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Date:      Mon, 29 Nov 1999 07:25:18 -0500
From:      "Daniel M. Eischen" <eischen@vigrid.com>
To:        Julian Elischer <julian@whistle.com>
Cc:        arch@freebsd.org
Subject:   Re: Threads stuff
Message-ID:  <384270AE.D0250340@vigrid.com>
References:  <Pine.BSF.4.10.9911282113490.544-100000@current1.whistle.com>

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Julian Elischer wrote:
> > Yes, I understood them just fine :)  I'm still not sold on the new
> > syscall gate and IOCB, because I think we have to make at least one
> > system call when threads are switched or resumed.
> >
> 
> I'm not completely sold on them either.
> I just have a gut feeling on it based on doing this for 25 years.

Well let's see if we can make them work, now that we know more
of the issues.

One potential problem I see with placing the IOCBs at a fixed location
in the calling threads stack is that you then are tied to having
to find TSD for every system call.  I say TSD, but really mean
you have to go through the same hoops as getting TSD.  We don't
know how fast this is going to be for i386.

I think if we allocate the IOCB from the stack at the time
of the system call, it will be faster.  If the thread blocks,
then kernel can provide enough information so that the UTS
upcall can find the IOCB, set the IOCBptr in the current
thread, mark the thread as blocked, etc.

Dan Eischen
eischen@vigrid.com




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