From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx131.postini.com [74.125.245.131]) by kanga.kvack.org (Postfix) with SMTP id 029AE6B002B for ; Mon, 24 Sep 2012 08:21:00 -0400 (EDT) Date: Mon, 24 Sep 2012 14:20:53 +0200 From: Borislav Petkov Subject: Re: divide error: bdi_dirty_limit+0x5a/0x9e Message-ID: <20120924122053.GD22303@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120924113447.GA25182@localhost> Sender: owner-linux-mm@kvack.org List-ID: To: Fengguang Wu Cc: "Srivatsa S. Bhat" , Borislav Petkov , 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 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? -- 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