Message 135087 - Python tracker (original) (raw)

Since the commit c9207c6ce24a, test_signal fails on OpenIndiana:

http://www.python.org/dev/buildbot/all/builders/x86%20OpenIndiana%203.x/builds/1179

ERROR: test_block_unlock (test.test_signal.PthreadSigmaskTests)

Traceback (most recent call last): File "/export/home/buildbot/64bits/3.x.cea-indiana-amd64/build/Lib/test/test_signal.py", line 539, in test_block_unlock self.assertEqual(set(old_mask) ^ set(blocked), {signum}) File "/export/home/buildbot/64bits/3.x.cea-indiana-amd64/build/Lib/test/test_signal.py", line 501, in handler 1/0 ZeroDivisionError: division by zero

This is because a thread different than the main thread receives the signal and calls the signal handler. Antoine found that "python -m test_pydoc test_signal" is enough to reproduce the problem (on any OS, or at least on Linux). test_pydoc loads a lot (all?) of Python modules including _tkinter, and _tkinter (libtcl) creates a C thread which waits events using select().

I see 3 solutions:

a) Use pthread_kill() to send the signal directly to the right thread (the main thread)

b) Destroy _tkinter: Tcl_Finalize() exits the thread, but this function is never called. _tkinter.c contains the following code: #if 0 /* This was not a good idea; through bindings, Tcl_Finalize() may invoke Python code but at that point the interpreter and thread state have already been destroyed! */ Py_AtExit(Tcl_Finalize); #endif

c) Skip the test if the _tkinter thread is present. Check if the _tkinter module is loaded should be enough to check if the Tcl thread is running. Unload the _tkinter module is not possible: modules written in C cannot be unloaded. But it is possible to remove all references from the Python object space, so check >'_tkinter' in sys.modules< is maybe not reliable.

I don't know if some platforms have pthread_sigmask() but not pthread_kill().

I have a patch to expose pthread_kill(), sigpending() and sigwait(). I will publish it tomorrow for a review.

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test_signal doesn't fail on all platforms. Possible reasons: