Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757968Ab1CaOUf (ORCPT ); Thu, 31 Mar 2011 10:20:35 -0400 Received: from terminus.zytor.com ([198.137.202.10]:59997 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752952Ab1CaOUa (ORCPT ); Thu, 31 Mar 2011 10:20:30 -0400 Message-ID: <4D948D86.2050607@zytor.com> Date: Thu, 31 Mar 2011 07:19:50 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110307 Fedora/3.1.9-1.fc15 Thunderbird/3.1.9 MIME-Version: 1.0 To: Ingo Molnar CC: Alan Cox , Len Brown , x86@kernel.org, linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, Len Brown , Linus Torvalds , Andrew Morton , Thomas Gleixner Subject: Re: [PATCH 2/9] x86 idle: remove NOP cpuinfo_x86.hlt_works_ok flag References: <67e90d97e0a77df4acd0c75e1bacc7714e011f3e.1301550524.git.len.brown@intel.com> <20110331061247.GA24786@elte.hu> <20110331081800.GH5938@elte.hu> <20110331102355.17d30a38@lxorguk.ukuu.org.uk> <20110331092721.GA16570@elte.hu> <20110331103320.5a72ff8c@lxorguk.ukuu.org.uk> <20110331093528.GA19288@elte.hu> In-Reply-To: <20110331093528.GA19288@elte.hu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1313 Lines: 34 On 03/31/2011 02:35 AM, Ingo Molnar wrote: > > * Alan Cox wrote: > >>> Btw., we used to auto-detect broken HLT systems IIRC - but that got lost >>> already. We should at least honor the boot parameter. >> >> I don't believe we ever auto detected them or found a way to do so. That >> was why the HLT message was printed before hlt was executed. > > Yeah - the CPU hang was unrecoverably deep so no auto-detection was possible. > > That's seriously ancient stuff - still, keeping the boot option around (<10 > lines of code) does not hurt anyone. > What it was was bad power supplies or low-capacitance, high-inductance power distribution that happened to work with MS-DOS which always burned the CPU at 100% and therefore left the power draw relatively consistent current. A proper OS putting the CPU in HLT produced a lot more high frequency noise on the power busses, with disastrous results without proper bypass. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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/