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

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Message-ID: <5cd0541d-148c-b131-076a-910f8a900770@redhat.com>
Date:   Tue, 19 Sep 2017 07:52:33 -0400
From:   Prarit Bhargava <prarit@...hat.com>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Mark Salyzyn <salyzyn@...roid.com>,
        Petr Mladek <pmladek@...e.com>
Cc:     linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        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 09/17/2017 06:46 AM, Sergey Senozhatsky wrote:

> I'm a bit uncomfortable with the "breaks user space" part. since this
> is a strictly debugging option, would it be sufficient to store those
> extended timestamps as prefixes of every message?
> see (sorry for "self-quoting"):
> 	lkml.kernel.org/r/20170917062608.GA512@...erII.localdomain
>

Sergey, I haven't forgotten about the above.  It's something
I'm going to look at after this initial patchset is done.

P.

> each message, thus, will be in the following format
> 
> [current header: loglevel, timestamp, etc] [extended printk data] message text
> 
> extended printk data can contain your monotonic/etc timestamps, and
> anything else.
> 
> and then it's up to you how do you grep the messages and process the
> extended data. but the point is - user space tools (journald, dmesg,
> etc.) stays intact. which is kinda nice.
> 
> so we can avoid that chicken and egg problem: we break user space
> by merging the patchset but user space people don't want to talk
> about any fixes until we break those tools.
> 
> 	-ss
>