linux-kernel - Re: [PATCH 3/3 v11] printk: Add monotonic, boottime, and realtime timestamps

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Date:   Fri, 15 Sep 2017 10:40:11 -0400
From:   Prarit Bhargava <prarit@...hat.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     linux-kernel@...r.kernel.org, Mark Salyzyn <salyzyn@...roid.com>,
        Jonathan Corbet <corbet@....net>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Christoffer Dall <cdall@...aro.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Olof Johansson <olof@...om.net>,
        Josh Poimboeuf <jpoimboe@...hat.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH 3/3 v11] printk: Add monotonic, boottime, and realtime
 timestamps



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.