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Date: Sun, 22 Jun 2003 23:16:38 -0700 (PDT)
From: Julian Elischer <julian@elischer.org>
To: Igor Sysoev <is@rambler-co.ru>
In-Reply-To: <Pine.BSF.4.21.0306211316500.29257-100000@is>
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cc: threads@freebsd.org
Subject: Re: Implementing TLS: step 1
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On Sat, 21 Jun 2003, Igor Sysoev wrote:

> On Fri, 20 Jun 2003, Julian Elischer wrote:
> 
> > > We can implement such scheme on x86:
> > > 
> > > gs -> [ TP                 ] ---> [ TLS                    ]
> > >       [ struct kse_mailbox ]  +-> [ struct kse_thr_mailbox ]
> > >       [      .km_curthread ] -+
> > > 
> > > When UTS would switch to the next thread it should set thread's TLS:
> > > 
> > >      kse_mailbox.km_curthread = NULL;
> > >      gs:[0] = next_thr_tls;
> > >      kse_mailbox.km_curthread = next_kse_thr_mailbox;  
> > 
> > yes and the last line is atomic.. But remember having a NULL curhtread
> > pointer stops upcalls but it is not the ONLY thing that stops upcalls..
> > A flag TMF_NOUPCALLS (spelling?) in the mailbox will also inhibit any
> > upcalls. 1:1 threads (BOUND) threads, (system scope threads?) set this
> > bit, but they still can have a mailbox for other purposes. (e.g. setting
> > mode flags and stuff).
> 
> So NULL curthread is the short term (in UTS only) and atomic method to
> disable upcalls while KMF_NOUPCALL flag is the long term and non-atomic (we
> can not atomically update bit masks in general) method ?

exactly.

> 
> 
> Igor Sysoev
> http://sysoev.ru/en/
> 
> 
>