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 935DEC43217 for ; Thu, 14 Apr 2022 09:18:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241610AbiDNJUo (ORCPT ); Thu, 14 Apr 2022 05:20:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241602AbiDNJUj (ORCPT ); Thu, 14 Apr 2022 05:20:39 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10E1251E4D; Thu, 14 Apr 2022 02:18:15 -0700 (PDT) From: Kurt Kanzenbach DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1649927893; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iLmCDPlHlx+4vJ7+eT/pCoYu1/+sbjT/6wC8EGaZi10=; b=Ouz9SoFspDW418thOwaQ0Wmr2WP5cb7znTdJES07Jqk9ljP7qEuX4Ja0bp2p9Bx1rL46+0 KEM/ThW4kR7QqxstcwNG1UBJMbrSEcivkYgDo2AA3pJHs6Vv+FzGnev/fhr1PZlTqUDAWd 6f2Z2ddOjcAn5KCI+LKeV41G5Wyutpu08s+KxiTMHy/EPTRQLGrsB+Xt4YKuI6fXJkLvno 4K89hh3dbaTp+7PlMhnUVQK4fYa+WiGDSzXbiAzGiLOtHyRA3iNtaSgJD9QlQ+dOltQ2nK RblARhI6wi4jP2x1Os0ZUdTxZUAMvhPMUzyZMgTeX2JXgl3mXcUdKIDh8hJV+g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1649927893; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iLmCDPlHlx+4vJ7+eT/pCoYu1/+sbjT/6wC8EGaZi10=; b=Fup1SrnNBv5FuCo7x/lZ5UGJZXakS/VRTQw77bfksXFJPu8+Pso4qvtggfACDwPEjBiz36 3b1SHOh6BLCvwJAA== To: John Stultz , Thomas Gleixner , Stephen Boyd , Steven Rostedt , Ingo Molnar , Jonathan Corbet Cc: Richard Cochran , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Kurt Kanzenbach Subject: [PATCH v2 3/3] tracing: Add documentation for trace clock tai Date: Thu, 14 Apr 2022 11:18:05 +0200 Message-Id: <20220414091805.89667-4-kurt@linutronix.de> In-Reply-To: <20220414091805.89667-1-kurt@linutronix.de> References: <20220414091805.89667-1-kurt@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Add documentation for newly introduced trace clock "tai". This clock corresponds to CLOCK_TAI. Signed-off-by: Kurt Kanzenbach --- 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 -- 2.30.2