From owner-freebsd-bugs@FreeBSD.ORG Fri Mar 12 22:20:04 2010 Return-Path: Delivered-To: freebsd-bugs@hub.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A4343106566B for ; Fri, 12 Mar 2010 22:20:04 +0000 (UTC) (envelope-from gnats@FreeBSD.org) Received: from freefall.freebsd.org (freefall.freebsd.org [IPv6:2001:4f8:fff6::28]) by mx1.freebsd.org (Postfix) with ESMTP id 78C2B8FC16 for ; Fri, 12 Mar 2010 22:20:04 +0000 (UTC) Received: from freefall.freebsd.org (localhost [127.0.0.1]) by freefall.freebsd.org (8.14.4/8.14.4) with ESMTP id o2CMK46x088818 for ; Fri, 12 Mar 2010 22:20:04 GMT (envelope-from gnats@freefall.freebsd.org) Received: (from gnats@localhost) by freefall.freebsd.org (8.14.4/8.14.4/Submit) id o2CMK4dj088817; Fri, 12 Mar 2010 22:20:04 GMT (envelope-from gnats) Date: Fri, 12 Mar 2010 22:20:04 GMT Message-Id: <201003122220.o2CMK4dj088817@freefall.freebsd.org> To: freebsd-bugs@FreeBSD.org From: Garrett Cooper Cc: Subject: Re: misc/144695: race condition in mounting a root-fs on an external usb-disk X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: Garrett Cooper List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 12 Mar 2010 22:20:04 -0000 The following reply was made to PR kern/144695; it has been noted by GNATS. From: Garrett Cooper To: Torsten Cc: freebsd-gnats-submit@freebsd.org Subject: Re: misc/144695: race condition in mounting a root-fs on an external usb-disk Date: Fri, 12 Mar 2010 14:18:44 -0800 On Fri, Mar 12, 2010 at 6:27 AM, Torsten wrote: > >>Number: =A0 =A0 =A0 =A0 144695 >>Category: =A0 =A0 =A0 misc >>Synopsis: =A0 =A0 =A0 race condition in mounting a root-fs on an external= usb-disk >>Confidential: =A0 no >>Severity: =A0 =A0 =A0 non-critical >>Priority: =A0 =A0 =A0 low >>Responsible: =A0 =A0freebsd-bugs >>State: =A0 =A0 =A0 =A0 =A0open >>Quarter: >>Keywords: >>Date-Required: >>Class: =A0 =A0 =A0 =A0 =A0sw-bug >>Submitter-Id: =A0 current-users >>Arrival-Date: =A0 Fri Mar 12 14:30:03 UTC 2010 >>Closed-Date: >>Last-Modified: >>Originator: =A0 =A0 Torsten >>Release: =A0 =A0 =A0 =A0freebsd 8.0 release >>Organization: > n/a >>Environment: >>Description: > Hello! > > I have installed FreeBSD 8 on my external usb-harddisk without any proble= ms. Just I cannot boot into it, but I always receive a mountroot-prompt. > Reading the news / archives I found a problem in the mountroot taking pla= ce too early -- before all of the usb-probe and device-setup is fully done. > There was (?) no really solution available, so I have made a small change= that caused everything to work -- but one may see this more a work-around = than rather a real fix. > The main idea is to put in an un-conditional wait at the beginning of vfs= _mountroot. And, of course make this configurable. The acutal change is jus= t a few lines that should not harm anything else. > For my system I have started with the default of 5000ms, but I needed to = go to 15000ms to mount my root-fs safely. > Please find attached the source-diff. >>How-To-Repeat: > >>Fix: > FreeBSD unixrest 8.0-RELEASE FreeBSD 8.0-RELEASE #0: Fri Mar 12 14:02:27 = CET 2010 =A0 =A0 root@unixrest:/usr/src/sys/i386/compile/BXGENERIC =A0i386 > > > Patch attached with submission follows: > > --- vfs_mount.c.orig =A0 =A02010-03-12 13:02:33.000000000 +0100 > +++ vfs_mount.c 2010-03-12 13:56:04.000000000 +0100 > @@ -1648,6 +1648,12 @@ > > =A0 =A0 =A0 =A0options =3D NULL; > > + =A0 =A0 =A0 =A0static int mountroot_wait_delay =3D 5000; > + =A0 =A0 =A0 =A0TUNABLE_INT_FETCH("hw.mountroot_wait_delay", &mountroot_= wait_delay); > + =A0 =A0 =A0 int mysec =3D mountroot_wait_delay / hz; > + =A0 =A0 =A0 printf("Waiting %d seconds for devices to settle.\n", mysec= ); > + =A0 =A0 =A0 =A0pause("Waiting for devices to settle", mountroot_wait_de= lay); > + > =A0 =A0 =A0 =A0root_mount_prepare(); > > =A0 =A0 =A0 =A0mount_zone =3D uma_zcreate("Mountpoints", sizeof(struct mo= unt), > @@ -2492,3 +2498,4 @@ > =A0 =A0 =A0 =A0error =3D kernel_mount(ma, flags); > =A0 =A0 =A0 =A0return (error); > =A0} > + 1. This was misfiled (should be under kern). 2. This is a well-known issue (devices in general not being available by the time mount of mountroot is attempted) that isn't trivial to resolve. 3. mav@ has a more scalable solution offered here that's been committed into CURRENT in the past couple months: http://www.mail-archive.com/freebsd-stable@freebsd.org/msg107696.html . Look for kern.cam.boot_delay. HTH, -Garrett