你如何查询pthread的，看它是否仍在运行？ [英] How do you query a pthread to see if it is still running?

问题描述

在我的析构函数我要干净摧毁一个线程。

In my destructor I want to destroy a thread cleanly.

我的目标是要等待一个线程执行完，然后销毁线程。

My goal is to wait for a thread to finish executing and THEN destroy the thread.

我发现了大约一个查询的pthread状态的唯一事情是<一个href=\"https://computing.llnl.gov/tutorials/pthreads/man/pthread_attr_getdetachstate.txt\">pthread_attr_setdetachstate但这只是告诉你，如果你的线程是：

The only thing I found about querying the state of a pthread is pthread_attr_setdetachstate but this only tells you if your thread is:

• PTHREAD_CREATE_DETACHED


• PTHREAD_CREATE_JOINABLE

这两项都无关线程是否仍在运行与否。

Both of those have nothing to do with whether the thread is still running or not.

如何查询pthread的，看它是否仍在运行？

推荐答案

这听起来像你这里有两个问题：

It sounds like you have two questions here:

答：这是直接由pthreads的支持 - 让你的线程要被停止可连接（当它第一次启动），并使用在pthread_join（）来阻止您当前线程，直到线程要被停止不再运行。

Answer: This is directly supported by pthreads -- make your thread-to-be-stopped JOINABLE (when it is first started), and use pthread_join() to block your current thread until the thread-to-be-stopped is no longer running.

答：您可以添加一个thread_complete标志做的伎俩：

Answer: You can add a "thread_complete" flag to do the trick:

场景：线程A想知道，如果线程B还活着。

Scenario: Thread A wants to know if Thread B is still alive.

当创建线程B，它被赋予一个指针thread_complete标记地址。在创建线程之前的thread_complete标志应被初始化为NOT_COMPLETED。线程B的入口点函数应该立即调用pthread_cleanup_push（）推动了清理处理程序，它设置了thread_complete标记为已完成。

When Thread B is created, it is given a pointer to the "thread_complete" flag address. The "thread_complete" flag should be initialized to NOT_COMPLETED before the thread is created. Thread B's entry point function should immediately call pthread_cleanup_push() to push a "cleanup handler" which sets the "thread_complete" flag to COMPLETED.

请参阅这里清理处理程序的详细信息： pthread的清除处理程序

See details about cleanup handlers here: pthread cleanup handlers

您将需要包括相应的​​pthread_cleanup_pop（1）调用，以确保清理处理程序被调用无论什么（即如果线程正常退出或由于取消，等等）。

You'll want to include a corresponding pthread_cleanup_pop(1) call to ensure that the cleanup handler gets called no matter what (i.e. if the thread exits normally OR due to cancellation, etc.).

然后，线程A可以简单地检查thread_complete标志来判断是否线程B已退出呢。

Then, Thread A can simply check the "thread_complete" flag to see if Thread B has exited yet.

注：您的thread_complete标志应宣布为动荡，应该是一个原子类型 - GNU编译器为此提供了sig_atomic_t。这允许两个线程一致访问相同的数据，而无需同步结构（互斥/信号灯）。

NOTE: Your "thread_complete" flag should be declared "volatile" and should be an atomic type -- the GNU compilers provide the sig_atomic_t for this purpose. This allows the two threads consistent access the same data without the need for synchronization constructs (mutexes/semaphores).

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