From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx161.postini.com [74.125.245.161]) by kanga.kvack.org (Postfix) with SMTP id 0AF336B002B for ; Mon, 24 Sep 2012 08:56:39 -0400 (EDT) Date: Mon, 24 Sep 2012 14:56:32 +0200 From: Borislav Petkov Subject: Re: divide error: bdi_dirty_limit+0x5a/0x9e Message-ID: <20120924125632.GE22303@aftab.osrc.amd.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120924122900.GA28627@localhost> Sender: owner-linux-mm@kvack.org List-ID: To: Fengguang Wu Cc: "Srivatsa S. Bhat" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jan Kara , Peter Zijlstra , Andrew Morton , Johannes Weiner , Conny Seidel , "Paul E. McKenney" 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. So it has to be hotplug-related. -- Regards/Gruss, Boris. Advanced Micro Devices GmbH Einsteinring 24, 85609 Dornach GM: Alberto Bozzo Reg: Dornach, Landkreis Muenchen HRB Nr. 43632 WEEE Registernr: 129 19551 -- 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