ID_STOP          3501 gc/os_dep.c        GC_mprotect_thread_notify(ID_STOP);
ID_STOP          3551 gc/os_dep.c                if(r == MACH_MSG_SUCCESS && (id == ID_STOP || id == ID_RESUME))
ID_STOP          3564 gc/os_dep.c                case ID_STOP: