Bugs item #1166660, was opened at 2005-03-19 21:48
Message generated for change (Comment added) made by mwh
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Category: Threads
Group: Platform-specific
Status: Open
Resolution: None
Priority: 5
Submitted By: Yariv Ido (dcoder)
Assigned to: Michael Hudson (mwh)
Summary: The readline module can cause python to segfault

Initial Comment:
When starting an interactive interpreter in another
thread, with readline's completion functionality, there
exists a race condition which causes the Python
interpreter to segfault. There's a small discussion
about this bug at
<http://www.scipy.net/roundup/ipython/issue30>.

Attached is a small proof-of-concept code. Please note
that some people couldn't reproduce this on slower
machines. I've managed to reproduce it on several Linux
systems (Dual Xeon computers), using Python 2.3.4, 2.4
and 2.4.1c2.

Thanks in advance.

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>Comment By: Michael Hudson (mwh)
Date: 2005-03-30 11:10

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While it does seem a bit odd to call the completer function in the thread 
that calls set_completer and not the thread that calls readline(), I don't 
immediately see how this is leading to segfaults.  Do you?

Anyway, I can reproduce the problem, so if your fix fixes it, I'll check it in 
(irrespective of fixing segfaults, it just makes more sense).

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Comment By: Michael Hudson (mwh)
Date: 2005-03-29 13:10

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Unless there's some reason to suspect they share a common
cause (and, I don't see one) a second report is more
appropriate.

Also, if you understand what's going on, you can explain
there :)

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Comment By: Yariv Ido (dcoder)
Date: 2005-03-28 23:33

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I haven't (Completely forgot about it, after finding the
main one...). Should I post a seperate bug report, or will
this one do?

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Comment By: Michael Hudson (mwh)
Date: 2005-03-27 21:43

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I'll take a look at this.

Did you submit a bug on the set_startup_hook problem mentioned in the 
ipython tracker?

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Comment By: Yariv Ido (dcoder)
Date: 2005-03-19 23:59

Message:
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I may be completely off track here, but shouldn't
on_completion(...) (readline.c) use _PyOS_ReadlineTState
instead of completer_tstate to restore the GIL?

Also, in readline_until_enter_or_signal(...), shouldn't
PyEval_SaveThread()'s return value be saved back to 
_PyOS_ReadlineTState?

It seems that these patches manage to fix the above
segmentation fault...

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