From owner-freebsd-current@FreeBSD.ORG Thu Aug 24 01:24:52 2006 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0D64116A4DD for ; Thu, 24 Aug 2006 01:24:52 +0000 (UTC) (envelope-from oleg@lath.rinet.ru) Received: from lath.rinet.ru (lath.rinet.ru [195.54.192.90]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7941B43D4C for ; Thu, 24 Aug 2006 01:24:51 +0000 (GMT) (envelope-from oleg@lath.rinet.ru) Received: from lath.rinet.ru (localhost [127.0.0.1]) by lath.rinet.ru (8.13.6/8.13.6) with ESMTP id k7O1Ookh028069 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 24 Aug 2006 05:24:50 +0400 (MSD) (envelope-from oleg@lath.rinet.ru) Received: (from oleg@localhost) by lath.rinet.ru (8.13.6/8.13.6/Submit) id k7O1Oo5F028068; Thu, 24 Aug 2006 05:24:50 +0400 (MSD) (envelope-from oleg) Date: Thu, 24 Aug 2006 05:24:50 +0400 From: Oleg Bulyzhin To: Pyun YongHyeon Message-ID: <20060824012450.GC27699@lath.rinet.ru> References: <20060822042023.GC12848@cdnetworks.co.kr> <20060822091107.A3909@fw.reifenberger.com> <20060822073201.GI12848@cdnetworks.co.kr> <20060822144341.L5561@fw.reifenberger.com> <20060822204342.GA4943@lath.rinet.ru> <20060823005554.GC17902@cdnetworks.co.kr> <20060823124035.GA18628@lath.rinet.ru> <20060824002632.GA22634@cdnetworks.co.kr> <20060824004225.GB25876@lath.rinet.ru> <20060824011116.GD22634@cdnetworks.co.kr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060824011116.GD22634@cdnetworks.co.kr> User-Agent: Mutt/1.5.11 Cc: Michael Reifenberger , freebsd-current@freebsd.org Subject: Re: call for bge(4) testers X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 24 Aug 2006 01:24:52 -0000 On Thu, Aug 24, 2006 at 10:11:16AM +0900, Pyun YongHyeon wrote: > On Thu, Aug 24, 2006 at 04:42:25AM +0400, Oleg Bulyzhin wrote: > > On Thu, Aug 24, 2006 at 09:26:32AM +0900, Pyun YongHyeon wrote: > > > On Wed, Aug 23, 2006 at 04:40:35PM +0400, Oleg Bulyzhin wrote: > > [...] > > > > > > > > My idea was: perhaps, under certain condition, concurrent access to PHY could > > > > lead to hardware deadlock. > > > > > > > > > > Yes. Because MII bus access needs several steps to access PHY > > > registers its operation shouldn't be interrupted until all pending > > > requests are served. > > > > > > I can't sure you remember my mail for MII lock which modifies > > > mii_phy_probe API to take an additional mutex. The driver mutex > > > could be used with MII bus access/callbacks. > > > > Yes, i remember that mail but i didnt had time to dig code deep enough > > to give an answer. I did it recently, while working on PR. > > > > Glad to hear that. :-) > > > > If interface is up/running and auto negotiation is in progress MII > > > layer would inspect BMSR register periodically to know the state > > > of link. During the time if you run ifconfig(8) to know the state > > > of the link or to change media type/duplex it will access PHY > > > registers. Normally it would end up with "link states coalesced" > > > messages. > > > > > > As you know the two callbacks(vge_ifmedia_upd/vge_ifmedia_sts) will > > > end up with calling mii_mediachg() or mii_pollstat() which in turn > > > access PHY registers. So if MII access is properly serialized we > > > wouldn't get stale data. I guess your fix solves it by protecting > > > callbacks with driver mutex but it wouldn't fix other cases. > > > For example see vge_miibus_statchg MII interface. > > > > MII layer does not have it's own callouts, i.e. those autonegotiation > > checks of BMSR are triggered by driver's _tick() function, which are locked. > > So if we have locked _tick() & _ifmedia_(upd|sts) functions, concurrent > > access to PHY is impossible. > > (If we are talking about vge_miibus_statchg(), it would be: > > vge_tick (here we obtain lock) -> mii_tick -> ciphy_service -> > > mii_phy_update -> vge_miibus_statchg). > > > > If we set media type manually while autonegotiation is in progress, > wouldn't it access PHY registers without driver lock? No (if we have _tick() & ifmedia callbacks locked): ioctl -> netioctl -> ifhwioctl -> vge_ioctl(SIOCSIFMEDIA) -> ifmedia_ioctl -> vge_ifmedia_upd (here we obtain lock) -> mii_mediachg -> ciphy_service(MII_MEDIACHG) -> mii_phy_update -> vge_miibus_statchg > > -- > Regards, > Pyun YongHyeon -- Oleg.