From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932388AbXCXWOb (ORCPT ); Sat, 24 Mar 2007 18:14:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932396AbXCXWOb (ORCPT ); Sat, 24 Mar 2007 18:14:31 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:36426 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932388AbXCXWO3 (ORCPT ); Sat, 24 Mar 2007 18:14:29 -0400 Date: Sat, 24 Mar 2007 23:09:45 +0100 From: Ingo Molnar To: Thomas Gleixner Cc: Linus Torvalds , LKML , john stultz , Andrew Morton , Adrian Bunk Subject: Re: [PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems Message-ID: <20070324220945.GA26168@elte.hu> References: <1174773769.10840.450.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1174773769.10840.450.camel@localhost.localdomain> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Thomas Gleixner wrote: > commit f9690982b8c2f9a2c65acdc113e758ec356676a3 removed the check for > cpu_khz from sched_clock(), which prevented early access to the TSC by > non obvious magic. > > This is harmless as long as the CPU has a TSC. On TSCless systems this > results in an illegal instruction trap. > > Replace tsc_disabled and tsc_unstable by tsc_enabled, which is only > set when the tsc is available and not unstable. > > Signed-off-by: Thomas Gleixner oops, indeed! I think this should also resolve one of the bugs (TSC-less Cyrix?) that were reported against -mm some time ago. Acked-by: Ingo Molnar Ingo