From owner-svn-src-projects@FreeBSD.ORG Wed Mar 11 14:54:19 2015 Return-Path: Delivered-To: svn-src-projects@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 2EF6F5C5; Wed, 11 Mar 2015 14:54:19 +0000 (UTC) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [IPv6:2001:470:1f11:75::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 0716B954; Wed, 11 Mar 2015 14:54:19 +0000 (UTC) Received: from ralph.baldwin.cx (pool-173-54-116-245.nwrknj.fios.verizon.net [173.54.116.245]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 178AEB97B; Wed, 11 Mar 2015 10:54:18 -0400 (EDT) From: John Baldwin To: Gleb Smirnoff Subject: Re: svn commit: r279882 - in projects/ifnet/sys/dev: bge msk xl Date: Wed, 11 Mar 2015 09:55:56 -0400 Message-ID: <7233313.sLAkjvMmOW@ralph.baldwin.cx> User-Agent: KMail/4.14.2 (FreeBSD/10.1-STABLE; KDE/4.14.2; amd64; ; ) In-Reply-To: <201503111043.t2BAhFCF028283@svn.freebsd.org> References: <201503111043.t2BAhFCF028283@svn.freebsd.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Wed, 11 Mar 2015 10:54:18 -0400 (EDT) Cc: svn-src-projects@freebsd.org, src-committers@freebsd.org X-BeenThere: svn-src-projects@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: "SVN commit messages for the src " projects" tree" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 Mar 2015 14:54:19 -0000 On Wednesday, March 11, 2015 10:43:15 AM Gleb Smirnoff wrote: > Author: glebius > Date: Wed Mar 11 10:43:14 2015 > New Revision: 279882 > URL: https://svnweb.freebsd.org/changeset/base/279882 > > Log: > For now use consistent softc lock in drivers transmit methods, due to a > theoretical race condition. Note that the condition exists in all > drbr(9) based drivers in head, but never was evidenced. Nevertheless, > leave this branch for KPI redesign instead of performance experiments. > > Discussed with: jhb To be clear, I certainly saw this race trigger in a production environment on a very quiet interface used for timing by transmitting multicast packets once a second. Every once in a while a ping from a monitoring system would coincide with the periodic transmit causing the trylock to fail (the ping locked the transmit ring to send the echo reply). This caused the timing multicast packet to be delayed for a full second until the next timing packet was sent. Just dropping the trylocks is indeed the simplest solution to this problem. -- John Baldwin