From owner-freebsd-hackers@FreeBSD.ORG Thu Aug 25 22:39:58 2011 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3A272106566B for ; Thu, 25 Aug 2011 22:39:58 +0000 (UTC) (envelope-from jamesbrandongooch@gmail.com) Received: from mail-ww0-f42.google.com (mail-ww0-f42.google.com [74.125.82.42]) by mx1.freebsd.org (Postfix) with ESMTP id C62ED8FC0C for ; Thu, 25 Aug 2011 22:39:57 +0000 (UTC) Received: by wwe5 with SMTP id 5so5469460wwe.1 for ; Thu, 25 Aug 2011 15:39:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=GwsEcA3dYBcTWYpEA7yoE/VARm1JsSWB2ptw+HEZJtA=; b=Jkhqutdvvqk7eqdMI2VXJzjvPtajvRWlbLRUd+ccK98OcQZP0qRrpULJFCXkdzXUDC 6kU3ALdJTZRLXY/ZoymqQPjle39468yRqz1Sn6lf6Cx98GoV9gv/uF8UJcIzqQcOmzz4 loGPXU1O8GRXcoGdLpn02QfQcjRKjlMuDdBh4= MIME-Version: 1.0 Received: by 10.216.230.194 with SMTP id j44mr246474weq.28.1314310329452; Thu, 25 Aug 2011 15:12:09 -0700 (PDT) Received: by 10.216.208.158 with HTTP; Thu, 25 Aug 2011 15:12:09 -0700 (PDT) In-Reply-To: <20110825215348.GW17489@deviant.kiev.zoral.com.ua> References: <4E56BB99.6030706@sgi.com> <20110825215348.GW17489@deviant.kiev.zoral.com.ua> Date: Thu, 25 Aug 2011 17:12:09 -0500 Message-ID: From: Brandon Gooch To: Kostik Belousov Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: freebsd-hackers@freebsd.org, Charlie Martin Subject: Re: Where to ask about a 7.2 bug, and debugging sys/queue.h errors X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 25 Aug 2011 22:39:58 -0000 On Thu, Aug 25, 2011 at 4:53 PM, Kostik Belousov wrot= e: > On Thu, Aug 25, 2011 at 03:16:09PM -0600, Charlie Martin wrote: >> We're having a crash in some internal code running on FreeBSD 7.2 >> (specifically =A07.2-PRERELEASE FreeBSD 7.2-PRERELEASE and yeah, I know >> it's quite a bit behind) in which after 18-30 hours of running load >> tests, the code panics with: >> >> panic: Bad link elm 0xffffff0044c09600 next->prev !=3D elm >> cpuid =3D 0 >> KDB: stack backtrace: >> db_trace_self_wrapper() at 0xffffffff8019119a =3D db_trace_self_wrapper+= 0x2a >> panic() at 0xffffffff80307c72 =3D panic+0x182 >> devfs_populate_loop() at 0xffffffff802a43a8 =3D devfs_populate_loop+0x54= 8 >> >> >> First question: where's the most appropriate place to ask about this >> kind of bug on a back version. > It is fine to ask there. > >> >> Second: does this remind anyone of any bugs? =A0Googling came up with a >> few somewhat similar things but hasn't provided much insight so far. > In 99% of the cases, it means that you forgot to dev_ref() some cdev. So dev_ref increments the reference count for a cdev. Even though the work "loop" seems to indicate that we will iterate over a list of objects (one of which we may be missing a reference to via a missing dev_ref()), I'm not seeing how this can cause a panic from inside devfs_populate_loop(). Can you help me understand this? -Brandon