From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755326AbbCGJep (ORCPT ); Sat, 7 Mar 2015 04:34:45 -0500 Received: from mail-wg0-f48.google.com ([74.125.82.48]:36895 "EHLO mail-wg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754482AbbCGJel (ORCPT ); Sat, 7 Mar 2015 04:34:41 -0500 Date: Sat, 7 Mar 2015 10:34:35 +0100 From: Ingo Molnar To: John Stultz Cc: lkml , Dave Jones , Linus Torvalds , Thomas Gleixner , Richard Cochran , Prarit Bhargava , Stephen Boyd , Peter Zijlstra Subject: Re: [PATCH 07/12] time: Try to catch clocksource delta underflows Message-ID: <20150307093435.GF30888@gmail.com> References: <1425696603-16878-1-git-send-email-john.stultz@linaro.org> <1425696603-16878-8-git-send-email-john.stultz@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1425696603-16878-8-git-send-email-john.stultz@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * John Stultz wrote: > In the case where there is a broken clocksource > where there are multiple actual clocks that > aren't perfectly aligned, we may see small "negative" > deltas when we subtract now from cycle_last. So this is a typical example where putting argument references is really helpful. Consider these two variants: deltas when we subtract now from cycle_last. deltas when we subtract 'now' from 'cycle_last'. I had to read the first variant three times until I realized that 'now' is a C variable misleadingly inserted into English text. > The values are actually negative with respect to the > clocksource mask value, not necessarily negative > if cast to a s64, but we can check by checking the > delta see if it is a small (relative to the mask) > negative value (again negative relative to the mask). typo. Thanks, Ingo