[pyOpenSSL] Python core dumps when using pyOpenSSL 0.8.0 and threads

[Gustavo Moreira]

I could reproduce the crash. This happens only (at least in my case) in
Win32 platform, I tried it on linux and does not occur.
Just add a couple of certificates in the test-crash-server.py, class
handler_class, method __init__. Run test-crash-server.py and then
test-crash-client.py, and in seconds python crashes!.

Gustavo.


On 03/17/2009, Jean-Paul Calderone <exarkun at divmod.com> wrote:
>
> On Tue, 17 Mar 2009 19:57:09 +0100, "M.-A. Lemburg" <mal at egenix.com>
> wrote:
> >On 2009-03-17 15:59, Jean-Paul Calderone wrote:
>
> > [snip]
>
> >
> >Perhaps it's related to this notice of caution in thread.c:
> >
> >"""
> >Use PyThread_set_key_value(thekey, value) to associate void* value with
> >thekey in the current thread.  Each thread has a distinct mapping of
> thekey
> >to a void* value.  Caution:  if the current thread already has a mapping
> >for thekey, value is ignored.
> >"""
>
>
> Oh, boy.  Yes, that could be it.  I assumed it was more like setting a key
> in a Python dictionary.
>
>
> >If value is ignored, MY_BEGIN_ALLOW_THREADS() won't save the current
> >thread state, but leave the old one in place.
>
>
> So only the first MY_BEGIN_ALLOW_THREADS per thread does anything.  That
> could break things, I guess. :)
>
>
> >
> >It's also possible for this API to fail in case of a memory issue,
> >but the macro doesn't check for this, so the application may end
> >up not storing anything at all.
>
>
> So the macros should do error checking as well (assuming it makes sense
> to continue to use TLS at all).
>
>
> >MY_END_ALLOW_THREADS() needs to remove the stored TLS value in order
> >to make room for the next MY_BEGIN_ALLOW_THREADS() call.
> >
> >Note that I'm not sure using TLS is a good idea: the implementations
> >are highly platform dependent and may have undocumented/unwanted
> >side-effects.
>
>
> Can you give some examples?  The only thing I'm aware of is that
> performance may differ wildly from platform to platform, but I thought
> it was pretty good on all mainstream platforms these days.
>
>
> >IMHO, it's safer to store the thread id together with the tstate
> >itself in the context and then check whether the thread id matches
> >before restoring the state.
> >
> >This has the additional benefit of making some form of error
> >raising possible in order to inform the programmer of the obvious
> >mistake in using the connections from multiple threads,
> >even if it's just a plain fprintf(stderr, ...).
>
>
> That sounds essentially like the idea I mentioned in my earlier reply
> (the one I compared to SQLite).  I see how all of that logic could be
> wrapped up in the MY_BEGIN/END_ALLOW_THREADS macro now, so I'm even
> more inclined to go that route now.
>
> Tests or scripts that produce failures would still be very helpful.
> Clearly the test suite doesn't exercise the buggy codepaths currently,
> and it seems neither does thread-crash.py (probably because it chokes
> so quickly due to its misuse of Connections in multiple threads).
>
> If I can reproduce the problem others are seeing, I'll be able to tell
> if a particular change actually fixes it.  Otherwise I'm just guessing. :)
>
>
> Jean-Paul
>
>
>
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