From owner-freebsd-threads@freebsd.org Fri Apr 1 14:43:05 2016 Return-Path: Delivered-To: freebsd-threads@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8BDF6AEBBAC for ; Fri, 1 Apr 2016 14:43:05 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 62E8A1622 for ; Fri, 1 Apr 2016 14:43:05 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id u31Eh4Om000122 for ; Fri, 1 Apr 2016 14:43:05 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-threads@FreeBSD.org Subject: [Bug 204426] Processes terminating cannot access memory Date: Fri, 01 Apr 2016 14:43:05 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 10.3-BETA2 X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: kib@FreeBSD.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-threads@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-threads@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Threading on FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Apr 2016 14:43:05 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D204426 --- Comment #80 from Konstantin Belousov --- (In reply to Robert Blayzor from comment #79) The page fault was not handled since some object in the shadow chain which backs the faulted region, has the OBJ_DEAD flag set. I do not see why would this state valid for the object in question. There is another PR 204764, w= here the same flag is set for a vnode object and the manifestation of the proble= m is different. Instead of vm_fault, the object was found by vnode_create_vobjec= t(), which sleeps forever waiting for the object termination to finish. Since t= he flag was not set by the termination conditions, termination does not happen= and lookup is stuck forever. Right now, I have no idea why does this happen. Either we have a bug in VM= by spuriously setting the flag (but code reading does not support this possibility), or some random memory access happens and corrupts the vm obje= ct memory. I do not know. I attached some additions to the debugging patch, which both asserts that t= he object is write-locked when object->flags are modified, and also it slightly changes the layout of struct vm_object. So if the issue is VM bug, most li= kely unlocked modifications, it could be catched. Or, if the problem is the mem= ory corruption, it should migrate to other place. Still, it is only speculation. Please make sure that you have INVARIANTS a= nd WITNESS in your kernel config enabled. --=20 You are receiving this mail because: You are the assignee for the bug.=