From owner-freebsd-arch  Tue Feb  5 14:53:18 2002
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Date: Tue, 5 Feb 2002 17:53:01 -0500 (EST)
From: Daniel Eischen <eischen@pcnet1.pcnet.com>
To: Julian Elischer <julian@elischer.org>
Cc: Matthew Dillon <dillon@apollo.backplane.com>,
	Dan Eischen <eischen@vigrid.com>, bde@FreeBSD.ORG, peter@FreeBSD.ORG,
	arch@FreeBSD.ORG
Subject: Re: getsetcontext system call
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On Tue, 5 Feb 2002, Julian Elischer wrote:
> On Tue, 5 Feb 2002, Daniel Eischen wrote:
> 
> > On Tue, 5 Feb 2002, Julian Elischer wrote:
> > > On Tue, 5 Feb 2002, Daniel Eischen wrote:
> > > 
> > > > On Tue, 5 Feb 2002, Matthew Dillon wrote:
> > > > >     I thought we were trying to avoid having to make any system calls on
> > > > >     a userland thread context switch.
> > > > 
> > > > In the threads library, we'll use our own library routines to
> > > > do this (hopefully) without having to make a system call.
> > > 
> > > Or maybe use kernel entries that are already hapenning anyway.....
> > 
> > Huh?
> 
> I was thinking that when saving thread context back to userland
> after completing a syscall but before going on to another
> syscall, we can save lots of FP state etc as well.

Yeah, I was assuming that under a KSE enabled process, the state
of blocked threads gets saved out to userland in mcontext_t format
(which would include the FPU state, if used).  But the threads
library can also force a context switch without having it blocked
in the kernel, so the threads library needs the equivalent of a 
getcontext() as well as setcontext().

-- 
Dan Eischen


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