From owner-freebsd-hackers@freebsd.org Tue Feb 13 21:49:09 2018 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id DBF24F03D68 for ; Tue, 13 Feb 2018 21:49:09 +0000 (UTC) (envelope-from mike@sentex.net) Received: from smarthost2.sentex.ca (smarthost2.sentex.ca [IPv6:2607:f3e0:80:80::2]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client CN "smarthost.sentex.ca", Issuer "smarthost.sentex.ca" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 680B9739C9; Tue, 13 Feb 2018 21:49:09 +0000 (UTC) (envelope-from mike@sentex.net) Received: from lava.sentex.ca (lava.sentex.ca [IPv6:2607:f3e0:0:5::11]) by smarthost2.sentex.ca (8.15.2/8.15.2) with ESMTPS id w1DLn820066589 (version=TLSv1 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Tue, 13 Feb 2018 16:49:09 -0500 (EST) (envelope-from mike@sentex.net) Received: from [192.168.43.26] (saphire3.sentex.ca [192.168.43.26]) by lava.sentex.ca (8.15.2/8.15.2) with ESMTP id w1DLn6uu031327; Tue, 13 Feb 2018 16:49:06 -0500 (EST) (envelope-from mike@sentex.net) Subject: Re: Stale memory during post fork cow pmap update To: Konstantin Belousov , Elliott.Rabe@dell.com Cc: Eric.Van.Gyzen@dell.com, freebsd-hackers@freebsd.org, truckman@FreeBSD.org, markj@FreeBSD.org, alc@FreeBSD.org References: <5A7E7F2B.80900@dell.com> <20180210111848.GL33564@kib.kiev.ua> <5A7F6A7C.80607@dell.com> <20180210225608.GM33564@kib.kiev.ua> <5A82AB7C.6090404@dell.com> <20180213133010.GD94212@kib.kiev.ua> From: Mike Tancsa Organization: Sentex Communications Message-ID: Date: Tue, 13 Feb 2018 16:49:08 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180213133010.GD94212@kib.kiev.ua> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.78 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 13 Feb 2018 21:49:10 -0000 On 2/13/2018 8:30 AM, Konstantin Belousov wrote: > Apparently Ryzen CPUs are able to demonstrate it quite reliably with the > python driver for the samba build. It was very surprising to me, esp. > because I tried to understand the Ryzen bug for the whole last week and > thought that it is more likely CPU store/load inconsistency than a software > thing. See https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=225584. Just tested on an AMD EPYC 7281 (16/32 cores), and it runs into this bug every time on the samba build. Applying the referenced patch fixes the problem, at least I was able to test 4 builds in a row without issue. ---Mike -- ------------------- Mike Tancsa, tel +1 519 651 3400 x203 Sentex Communications, mike@sentex.net Providing Internet services since 1994 www.sentex.net Cambridge, Ontario Canada