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Date:      Mon, 15 Jun 1998 10:43:23 -0500
From:      Jonathan Lemon <jlemon@americantv.com>
To:        Matthew Dillon <dillon@backplane.com>
Cc:        freebsd-bugs@FreeBSD.ORG
Subject:   Re: i386/6944: bug in i386/isa/icu_ipl.s - AST gets lost, causes extreme network slowdown when cpu-bound processes present, possibly other problems
Message-ID:  <19980615104323.11642@right.PCS>
In-Reply-To: <199806150210.TAA17801@freefall.freebsd.org>; from Matthew Dillon on Jun 06, 1998 at 07:10:01PM -0700
References:  <199806150210.TAA17801@freefall.freebsd.org>

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On Jun 06, 1998 at 07:10:01PM -0700, Matthew Dillon wrote:
> The following reply was made to PR i386/6944; it has been noted by GNATS.
> 
> From: Matthew Dillon <dillon@backplane.com>
> To: Bruce Evans <bde@zeta.org.au>
> Cc: bde@zeta.org.au, dillon@backplane.com, FreeBSD-gnats-submit@FreeBSD.ORG
> Subject: Re: i386/6944: bug in i386/isa/icu_ipl.s - AST gets lost, causes extreme network slowdown when cpu-bound processes present, possibly other problems
> Date: Sun, 14 Jun 1998 19:00:43 -0700 (PDT)
> 
>      Fubar.  I can't reproduce the xterm example on BEST's machines (running
>      2.2.6).  It's definitely reproduceable on my machine (3.0-current).
>  
>      I would like to track down what is causing the problem, so if anyone has
>      any suggestions on where the cpl can be checked for illegal values,
>      I'd appreciate it.  I'll retest the VM86 removal to make sure that didn't
>      fix the problem and I'll test the AUTOEOI configs as well.
>  
>      As far as I can tell, the only two places where the bug can possibly be
>      are in the interface driver (pci/if_de.c) or the UDP/IP stack.
>  

I recently observed something similar with doscmd/VM886.  When running
a cpu-bound process (rc5, for example), the cpl is not being reset to 0
when the doscmd process exits.  Breaking to ddb and single-stepping 
across the iret instruction in doreti will sometimes `reset' the cpl.

I'm pretty sure that this isn't a problem with the VM86 code, as I've
seen this problem before (cf: doreti_stop in ipl.s), but this also happens
even when not attempting to run in vm86 mode.
--
Jonathan

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