1 files changed, 76 insertions, 0 deletions
diff --git a/lib/python2.7/test/test_threaded_import.py b/lib/python2.7/test/test_threaded_import.py
new file mode 100644
index 0000000..b31fdf1
--- /dev/null
+++ b/lib/python2.7/test/test_threaded_import.py
@@ -0,0 +1,76 @@
+# This is a variant of the very old (early 90's) file
+# Demo/threads/bug.py.  It simply provokes a number of threads into
+# trying to import the same module "at the same time".
+# There are no pleasant failure modes -- most likely is that Python
+# complains several times about module random having no attribute
+# randrange, and then Python hangs.
+
+import unittest
+from test.test_support import verbose, TestFailed, import_module
+thread = import_module('thread')
+
+critical_section = thread.allocate_lock()
+done = thread.allocate_lock()
+
+def task():
+    global N, critical_section, done
+    import random
+    x = random.randrange(1, 3)
+    critical_section.acquire()
+    N -= 1
+    # Must release critical_section before releasing done, else the main
+    # thread can exit and set critical_section to None as part of global
+    # teardown; then critical_section.release() raises AttributeError.
+    finished = N == 0
+    critical_section.release()
+    if finished:
+        done.release()
+
+def test_import_hangers():
+    import sys
+    if verbose:
+        print "testing import hangers ...",
+
+    import test.threaded_import_hangers
+    try:
+        if test.threaded_import_hangers.errors:
+            raise TestFailed(test.threaded_import_hangers.errors)
+        elif verbose:
+            print "OK."
+    finally:
+        # In case this test is run again, make sure the helper module
+        # gets loaded from scratch again.
+        del sys.modules['test.threaded_import_hangers']
+
+# Tricky:  When regrtest imports this module, the thread running regrtest
+# grabs the import lock and won't let go of it until this module returns.
+# All other threads attempting an import hang for the duration.  Since
+# this test spawns threads that do little *but* import, we can't do that
+# successfully until after this module finishes importing and regrtest
+# regains control.  To make this work, a special case was added to
+# regrtest to invoke a module's "test_main" function (if any) after
+# importing it.
+
+def test_main():        # magic name!  see above
+    global N, done
+
+    import imp
+    if imp.lock_held():
+        # This triggers on, e.g., from test import autotest.
+        raise unittest.SkipTest("can't run when import lock is held")
+
+    done.acquire()
+    for N in (20, 50) * 3:
+        if verbose:
+            print "Trying", N, "threads ...",
+        for i in range(N):
+            thread.start_new_thread(task, ())
+        done.acquire()
+        if verbose:
+            print "OK."
+    done.release()
+
+    test_import_hangers()
+
+if __name__ == "__main__":
+    test_main()