Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752358AbbG2MgG (ORCPT ); Wed, 29 Jul 2015 08:36:06 -0400 Received: from casper.infradead.org ([85.118.1.10]:49585 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751246AbbG2MgD (ORCPT ); Wed, 29 Jul 2015 08:36:03 -0400 Date: Wed, 29 Jul 2015 14:35:55 +0200 From: Peter Zijlstra To: Richard Cochran Cc: Thomas Gleixner , John Stultz , Christopher Hall , Ingo Molnar , Jeff Kirsher , john.ronciak@intel.com, "H. Peter Anvin" , "x86@kernel.org" , lkml , netdev@vger.kernel.org Subject: Re: [PATCH 1/5] Add functions producing system time given a backing counter value Message-ID: <20150729123555.GP19282@twins.programming.kicks-ass.net> References: <1438044416-15588-1-git-send-email-christopher.s.hall@intel.com> <1438044416-15588-2-git-send-email-christopher.s.hall@intel.com> <20150729104944.GM19282@twins.programming.kicks-ass.net> <20150729114840.GA16880@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150729114840.GA16880@localhost.localdomain> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 972 Lines: 21 On Wed, Jul 29, 2015 at 01:48:41PM +0200, Richard Cochran wrote: > On Wed, Jul 29, 2015 at 12:49:44PM +0200, Peter Zijlstra wrote: > > This is still fuzzy, right? The hardware ART timestamp could be from > > _before_ the NTP adjust; or the NTP adjust could happen while we do this > > conversion and we'll take the retry loop. > > In the original series, yes. > > > In both cases, the resulting value is computed using a different slope > > than was in effect at the time of the stamp. With the end result being > > slightly off from what it should be. > > In Thomas' patch the get_ts() is meant to read fresh pairs of time > stamps from within the loop. Ah, indeed, I missed that. Yes if that's possible we get it right. -- 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/