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Date:      Tue, 28 Nov 2000 15:26:59 -0800 (PST)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Julian Elischer <julian@elischer.org>
Cc:        arch@FreeBSD.org, Daniel Eischen <eischen@vigrid.com>
Subject:   Re: Thread-specific data and KSEs
Message-ID:  <XFMail.001128152659.jhb@FreeBSD.org>
In-Reply-To: <3A242FAF.313295F0@elischer.org>

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On 28-Nov-00 Julian Elischer wrote:
> Daniel Eischen wrote:
>> 
>> On Mon, 27 Nov 2000, Julian Elischer wrote:
>> >
>> > One thing I just realised:
>> >
>> > If we are using defered FP state saving and restoring in the kernel, then
>> > we
>> > will have troubles with that when switching threads in userland, since the
>> > handler for that is in the kernel. Of course we could set the place for it
>> > in
>> > the KSE mailbox and let the kernel save the information when it needs it.
>> 
>> Our current threads library knows when to save and restore FP state;
>> it currently only happens when a signal is received (for i386, I think
>> alpha FP state is always saved both in jmp_buf and ucontext_t)
> 
> That's comforting.
> 
> I was looking at the ia64 specs..
> that thing presents some interesting challenges in regards to 
> the 'intelligent' stack it has. It will be very hard to play 
> games with it's stack when it's cached inside the chip. I 
> presume they have a scheme to allow such things as threads, 
> but it looks a mess from here.

You can disable the RSE and flush it out.  This is done during context switches
for example, and to setup the stack frame for signal handling I believe, though
signal handling isn't quite finished yet.

-- 

John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/


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