From owner-freebsd-current@FreeBSD.ORG  Fri Feb 20 16:38:46 2004
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Date: Fri, 20 Feb 2004 19:38:45 -0500 (EST)
From: Daniel Eischen <eischen@vigrid.com>
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To: "Brian F. Feldman" <green@FreeBSD.org>
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Subject: Re: Testers wanted: reentrant resolver 
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On Fri, 20 Feb 2004, Brian F. Feldman wrote:

> Daniel Eischen <eischen@vigrid.com> wrote:
> > Ugh, can you put h_errno inside the per-thread res stuff.
> > We shouldn't need to have to add special hooks in the
> > threads libraries for this.
> 
> Please explain what you're saying further.  On correctly-threaded operating 
> systems, h_errno is just like errno -- and I made it act EXACTLY as errno 
> acts, and is per-thread storage for everything but the first thread.  It's 
> absolutely necessary if we want to return the correct errors; even if 
> everything else in the world is totally reentrant, if h_errno isn't, the 
> wrong errors can be returned!  What "special hooks" do you mean?  There's no 
> way to not change probably hundreds of lines of code without actually doing 
> the work to make h_errno thread-safe.  It's the only proper thing to do.

The implementation of __h_errno() need not depend on something
special stuffed in struct pthread.  Use thread-local storage
(pthread_getspecific()) like you did for the res_send_private
stuff.  Especially since these interfaces should be deprecated
in favor of what looks to be BIND 8.2.2 interfaces (according
to the Solaris man pages).

-- 
Dan Eischen