
+static gboolean
+e_async_closure_unlock_mutex_cb (gpointer user_data)
+{
+       EAsyncClosure *closure = user_data;
+
+       g_return_val_if_fail (closure != NULL, FALSE);
+
+       g_mutex_unlock (&closure->lock);
+
+       return FALSE;
+}
+
 /**
  * e_async_closure_wait:
  * @closure: an #EAsyncClosure
@@ -1653,7 +1669,22 @@ e_async_closure_wait (EAsyncClosure *closure)
 {
        g_return_val_if_fail (closure != NULL, NULL);
 
-       g_main_loop_run (closure->loop);
+       g_mutex_lock (&closure->lock);
+       if (closure->finished) {
+               g_mutex_unlock (&closure->lock);
+       } else {
+               GSource *idle_source;
+
+               /* Unlock the closure->lock in the main loop, to ensure thread safety.
+                  It should be processed before anything else, otherwise deadlock happens. */
+               idle_source = g_idle_source_new ();
+               g_source_set_callback (idle_source, e_async_closure_unlock_mutex_cb, closure, NULL);
+               g_source_set_priority (idle_source, G_PRIORITY_HIGH * 2);
+               g_source_attach (idle_source, closure->context);
+               g_source_unref (idle_source);
+
+               g_main_loop_run (closure->loop);
+       }
 
        return closure->result;
 }
@@ -1676,8 +1707,10 @@ e_async_closure_free (EAsyncClosure *closure)
        g_main_loop_unref (closure->loop);
        g_main_context_unref (closure->context);
 
-       if (closure->result != NULL)
-               g_object_unref (closure->result);
+       g_mutex_lock (&closure->lock);
+       g_clear_object (&closure->result);
+       g_mutex_unlock (&closure->lock);
+       g_mutex_clear (&closure->lock);
 
        g_slice_free (EAsyncClosure, closure);
 }
@@ -1707,10 +1740,15 @@ e_async_closure_callback (GObject *object,
 
        real_closure = closure;
 
+       g_mutex_lock (&real_closure->lock);
+
        /* Replace any previous result. */
        if (real_closure->result != NULL)
                g_object_unref (real_closure->result);
        real_closure->result = g_object_ref (result);
+       real_closure->finished = TRUE;
+
+       g_mutex_unlock (&real_closure->lock);
 
        g_main_loop_quit (real_closure->loop);
 }