From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Tue, 14 Oct 2008 10:28:55 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-core] __thread instead of pthread_get/setspecific
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To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: xenomai-core <xenomai@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.