From owner-freebsd-arch@FreeBSD.ORG Thu Aug 8 21:57:24 2013 Return-Path: <owner-freebsd-arch@FreeBSD.ORG> Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id C11FA258 for <freebsd-arch@freebsd.org>; Thu, 8 Aug 2013 21:57:24 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 21BB1262E for <freebsd-arch@freebsd.org>; Thu, 8 Aug 2013 21:57:23 +0000 (UTC) Received: from tom.home (kostik@localhost [127.0.0.1]) by kib.kiev.ua (8.14.7/8.14.7) with ESMTP id r78LvJ1B093968; Fri, 9 Aug 2013 00:57:19 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.8.3 kib.kiev.ua r78LvJ1B093968 Received: (from kostik@localhost) by tom.home (8.14.7/8.14.7/Submit) id r78LvJrm093967; Fri, 9 Aug 2013 00:57:19 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Fri, 9 Aug 2013 00:57:19 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Masao Uebayashi <uebayasi@gmail.com> Subject: Re: panic(9) vs. RB_NOSYNC Message-ID: <20130808215719.GP4972@kib.kiev.ua> References: <CADbF7edYLBrKQrU9E7HX4Hh_emthRCPcr9WbUPDuLDe5kwNfZQ@mail.gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="u/BH/w+/n8IGbYqX" Content-Disposition: inline In-Reply-To: <CADbF7edYLBrKQrU9E7HX4Hh_emthRCPcr9WbUPDuLDe5kwNfZQ@mail.gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on tom.home Cc: freebsd-arch@freebsd.org X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org> List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-arch>, <mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe> List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch> List-Post: <mailto:freebsd-arch@freebsd.org> List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help> List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>, <mailto:freebsd-arch-request@freebsd.org?subject=subscribe> X-List-Received-Date: Thu, 08 Aug 2013 21:57:24 -0000 --u/BH/w+/n8IGbYqX Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Aug 08, 2013 at 02:36:51PM +0900, Masao Uebayashi wrote: > panic(9) (actually vpanic()) sets RB_NOSYNC when panicstr is already > set. What is the reasoning of this? >=20 > My understanding is that panic() attempts VFS "sync" operation at > first. If another panic() is triggered during that, give up VFS > "sync". Is this correct? If so, how reliable is this design? I > wonder if attempting such a complex task like VFS "sync" after a panic > is a good idea. Look at the end of the vpanic(), right before kern_reboot() call. There, kernel does if (!sync_on_panic) bootopt |=3D RB_NOSYNC; so it only syncs when sync_on_panic sysctl is set to non-zero, which is zero by default. Basically, this option might be reasonable when you debug something not related to i/o+VM+storage drivers, and you know what you do. --u/BH/w+/n8IGbYqX Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.20 (FreeBSD) iQIcBAEBAgAGBQJSBBQ+AAoJEJDCuSvBvK1Bo2wP/1npprp+pVPGSxJ7BjPg8Cbk rZcHoJryghaPaZ0TL+u639bEdweTtt5eAZAdLt1FkUmDiQhHj01EDTIwwc8kc4Kw NDMQHOCNwS6Qg5e8OAK7GfkYwJcECsaAlDozWYS7AmnnZRKaey49crFpLJIaIHd+ EFi3zbg8V/2+x1oUghSdi+nuo6Dm8IinByEnnIqQfJ77Cj6QwQA5aaUkj6RryqkV iHb9Ti/i11pMseczszbCi7LIzD/LQdXVHPQHRUevdJylxFzA079XMQ3vRXcOlhmc +sK7oa42+98eyAZQIoFNsa+MYVumyScydD+OBdKl0NIvqOrVRWhilyArrOm/W6tm GsYt0QjD3/KKIH6R/syMLIjEL9cKerzdwSe/c37VzyC4e2d909qFDyMRnZNEuvEN mkaX5o5Ba+bnSphTVx/Ed5T/ZV57+xvhHOYL5HUEcdgm+3vFzJX9csGYyfvzvS0z I9I29DeYv9dt2TX0q7qV34WI/1dxQzpqueoNzVyX26Wy7BA/wxhjgPqHiXvpUx76 bJVnwpg8n2T3i9vmBd6OVLeMtF0/excjhITb1qayW28O996ThecOXfm53rfMMDza KHLrqv4fgnNeQ6xHfH+9lII5mr39lo7C6KKhP+gznCxV9ZFm6XTOvcS11xPn3Irt 7c0DoH2//fB7xX6SQCWI =BA8V -----END PGP SIGNATURE----- --u/BH/w+/n8IGbYqX--