From owner-freebsd-ia64@FreeBSD.ORG Wed Jul 8 00:29:08 2009 Return-Path: Delivered-To: freebsd-ia64@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 88F031065702; Wed, 8 Jul 2009 00:29:08 +0000 (UTC) (envelope-from xcllnt@mac.com) Received: from asmtpout029.mac.com (asmtpout029.mac.com [17.148.16.104]) by mx1.freebsd.org (Postfix) with ESMTP id 7137F8FC16; Wed, 8 Jul 2009 00:29:08 +0000 (UTC) (envelope-from xcllnt@mac.com) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=us-ascii; format=flowed Received: from macbook-pro.lan.xcllnt.net (mail.xcllnt.net [75.101.29.67]) by asmtp029.mac.com (Sun Java(tm) System Messaging Server 6.3-8.01 (built Dec 16 2008; 32bit)) with ESMTPSA id <0KMF00IBXTCIG970@asmtp029.mac.com>; Tue, 07 Jul 2009 17:29:08 -0700 (PDT) From: Marcel Moolenaar In-reply-to: <20090707133611.GA66072@rink.nu> Date: Tue, 07 Jul 2009 17:29:06 -0700 Message-id: <93B562A8-9FE7-44D5-91E4-C9AB1A25BD2A@mac.com> References: <20090707094808.GA93317@mech-cluster238.men.bris.ac.uk> <20090707095058.GC7827@rink.nu> <20090707124405.GA46091@mech-cluster238.men.bris.ac.uk> <20090707133611.GA66072@rink.nu> To: Rink Springer X-Mailer: Apple Mail (2.1068) Cc: freebsd-current@freebsd.org, freebsd-ia64@freebsd.org Subject: Re: buildworld panic on ia64 X-BeenThere: freebsd-ia64@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Porting FreeBSD to the IA-64 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 08 Jul 2009 00:29:09 -0000 On Jul 7, 2009, at 6:36 AM, Rink Springer wrote: >> I tried to reproduce the error, got this on the way: >> >> # XXX: bogusly disabled high FP regs > > I get this message quite often as well; I intend to figure out what's > going on. Marcel, if you have any idea, please let me know. It's a race condition. The high FP registers are lazily context-switched and this error is emitted when a thread wants to use the high FP registers when they are disabled and the CPU onto which the thread is running has the high FP registers corresponding to that thread in registers. In that scenario the high FP registers should not even be disabled. In the above case the kernel simply enables the high FP registers and continues the thread. For the most part the condition is harmless, but I've been looking at a panic that's the result of inconsistency in the high FP state, so the race is potentially fatal. BTW: I never got the error when doing a buildworld. I think Anton's non-standard compiler options make GCC much more FP intensive and thus prone to causing the race. FYI, -- Marcel Moolenaar xcllnt@mac.com