linux-kernel - Re: [PATCH -v4 2/2] printk: Add kernel parameter to control writes to /dev/kmsg

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Message-ID: <20160718081712.GA9239@dhcp-128-65.nay.redhat.com>
Date:	Mon, 18 Jul 2016 16:17:12 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Franck Bui <fbui@...e.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH -v4 2/2] printk: Add kernel parameter to control writes
 to /dev/kmsg

On 07/18/16 at 10:08am, Borislav Petkov wrote:
> On Mon, Jul 18, 2016 at 03:38:45PM +0800, Dave Young wrote:
> > no printk.devkmsg= on kernel cmdline
> >    -> unlocked, default is off, writing to /dev/kmsg is forbidded
> >       -> usespace set sysctl printk.devkmsg=on
> >          -> writing to /dev/kmsg is allowed.
> 
> And that helps how exactly?
> 
> I don't understand why you're harping on the ratelimiting. It is a sane
> default for the *default* case. Userspace should switch to its own
> logging scheme when it has started anyway.

Because IMHO it is wrong, they can not be ratelimited because the writing could
be from different userspace programs. Simply ratelimiting different sources of
writing is pointless to me. One can only see messages they would like to see
by luck, it is worse than off.

> 
> If you still want to see *all* messages, you boot with "=on" or set it
> through sysctl.
> 
> So what is the problem?!

As above mentioned..

Thanks
Dave