Re: per-thread init for overlays?

[Howard Chu <hyc@symas.com>]

Aaron Richton wrote:
> I'm linking an external library with my overlay that needs per-process
> initialization, which I handle in my overlay_init function. I clean that
> initialization up in the on_bi.bi_destroy function. (Feel free to yell at
> me if that's the wrong place, but it seems to work.)
>   
That sounds fine.
> My question is for thread-specific initialization. The external library
> claims thread safety, but in addition to the process init() call, there is
> a per-thread thread_init()/thread_end() call. They recommend,
> unsurprisingly, placing this near a pthread_create()/pthread_destroy() or
> moral equivalent. Is there any appropriate place to do this in the
> overlay?
>   
Not really. Operations execute from a thread pool; thread 
creation/destruction are hidden in the pool manager (and typically there 
is no thread destruction at all). I can't really imagine what they need 
to init and destroy, but if the issue is to make sure that each 
operation gets a fresh context then you probably have to call 
thread_init at the beginning of each operation the overlay intercepts, 
and thread_end in the cleanup handler. If they really only care about 
getting called once per created thread (and they don't care that each 
thread is long-lived and gets re-used over and over) then you may have 
to use the ldap_pvt_thread_pool_getkey/setkey functions. Set a key to 
indicate that you've done the init, with a free handler that calls 
thread_end. You'll have to test for the key at the beginning of each 
operation, and set it if the key doesn't exist yet.

--
 -- Howard Chu
 Chief Architect, Symas Corp.  http://www.symas.com
 Director, Highland Sun        http://highlandsun.com/hyc
 OpenLDAP Core Team            http://www.openldap.org/project/