Nvidia, TLS and __thread keyword -- an observation

[Marcel Moolenaar]

On Tue, Jun 17, 2003 at 03:02:20PM -0700, Julian Elischer wrote:
> 
> 
> On Tue, 17 Jun 2003, Marcel Moolenaar wrote:
> 
> > Guys,
> > 
> > In short: Don't bash Nvidia. What they do is not uncommon. Well,
> > maybe in Open Source environments. So please end this thread,
> > unless people get constructive.
> 
> I think its already ended..
> 
> basically:
> We should alwasy be able to use (on i386) the sam amethods outlined for
> solaris. 
> Not quite as quick as those for Linux but more general.

I'm not sure you understand the issue (I can easily be wrong, I just
don't see the evidence in your statement). To support the __thread
keyword, our thread library needs to create the TLS as defined in the
binary and its dependent shared libraries by virtue of the .tdata and
.tbss sections/segments, based on the image of the TLS as constructed
by the RTLD for the initial set of modules (created for the initial
thread) and amended by TLS space defined in the dynamicly loaded
libraries; and the TLS has to be created for every new thread at the
time the thread itself is created. This TLS allocation has to be made
accessable in accordance with runtime specifications for the supported
architectures (libthr: i386 & ia64; libkse: i386 currently -- more to
follow) and in line with the access sequences created by the compiler,
and using the static relocations known to the static linker and dynamic
relocations of which the support needs to be added to RTLD.

The static TLS model requires the least amount of work: add support
to allocate the TLS image for every thread creation and point the
thread pointer to it in a way compatible with the runtime spec.

The dynamic TLS model requires more substantial changes and involves
RTLD as well. This is the model that requires __tls_get_addr().

-- 
 Marcel Moolenaar	  USPA: A-39004		 marcel at xcllnt.net