From owner-svn-src-head@freebsd.org Sat Feb 18 20:58:32 2017 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 95D28CE35D2; Sat, 18 Feb 2017 20:58:32 +0000 (UTC) (envelope-from mjguzik@gmail.com) Received: from mail-lf0-x241.google.com (mail-lf0-x241.google.com [IPv6:2a00:1450:4010:c07::241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 16A56119D; Sat, 18 Feb 2017 20:58:32 +0000 (UTC) (envelope-from mjguzik@gmail.com) Received: by mail-lf0-x241.google.com with SMTP id z134so42630lff.3; Sat, 18 Feb 2017 12:58:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to:user-agent; bh=rt53Xsm9IestMXEo0DfjcrGdtqEWo922J6ohJKIDsgc=; b=sm7ajQQRNNj+ZgR+fPvubXlunyxKdqMPmjTdVGCuk/J/bibQbkLUZmo2qkh174+f/V wDILeiTQ0w/urSGz2b2/GRL+waooWk3trHQKBwegD+daupxhpAewTajfG08umMagrKNM G07AKM4bhqlpdQeYC1d/kg1F4EHGZfmJZDovlZIsOUOMHX4P5aKiLn2Err73Y8yf50YG vFL+lm/YFYCmqAA8wV+P41X2E20k3v9if6vPvugQoQmveNeTUXrFHrCbPICJ5N+Lmnum 9cvj+Klpmcc8F9aWcwYk004ORN4V6Q476WsFvSy/V6CbbErttmKGYjYjXTJXyhCnORHy MLYQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to:user-agent; bh=rt53Xsm9IestMXEo0DfjcrGdtqEWo922J6ohJKIDsgc=; b=ApAzPdsUHnl3CUtVzeo37+MUdcof8SkH/+15WDfRQEtJzJKD2+2wlwpEyWmdLheVve 1oy0P0puuBmQPxWV2IT5x4JaqMwvwIpvbHpFWkati9/nAlSmFo1SnW0zjuxx2NO0LXJ6 sK0hifC54wcT39dyhamAdh2ViG90j6penp4YhURAPqMde//XhPOgHcvPN2ys6TfsZWWm o97b6g0XyW7qB6EcDve+EOzp5M3XqCQdPO8Jurx4UQbEFd09R3C4nqNsOA21J8mAflDx 4pGy9YrMRmV4OsAky5mo2tBEjKT8HB8Tqi2jBmOl1kJ/RpSldHl39U91d1hIE0E+oaC5 2QtQ== X-Gm-Message-State: AMke39kEFb/GoCSJkNPJcTS2XaT6t10c1ZAjdPaIz/FvKskp+LpfyfTkIMQ6f0Hi1VLkEA== X-Received: by 10.25.153.69 with SMTP id b66mr2789241lfe.85.1487451509645; Sat, 18 Feb 2017 12:58:29 -0800 (PST) Received: from dft-labs.eu (n1x0n-1-pt.tunnel.tserv5.lon1.ipv6.he.net. [2001:470:1f08:1f7::2]) by smtp.gmail.com with ESMTPSA id a71sm3776775lfe.36.2017.02.18.12.58.28 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Sat, 18 Feb 2017 12:58:29 -0800 (PST) Date: Sat, 18 Feb 2017 21:58:25 +0100 From: Mateusz Guzik To: Mark Millard Cc: mjg@freebsd.org, Justin Hibbits , svn-src-head@freebsd.org, FreeBSD PowerPC ML , FreeBSD Current Subject: Re: svn commit: r313268 - head/sys/kern [through -r313271 for atomic_fcmpset use and later: fails on PowerMac G5 "Quad Core"; -r313266 works] Message-ID: <20170218205825.GA24384@dft-labs.eu> Mail-Followup-To: Mateusz Guzik , Mark Millard , mjg@freebsd.org, Justin Hibbits , svn-src-head@freebsd.org, FreeBSD PowerPC ML , FreeBSD Current References: <2FD12B8F-2255-470A-98D4-2DCE9C7495F5@dsl-only.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 18 Feb 2017 20:58:32 -0000 On Sat, Feb 18, 2017 at 12:49:29PM -0800, Mark Millard wrote: > On 2017-Feb-18, at 4:18 AM, Mark Millard wrote: > > > [Note: I experiment with clang based powerpc64 builds, > > reporting problems that I find. Justin is familiar > > with this, as is Nathan.] > > > > I tried to update the PowerMac G5 (a so-called "Quad Core") > > that I have access to from head -r312761 to -r313864 and > > ended up with random panics and hang ups in fairly short > > order after booting. > > > > Some approximate bisecting for the kernel lead to: > > (sometimes getting part way into a buildkernel attempt > > for a different version before a failure happens) > > > > -r313266: works (just before use of atomic_fcmpset) > > vs. > > -r313271: fails (last of the "use atomic_fcmpset" check-ins) > > > > (I did not try -r313268 through -r313270 as the use was > > gradually added.) > > > > So I'm currently running a -r313864 world with a -r313266 > > kernel. > > > > No kernel that I tried that was from before -r313266 had the > > problems. > > > > Any kernel that I tried that was from after -r313271 had the > > problems. > > > > Of course I did not try them all in other direction. :) > > [Of course: "either direction".] > > I'll note that the -r313864 buildworld was without > MALLOC_PRODUCTION being defined. (Unusual for me but > I'm testing if a jemalloc assert problem on arm64 > also happens on powerpc64.) > > By contrast the buildkernels were production style > (as is normal for me unless I'm trying to track > something down that I think might be exposed by > the extra checks). > Well either the primitive itself is buggy or the somewhat (now) unusual condition of not providing the failed value (but possibly a stale one) is not handled correctly in locking code. That said, I would start with putting barriers "on both sides" of powerpc's fcmpset for debugging purposes and if the problem persists I can add some debugs to locking priitmives. -- Mateusz Guzik