Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754610Ab3COSPB (ORCPT ); Fri, 15 Mar 2013 14:15:01 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:36447 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752452Ab3COSPA (ORCPT ); Fri, 15 Mar 2013 14:15:00 -0400 Date: Fri, 15 Mar 2013 18:14:49 +0000 From: Russell King - ARM Linux To: chpoph Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Viresh Kumar , Nicolas Pitre , Liviu Dudau , Greg Kroah-Hartman , will.deacon@arm.com 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. Message-ID: <20130315181449.GX4977@n2100.arm.linux.org.uk> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 776 Lines: 15 On Sat, Mar 16, 2013 at 12:08:54AM +0800, chpoph wrote: > If ARCH_HAS_READ_CURRENT_TIMER is not defined and on current timer is > used for udelay, then __loop_delay and __loop_const_udelay is used to > delay a specific time interval. but in delay-loop.S, loops_per_jiffy > (not per cpu data) is used to calculate the number of loops. in SMP > system, udelay delays the wrong time interval if two cpus running at > different frequency. We don't support different CPUs running at different frequencies with the delay loop. Sorry. -- 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/