為什么不ulimit -t殺死一個超出time.sleep限制的進程？

Question

我試圖使用ulimit -t限制一個python腳本的CPU使用率。 該腳本包含一個time.sleep()語句，並且在指定的時間限制后不會被殺死。 這是名為test.py的簡化python腳本：

import time

while True:
    time.sleep(0.1)

我運行命令如下：

ulimit -v 400000; ulimit -t 30; python test.py

該腳本將永遠運行。 有什么解釋嗎？ 謝謝。

mata的答案是正確的。 我更新了我的真實代碼，其中包含一個隱藏的東西，即ulimit -t不計算生成的子進程的運行時間。

#!/usr/bin/env python
# Run: python smt.py filename.smt2 timeout
# timeout is in seconds

import os
import subprocess
import sys
import stat
import time

current_path = os.path.dirname(os.path.realpath(__file__))

def remove_tmp (filename, version):
  try:
    os.remove(filename + '.' + version + '.tmp')
  except OSError:
    pass

  try:
    os.remove(os.path.splitext(filename)[0] + '.' + version +  '.out')
  except OSError:
    pass

  try:
    os.remove(os.path.splitext(filename)[0] + '.' + version +  '.in')
  except OSError:
    pass

def run_raSAT (filename, bounds, sbox, timeout):
  startTime = time.time()  

  raSATResult = "unknown"

  # remove tmps files:
  remove_tmp(filename, "0.2")
  remove_tmp(filename, "0.3")

  proc2 = subprocess.Popen([os.path.join(current_path, "./raSAT-0.2"), filename, bounds, 'sbox=' + str(sbox), 'tout=' + str(timeout-(time.time() - startTime))])
  proc3 = subprocess.Popen([os.path.join(current_path, "./raSAT-0.3"), filename, bounds])
  while True:
    if proc2.poll():
      # try read output of 0.2
      try:
        with open(filename + '.0.2.tmp', 'r') as outfile:
          raSATResult = outfile.read().rstrip()
          outfile.close()
          if raSATResult == "unknown":
            sbox /= 10
            remove_tmp(filename, "0.2")
            proc2 = subprocess.Popen([os.path.join(current_path, "./raSAT-0.2"), filename, bounds, 'sbox=' + str(sbox), 'tout=' + str(timeout-(time.time() - startTime))])
      except IOError:
        pass  

    if proc3.poll():      
      # try read output of 0.3
      try:
        with open(filename + '.0.3.tmp', 'r') as outfile:
          raSATResult = outfile.read().rstrip()
          outfile.close()
      except IOError:
        pass

    if raSATResult == "sat" or raSATResult == "unsat":
      if not proc3.poll():
        proc3.kill()
      if not proc2.poll():
        proc2.kill()
      break

    time.sleep(0.01)


  return raSATResult, sbox

def run(filename, initLowerBound, initUpperBound, sbox, timeout):
  lowerBound = initLowerBound
  upperBound = initUpperBound
  raSATResult = "unknown"
  startTime = time.time()
  while (raSATResult == 'unknown'):
    (raSATResult, sbox) = run_raSAT(filename, 'lb=' + str(lowerBound) + ' ' + str(upperBound), sbox, timeout - (time.time() - startTime))
    if raSATResult == 'unsat':
      (raSATResult, sbox) = run_raSAT(filename, 'lb=-inf inf', sbox, timeout - (time.time() - startTime))  
  print (raSATResult)

  # remove tmps files:
  remove_tmp(filename, "0.2")
  remove_tmp(filename, "0.3")

# get timeout from environment
timeout = float(os.environ.get('STAREXEC_CPU_LIMIT'))

run(sys.argv[1], -10, 10,  0.1, timeout)

Answer 1

ulimit -t設置CPU時間限制。 當程序處於睡眠狀態時，它不占用任何CPU時間，因此該時間不計在內。 它只會占用幾個CPU周期才能再次進入睡眠狀態，這就是為什么它不會被殺死。

您不能使用ulimit指定實時限制。