linux-kernel - Re: [GIT pull] printk updates for 4.15

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Message-ID: <CA+55aFwNo9CDzuDWue7QJYd_iip4bgEqduVjNAHjxwdxjiur1g@mail.gmail.com>
Date:   Tue, 14 Nov 2017 13:07:15 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mark Salyzyn <salyzyn@...roid.com>,
        Prarit Bhargava <prarit@...hat.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [GIT pull] printk updates for 4.15

On Tue, Nov 14, 2017 at 12:21 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
>
> First of all sched_clock() and CLOCK_MONOTONIC can drift apart frequency
> wise pretty bad.

Yes. And I would actuall ynot object to just making the printk buffers
use CLOCK_MONOTONIC.

The reason we avoided that was we didn't want to take the locks, though.

sched_clock() is used not because it's the right clock, or
particularly good, but because it is fast and doesn't have locking
issues.

But all of this is entirely separate from the "changing from one clock
that has small issues for good reasons to FOUR DIFFERENT CLOCKS THAT
THE USER CHOOSES RANDOMLY".

See my objection?

One is "let's improve the clock".

The other is "let's do something crazy and idiotic".

                 Linus