解读Android LOG机制的实现(3)

static int __write_to_log_init(log_id_t log_id, struct iovec *vec, size_t nr)   {   #ifdef HAVE_PTHREADS        pthread_mutex_lock(&log_init_lock);   #endif           if (write_to_log == __write_to_log_init) {           log_fds[LOG_ID_MAIN] = log_open("/dev/"LOGGER_LOG_MAIN, O_WRONLY);           log_fds[LOG_ID_RADIO] = log_open("/dev/"LOGGER_LOG_RADIO, O_WRONLY);           log_fds[LOG_ID_EVENTS] = log_open("/dev/"LOGGER_LOG_EVENTS, O_WRONLY);           log_fds[LOG_ID_SYSTEM] = log_open("/dev/"LOGGER_LOG_SYSTEM, O_WRONLY);              write_to_log = __write_to_log_kernel;              if (log_fds[LOG_ID_MAIN] < 0 || log_fds[LOG_ID_RADIO] < 0 ||                   log_fds[LOG_ID_EVENTS] < 0) {               log_close(log_fds[LOG_ID_MAIN]);               log_close(log_fds[LOG_ID_RADIO]);               log_close(log_fds[LOG_ID_EVENTS]);               log_fds[LOG_ID_MAIN] = -1;               log_fds[LOG_ID_RADIO] = -1;               log_fds[LOG_ID_EVENTS] = -1;               write_to_log = __write_to_log_null;           }              if (log_fds[LOG_ID_SYSTEM] < 0) {               log_fds[LOG_ID_SYSTEM] = log_fds[LOG_ID_MAIN];           }       }      #ifdef HAVE_PTHREADS        pthread_mutex_unlock(&log_init_lock);   #endif           return write_to_log(log_id, vec, nr);   }