From owner-cvs-src@FreeBSD.ORG Wed Sep 21 19:34:44 2005 Return-Path: X-Original-To: cvs-src@freebsd.org Delivered-To: cvs-src@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id D85B616A420; Wed, 21 Sep 2005 19:34:43 +0000 (GMT) (envelope-from ru@ip.net.ua) Received: from tigra.ip.net.ua (tigra.ip.net.ua [82.193.96.10]) by mx1.FreeBSD.org (Postfix) with ESMTP id EB63743D46; Wed, 21 Sep 2005 19:34:42 +0000 (GMT) (envelope-from ru@ip.net.ua) Received: from localhost (rocky.ip.net.ua [82.193.96.2]) by tigra.ip.net.ua (8.12.11/8.12.11) with ESMTP id j8LJYcvi051358; Wed, 21 Sep 2005 22:34:39 +0300 (EEST) (envelope-from ru@ip.net.ua) Received: from tigra.ip.net.ua ([82.193.96.10]) by localhost (rocky.ipnet [82.193.96.2]) (amavisd-new, port 10024) with LMTP id 06056-13; Wed, 21 Sep 2005 22:34:32 +0300 (EEST) Received: from heffalump.ip.net.ua (heffalump.ip.net.ua [82.193.96.213]) by tigra.ip.net.ua (8.12.11/8.12.11) with ESMTP id j8LJXrNI051201 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 21 Sep 2005 22:33:53 +0300 (EEST) (envelope-from ru@ip.net.ua) Received: (from ru@localhost) by heffalump.ip.net.ua (8.13.3/8.13.3) id j8LJYARx049353; Wed, 21 Sep 2005 22:34:10 +0300 (EEST) (envelope-from ru) Date: Wed, 21 Sep 2005 22:34:10 +0300 From: Ruslan Ermilov To: "M. Warner Losh" Message-ID: <20050921193410.GC24516@ip.net.ua> References: <200509211455.59154.jhb@FreeBSD.org> <20050921.130241.102576086.imp@bsdimp.com> <20050921191906.GA24516@ip.net.ua> <20050921.132322.116350250.imp@bsdimp.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="E13BgyNx05feLLmH" Content-Disposition: inline In-Reply-To: <20050921.132322.116350250.imp@bsdimp.com> User-Agent: Mutt/1.5.9i X-Virus-Scanned: by amavisd-new at ip.net.ua Cc: cvs-src@freebsd.org, src-committers@freebsd.org, rwatson@freebsd.org, cvs-all@freebsd.org, jhb@freebsd.org Subject: Re: cvs commit: src/sys/dev/an if_an.c src/sys/dev/arl if_arl_isa.c src/sys/dev/awi if_awi_pccard.c src/sys/dev/cm if_cm_isa.c src/sys/dev/cnw if_cnw.c src/sys/dev/cp if_cp.c src/sys/dev/cs if_cs.c src/sys/dev/ed if_ed.c src/sys/dev/em if_em.c ... X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Sep 2005 19:34:44 -0000 --E13BgyNx05feLLmH Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Sep 21, 2005 at 01:23:22PM -0600, M. Warner Losh wrote: > In message: <20050921191906.GA24516@ip.net.ua> > Ruslan Ermilov writes: > : On Wed, Sep 21, 2005 at 01:02:41PM -0600, M. Warner Losh wrote: > : > In message: <200509211455.59154.jhb@FreeBSD.org> > : > John Baldwin writes: > : > : > 5. Fix all drivers to set some flag in foo_detach() and foo_shut= down() > : > : > and refuse to work in foo_ioctl() if it's set. This should f= ix > : > : > panics when BPF listener is attached while interface goes awa= y or > : > : > module is unloaded. > : >=20 > : > : I'd rather 5) be simpler in=20 > : > : that it only check in the flags case to not force the driver lock t= o be=20 > : > : acquired for all the ioctls that the driver doesn't actually handle= =2E =20 > : > : Actually, I think I'd really prefer that we think about how to fix = the BPF=20 > : > : issue in BPF itself if possible. It may be that we don't need to s= et the=20 > : > : flags (i.e. skip the actual ioctl) if the interface is in the proce= ss of=20 > : > : detaching and we can make that change centrally without having to s= catter=20 > : > : gone flags in all the drivers. > : >=20 > : > This would solve the race at hand. However, it wouldn't solve the > : > problems with driver shutdown racing with other things in the system > : > (like ifconfig during detach). > : >=20 > : > I've knocked around the idea of creating a if_dead() function that one > : > would call before foo_stop(). if_dead would just return (possibly an > : > error) for all the entry points before the device is actually > : > detached. This would mean that we don't need to add flags to all the > : > drivers, but we do need to change all the detach routine. This would > : > avoid the LOCK operations that you are worried about... > : >=20 > : I'm afraid you cannot safely change the ifnet method pointers, if > : you mean that foo_detach() should set ifp->if_start etc. to point > : to if_dead(). >=20 > Why not? What's the problem? >=20 The time you change say ifp->if_start in foo_detach(), stack may call it and get a half-changed pointer. Unless we invent locking shared between stack and the drivers. Cheers, --=20 Ruslan Ermilov ru@FreeBSD.org FreeBSD committer --E13BgyNx05feLLmH Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (FreeBSD) iD8DBQFDMbWyqRfpzJluFF4RAlTxAJsHWS0yXLMwj7xT/kguznmrHu2RYACeIf6L UrnAWhDDQ+iuEk6KOXScVXY= =rcbv -----END PGP SIGNATURE----- --E13BgyNx05feLLmH--