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From Joe Orton <jor...@redhat.com>
Subject Re: slotmem API notes
Date Fri, 15 May 2009 16:06:56 GMT
On Thu, May 14, 2009 at 04:23:22PM -0700, Chris Darroch wrote:
>   However, note that any choices we make here also, I believe,
> impacts the socache API, which has identical issues around data
> consistency in multi-process/multi-thread contexts.  Personally
> I'd love to see these two APIs be as congruent as possible
> since they both do very similar things.  (Joe, any comments?)

w.r.t. locking, my take for socache was: you either duplicate the code 
in every provider, or you duplicate the code in every API consumer, so 
it wasn't obvious what was best.  I expected the latter would be both 
simpler and more flexible, so went for that.

There's a general problem that we have mutex code duplicated poorly 
across the server:

1) config hooks allowing the admin to specify location and maybe lock 
type,
2) initialization, mostly unified via _set_global_mutex_perms,
3) lock/unlock calls which maybe log errors, and maybe fail correctly

which is a bit of a mess.  I've wondered before whether some central API 
could simplify this, such that with little extra module code, you could 
get a mutex which could be configured via e.g.:

  Mutex slotmem fcntl:/var/run/slotmem.lck

and if not configured, sensible defaults are used.  But I'm not sure 
whether it could be done to really improve the server and avoid being an 
abstraction-fest code-bloat effort.

Regards, Joe




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