From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx146.postini.com [74.125.245.146]) by kanga.kvack.org (Postfix) with SMTP id 34FF86B002B for ; Mon, 24 Sep 2012 08:29:44 -0400 (EDT) Date: Mon, 24 Sep 2012 20:29:00 +0800 From: Fengguang Wu Subject: Re: divide error: bdi_dirty_limit+0x5a/0x9e Message-ID: <20120924122900.GA28627@localhost> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120924122053.GD22303@aftab.osrc.amd.com> Sender: owner-linux-mm@kvack.org List-ID: To: Borislav Petkov 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 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.. Thanks, Fengguang -- 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