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

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Message-ID: <CA+55aFw=iwt0Dy16fgVUZnEVn4PqJExxYvtxyb5x+TCEMWHYOw@mail.gmail.com>
Date:   Mon, 13 Nov 2017 18:48:01 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     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>
Subject: Re: [GIT pull] printk updates for 4.15

On Mon, Nov 13, 2017 at 5:18 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
>  (b) just emit a "synchronization printk" every once in a while, which
> is obviously also using the same standard time source, but the line
> actually _says_ what the other time sources are.

Side note: there's a few good obvious times to do this. After a NTP
synchronization, after a resume, and maybe "every X hours if nothing
else is happening".

That "if nothing else is happening" would actually be a nice heartbeat
thing for people who care about that. I've had machines crash
overnight, and later wondered when it happened. Of course, these days
other system journal sources tend to be so chatty that it doesn't much
happen, but maybe it would still be appreciated in embedded places
where that isn't yet the case..

And that "how often you do the time sync printk" really could be a
kernel configuration thing then, but it wouldn't actually affect any
existing machinery unlike the "let's just change what the printk
header timestamp means".

              Linus