Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752853AbaATI5p (ORCPT ); Mon, 20 Jan 2014 03:57:45 -0500 Received: from terminus.zytor.com ([198.137.202.10]:41882 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750942AbaATI5n (ORCPT ); Mon, 20 Jan 2014 03:57:43 -0500 Message-ID: <52DCE4CF.2060605@zytor.com> Date: Mon, 20 Jan 2014 00:56:47 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Peter Zijlstra , Len Brown CC: Stephen Rothwell , Thomas Gleixner , Ingo Molnar , linux-next@vger.kernel.org, "linux-kernel@vger.kernel.org" Subject: Re: linux-next: build failure after merge of the tip tree References: <20140116145829.5e4fcab103b1c5c77501ee77@canb.auug.org.au> <20140116121955.GQ31570@twins.programming.kicks-ass.net> <20140117074628.88698f59939c9002b7c12968@canb.auug.org.au> <20140120082620.GB30183@twins.programming.kicks-ass.net> In-Reply-To: <20140120082620.GB30183@twins.programming.kicks-ass.net> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/20/2014 12:26 AM, Peter Zijlstra wrote: > On Sun, Jan 19, 2014 at 11:45:43PM -0500, Len Brown wrote: >> +static void mwait_idle(void) >> +{ >> + mwait_idle_with_hints(0, 0); >> +} >> + >> >> The reason the patch above will crash Core2 machines is because >> core2 machines don't support mwait_idle_with_hints(). >> >> The calling sequence for old and new MWAIT instructions is different. >> The former must be invoked with interrupts enabled, >> and the later can be invoked with interrupts disabled, >> which is a feature that Linux takes advantage of. > > What old and new? They're the same byte sequence: 0x0f 0x01 0xc9 > > And your 'old' __sti_mwait(0,0) has the exact same arguments as > mwait_idle_with_hints(0,0). > The difference is the STI! -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/