From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751348AbdIOOkQ (ORCPT <rfc822;w@1wt.eu>);
        Fri, 15 Sep 2017 10:40:16 -0400
Received: from mx1.redhat.com ([209.132.183.28]:47224 "EHLO mx1.redhat.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751111AbdIOOkP (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 15 Sep 2017 10:40:15 -0400
DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 825994E4CB
Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com
Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=prarit@redhat.com
Subject: Re: [PATCH 3/3 v11] printk: Add monotonic, boottime, and realtime
 timestamps
To: Petr Mladek <pmladek@suse.com>
References: <1504613201-23868-1-git-send-email-prarit@redhat.com>
 <1504613201-23868-4-git-send-email-prarit@redhat.com>
 <20170915132808.GL2908@pathway.suse.cz>
Cc: linux-kernel@vger.kernel.org, Mark Salyzyn <salyzyn@android.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        John Stultz <john.stultz@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Stephen Boyd <sboyd@codeaurora.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Christoffer Dall <cdall@linaro.org>,
        Deepa Dinamani <deepa.kernel@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Joel Fernandes <joelaf@google.com>,
        Kees Cook <keescook@chromium.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Olof Johansson <olof@lixom.net>, Josh Poimboeuf <jpoimboe@redhat.com>,
        linux-doc@vger.kernel.org
From: Prarit Bhargava <prarit@redhat.com>
Message-ID: <4395c49b-5719-f6f8-6580-4c3f7abaed79@redhat.com>
Date: Fri, 15 Sep 2017 10:40:11 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.7.0
MIME-Version: 1.0
In-Reply-To: <20170915132808.GL2908@pathway.suse.cz>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 15 Sep 2017 14:40:15 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org



On 09/15/2017 09:28 AM, Petr Mladek wrote:
> 
> I am still slightly nervous that external tools would need updating.
> Also they might have troubles to interpret the time stamps especially
> when the source is changed at runtime via
> /sys/module/printk/parameters/time.

In earlier versions I had logic to prevent switching during runtime.  tglx
requested that it be removed and I removed it.  Personally I fall into the "I'm
going to set it once and never change it" however, as Mark will offer there are
cases where it might be advantageous to change the timestamp.  I think he has a
patch that will append a b/r/etc. to the timestamp so that userspace can
interpret the different timestamps.

P.