From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DCFCEC433F5 for ; Thu, 28 Apr 2022 21:52:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352682AbiD1Vzq (ORCPT ); Thu, 28 Apr 2022 17:55:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237165AbiD1Vy6 (ORCPT ); Thu, 28 Apr 2022 17:54:58 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9465221E3B for ; Thu, 28 Apr 2022 14:51:42 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1AC0461FB9 for ; Thu, 28 Apr 2022 21:51:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 809CAC385B9; Thu, 28 Apr 2022 21:51:41 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.95) (envelope-from ) id 1nkC32-003MaG-Jh; Thu, 28 Apr 2022 17:51:40 -0400 Message-ID: <20220428215140.438634489@goodmis.org> User-Agent: quilt/0.66 Date: Thu, 28 Apr 2022 17:51:06 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Kurt Kanzenbach Subject: [for-next][PATCH 4/8] tracing: Add documentation for trace clock tai References: <20220428215102.260147624@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kurt Kanzenbach Add documentation for newly introduced trace clock "tai". This clock corresponds to CLOCK_TAI. Link: https://lkml.kernel.org/r/20220414091805.89667-4-kurt@linutronix.de Signed-off-by: Kurt Kanzenbach Signed-off-by: Steven Rostedt (Google) --- Documentation/trace/ftrace.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 45b8c56af67a..b37dc19e4d40 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -517,6 +517,18 @@ of ftrace. Here is a list of some of the key files: processing should be able to handle them. See comments in the ktime_get_boot_fast_ns() function for more information. + tai: + This is the tai clock (CLOCK_TAI) and is derived from the wall- + clock time. However, this clock does not experience + discontinuities and backwards jumps caused by NTP inserting leap + seconds. Since the clock access is designed for use in tracing, + side effects are possible. The clock access may yield wrong + readouts in case the internal TAI offset is updated e.g., caused + by setting the system time or using adjtimex() with an offset. + These effects are rare and post processing should be able to + handle them. See comments in the ktime_get_tai_fast_ns() + function for more information. + To set a clock, simply echo the clock name into this file:: # echo global > trace_clock -- 2.35.1