Lib/test/fork_wait.py

   1 """This test case provides support for checking forking and wait behavior.
   2
   3 To test different wait behavior, override the wait_impl method.
   4
   5 We want fork1() semantics -- only the forking thread survives in the
   6 child after a fork().
   7
   8 On some systems (e.g. Solaris without posix threads) we find that all
   9 active threads survive in the child after a fork(); this is an error.
  10
  11 While BeOS doesn't officially support fork and native threading in
  12 the same application, the present example should work just fine.  DC
  13 """
  14
  15 import os, sys, time, unittest
  16 import test.test_support as test_support
  17 thread = test_support.import_module('thread')
  18
  19 LONGSLEEP = 2
  20 SHORTSLEEP = 0.5
  21 NUM_THREADS = 4
  22
  23 class ForkWait(unittest.TestCase):
  24
  25     def setUp(self):
  26         self.alive = {}
  27         self.stop = 0
  28
  29     def f(self, id):
  30         while not self.stop:
  31             self.alive[id] = os.getpid()
  32             try:
  33                 time.sleep(SHORTSLEEP)
  34             except IOError:
  35                 pass
  36
  37     def wait_impl(self, cpid):
  38         for i in range(10):
  39             # waitpid() shouldn't hang, but some of the buildbots seem to hang
  40             # in the forking tests.  This is an attempt to fix the problem.
  41             spid, status = os.waitpid(cpid, os.WNOHANG)
  42             if spid == cpid:
  43                 break
  44             time.sleep(2 * SHORTSLEEP)
  45
  46         self.assertEquals(spid, cpid)
  47         self.assertEquals(status, 0, "cause = %d, exit = %d" % (status&0xff, status>>8))
  48
  49     def test_wait(self):
  50         for i in range(NUM_THREADS):
  51             thread.start_new(self.f, (i,))
  52
  53         time.sleep(LONGSLEEP)
  54
  55         a = self.alive.keys()
  56         a.sort()
  57         self.assertEquals(a, range(NUM_THREADS))
  58
  59         prefork_lives = self.alive.copy()
  60
  61         if sys.platform in ['unixware7']:
  62             cpid = os.fork1()
  63         else:
  64             cpid = os.fork()
  65
  66         if cpid == 0:
  67             # Child
  68             time.sleep(LONGSLEEP)
  69             n = 0
  70             for key in self.alive:
  71                 if self.alive[key] != prefork_lives[key]:
  72                     n += 1
  73             os._exit(n)
  74         else:
  75             # Parent
  76             self.wait_impl(cpid)
  77             # Tell threads to die
  78             self.stop = 1
  79             time.sleep(2*SHORTSLEEP) # Wait for threads to die