Re: Moving pthread_(cond|mutex) to libc

[Alan Barrett <apb%cequrux.com@localhost>]

On Tue, 22 Jan 2013, Emmanuel Dreyfus wrote:
> Starting with NetBSD 6.0, libpthread is cursed with the NOLOAD 
> flag, which means it cannot be loaded by dlopen(). The problem 
> is that we can easily get to dlopen'able modules that do not 
> use pthreads, but are linked to libraries that are linked with 
> -lpthread. Such module cannot be loaded anymore in NetBSD 6.0.

Yes.  And such modules would not work properly even if they were 
allowed to be loaded.

> It seems there is a conensus that pthread_(cond|mutex) should 
> move to libc so that libpthread could be freed from NOLOAD [See 
> http://mail-index.netbsd.org/tech-pkg/2013/01/19/msg010635.html]. 
> I started looking at it and of course it raises a few 
> problems.

Please don't cite a thread from tech-pkg as consensus for 
anything in the base system.  You could use it as the start of a 
discussion, but it's possible that a different conclusion will be 
reached.

Also, please lets get the overall design clarified before you 
write any code.  I'd like to see a description of what would 
happen if a program starts without pthreads, creates and uses some 
condvars and mutexes, and then loads libpthread and continues 
using the already-created condvars and mutexes.

--apb (Alan Barrett)