Date: Tue, 30 Mar 2004 09:35:49 +0100 From: Doug Rabson <dfr@nlsystems.com> To: Daniel Eischen <eischen@vigrid.com> Cc: freebsd-threads@freebsd.org Subject: Re: Thread Local Storage Message-ID: <200403300935.49999.dfr@nlsystems.com> In-Reply-To: <Pine.GSO.4.10.10403291718320.29683-100000@pcnet5.pcnet.com> References: <Pine.GSO.4.10.10403291718320.29683-100000@pcnet5.pcnet.com>
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On Monday 29 March 2004 23:36, Daniel Eischen wrote: > On Mon, 29 Mar 2004, Doug Rabson wrote: > > On Monday 29 March 2004 22:56, Daniel Eischen wrote: > > > On Mon, 29 Mar 2004, Doug Rabson wrote: > > > > On Monday 29 March 2004 22:26, Daniel Eischen wrote: > > > > > On Mon, 29 Mar 2004, Doug Rabson wrote: > > > > > > Surely the GNU TLS ABI is preferable? It generates much > > > > > > smaller code and needs many fewer relocations. > > > > > > > > > > No, we don't want an LDT for every thread and don't want > > > > > to force a syscall for a thread switch. > > > > > > > > But the code it generates is at least twice the size for > > > > dynamic TLS. It seems that the GNU people have done a better > > > > job defining the TLS abi for i386. > > > > > > About the only thing that uses TLS that I know is nvidia's > > > openGL. If you design an API correctly, there's no need > > > for TLS. I would hope that it's usage would be limited. > > > > I'd quite like to see us use it for stuff like errno, _res and > > other uglification currently in libc. Not until the 6.x timeframe > > though. > > I'd like to see libc free of TLS ;-) The _res stuff can be > avoided by modifying the implementation to use thread-safe > APIs. The current _res stuff can _almost_ be eliminated > by passing using pthread_getspecific() once and passing > the _res around internal APIs. That's actually a pretty > simple change. Unfortunately pthread_setspecific() and pthread_getspecific() don't work for non-threaded programs whereas 'int __thread errno' works anywhere. It would even work for evil cases where libpthread is loaded after program startup with dlopen.
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