linux-kernel - Re: [RFC][PATCH] printk: increase devkmsg write() ratelimit

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Date:   Tue, 18 Dec 2018 22:07:50 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [RFC][PATCH] printk: increase devkmsg write() ratelimit

On (12/18/18 12:47), Borislav Petkov wrote:
[..]
> >  systemd[1]: Unmounting /home...
> >  systemd[1]: Unmounting Temporary Directory (/tmp)...
> >  systemd[1]: Unmounted Temporary Directory (/tmp).
> >  systemd[1]: Stopped target Swap.
> >  systemd[1]: Unmounted /boot.
> >  systemd[1]: Stopped File System Check on /dev/disk/by-uuid/a0737dff-e797-44f0-aea7-d0df1107ff63.
> >  systemd[1]: Stopped File System Check on /dev/disk/by-uuid/5d773b72-e200-4d11-a219-176d62a16d8d.
> >  systemd[1]: Unmounted /home.
> >  systemd[1]: Stopped File System Check on /dev/disk/by-uuid/35319ddc-9b92-4ab0-aaa4-9922db636a5e.
> >  systemd[1]: Unmounted /media/edev.
> >  systemd[1]: Stopped File System Check on /dev/disk/by-uuid/da00daaf-5601-4531-912e-bd69103b379d.
> >  systemd[1]: Unmounted /media/dump.
> >  systemd[1]: Reached target Unmount All Filesystems.
> >  systemd[1]: Stopped File System Check on /dev/disk/by-uuid/b52da2df-161b-4c33-b700-277d95b9672f.
> >  systemd[1]: Removed slice system-systemd\x2dfsck.slice.
> >  systemd[1]: Stopped target Local File Systems (Pre).
> >  systemd[1]: Stopped Create Static Device Nodes in /dev.
> >  systemd[1]: Stopped Create System Users.
> >  systemd[1]: Stopped Remount Root and Kernel File Systems.
> >  systemd[1]: Reached target Shutdown.
> >  systemd[1]: Reached target Final Step.
> >  systemd[1]: Starting Reboot...
> 
> And we wanna see all those "very useful" messages in dmesg because...?

This is right before shutdown. dmesg is not really available anymore.
I can only guess why do they write it to devkmsg - to make it appear
on the serial/net console, perhaps. Dunno.

	-ss