[glib/wip/oholy/gunixmountmonitor-thread-safe: 3/4] gunixmounts: Prevent race when mtab file changed

[Ondrej Holy <oholy src gnome org>]

commit ab278c0072f8e690ca4e7c3143a979dcc06e0a44
Author: Ondrej Holy <oholy redhat com>
Date:   Mon Feb 17 11:05:07 2020 +0100

    gunixmounts: Prevent race when mtab file changed
    
    mtab_file_changed_id might be set on thread default context, but it is
    always cleared on the global context because of usage of g_idle_add. This
    can cause the emission of redundant "mounts-change" signals. This should
    not cause any issues to the client application, but let's attach the idle
    source to the thread-default context instead to avoid those races for sure.

 gio/gunixmounts.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)
---
diff --git a/gio/gunixmounts.c b/gio/gunixmounts.c
index 8b12d8fbc..1f7077c11 100644
--- a/gio/gunixmounts.c
+++ b/gio/gunixmounts.c
@@ -1756,6 +1756,9 @@ mtab_file_changed (GFileMonitor      *monitor,
                    GFileMonitorEvent  event_type,
                    gpointer           user_data)
 {
+  GMainContext *context;
+  GSource *source;
+
   if (event_type != G_FILE_MONITOR_EVENT_CHANGED &&
       event_type != G_FILE_MONITOR_EVENT_CREATED &&
       event_type != G_FILE_MONITOR_EVENT_DELETED)
@@ -1768,7 +1771,16 @@ mtab_file_changed (GFileMonitor      *monitor,
   if (mtab_file_changed_id > 0)
     return;
 
-  mtab_file_changed_id = g_idle_add (mtab_file_changed_cb, NULL);
+  context = g_main_context_get_thread_default ();
+  if (!context)
+    context = g_main_context_default ();
+
+  source = g_idle_source_new ();
+  g_source_set_priority (source, G_PRIORITY_DEFAULT);
+  g_source_set_callback (source, mtab_file_changed_cb, NULL, NULL);
+  g_source_set_name (source, "[gio] mtab_file_changed_cb");
+  g_source_attach (source, context);
+  g_source_unref (source);
 }
 
 static gboolean