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53 lines
1.7 KiB
Python
53 lines
1.7 KiB
Python
# This is a variant of the very old (early 90's) file
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# Demo/threads/bug.py. It simply provokes a number of threads into
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# trying to import the same module "at the same time".
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# There are no pleasant failure modes -- most likely is that Python
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# complains several times about module random having no attribute
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# randrange, and then Python hangs.
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import thread
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from test_support import verbose, TestSkipped
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critical_section = thread.allocate_lock()
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done = thread.allocate_lock()
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def task():
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global N, critical_section, done
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import random
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x = random.randrange(1, 3)
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critical_section.acquire()
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N -= 1
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if N == 0:
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done.release()
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critical_section.release()
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# Tricky: When regrtest imports this module, the thread running regrtest
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# grabs the import lock and won't let go of it until this module returns.
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# All other threads attempting an import hang for the duration. Since
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# this test spawns threads that do little *but* import, we can't do that
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# successfully until after this module finishes importing and regrtest
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# regains control. To make this work, a special case was added to
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# regrtest to invoke a module's "test_main" function (if any) after
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# importing it.
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def test_main(): # magic name! see above
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global N, done
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import imp
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if imp.lock_held():
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# This triggers on, e.g., from test import autotest.
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raise TestSkipped("can't run when import lock is held")
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done.acquire()
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for N in (20, 50) * 3:
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if verbose:
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print "Trying", N, "threads ...",
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for i in range(N):
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thread.start_new_thread(task, ())
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done.acquire()
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if verbose:
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print "OK."
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if __name__ == "__main__":
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test_main()
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