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Date: Sun, 5 Apr 2015 18:47:21 +0300
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: David Wolfskill <david@catwhisker.org>, current@freebsd.org
Subject: Re: panic: Lock vm object not exclusively locked @
 /usr/src/sys/vm/vm_page.c:2637
Message-ID: <20150405154721.GO64665@FreeBSD.org>
References: <20150405133758.GA40261@albert.catwhisker.org>
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On Sun, Apr 05, 2015 at 06:37:58AM -0700, David Wolfskill wrote:
D> It ocurred rather late in the transition to multi-user mode, but
D> prior to starting xdm (on my laptop).
D> 
D> Previous (working) head/i386 for this machine was r281074.
D> 
D> Here's the first bit of the crashinfo (yes, I have a crash dump):
D> 
D> g1-254.catwhisker.org dumped core - see /var/crash/vmcore.3
D> 
D> Sun Apr  5 06:18:44 PDT 2015
D> 
D> FreeBSD g1-254.catwhisker.org 11.0-CURRENT FreeBSD 11.0-CURRENT #1561  r281106M/281106:1100067: Sun Apr  5 06:01:06 PDT 2015     root@g1-254.catwhisker.org:/common/S4/obj/usr/src/sys/CANARY  i386
D> 
D> panic: Lock vm object not exclusively locked @ /usr/src/sys/vm/vm_page.c:2637

This is r281079.

Since vm_page_advise() may call vm_page_dirty() in the MADV_DONTNEED case,
the assertion is valid. So, looks like vm_fault_dontneed() needs W-lock on
the first_object.

-- 
Totus tuus, Glebius.