From owner-freebsd-current@FreeBSD.ORG Mon Apr 6 02:06:45 2015 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 26600C6; Mon, 6 Apr 2015 02:06:45 +0000 (UTC) Received: from pp1.rice.edu (proofpoint1.mail.rice.edu [128.42.201.100]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id DF120D8F; Mon, 6 Apr 2015 02:06:44 +0000 (UTC) Received: from pps.filterd (pp1.rice.edu [127.0.0.1]) by pp1.rice.edu (8.14.5/8.14.5) with SMTP id t3622gBS020324; Sun, 5 Apr 2015 21:06:42 -0500 Received: from mh1.mail.rice.edu (mh1.mail.rice.edu [128.42.201.20]) by pp1.rice.edu with ESMTP id 1tkfwng0g5-1; Sun, 05 Apr 2015 21:06:42 -0500 X-Virus-Scanned: by amavis-2.7.0 at mh1.mail.rice.edu, auth channel Received: from 108-254-203-201.lightspeed.hstntx.sbcglobal.net (108-254-203-201.lightspeed.hstntx.sbcglobal.net [108.254.203.201]) (using TLSv1 with cipher RC4-MD5 (128/128 bits)) (No client certificate requested) (Authenticated sender: alc) by mh1.mail.rice.edu (Postfix) with ESMTPSA id F21FD4600F9; Sun, 5 Apr 2015 21:06:41 -0500 (CDT) Message-ID: <5521EA31.3000007@rice.edu> Date: Sun, 05 Apr 2015 21:06:41 -0500 From: Alan Cox User-Agent: Mozilla/5.0 (X11; FreeBSD i386; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Rui Paulo Subject: Re: panic: Lock vm object not exclusively locked @ /usr/src/sys/vm/vm_page.c:2637 References: <20150405133758.GA40261@albert.catwhisker.org> <20150405154721.GO64665@FreeBSD.org> <5521749C.4020408@rice.edu> <20150405193425.GR64665@glebius.int.ru> <5521961C.8010808@rice.edu> <3A9C264F-3DAD-473B-A030-3FD026C2E8E3@me.com> In-Reply-To: <3A9C264F-3DAD-473B-A030-3FD026C2E8E3@me.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 kscore.is_bulkscore=2.15167883510503e-11 kscore.compositescore=0 circleOfTrustscore=0 compositescore=0.125204025642914 suspectscore=13 recipient_domain_to_sender_totalscore=0 phishscore=0 bulkscore=0 kscore.is_spamscore=0 rbsscore=0.125204025642914 recipient_to_sender_totalscore=0 recipient_domain_to_sender_domain_totalscore=0 spamscore=0 recipient_to_sender_domain_totalscore=0 urlsuspectscore=0.125204025642914 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=7.0.1-1402240000 definitions=main-1504060018 Cc: alc@FreeBSD.org, Gleb Smirnoff , current@freebsd.org X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 06 Apr 2015 02:06:45 -0000 On 04/05/2015 19:49, Rui Paulo wrote: > On Apr 5, 2015, at 13:07, Alan Cox wrote: >> On 04/05/2015 14:34, Gleb Smirnoff wrote: >>> On Sun, Apr 05, 2015 at 12:45:00PM -0500, Alan Cox wrote: >>> A> On 04/05/2015 10:47, Gleb Smirnoff wrote: >>> A> > On Sun, Apr 05, 2015 at 06:37:58AM -0700, David Wolfskill wrote: >>> A> > D> It ocurred rather late in the transition to multi-user mode, but >>> A> > D> prior to starting xdm (on my laptop). >>> A> > D> >>> A> > D> Previous (working) head/i386 for this machine was r281074. >>> A> > D> >>> A> > D> Here's the first bit of the crashinfo (yes, I have a crash dump): >>> A> > D> >>> A> > D> g1-254.catwhisker.org dumped core - see /var/crash/vmcore.3 >>> A> > D> >>> A> > D> Sun Apr 5 06:18:44 PDT 2015 >>> A> > D> >>> A> > 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 >>> A> > D> >>> A> > D> panic: Lock vm object not exclusively locked @ /usr/src/sys/vm/vm_page.c:2637 >>> A> > >>> A> > This is r281079. >>> A> > >>> A> > Since vm_page_advise() may call vm_page_dirty() in the MADV_DONTNEED case, >>> A> > the assertion is valid. So, looks like vm_fault_dontneed() needs W-lock on >>> A> > the first_object. >>> A> > >>> A> >>> A> Actually, what I forgot was that vm_page_advise(MADV_FREE) clears the >>> A> page's dirty field, and that is why an exclusive lock is asserted. As >>> A> explained in vm_page.h, the pmap is allowed to set the dirty field to >>> A> all ones without any locking. Moreover, the new "fast" path in >>> A> vm_fault() sets the dirty field with only a read lock held. >>> A> vm_page_advise(MADV_DONTNEED) isn't really any different from the fast path. >>> A> >>> A> Need to think a bit ... >>> >>> Can you please plug the panic somehow interim? For me the assert fires 100% >>> reliably on any build attempt. Right now I changed vm_fault_dontneed() to >>> take W-lock, so that I can continue running head. Not sure this is correct >>> measure. >>> >> Just curious, amd64 or i386? > Alan, this is caused by your r281079. Are you working on it? If you don't have a resolution soon, I think we should revert it ASAP as it's extremely easy to panic the system. It was fixed about six hours ago: r281118.