Re: [PATCH v2] printk: Add kernel parameter to disable writes to /dev/kmsg

[Linus Torvalds <torvalds@linux-foundation.org>]

On Mon, Apr 25, 2016 at 1:00 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> For the purpose to pass messages from early init through to final boot.
> Systemd continued this for the same purpose. Which I agree is totally
> legit. But where systemd fails, is that it continues to use this
> interface far beyond the need.
>
> I agree with Andrew, we should have had a way to close the pipe after
> the system was up and running.

I really don't think this should be about open/close, but about rate
limiting writes.

I think we'd be much better off allowing writes during early boot
(when the real root filesystem hasn't been started yet, so logging to
disk doesn't work - at that point the kernel log really is a better
alternative), and then just start throttling it later (possibly very
aggressively).

But the other issue is that once you actually have logging working, I
don't see why you don't just look at the system logs. Yeah, it's not
/var/log/messages any more, but it's not *that* hard to do. Just use
"journalctl -k" instead of dmesg, and you won't be missing data.

This is why I harp on rate limiting, and I think your patch is silly:
it solves the wrong problem (the one that isn't a real problem), and
it does it with a sledgehammer when a flyswatter would be more
appropriate.

              Linus