From owner-cvs-sys  Wed Jun 25 17:26:02 1997
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To: Tor Egge <tegge@FreeBSD.ORG>
cc: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG, cvs-sys@FreeBSD.ORG
Subject: Re: cvs commit: src/sys/i386/i386 vm_machdep.c 
In-reply-to: Your message of "Wed, 25 Jun 1997 12:49:46 PDT."
             <199706251949.MAA26823@freefall.freebsd.org> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Wed, 25 Jun 1997 17:27:02 -0700
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>tegge       1997/06/25 12:49:46 PDT
>
>  Modified files:
>    sys/i386/i386        vm_machdep.c 
>  Log:
>  Block some interrupts during the call to pmap_zero_page in
>  vm_page_zero_idle. This fixes some occurences of the problem
>  reported in PR kern/3216: "panic: pmap_zero_page: CMAP busy"

   This change is wrong. pmap_zero_page() is called to zero-fill pages as the
result of a page fault (trap 12). Page faults are NOT allowed in interrupts,
so the real problem was the page fault, not what you fixed above. The change
above is bad because it introduces long latencies in processing of interrupts,
and this is bad.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project