realtime: Include PID/TID in some error messages

The PID is useful when debugging issues related to these messages,
so we can check whether the PID has some strange property
that caused the problem.

src/realtime.c

@@ -65,21 +65,21 @@ map_pid (XdpAppInfo *app_info, pid_t *pid, pid_t *tid, GError **error)
 
   if (!xdp_app_info_get_pidns (app_info, &pidns_id, error))
     {
-      g_prefix_error (error, "Could not get pidns: ");
+      g_prefix_error (error, "Could not get pidns for pid %d: ", *pid);
       g_warning ("Realtime error: %s", (*error)->message);
       return FALSE;
     }
 
   if (pidns_id != 0 && !xdp_map_pids (pidns_id, pid, 1, error))
     {
-      g_prefix_error (error, "Could not map pid: ");
+      g_prefix_error (error, "Could not map pid %d: ", *pid);
       g_warning ("Realtime error: %s", (*error)->message);
       return FALSE;
     }
 
   if (pidns_id != 0 && !xdp_map_tids (pidns_id, *pid, tid, 1, error))
     {
-      g_prefix_error (error, "Could not map tid: ");
+      g_prefix_error (error, "Could not map tid %d of mapped pid %d: ", *tid, *pid);
       g_warning ("Realtime error: %s", (*error)->message);
       return FALSE;
     }