Date: Fri, 9 Aug 2013 00:57:19 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Masao Uebayashi <uebayasi@gmail.com> Cc: freebsd-arch@freebsd.org Subject: Re: panic(9) vs. RB_NOSYNC Message-ID: <20130808215719.GP4972@kib.kiev.ua> In-Reply-To: <CADbF7edYLBrKQrU9E7HX4Hh_emthRCPcr9WbUPDuLDe5kwNfZQ@mail.gmail.com> References: <CADbF7edYLBrKQrU9E7HX4Hh_emthRCPcr9WbUPDuLDe5kwNfZQ@mail.gmail.com>
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--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--
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