test_3_join_in_forked_from_thread() of test_threading failed on "x86 Ubuntu Shared 3.x" buildbot:
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[201/354] test_threading
[41179 refs]
[40407 refs]
[40407 refs]
[40407 refs]
Timeout (1:00:00)!
Thread 0x404218c0:
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/subprocess.py", line 466 in _eintr_retry_call
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/subprocess.py", line 1486 in _try_wait
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/subprocess.py", line 1528 in wait
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/test_threading.py", line 455 in _run_and_join
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/test_threading.py", line 518 in test_3_join_in_forked_from_thread
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/unittest/case.py", line 387 in _executeTestPart
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/unittest/case.py", line 442 in run
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/unittest/case.py", line 494 in __call__
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/unittest/suite.py", line 105 in run
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/unittest/suite.py", line 67 in __call__
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/unittest/suite.py", line 105 in run
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/unittest/suite.py", line 67 in __call__
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/support.py", line 1078 in run
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/support.py", line 1166 in _run_suite
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/support.py", line 1192 in run_unittest
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/test_threading.py", line 728 in test_main
  File "./Lib/test/regrtest.py", line 1041 in runtest_inner
  File "./Lib/test/regrtest.py", line 835 in runtest
  File "./Lib/test/regrtest.py", line 659 in main
  File "./Lib/test/regrtest.py", line 1619 in <module>
make: *** [buildbottest] Error 1
program finished with exit code 2
elapsedTime=4426.776675
http://www.python.org/dev/buildbot/all/builders/x86%20Ubuntu%20Shared%203.x/builds/3577/steps/test/logs/stdio
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Code of the test:
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    def _run_and_join(self, script):
        script = """if 1:
            import sys, os, time, threading

            # a thread, which waits for the main program to terminate
            def joiningfunc(mainthread):
                mainthread.join()
                print('end of thread')
                # stdout is fully buffered because not a tty, we have to flush
                # before exit.
                sys.stdout.flush()
        \n""" + script

        p = subprocess.Popen([sys.executable, "-c", script], stdout=subprocess.PIPE)
        rc = p.wait() <~~~ HANG HERE ~~~~
        data = p.stdout.read().decode().replace('\r', '')
        p.stdout.close()
        self.assertEqual(data, "end of main\nend of thread\n")
        self.assertFalse(rc == 2, "interpreter was blocked")
        self.assertTrue(rc == 0, "Unexpected error")

    @unittest.skipUnless(hasattr(os, 'fork'), "needs os.fork()")
    def test_3_join_in_forked_from_thread(self):
        # Like the test above, but fork() was called from a worker thread
        # In the forked process, the main Thread object must be marked as stopped.

        # Skip platforms with known problems forking from a worker thread.
        # See http://bugs.python.org/issue3863.
        if sys.platform in ('freebsd4', 'freebsd5', 'freebsd6', 'netbsd5',
                           'os2emx'):
            raise unittest.SkipTest('due to known OS bugs on ' + sys.platform)
        script = """if 1:
            main_thread = threading.current_thread()
            def worker():
                childpid = os.fork()
                if childpid != 0:
                    os.waitpid(childpid, 0)
                    sys.exit(0)

                t = threading.Thread(target=joiningfunc,
                                     args=(main_thread,))
                print('end of main')
                t.start()
                t.join() # Should not block: main_thread is already stopped

            w = threading.Thread(target=worker)
            w.start()
            """
        self._run_and_join(script)
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