Date: Sat, 15 Apr 2000 11:23:11 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Brian Fundakowski Feldman <green@FreeBSD.ORG> Cc: Alfred Perlstein <bright@wintelcom.net>, Michael Reifenberger <root@nihil.plaut.de>, <current@FreeBSD.ORG>, alc@FreeBSD.ORG Subject: Re: panic: vm_object_shadow: source object has OBJ_ONEMAPPING set. Message-ID: <200004151823.LAA79731@apollo.backplane.com> References: <Pine.BSF.4.21.0004151328500.16430-100000@green.dyndns.org>
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:Well, first the question must be answered, in an absolute yes or no:
:is it wrong in the first place to have OBJ_ONEMAPPING set with a ref_count
:of more than 1? I'd accept an authoritative answer about this from
:alc, dillon, dyson, or luoqi, who are all very familiar with the new
:VM.
:--
: Brian Fundakowski Feldman \ FreeBSD: The Power to Serve! /
: green@FreeBSD.org `------------------------------'
It is totally legal for OBJ_ONEMAPPING to be set even if the ref_count
is greater then 1. The ref_count has no bearing on the shareability
of the object any more. The tests were there before due to all sorts
of crud that had been hacked in in the 2.2.x and 3.x era to get around
serious bugs in the OBJ_ONEMAPPING flag and elsewhere in the VM system.
Note that the ref_count == 1 test in the vm_object_shadow optimization
should be left intact. This optimization requires a much stricter set
of tests because we do not want to assume sharability of an object
if someone else (the 'else' being 'someone unknown to us') has a reference
on it, even if OBJ_ONEMAPPING is set.
-Matt
Matthew Dillon
<dillon@backplane.com>
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