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Petr Mladek 757055ae8d init/console: Use ttynull as a fallback when there is no console
stdin, stdout, and stderr standard I/O stream are created for the init
process. They are not available when there is no console registered
for /dev/console. It might lead to a crash when the init process
tries to use them, see the commit 48021f9813 ("printk: handle
blank console arguments passed in.").

Normally, ttySX and ttyX consoles are used as a fallback when no consoles
are defined via the command line, device tree, or SPCR. But there
will be no console registered when an invalid console name is configured
or when the configured consoles do not exist on the system.

Users even try to avoid the console intentionally, for example,
by using console="" or console=null. It is used on production
systems where the serial port or terminal are not visible to
users. Pushing messages to these consoles would just unnecessary
slowdown the system.

Make sure that stdin, stdout, stderr, and /dev/console are always
available by a fallback to the existing ttynull driver. It has
been implemented for exactly this purpose but it was used only
when explicitly configured.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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/20201111135450.11214-2-pmladek@suse.com
2020-11-20 12:23:50 +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 Urgent printk fix for 5.10 2020-10-16 12:52:37 -07:00
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
.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

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.