A potential data race problem 一个潜在的数据竞争问题

[Mr-zhang-97]

void elog_async_output(uint8_t level, const char *log, size_t size) {
    /* this function must be implement by user when ELOG_ASYNC_OUTPUT_USING_PTHREAD is not defined */
    extern void elog_async_output_notice(void);
    size_t put_size;

    if (is_enabled) {
        if (level >= OUTPUT_LVL) {
            put_size = async_put_log(log, size);
            /* notify output log thread */
            if (put_size > 0) {
                elog_async_output_notice();
            }
        } else {
            elog_port_output(log, size);
        }
    } else {
        elog_port_output(log, size);
    }
}

对于上述函数，如果混合输出不同级别的日志，将会出现两个线程操作一个日志文件的的场景，容易出现数据竞争。有两种修改方法：1，开启异步输出后，所有的日志全部异步输出。2，在文件操作上加锁。
For the above function, if you output different levels of log , there will be two threads operating on a log file , which will lead to data race easily. There are two ways to modify this: 1. When asynchronous output mode is turned on, all logs are output asynchronously. 2, lock the file when operate it.

[Mr-zhang-97]

进一步阅读源码，可以看到elog_file_write中有加锁操作elog_file_port_lock。该操作在linux下已被实现，在Windows环境下未被实现。
我在有空会添加这部分实现。预计采用互斥锁这一方法。