linux-kernel - Re: [PATCH 2/2] printk: Add boottime and real timestamps

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Date:   Fri, 28 Jul 2017 18:28:13 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Prarit Bhargava <prarit@...hat.com>
cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Mark Salyzyn <salyzyn@...roid.com>,
        Jonathan Corbet <corbet@....net>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Stultz <john.stultz@...aro.org>,
        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>,
        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>, Theodore Ts'o <tytso@....edu>,
        Josh Poimboeuf <jpoimboe@...hat.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH 2/2] printk: Add boottime and real timestamps

On Fri, 28 Jul 2017, Prarit Bhargava wrote:
> On 07/25/2017 09:00 AM, Peter Zijlstra wrote:
> Thanks for the above change.  I can see that makes the code simpler.
> 
> > Although I must strongly discourage using REALTIME, DST will make
> > untangling your logs an absolute nightmare. I would simply not provide
> > it.
> 
> I understand your concern, however, I've been in situations where REALTIME
> stamping has pointed me in the direction of where a bug was.  Even with the
> complicated logs I think it is worthwhile.

As Mark pointed out. ktime_get_real() and the fast variant return UTC. The
timezone mess plus the DST nonsense are done in user space.

Thanks,

	tglx