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Subject[PATCH -v3 0/2] printk.devkmsg: Ratelimit it by default
From: Borislav Petkov <>

Hi all,

here's v3 integrating Ingo's comments. The thing is called
printk.devkmsg= or printk_devkmsg now, depending on cmdline option or



here's v2 with the requested sysctl option kernel.printk_kmsg and
locking of the setting when printk.kmsg= is supplied on the command

Patch 1 is unchanged.

Patch 2 has grown the sysctl addition.


Rostedt is busy so I took Linus' old patch and Steven's last v2 and
split and extended them with the comments people had on the last thread:

I hope, at least.

So it is ratelimiting by default, with "on" and "off" cmdline options. I
called the option somewhat a bit shorter too: "printk.kmsg"

The current use cases of this and of which I'm aware are:

* debug the kernel and thus shut up all interfering input from
userspace, i.e. boot with "printk.kmsg=off"

* debug userspace (and by that I mean systemd) by booting with
"printk.kmsg=on" so that the ratelimiting is disabled and the kernel log
gets all the spew.



Borislav Petkov (2):
ratelimit: Extend to print suppressed messages on release
printk: Add kernel parameter to control writes to /dev/kmsg

Documentation/kernel-parameters.txt | 6 +++
Documentation/sysctl/kernel.txt | 14 +++++++
include/linux/printk.h | 7 ++++
include/linux/ratelimit.h | 36 +++++++++++++---
kernel/printk/printk.c | 83 +++++++++++++++++++++++++++++++++----
kernel/sysctl.c | 9 ++++
lib/ratelimit.c | 6 ++-
7 files changed, 146 insertions(+), 15 deletions(-)


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