From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752710AbaATKOM (ORCPT ); Mon, 20 Jan 2014 05:14:12 -0500 Received: from merlin.infradead.org ([205.233.59.134]:52364 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750756AbaATKOK (ORCPT ); Mon, 20 Jan 2014 05:14:10 -0500 Date: Mon, 20 Jan 2014 11:13:45 +0100 From: Peter Zijlstra To: Len Brown Cc: Stephen Rothwell , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , linux-next@vger.kernel.org, "linux-kernel@vger.kernel.org" Subject: Re: linux-next: build failure after merge of the tip tree Message-ID: <20140120101345.GC3694@twins.programming.kicks-ass.net> References: <20140116145829.5e4fcab103b1c5c77501ee77@canb.auug.org.au> <20140120083021.GC30183@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140120083021.GC30183@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 20, 2014 at 09:30:21AM +0100, Peter Zijlstra wrote: > Then make them so. The fact was that most of the mwait idle sites > were bloody broken. And the single mwait_idle_with_hints() function > presents a single nice function that does all the required magics. To stress this a bit more; have a look see at mwwait_idle_with_hints(); it does a whole lot of subtle magic. - current_{set,clr}_polling*(), these are crucial in not missing and wrecking NEED_RESCHED state. - X86_FEATURE_CLFLUSH_MONTIOR quirk - Does the monitor(); if (!need_resched()) mwait() thing. All of those are required for a correct and functional idle loop. And I've seen sites where any or all of the above were missing/broken. Not unifying the lot into a simple usable function is just stupid -- history has shown people simply cannot be trusted to get this right.