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Petr Mladek 3cffa06aee printk/console: Allow to disable console output by using console="" or console=null
The commit 48021f9813 ("printk: handle blank console arguments
passed in.") prevented crash caused by empty console= parameter value.

Unfortunately, this value is widely used on Chromebooks to disable
the console output. The above commit caused performance regression
because the messages were pushed on slow console even though nobody
was watching it.

Use ttynull driver explicitly for console="" and console=null
parameters. It has been created for exactly this purpose.

It causes that preferred_console is set. As a result, ttySX and ttyX
are not used as a fallback. And only ttynull console gets registered by
default.

It still allows to register other consoles either by additional console=
parameters or SPCR. It prevents regression because it worked this way even
before. Also it is a sane semantic. Preventing output on all consoles
should be done another way, for example, by introducing mute_console
parameter.

Link: https://lore.kernel.org/r/20201006025935.GA597@jagdpanzerIV.localdomain
Suggested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20201111135450.11214-3-pmladek@suse.com
2020-11-20 12:29:05 +01:00
arch MIPS updates for v5.10: 2020-10-16 12:40:55 -07:00
block - Improve DM core's bio splitting to use blk_max_size_offset(). Also 2020-10-14 15:05:38 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto drivers-5.10-2020-10-12 2020-10-13 13:04:41 -07:00
Documentation MIPS updates for v5.10: 2020-10-16 12:40:55 -07:00
drivers init/console: Use ttynull as a fallback when there is no console 2020-11-20 12:23:50 +01:00
fs powerpc updates for 5.10 2020-10-16 12:21:15 -07:00
include init/console: Use ttynull as a fallback when there is no console 2020-11-20 12:23:50 +01:00
init init/console: Use ttynull as a fallback when there is no console 2020-11-20 12:23:50 +01:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel printk/console: Allow to disable console output by using console="" or console=null 2020-11-20 12:29:05 +01:00
lib kgdb patches for 5.10-rc1 2020-10-16 12:47:18 -07:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm Merge branch 'akpm' (patches from Andrew) 2020-10-16 11:31:55 -07:00
net networking changes for the 5.10 merge window 2020-10-15 18:42:13 -07:00
samples networking changes for the 5.10 merge window 2020-10-15 18:42:13 -07:00
scripts Merge branch 'akpm' (patches from Andrew) 2020-10-16 11:31:55 -07:00
security networking changes for the 5.10 merge window 2020-10-15 18:42:13 -07:00
sound dma-mapping updates for 5.10 2020-10-15 14:43:29 -07:00
tools powerpc updates for 5.10 2020-10-16 12:21:15 -07:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: fix memory leak in kvm_io_bus_unregister_dev() 2020-09-11 13:15:11 -04:00
.clang-format memblock: use separate iterators for memory and reserved regions 2020-10-13 18:38:35 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap MAINTAINERS: jarkko.sakkinen@linux.intel.com -> jarkko@kernel.org 2020-10-16 11:11:19 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS networking changes for the 5.10 merge window 2020-10-15 18:42:13 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MIPS updates for v5.10: 2020-10-16 12:40:55 -07:00
Makefile networking changes for the 5.10 merge window 2020-10-15 18:42:13 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.