From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262832AbVG3Ag0 (ORCPT ); Fri, 29 Jul 2005 20:36:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262825AbVG3Adp (ORCPT ); Fri, 29 Jul 2005 20:33:45 -0400 Received: from omx3-ext.sgi.com ([192.48.171.20]:11750 "EHLO omx3.sgi.com") by vger.kernel.org with ESMTP id S262761AbVG3AcY (ORCPT ); Fri, 29 Jul 2005 20:32:24 -0400 Date: Fri, 29 Jul 2005 17:32:13 -0700 (PDT) From: Christoph Lameter To: tony.luck@intel.com cc: linux-kernel@vger.kernel.org, alex.williamson@hp.com Subject: Re: long delays (possibly infinite) in time_interpolator_get_counter In-Reply-To: <200507292206.j6TM6w4k004594@agluck-lia64.sc.intel.com> Message-ID: References: <200507292206.j6TM6w4k004594@agluck-lia64.sc.intel.com> 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 > diff --git a/include/linux/timex.h b/include/linux/timex.h Oh. Before I forget: You need to make the same changes to the asm code in arch/ia64/kernel/fsys.S in order for this to work properly. The asm code has been optimized to the hilt to save every cycle possible. Please dont add any. The C code is typically bypassed for all user space gettimeofday / clock_gettime calls. Hmm.. However, if you did not see the problem in the asm code (which does not have the nesting issue of C and wastes some time doing other things) then we may solve the issue by either also calling asm from kernel space or making sure that some time is wasted on something else then the cmpxchg in the inner loop. Or we can make "nojitter" the default? Then do a if (nojitter) printk(KERN_ERR "Beware: SMP system using ITC as a time source!" "Time may fluctuate.\n"); at bootup and hope for the best?