From owner-freebsd-net Mon Jun 3 15:20:14 2002 Delivered-To: freebsd-net@freebsd.org Received: from rwcrmhc54.attbi.com (rwcrmhc54.attbi.com [216.148.227.87]) by hub.freebsd.org (Postfix) with ESMTP id 6FFA537B404 for ; Mon, 3 Jun 2002 15:20:07 -0700 (PDT) Received: from InterJet.elischer.org ([12.232.206.8]) by rwcrmhc54.attbi.com (InterMail vM.4.01.03.27 201-229-121-127-20010626) with ESMTP id <20020603222007.KFQZ13253.rwcrmhc54.attbi.com@InterJet.elischer.org>; Mon, 3 Jun 2002 22:20:07 +0000 Received: from localhost (localhost.elischer.org [127.0.0.1]) by InterJet.elischer.org (8.9.1a/8.9.1) with ESMTP id PAA44360; Mon, 3 Jun 2002 15:08:02 -0700 (PDT) Date: Mon, 3 Jun 2002 15:08:01 -0700 (PDT) From: Julian Elischer To: Archie Cobbs Cc: Alfred Perlstein , freebsd-net@freebsd.org Subject: Re: Race condition with M_EXT ref count? In-Reply-To: <200206032143.g53Lh5c47636@arch20m.dellroad.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org well, it's a valid problem form the point of view of some interrupt code changing the ext reference at teh same time that some other code is planning on incrementing it, but while Giant is in place it's not likely to affect anything.. I presume you are talking about 4.x however right? we can presume that each manipulator has a reference so it's not going to GA AWAY due to a zero reference being reached, so the link can be followed safely, which just elaves the atomicity of the addition operation. who are the contenders? 1/ network mid-level code? (protected by: splnet and the BGL. Only one cpu at a time.. 2/ Interrupt code running at splimp probably freeing stuff after transmit. (receivers should have pre-allocated buffers) it IS possible that there could need to be an splimp() added but I am not clear on what part the 4.4 BGL (Big Giant Lock) plays in this.. it may make it safe... On Mon, 3 Jun 2002, Archie Cobbs wrote: > Julian Elischer writes: > > Not denying that, just that JHB has a preliminary implementation > > he's been showing around... > > > > > > this is YET ANOTHER case for the Atomic reference counting ABI that > > > > jhb has been talking about... > > > > > > I was the initial person to request an atomic_t API. > > You guys please stop changing the subject :-) > > Can somebody confirm that they think this bug is real/valid? > > Thanks, > -Archie > > __________________________________________________________________________ > Archie Cobbs * Packet Design * http://www.packetdesign.com > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message