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      1 """This test checks for correct fork() behavior.
      2 """
      3 
      4 import imp
      5 import os
      6 import signal
      7 import sys
      8 import time
      9 
     10 from test.fork_wait import ForkWait
     11 from test.test_support import run_unittest, reap_children, get_attribute, import_module
     12 threading = import_module('threading')
     13 
     14 #Skip test if fork does not exist.
     15 get_attribute(os, 'fork')
     16 
     17 
     18 class ForkTest(ForkWait):
     19     def wait_impl(self, cpid):
     20         for i in range(10):
     21             # waitpid() shouldn't hang, but some of the buildbots seem to hang
     22             # in the forking tests.  This is an attempt to fix the problem.
     23             spid, status = os.waitpid(cpid, os.WNOHANG)
     24             if spid == cpid:
     25                 break
     26             time.sleep(1.0)
     27 
     28         self.assertEqual(spid, cpid)
     29         self.assertEqual(status, 0, "cause = %d, exit = %d" % (status&0xff, status>>8))
     30 
     31     def test_import_lock_fork(self):
     32         import_started = threading.Event()
     33         fake_module_name = "fake test module"
     34         partial_module = "partial"
     35         complete_module = "complete"
     36         def importer():
     37             imp.acquire_lock()
     38             sys.modules[fake_module_name] = partial_module
     39             import_started.set()
     40             time.sleep(0.01) # Give the other thread time to try and acquire.
     41             sys.modules[fake_module_name] = complete_module
     42             imp.release_lock()
     43         t = threading.Thread(target=importer)
     44         t.start()
     45         import_started.wait()
     46         pid = os.fork()
     47         try:
     48             if not pid:
     49                 m = __import__(fake_module_name)
     50                 if m == complete_module:
     51                     os._exit(0)
     52                 else:
     53                     os._exit(1)
     54             else:
     55                 t.join()
     56                 # Exitcode 1 means the child got a partial module (bad.) No
     57                 # exitcode (but a hang, which manifests as 'got pid 0')
     58                 # means the child deadlocked (also bad.)
     59                 self.wait_impl(pid)
     60         finally:
     61             try:
     62                 os.kill(pid, signal.SIGKILL)
     63             except OSError:
     64                 pass
     65 
     66 def test_main():
     67     run_unittest(ForkTest)
     68     reap_children()
     69 
     70 if __name__ == "__main__":
     71     test_main()
     72