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From Edgar Frank <ef-li...@email.de>
Subject Re: [long] problems with brigade handling and thread safety
Date Thu, 03 Dec 2009 14:12:39 GMT
Graham Leggett wrote:
> As soon as I read this the first thing that leaped to mind was
> "pool lifetimes".

Thank you very much for your detailled reply. I thought I
was aware of pool lifetimes before encountering this issue. What
really surprised me was that if I put e.g. a heap bucket (as
apr_brigade_split_line does) from one brigade into another, this
couples these brigades in terms of pools and thread safety.

In my opinion this creates a very dangerous situation in very
harmlessly looking code and is really hard to debug if you don't
know that you're up to. As I had race conditions instead of
crashes, the APR_BUCKET_DEBUG and APR_RING_DEBUG macros could
just bounce me a little bit into the right direction (by crashing
sometimes instead of weird things happening). But as I was not
aware of the problem, the stack traces left me clueless.

I understand it now, but I think it would help people who are new
to bucket brigades very much, if this behaviour would be clearly
pointed out (personally preferred in code/doxygen doc). I
could also think of special debug code to test such cases, but
would imagine that this is really difficult to implement.

By the way, I don't want to bother you with the full details of
my problem unsolicited. If you're interested, just let me know.

Regards,
Edgar


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