Date: Mon, 7 May 2001 13:12:05 -0400 (EDT) From: Daniel Eischen <eischen@vigrid.com> To: John Polstra <jdp@polstra.com> Cc: current@freebsd.org Subject: Re: Rfork'd threads, signals, and LDTs Message-ID: <Pine.SUN.3.91.1010507130624.20611A@pcnet1.pcnet.com> In-Reply-To: <200105071647.f47GlgQ64138@vashon.polstra.com>
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On Mon, 7 May 2001, John Polstra wrote: > In article > <Pine.SUN.3.91.1010507073832.26371A-100000@pcnet1.pcnet.com>, Daniel > Eischen <eischen@vigrid.com> wrote: > > > I think the only reason we used %fs instead of %gs was WINE. I > > think Linux uses %gs for TSD, so if WINE were to ever depend on > > linuxthreads, one of them would have to change. > > At least on Red Hat 7.0 (glibc-2.1.92-14), Linux does not use a > segment register to find TSD. It aligns all stacks at a multpile > of 2MB and then does bit ops on the current stack pointer to find a > thread control block at the base (highest address) of the stack. > > There is an alternate implementation in that version of glibc which > uses %gs to find TSD. However, it is not used in this version of > Linux. I don't know whether it's used in other versions or not. I was looking at our linuxthreads port and noticed some %gs fiddling. If linuxthreads wants to allow POSIX semantics for specifying thread stack allocation, they'll have to stop relying on stack alignments for TSD. -- Dan Eischen To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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