static void *do_monitor(void *data)
 {
 for (sip = iflist; !fastrestart && sip; sip = sip->next) {
                        /*! \note If we can't get a lock on an interface, skip it and come
                         * back later. Note that there is the possibility of a deadlock with
                         * sip_hangup otherwise, because sip_hangup is called with the channel
                         * locked first, and the iface lock is attempted second.
                         */
                        if (ast_mutex_trylock(&sip->lock))//16145ÐÐ
                                continue;