Re: [Xenomai-core] __thread instead of pthread_get/setspecific

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Jan Kiszka wrote:
> Hi,
> 
> looking into the "xeno_in_primary_mode" thing I wondered how to make the
> thread state quickly retrievable. Going via pthread_getspecific as we do
> for xeno_get_current appears logical - but not optimal. Though
> getspecific is optimized for speed, it remains a function call, a few
> sanity checks, and only finally a TLS variable access. That could be
> achieved in a much lighter way by using a __thread variable.
> 
> But can we assume that all target we support also support the __thread
> storage class? TLS is surely mandatory now: I assume pthread_getspecific
> would become non-RT safe without it, right? Is there anything we
> can/must check for during configure to verify __thread support?

I really think that this optimization is not worth the trouble. Anyway,
I have one question: is an implementation guaranteed to support more
than one __thread variable? Because from ARM implementation I would say
that ARM has only one __thread variable.

-- 
                                                 Gilles.