用C实现的工作线程定时器方式

问题描述：

我有一个工作线程，从管道得到的工作。事情是这样的。

I have a worker thread that gets work from pipe. Something like this

void *worker(void *param) {
  while (!work_done) {
    read(g_workfds[0], work, sizeof(work));
    do_work(work);
  }
}

我需要实现在同一个线程1秒计时器做一些簿记有关的工作。以下是我在心中已经：

I need to implement a 1 second timer in the same thread do to some book-keeping about the work. Following is what I've in mind:

void *worker(void *param) {
  prev_uptime = get_uptime();
  while (!work_done) {
    // set g_workfds[0] as non-block
    now_uptime = get_uptime();
    if (now_uptime - prev_uptime > 1) {
       do_book_keeping();
       prev_uptime = now_uptime;
    }
    n = poll(g_workfds[0], 1000); // Wait for 1 second else timeout
    if (n == 0) // timed out 
       continue;
    read(g_workfds[0], work, sizeof(work));
    do_work(work);   // This can take more than 1 second also
  }
}

我使用的系统正常运行时间，而不是系统时间，因为虽然这线程在运行系统时可以得到改变。我不知道是否有其他更好的方法来做到这一点。我不想考虑使用其他的线程。使用报警（）不是因为它已经用在同一进程中另一个线程的选项。这是在Linux环境中得到实现。

I am using system uptime instead of system time because system time can get changed while this thread is running. I was wondering if there is any other better way to do this. I don't want to consider using another thread. Using alarm() is not an option as it already used by another thread in same process. This is getting implemented in Linux environment.

答

我已经找到了更好的办法，但它使用的 timerfd_create（）系统调用。它负责系统时间的改变。以下是可能的伪code：

I have found a better way but it is Linux specific using timerfd_create() system call. It takes care of system time change. Following is possible psuedo code:

void *worker(void *param) {
  int timerfd = timerfd_create(CLOCK_MONOTONIC, 0);  // Monotonic doesn't get affected by system time change
  // set timerfd to non-block 
  timerfd_settime(timerfd, 1 second timer);     // timer starts 
  while (!work_done) {
    // set g_workfds[0] as non-block
    n = poll(g_workfds[0] and timerfd, 0); // poll on both pipe and timerfd and Wait indefinetly 
    if (timerfd is readable) 
       do_book_keeping();
    if (g_workfds[0] is readable) {
       read(g_workfds[0], work, sizeof(work));
       do_work(work);   // This can take more than 1 second also
    }
  }
}

这似乎更清洁和阅读（）在 timerfd 返回的情况下，经过加时赛 do_work（）时间长这是相当有用，因为 do_book_keeping（）期望得到所谓的每一秒。

It seems cleaner and read() on timerfd returns extra time elapsed in case do_work() takes long time which is quite useful as do_book_keeping() expects to get called every second.

用C实现的工作线程定时器方式

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