Lib/test/fork_wait.py

   1 """This test case provides support for checking forking and wait behavior.
   2
   3 To test different wait behavior, overrise 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
  12 import os, sys, time, _thread, unittest
  13
  14 LONGSLEEP = 2
  15 SHORTSLEEP = 0.5
  16 NUM_THREADS = 4
  17
  18 class ForkWait(unittest.TestCase):
  19
  20     def setUp(self):
  21         self.alive = {}
  22         self.stop = 0
  23
  24     def f(self, id):
  25         while not self.stop:
  26             self.alive[id] = os.getpid()
  27             try:
  28                 time.sleep(SHORTSLEEP)
  29             except IOError:
  30                 pass
  31
  32     def wait_impl(self, cpid):
  33         for i in range(10):
  34             # waitpid() shouldn't hang, but some of the buildbots seem to hang
  35             # in the forking tests.  This is an attempt to fix the problem.
  36             spid, status = os.waitpid(cpid, os.WNOHANG)
  37             if spid == cpid:
  38                 break
  39             time.sleep(2 * SHORTSLEEP)
  40
  41         self.assertEquals(spid, cpid)
  42         self.assertEquals(status, 0, "cause = %d, exit = %d" % (status&0xff, status>>8))
  43
  44     def test_wait(self):
  45         for i in range(NUM_THREADS):
  46             _thread.start_new(self.f, (i,))
  47
  48         time.sleep(LONGSLEEP)
  49
  50         a = sorted(self.alive.keys())
  51         self.assertEquals(a, list(range(NUM_THREADS)))
  52
  53         prefork_lives = self.alive.copy()
  54
  55         if sys.platform in ['unixware7']:
  56             cpid = os.fork1()
  57         else:
  58             cpid = os.fork()
  59
  60         if cpid == 0:
  61             # Child
  62             time.sleep(LONGSLEEP)
  63             n = 0
  64             for key in self.alive:
  65                 if self.alive[key] != prefork_lives[key]:
  66                     n += 1
  67             os._exit(n)
  68         else:
  69             # Parent
  70             self.wait_impl(cpid)
  71             # Tell threads to die
  72             self.stop = 1
  73             time.sleep(2*SHORTSLEEP) # Wait for threads to die