Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161190AbWJRQQZ (ORCPT ); Wed, 18 Oct 2006 12:16:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161227AbWJRQQZ (ORCPT ); Wed, 18 Oct 2006 12:16:25 -0400 Received: from pollux.ds.pg.gda.pl ([153.19.208.7]:46095 "EHLO pollux.ds.pg.gda.pl") by vger.kernel.org with ESMTP id S1161190AbWJRQQY (ORCPT ); Wed, 18 Oct 2006 12:16:24 -0400 Date: Wed, 18 Oct 2006 17:16:23 +0100 (BST) From: "Maciej W. Rozycki" To: Andrew Morton cc: john stultz , Andi Kleen , lkml Subject: Re: [PATCH] i386 Time: Avoid PIT SMP lockups In-Reply-To: <20061011142646.eb41fac3.akpm@osdl.org> Message-ID: References: <1160596462.5973.12.camel@localhost.localdomain> <20061011142646.eb41fac3.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1017 Lines: 21 On Wed, 11 Oct 2006, Andrew Morton wrote: > So this patch has the potential to screw up people who have 2-way or 4-way, > no hpet/pm-timer and dodgy TSCs. Note that all APIC-based SMP systems (even these rare i486 beasts) by definition do have local APIC timers, one per CPU, with a reasonable resolution which could likely be used instead. There is an erratum in some early Pentium integrated APICs, where a tick is lost when 0 is reached (the timer counts downwards), so it may be needed to be taken into account for good timekeeping, but otherwise the timers look like a reasonable choice. The timers are local to their respective CPUs and are never written by Linux (see references to APIC_TMCCT), so there is no need for locking to access them. Maciej - 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/