使用 stderr=PIPE 和 Popen.communicate() 获取竞争条件

我正在开发一个 kubernetes flexvolume 驱动程序，用于创建 LVM 设备，并创建和挂载文件系统。

由于某种原因，我偶尔会遇到死锁，根据文档，使用 Popen.communicate() 时不应发生这种死锁。

 Traceback (most recent call last):
  File "/usr/libexec/kubernetes/kubelet/plugins/volume/exec/example~lvm/lvm", line 356, in <module>
    attach(cfg)
  File "/usr/libexec/kubernetes/kubelet/plugins/volume/exec/example~lvm/lvm", line 231, in attach
    result = _lvcreate(cfg['lv_name'], cfg['lv_size'], cfg['vg_name'])
  File "/usr/libexec/kubernetes/kubelet/plugins/volume/exec/example~lvm/lvm", line 148, in _lvcreate
    _out, _err = proc.communicate()
  File "/usr/lib64/python2.7/subprocess.py", line 800, in communicate
    return self._communicate(input)
  File "/usr/lib64/python2.7/subprocess.py", line 1401, in _communicate
    stdout, stderr = self._communicate_with_poll(input)
  File "/usr/lib64/python2.7/subprocess.py", line 1455, in _communicate_with_poll
    ready = poller.poll()
KeyboardInterrupt

在我的 lvcreate 和 mkfs 调用期间有时会发生这种情况。环境shell=True似乎并不重要。

_lv  = None
_cmd = [ '/sbin/lvcreate', '--type', 'linear', '--size', lv_size, '--name', lv_name, vg_name ]
_out, _err = None, None
proc = subprocess.Popen(_cmd, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
_out, _err = proc.communicate()
if proc.returncode != 0:
    return (_lv, _err, proc.returncode)

环境：

$ uname -a
Linux myhost.example.com 4.1.12-124.17.2.el7uek.x86_64 #2 SMP Tue Jul 17 20:28:07 PDT 2018 x86_64 x86_64 x86_64 GNU/Linux

# python -V
Python 2.7.5

如果我设置stderr=None代替stderr=subprocess.PIPE我从来没有看到这个问题。