Fix data race by reloading satellites on the main thread

src/main.c

@@ -84,6 +84,7 @@ static void     gpredict_sig_handler(int sig);
 static gboolean tle_mon_task(gpointer data);
 static void     tle_mon_stop(void);
 static gpointer update_tle_thread(gpointer data);
+static gboolean reload_sats_idle_cb(gpointer data);
 static void     clean_tle(void);
 static void     clean_trsp(void);
 
@@ -557,19 +558,33 @@ static void tle_mon_stop()
     /* if TLE update is running wait until it is finished */
     while (tle_upd_running)
     {
+        /* iterate the main loop so the reload idle callback can run */
+        g_main_context_iteration(NULL, FALSE);
         g_usleep(1000);
     }
 }
 
+/* Reload satellites on the main loop after a TLE update. */
+static gboolean reload_sats_idle_cb(gpointer data)
+{
+    (void)data;
+
+    mod_mgr_reload_sats();
+    tle_upd_running = FALSE;
+
+    return G_SOURCE_REMOVE;
+}
+
 /* Thread function which invokes TLE update */
 static          gpointer update_tle_thread(gpointer data)
 {
     (void)data;
 
     tle_upd_running = TRUE;
     tle_update_from_network(TRUE, NULL, NULL, NULL);
-    mod_mgr_reload_sats();
-    tle_upd_running = FALSE;
+
+    /* reloading touches GTK, so run it on the main thread, not here */
+    gdk_threads_add_idle(reload_sats_idle_cb, NULL);
 
     return NULL;
 }