Apply patch for 874900: threading module can deadlock after fork
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index db6b0d7..8c1ecce 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -323,6 +323,82 @@
sys.getrefcount(weak_raising_cyclic_object())))
+class ThreadJoinOnShutdown(unittest.TestCase):
+
+ 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'
+ \n""" + script
+
+ import subprocess
+ p = subprocess.Popen([sys.executable, "-c", script], stdout=subprocess.PIPE)
+ rc = p.wait()
+ self.assertEqual(p.stdout.read(), "end of main\nend of thread\n")
+ self.failIf(rc == 2, "interpreter was blocked")
+ self.failUnless(rc == 0, "Unexpected error")
+
+ def test_1_join_on_shutdown(self):
+ # The usual case: on exit, wait for a non-daemon thread
+ script = """if 1:
+ import os
+ t = threading.Thread(target=joiningfunc,
+ args=(threading.current_thread(),))
+ t.start()
+ time.sleep(0.1)
+ print 'end of main'
+ """
+ self._run_and_join(script)
+
+
+ def test_2_join_in_forked_process(self):
+ # Like the test above, but from a forked interpreter
+ import os
+ if not hasattr(os, 'fork'):
+ return
+ script = """if 1:
+ childpid = os.fork()
+ if childpid != 0:
+ os.waitpid(childpid, 0)
+ sys.exit(0)
+
+ t = threading.Thread(target=joiningfunc,
+ args=(threading.current_thread(),))
+ t.start()
+ print 'end of main'
+ """
+ self._run_and_join(script)
+
+ 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.
+ import os
+ if not hasattr(os, 'fork'):
+ return
+ 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)
+
+
class ThreadingExceptionTests(unittest.TestCase):
# A RuntimeError should be raised if Thread.start() is called
# multiple times.
@@ -363,7 +439,9 @@
def test_main():
test.test_support.run_unittest(ThreadTests,
- ThreadingExceptionTests)
+ ThreadJoinOnShutdown,
+ ThreadingExceptionTests,
+ )
if __name__ == "__main__":
test_main()
diff --git a/Lib/threading.py b/Lib/threading.py
index bfca44c..8a1de42 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -825,6 +825,37 @@
from _threading_local import local
+def _after_fork():
+ # This function is called by Python/ceval.c:PyEval_ReInitThreads which
+ # is called from PyOS_AfterFork. Here we cleanup threading module state
+ # that should not exist after a fork.
+
+ # Reset _active_limbo_lock, in case we forked while the lock was held
+ # by another (non-forked) thread. http://bugs.python.org/issue874900
+ global _active_limbo_lock
+ _active_limbo_lock = _allocate_lock()
+
+ # fork() only copied the current thread; clear references to others.
+ new_active = {}
+ current = current_thread()
+ with _active_limbo_lock:
+ for ident, thread in _active.iteritems():
+ if thread is current:
+ # There is only one active thread.
+ new_active[ident] = thread
+ else:
+ # All the others are already stopped.
+ # We don't call _Thread__stop() because it tries to acquire
+ # thread._Thread__block which could also have been held while
+ # we forked.
+ thread._Thread__stopped = True
+
+ _limbo.clear()
+ _active.clear()
+ _active.update(new_active)
+ assert len(_active) == 1
+
+
# Self-test code
def _test():