WindowsError:[错误5]尝试杀死子进程(python)时，访问被拒绝 [英] WindowsError: [Error 5] Access is denied when trying to kill a subprocess (python)

问题描述

所以我有一个python脚本，它运行一个循环，在该循环中它通过子进程调用程序A.Popen等待其输出，然后保存输出，然后再次调用，依此类推. (在我设置为输入的多次运行中，这种情况一直发生)

So I have a python script that runs a loop in which it calls a program A through subprocess.Popen waits for its output, then saves the output and then calls it again and so on. (This keeps happening for a number of runs I set as an input)

问题是我有一个计时器，以便每当程序A花费的时间超过特定的threshold_time时，脚本就会使用process.kill()杀死该进程并继续进行下一个迭代.

The thing is that I have a timer so that whenever the program A takes more than a particular threshold_time, the script kills the process with process.kill() and moves on to the next iteration.

问题是，即使运行300次后，一切似乎都可以正常工作，但有时还是会出现此错误:

The problem is that even though everything seems to work fine even for 300 runs, sometimes I get this error:

    File "C:\Python27\lib\subprocess.py", line 1002, in terminate
    _subprocess.TerminateProcess(self._handle, 1)
    WindowsError: [Error 5] Access is denied

，然后脚本死亡.

所引用的脚本部分:

timeout = TIME_CONST
for run in runs:
    killed = False
    start = time.clock()
    p = subprocess.Popen("SOME.CMD", cwd=r"some_dir") 
    # Monitor process. If it hits threshold, kill it and go to the next run
    while p.poll() is None:
        time.sleep(20) 
        secs_passed = time.clock() - start

        ### the following was my initial buggy line ###
        #if secs_passed >= timeout: 

        ### corrected line after jedislight's answer ###
        #if the time is over the threshold and process is still running, kill it
        if secs_passed >= timeout and p.poll is None: 
            p.kill()
            killed = True  
            break
    if killed: continue   

您有什么建议可能是什么问题?

Do you have any suggestions what the problem might be?

接受答案并修复代码.感谢@jedislight的反馈！

Accepted answer and fixed the code. Thanks @jedislight for your feedback!

推荐答案

您正在将p.poll()和p.kill()分开20秒.到那时，该过程可能已经完成.我建议移动time.sleep(20)调用，以便您轮询并杀死在同一时间范围内发生的事件，以避免杀死死进程.以下是在iPython中运行的示例，该示例在杀死已完成的进程时显示了类似的错误:

You are seperating your p.poll() and your p.kill() by 20 seconds. By then the process could have finished. I would suggest moving the time.sleep(20) call around so that you poll and kill happen in the same time frame, to avoid killing a dead process. Below is an example run in iPython showing a similar error when killing a completed process:

In [2]: import subprocess

In [3]: p = subprocess.Popen("dir")

In [4]: p.poll()
Out[4]: 0

In [5]: p.kill()
---------------------------------------------------------------------------
WindowsError                              Traceback (most recent call last)

C:\Users\---\<ipython console> in <module>()

C:\Python26\lib\subprocess.pyc in terminate(self)
    947             """Terminates the process
    948             """
--> 949             _subprocess.TerminateProcess(self._handle, 1)
    950
    951         kill = terminate

WindowsError: [Error 5] Access is denied

即使您在显示进程正在运行的民意测验之后直接杀死，它也可以在执行下一行之前完成.我还建议为此异常添加一个try-catch块，如果再次发生，则再次轮询以查看该过程是否真正完成.

Even if you kill directly after a poll that shows the processes is running it can finish before the next line is executed. I would also suggest adding a try-catch block for this exception and if it occurs poll again to see if the process actually completed.

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