From owner-freebsd-ppc@freebsd.org Tue Feb 21 09:37:29 2017 Return-Path: Delivered-To: freebsd-ppc@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 CC4EECE68A8 for ; Tue, 21 Feb 2017 09:37:29 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: from asp.reflexion.net (outbound-mail-210-73.reflexion.net [208.70.210.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 7A5CCF2A for ; Tue, 21 Feb 2017 09:37:28 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: (qmail 2810 invoked from network); 21 Feb 2017 09:37:27 -0000 Received: from unknown (HELO mail-cs-02.app.dca.reflexion.local) (10.81.19.2) by 0 (rfx-qmail) with SMTP; 21 Feb 2017 09:37:27 -0000 Received: by mail-cs-02.app.dca.reflexion.local (Reflexion email security v8.30.0) with SMTP; Tue, 21 Feb 2017 04:37:27 -0500 (EST) Received: (qmail 12940 invoked from network); 21 Feb 2017 09:37:26 -0000 Received: from unknown (HELO iron2.pdx.net) (69.64.224.71) by 0 (rfx-qmail) with (AES256-SHA encrypted) SMTP; 21 Feb 2017 09:37:26 -0000 Received: from [192.168.1.111] (c-67-170-167-181.hsd1.or.comcast.net [67.170.167.181]) by iron2.pdx.net (Postfix) with ESMTPSA id 32402EC903F; Tue, 21 Feb 2017 01:37:26 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 10.2 \(3259\)) Subject: Re: svn commit: r313268 - head/sys/kern [through -r313271 for atomic_fcmpset use and later: fails on PowerMac G5 "Quad Core"; -r313266 works] From: Mark Millard In-Reply-To: <20170220191044.GA8526@dft-labs.eu> Date: Tue, 21 Feb 2017 01:37:25 -0800 Cc: mjg@freebsd.org, Justin Hibbits , svn-src-head@freebsd.org, FreeBSD PowerPC ML , FreeBSD Current , Nathan Whitehorn Content-Transfer-Encoding: 7bit Message-Id: <5D5235E1-6F84-4329-8ED5-35FCDB0A6A71@dsl-only.net> References: <2FD12B8F-2255-470A-98D4-2DCE9C7495F5@dsl-only.net> <20170220191044.GA8526@dft-labs.eu> To: Mateusz Guzik X-Mailer: Apple Mail (2.3259) X-BeenThere: freebsd-ppc@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Porting FreeBSD to the PowerPC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Feb 2017 09:37:29 -0000 [Back to the powerpc64 context.] On 2017-Feb-20, at 11:10 AM, Mateusz Guzik wrote: > On Sat, Feb 18, 2017 at 04:18:05AM -0800, 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. :) >> > > I found that spin mutexes were not properly handling this, fixed in > r313996. > > Locally I added a if (cpu_tick() % 2) return (0); snipped to amd64 > fcmpset to simulate failures. Everything works, while it would easily > fail without the patch. > > That said, I hope this concludes the 'missing check for not-reread value > of failed fcmpset' saga. > > -- > Mateusz Guzik -r313999 is an improvement for powerpc64: it boots and I can log in on the old PowerMac G5 so-called "Quad Core". But, e.g., buildworld buildkernel eventually hangs and later the powerpc64 panics for "spin lock held too long". === Mark Millard markmi at dsl-only.net