TLS, 2015 edition

[Szabolcs Nagy]

* Stan Shebs <stanshebs@google.com> [2015-03-31 11:33:06 -0500]:
> On Tue, Mar 31, 2015 at 10:59 AM, Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
> >
> > can you give more details?
> 
> It was getting quite a bit of libc-alpha traffic in late 2013 and
> early 2014, and there is a wiki page:
> 
> https://sourceware.org/glibc/wiki/TLSandSignals
> 

this is a c11 conformance issue

the cited 7.14.1.1p5 is overly strict i think (it is in conflict with
5.1.2.3p5 and renders read access to global consts and floatig-point
arithmetics ub in an asyc signal handler), but even the strict
7.14.1.1p5 allows writing _Thread_local volatile sig_atomic_t variables
from a signal handler (which is broken in glibc now)

> The following posting is the leader for one of several versions that
> Andrew Hunter posted:
> 
> https://sourceware.org/ml/libc-alpha/2013-12/msg00212.html
> 
> The Google-local patch is a descendant of that code. (In theory Google
> ought to have a git branch, but I only see ones for Roland?)
> 

i dont think making lazy binding signal safe is the right approach
because of the increased complexity

removing lazy binding for tls seems simpler

> Stan