Python:当父母去世时，如何杀死子进程? [英] Python: how to kill child process(es) when parent dies?

问题描述

子进程始于

subprocess.Popen(arg)

有没有一种方法可以确保在父项异常终止时将其杀死?我需要在Windows和Linux上都能使用.我知道这个

Is there a way to ensure it is killed when parent terminates abnormally? I need this to work both on Windows and Linux. I am aware of this solution for Linux.

如果存在使用其他启动进程的方法的解决方案，则可以放宽使用subprocess.Popen(arg)启动子进程的要求.

the requirement of starting a child process with subprocess.Popen(arg) can be relaxed, if a solution exists using a different method of starting a process.

推荐答案

呵呵，我昨天才在自己研究这个问题！假设您无法更改子程序:

Heh, I was just researching this myself yesterday! Assuming you can't alter the child program:

在Linux上，prctl(PR_SET_PDEATHSIG, ...)可能是唯一可靠的选择. (如果绝对有必要终止子进程，那么您可能希望将终止信号设置为SIGKILL而不是SIGTERM；链接到的代码使用SIGTERM，但是子级可以选择忽略SIGTERM. )

On Linux, prctl(PR_SET_PDEATHSIG, ...) is probably the only reliable choice. (If it's absolutely necessary that the child process be killed, then you might want to set the death signal to SIGKILL instead of SIGTERM; the code you linked to uses SIGTERM, but the child does have the option of ignoring SIGTERM if it wants to.)

在Windows上，最可靠的选择是使用作业对象.这个想法是先创建一个作业"(一种用于流程的容器)，然后将子流程放入作业中，然后设置一个魔术选项，上面写着当没有人握住该作业的句柄"时，然后杀死其中的进程".默认情况下，作业的唯一句柄"是父进程持有的句柄，并且当父进程死掉时，操作系统将检查并关闭其所有句柄，然后注意这意味着没有打开的句柄工作.因此，它会按要求杀死孩子. (如果您有多个子进程，则可以将它们全部分配给同一作业.)此答案具有执行此操作的示例代码使用win32api模块.该代码使用CreateProcess而不是subprocess.Popen来启动子级.原因是它们需要为生成的子项获取进程句柄"，并且CreateProcess默认情况下将其返回.如果您更愿意使用subprocess.Popen，那么这是该答案中代码的(未经测试的)副本，该副本使用subprocess.Popen和OpenProcess而不是CreateProcess:

On Windows, the most reliable options is to use a Job object. The idea is that you create a "Job" (a kind of container for processes), then you place the child process into the Job, and you set the magic option that says "when no-one holds a 'handle' for this Job, then kill the processes that are in it". By default, the only 'handle' to the job is the one that your parent process holds, and when the parent process dies, the OS will go through and close all its handles, and then notice that this means there are no open handles for the Job. So then it kills the child, as requested. (If you have multiple child processes, you can assign them all to the same job.) This answer has sample code for doing this, using the win32api module. That code uses CreateProcess to launch the child, instead of subprocess.Popen. The reason is that they need to get a "process handle" for the spawned child, and CreateProcess returns this by default. If you'd rather use subprocess.Popen, then here's an (untested) copy of the code from that answer, that uses subprocess.Popen and OpenProcess instead of CreateProcess:

import subprocess
import win32api
import win32con
import win32job

hJob = win32job.CreateJobObject(None, "")
extended_info = win32job.QueryInformationJobObject(hJob, win32job.JobObjectExtendedLimitInformation)
extended_info['BasicLimitInformation']['LimitFlags'] = win32job.JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE
win32job.SetInformationJobObject(hJob, win32job.JobObjectExtendedLimitInformation, extended_info)

child = subprocess.Popen(...)
# Convert process id to process handle:
perms = win32con.PROCESS_TERMINATE | win32con.PROCESS_SET_QUOTA
hProcess = win32api.OpenProcess(perms, False, child.pid)

win32job.AssignProcessToJobObject(hJob, hProcess)

从技术上讲，如果孩子在Popen和OpenProcess通话之间死亡，这里有一个很小的比赛条件，您可以决定是否要为此担心.

Technically, there's a tiny race condition here in case the child dies in between the Popen and OpenProcess calls, you can decide whether you want to worry about that.

使用作业对象的一个​​缺点是，在Vista或Win7上运行时，如果从Windows Shell启动程序(即通过单击图标)，则可能会已经是分配的作业对象，尝试创建新的作业对象将失败. Win8可以解决此问题(通过允许嵌套作业对象)，或者如果您的程序是从命令行运行的，那么应该没问题.

One downside to using a job object is that when running on Vista or Win7, if your program is launched from the Windows shell (i.e., by clicking on an icon), then there will probably already be a job object assigned and trying to create a new job object will fail. Win8 fixes this (by allowing job objects to be nested), or if your program is run from the command line then it should be fine.

如果您可以修改子级(例如，像使用multiprocessing时一样)，那么最好的选择可能是以某种方式将父级的PID传递给子级(例如，作为命令行参数，或multiprocessing.Process的args=参数中)，然后:

If you can modify the child (e.g., like when using multiprocessing), then probably the best option is to somehow pass the parent's PID to the child (e.g. as a command line argument, or in the args= argument to multiprocessing.Process), and then:

在POSIX上:在子级中生成一个线程，该线程偶尔会调用os.getppid()，如果返回值停止与从父级传入的pid匹配，则调用os._exit(). (这种方法可移植到包括OS X在内的所有Unix上，而prctl技巧是特定于Linux的.)

On POSIX: Spawn a thread in the child that just calls os.getppid() occasionally, and if the return value ever stops matching the pid passed in from the parent, then call os._exit(). (This approach is portable to all Unixes, including OS X, while the prctl trick is Linux-specific.)

在Windows上:在使用OpenProcess和os.waitpid的子代中生成线程.使用ctypes的示例:

On Windows: Spawn a thread in the child that uses OpenProcess and os.waitpid. Example using ctypes:

from ctypes import WinDLL, WinError
from ctypes.wintypes import DWORD, BOOL, HANDLE
# Magic value from http://msdn.microsoft.com/en-us/library/ms684880.aspx
SYNCHRONIZE = 0x00100000
kernel32 = WinDLL("kernel32.dll")
kernel32.OpenProcess.argtypes = (DWORD, BOOL, DWORD)
kernel32.OpenProcess.restype = HANDLE
parent_handle = kernel32.OpenProcess(SYNCHRONIZE, False, parent_pid)
# Block until parent exits
os.waitpid(parent_handle, 0)
os._exit(0)

这避免了我提到的作业对象的任何可能的问题.

This avoids any of the possible issues with job objects that I mentioned.

如果您想真正确定，那么可以结合使用所有这些解决方案.

If you want to be really, really sure, then you can combine all these solutions.

希望有帮助！

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