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