Python Timer回调阻止？

Question

使用一个简单的线程化Timer（）来终止超时的子proc时，直接调用proc.kill可以按预期方式工作，但是通过另一个回调调用proc.kill则无法正常工作。回调已执行但subproc没有被杀死？

from subprocess import Popen, PIPE
from threading import Timer


def pkill(p):
  pid = p.pid
  print("Killing process pid=[%s]\n" % (pid))
  p.kill


def run(cmd, timeout_sec):
  print("Popen() for cmd=[%s]\n" % (command))
  proc = Popen(shlex.split(cmd), stdout=PIPE, stderr=PIPE)
  pid = proc.pid
  print("Starting subprocess with pid=[%s]\n" % (pid))

  ## works as expected when kill called directly
  timer = Timer(timeout_sec, proc.kill )

  ## doesn't work when given to a callback
  ## timer = Timer(timeout_sec, pkill, [proc] )

  try:
    print("Starting timer() for [%d] seconds\n" % (timeout_sec))
  timer.start()
    stdout, stderr = proc.communicate()
  finally:
    timer.cancel()

run("sleep 5", 1)