[XML-SIG] Advice on how to deal with locking problems using python-wrapped
C libs in MT frameworks like Zope/Twisted?
Craeg K Strong
Sun, 30 Mar 2003 16:33:10 -0500
Martin v. L=F6wis wrote:
>Craeg K Strong <firstname.lastname@example.org> writes:
>>When libxslt tries to resolve the relative URL, a request is going out
>>which ends up coming back in to Zope. Zope is multi-threaded, so why
>>shouldn't that be able to return successfully? Is libxslt-python someh=
>>holding on to the GIL or-- maybe it is still in the middle of the "read=
>>call and is therefore holding a lock on that resource?
>One would have to know a lot of internal details here that you
>probably have to investigate yourself, unless you can find some
>Zope-and-libxslt guru. Here are some theories:
>1. Zope is not responding since it considers the request incomplete
> One would have to study the 88 bytes request data (use -s2000 on
> strace) to determine whether the request is complete - yet Zope
> may *still* waiting for more data for some reason (e.g. a bug).
>2. Zope is not configured to process more than one request. It accepts
> the connection only since this is in the listen backlog; it doesn't
> actually read the data - not because it couldn't, but because it
> does not want to.
>3. The GIL is held while libxslt makes this request.
>If I think long enough, I can come up with more consistent theories :-)
>Which of these are plausible, I don't know; most likely, the real
>reason would not give a plausible theory.
>What mechanism in libxslt does make the callback? Is that Python code,
>or code implemented in libxslt itself?
I am not sure. The callback is probably in C code. However, the GIL=20
been locked before that by the Python wrapper. libxslt-python may=20
strategy-- lock GIL, descend into C code, return, unlock GIL. I don't=20
Are there some specified questions to ask Daniel?
Craeg K Strong, General Partner
Ariel Partners LLC
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