Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753539AbYJFKox (ORCPT ); Mon, 6 Oct 2008 06:44:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752393AbYJFKoo (ORCPT ); Mon, 6 Oct 2008 06:44:44 -0400 Received: from mx2.redhat.com ([66.187.237.31]:57255 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752334AbYJFKon (ORCPT ); Mon, 6 Oct 2008 06:44:43 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20080924164826.14867.63020.stgit@warthog.procyon.org.uk> <1222426580.16700.258.camel@lappy.programming.kicks-ass.net> <1222431635.16700.278.camel@lappy.programming.kicks-ass.net> <29968.1222871650@redhat.com> <1703.1222986215@redhat.com> To: Nicolas Pitre Cc: dhowells@redhat.com, Peter Zijlstra , torvalds@osdl.org, akpm@linux-foundation.org, linux-am33-list@redhat.com, lkml Subject: Re: [PATCH 1/2] MN10300: Move asm-arm/cnt32_to_63.h to include/linux/ Date: Mon, 06 Oct 2008 11:44:22 +0100 Message-ID: <19168.1223289862@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 945 Lines: 24 Nicolas Pitre wrote: > If so then you're using this interface in an inappropriate way. > > The _absolute_ minimum frequency with which this should be fully > executed is once per half period of the base counter. I hope that in > practice it happens far more often than that. I think you're misunderstanding my contention. If preemption is enabled, cnt32_to_63() can be called with greater than minimum frequency and yet reversions can still happen. The problem is that a process that's half way through executing cnt32_to_63() can be preempted for a period of time sufficient that when it is rescheduled and writes __m_cnt_hi, it corrupts it with an out of date value. David -- 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/