Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932587Ab3CPDcr (ORCPT ); Fri, 15 Mar 2013 23:32:47 -0400 Received: from mail-lb0-f180.google.com ([209.85.217.180]:36891 "EHLO mail-lb0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755438Ab3CPDcp (ORCPT ); Fri, 15 Mar 2013 23:32:45 -0400 MIME-Version: 1.0 In-Reply-To: <20130315181449.GX4977@n2100.arm.linux.org.uk> References: <20130315181449.GX4977@n2100.arm.linux.org.uk> Date: Sat, 16 Mar 2013 11:32:43 +0800 Message-ID: Subject: Re: udelay function delays the wrong time interval in multiprocessor system, if ARCH_HAS_READ_CURRENT_TIMER is not defined and on current timer is used. From: chpoph To: Russell King - ARM Linux Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Viresh Kumar , Nicolas Pitre , Liviu Dudau , Greg Kroah-Hartman , will.deacon@arm.com Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 712 Lines: 15 On Sat, Mar 16, 2013 at 2:14 AM, Russell King - ARM Linux wrote: > We don't support different CPUs running at different frequencies with > the delay loop. Sorry. Does it means that a timer-based delay implementation must be used to get an accurate delay in SMP. I think it should print a warning message if the CPU delay loop is used in SMP. In my system, the wrong delay interval fluctuated with CPU frequencies caused a control problem. -- 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/