From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx152.postini.com [74.125.245.152]) by kanga.kvack.org (Postfix) with SMTP id E96D26B002B for ; Mon, 24 Sep 2012 14:55:55 -0400 (EDT) Received: from /spool/local by e28smtp02.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 25 Sep 2012 00:25:52 +0530 Received: from d28av03.in.ibm.com (d28av03.in.ibm.com [9.184.220.65]) by d28relay03.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q8OItFtk40108128 for ; Tue, 25 Sep 2012 00:25:15 +0530 Received: from d28av03.in.ibm.com (loopback [127.0.0.1]) by d28av03.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q8OItE55027462 for ; Tue, 25 Sep 2012 04:55:15 +1000 Message-ID: <5060AC71.2080609@linux.vnet.ibm.com> Date: Tue, 25 Sep 2012 00:24:41 +0530 From: "Srivatsa S. Bhat" MIME-Version: 1.0 Subject: Re: divide error: bdi_dirty_limit+0x5a/0x9e References: <20120924102324.GA22303@aftab.osrc.amd.com> <50603829.9050904@linux.vnet.ibm.com> <20120924110554.GC22303@aftab.osrc.amd.com> <50604047.7000908@linux.vnet.ibm.com> <20120924113447.GA25182@localhost> <20120924122053.GD22303@aftab.osrc.amd.com> <20120924122900.GA28627@localhost> <20120924125632.GE22303@aftab.osrc.amd.com> In-Reply-To: <20120924125632.GE22303@aftab.osrc.amd.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Borislav Petkov Cc: Fengguang Wu , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jan Kara , Peter Zijlstra , Andrew Morton , Johannes Weiner , Conny Seidel , "Paul E. McKenney" , Tejun Heo On 09/24/2012 06:26 PM, Borislav Petkov wrote: > On Mon, Sep 24, 2012 at 08:29:00PM +0800, Fengguang Wu wrote: >> On Mon, Sep 24, 2012 at 02:20:53PM +0200, Borislav Petkov wrote: >>> On Mon, Sep 24, 2012 at 07:34:47PM +0800, Fengguang Wu wrote: >>>> Will you test such a line? At least the generic do_div() only uses the >>>> lower 32bits for division. >>>> >>>> WARN_ON(!(den & 0xffffffff)); >>> >>> But, but, the asm output says: >>> >>> 28: 48 89 c8 mov %rcx,%rax >>> 2b:* 48 f7 f7 div %rdi <-- trapping instruction >>> 2e: 31 d2 xor %edx,%edx >>> >>> and this version of DIV does an unsigned division of RDX:RAX by the >>> contents of a *64-bit register* ... in our case %rdi. >>> >>> Srivatsa's oops shows the same: >>> >>> 28: 48 89 f0 mov %rsi,%rax >>> 2b:* 48 f7 f7 div %rdi <-- trapping instruction >>> 2e: 41 8b 94 24 74 02 00 mov 0x274(%r12),%edx >>> >>> Right? >> >> Right, that's why I said "at least". As for x86, I'm as clueless as you.. > > Right, both oopses are on x86 so I don't think it is the bitness of the > division. > > Another thing those two have in common is that both happen when a CPU > comes online. Srivatsa's is when CPU9 comes online (oops is detected on > CPU9) and in our case CPU4 comes online but the oops says CPU0. > I had posted another dump from one of my tests. That one triggers while offlining a CPU (CPU 9). https://lkml.org/lkml/2012/9/14/235 > So it has to be hotplug-related. Regards, Srivatsa S. Bhat -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org