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

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Date:	Sun, 17 Jul 2016 07:40:35 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Dave Young <dyoung@...hat.com>
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 Sat, Jul 16, 2016 at 06:44:25PM +0800, Dave Young wrote:

...

> Mis-ratelimit cause critical userspace messages being lost, that is worse

The current setting is quite generous so that all critical messages
should land in dmesg. Besides, we don't ratelimit during boot. The idea
is that userspace should switch to a different logging facility once the
system is up... which userspace does reportedly.

IOW, /dev/kmsg should handle a relatively big logging amount without
ratelimiting.

> than use off as default. Suppose we turn off devkmsg by default distributions
> can still turn on it with sysctl and for us who do not want the flooding we can
> use printk.devkmsg=off in kernel cmdline to override it.

That part I cannot parse.

> Of course if we turn off it by default we can print a warning to alert user.
> 
> BTW, for userspace messages maybe they should not go to same log buffer, maybe
> a separate log buffer for /dev/msg will be better.

See above.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--