Petr Mladek ab4af56ae2 printk/console: Allow to disable console output by using console="" or console=null ... commit 3cffa06aeef7ece30f6b5ac0ea51f264e8fea4d0 upstream. 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 Cc: Yi Fan <yfa@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-11-12 14:58:33 +01:00
..
braille.c	printk: Replace strncmp() with str_has_prefix()	2019-08-16 09:54:08 +02:00
braille.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
console_cmdline.h	printk: Fix preferred console selection with multiple matches	2020-02-18 09:34:42 +01:00
internal.h	printk: move dictionary keys to dev_printk_info	2020-09-22 11:27:48 +02:00
Makefile	printk: add lockless ringbuffer	2020-07-10 08:48:19 +02:00
printk_ringbuffer.c	printk: ringbuffer: fix line counting	2021-01-27 11:55:08 +01:00
printk_ringbuffer.h	printk: avoid and/or handle record truncation	2020-09-30 13:30:28 +02:00
printk_safe.c	printk: fix deadlock when kernel panic	2021-03-04 11:38:41 +01:00
printk.c	printk/console: Allow to disable console output by using console="" or console=null	2021-11-12 14:58:33 +01:00