Milter-greylist

> I figured out that sometimes it takes me ages
> to reload the configuration file. The last time it
> took 109 seconds. (I am still investigating the
> reason, I suspect that it was due to an overloaded
> MX peer. The system which was loading the new config file
> wasn't under heavy load.)

What takes so long? Do we have DNS resolutions at config file reload
time?
 
> The problem is that during the long reload time a lot
> of sendmail processes went into error state timing out
> on the milter-greylist.
> 
> The patch I sent months ago are blocking all the threads during the config
> reload. I am attaching now an other patch which fixes this behaviour. One
> thread will be used to load the config file. The other threads may go
> ahead returning immediately from conf_update() and use the old in memory
> configuration during the new config load.

That's nice. This could be improved a bit by letting the thread that
calls conf_update return and use the old config. It can be done easily
by tweaking conf_load:
- Remove pthread_join
- Handle a structure containing the attribute and the config file stream
to the spawned thread that reloads the config, and free the attribute
and close the config file from that thread. 

What do you think?

> Actually it would be possible to
> have more than one config load to run simultaneously if the config load
> takes too long and the config file has been modified again during this
> time. This would be a problem due to some unprotected external variable
> use from multiple threads. To avoid this I introduced a new variable to
> limit the number of threads to one loading the new config file.
> 
> I suspect that the problem with SIGSEGV (see comments in the code)
> may be rather related to multiple simultaneous config loads.

No I tracked it down on a test machine, with no activity at all except
what I produced. The SIGSEGV was produced by a stack overflow. The way
the yacc parser was made caused huge memory usage. This has been fixed,
but we still book 2MB just in case.

-- 
Emmanuel Dreyfus
Il y a 10 sortes de personnes dans le monde: ceux qui comprennent 
le binaire et ceux qui ne le comprennent pas.
manu@...