imapd's hang when maxchild count is reached

[Sebastian Hagedorn]

-- Lawrence Greenfield <leg+ at andrew.cmu.edu> is rumored to have mumbled on 
Samstag, 1. Februar 2003 16:34 Uhr -0500 regarding Re: imapd's hang when 
maxchild count is reached:

>    Date: Fri, 31 Jan 2003 23:25:29 +0100
>    From: Sebastian Hagedorn <Hagedorn at uni-koeln.de>
> [...]
>    When the number of impad processes reaches 200, no more processes are
>    spawned, just as it should be. However, sometimes, not immediately,
> but     definitely after a while *all* imapd processes will hang if we
> try to open     more connections to port 143. This is 100% reproducible.
> If we kill one of     the scripts and the number of processes goes down,
> all the imapd's get     unstuck, but not until that happens.
>
> What do you mean by "hang"? Do they actually stop answering their
> current IMAP commands? Do they stop answering new connections when
> their current one goes away?

Sorry, I should've been more precise. I mean the former: *all* existing 
imapd processes stop functioning, i.e. they don't respond to commands 
anymore. I verified that at this point it is still possible to open other 
types of connections, e.g. POP. So master seems to be principally 
functional.

> I don't see any particular reason for (either) phenomenon making a quick
> gaze at the code.
>
> Probably grabbing the "strace" and a gdb backtrace of a "hung" imapd
> process would help figure out what they're waiting for. Might as well
> do master, too.

We straced master, which stayed in a select() call. I'll do the other 
things you recommend next week.

Thanks, Sebastian
--
Sebastian Hagedorn M.A. - RZKR-R1 (Flachbau), Zi. 18, Robert-Koch-Str. 10
Zentrum für angewandte Informatik - Universitätsweiter Service RRZK
Universität zu Köln / Cologne University - Tel. +49-221-478-5587
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