Commit d3eb5211 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux 

Pull printk updates from Petr Mladek:

 - Finally allow parallel writes and reads into/from the lockless
   ringbuffer. But it is not a complete solution. Readers are still
   serialized against each other. And nested writes are still prevented
   by printk_safe per-CPU buffers.

 - Use ttynull as the ultimate fallback for /dev/console.

 - Officially allow disabling console output by using console="" or
   console=null

 - A few code cleanups

* tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: remove logbuf_lock writer-protection of ringbuffer
  printk: inline log_output(),log_store() in vprintk_store()
  printk: remove obsolete dead assignment
  printk/console: Allow to disable console output by using console="" or console=null
  init/console: Use ttynull as a fallback when there is no console
  printk: ringbuffer: Reference text_data_ring directly in callees.
parents 5e60366d 5ed37174

drivers/tty/Kconfig

+0 −14
Original line number Diff line number Diff line
@@ -401,20 +401,6 @@ config MIPS_EJTAG_FDC_KGDB_CHAN 
	help

	  FDC channel number to use for KGDB.



config NULL_TTY

	tristate "NULL TTY driver"

	help

	  Say Y here if you want a NULL TTY which simply discards messages.



	  This is useful to allow userspace applications which expect a console

	  device to work without modifications even when no console is

	  available or desired.



	  In order to use this driver, you should redirect the console to this

	  TTY, or boot the kernel with console=ttynull.



	  If unsure, say N.



config TRACE_ROUTER

	tristate "Trace data router for MIPI P1149.7 cJTAG standard"

	depends on TRACE_SINK

drivers/tty/Makefile

+1 −2
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ 
obj-$(CONFIG_TTY)		+= tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o \

				   tty_buffer.o tty_port.o tty_mutex.o \

				   tty_ldsem.o tty_baudrate.o tty_jobctrl.o \

				   n_null.o

				   n_null.o ttynull.o

obj-$(CONFIG_LEGACY_PTYS)	+= pty.o

obj-$(CONFIG_UNIX98_PTYS)	+= pty.o

obj-$(CONFIG_AUDIT)		+= tty_audit.o
@@ -25,7 +25,6 @@ obj-$(CONFIG_ISI) += isicom.o 
obj-$(CONFIG_MOXA_INTELLIO)	+= moxa.o

obj-$(CONFIG_MOXA_SMARTIO)	+= mxser.o

obj-$(CONFIG_NOZOMI)		+= nozomi.o

obj-$(CONFIG_NULL_TTY)	        += ttynull.o

obj-$(CONFIG_ROCKETPORT)	+= rocket.o

obj-$(CONFIG_SYNCLINK_GT)	+= synclink_gt.o

obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o

drivers/tty/ttynull.c

+18 −0
Original line number Diff line number Diff line
@@ -2,6 +2,13 @@ 
/*

 * Copyright (C) 2019 Axis Communications AB

 *

 * The console is useful for userspace applications which expect a console

 * device to work without modifications even when no console is available

 * or desired.

 *

 * In order to use this driver, you should redirect the console to this

 * TTY, or boot the kernel with console=ttynull.

 *

 * Based on ttyprintk.c:

 *  Copyright (C) 2010 Samo Pogacnik

 */
@@ -59,6 +66,17 @@ static struct console ttynull_console = { 
	.device = ttynull_device,

};



void __init register_ttynull_console(void)

{

	if (!ttynull_driver)

		return;



	if (add_preferred_console(ttynull_console.name, 0, NULL))

		return;



	register_console(&ttynull_console);

}



static int __init ttynull_init(void)

{

	struct tty_driver *driver;

include/linux/console.h

+3 −0
Original line number Diff line number Diff line
@@ -186,9 +186,12 @@ extern int braille_register_console(struct console *, int index, 
extern int braille_unregister_console(struct console *);

#ifdef CONFIG_TTY

extern void console_sysfs_notify(void);

extern void register_ttynull_console(void);

#else

static inline void console_sysfs_notify(void)

{ }

static inline void register_ttynull_console(void)

{ }

#endif

extern bool console_suspend_enabled;

init/main.c

+8 −2
Original line number Diff line number Diff line
@@ -1480,9 +1480,15 @@ void __init console_on_rootfs(void) 
	struct file *file = filp_open("/dev/console", O_RDWR, 0);



	if (IS_ERR(file)) {

		pr_err("Warning: unable to open an initial console.\n");

		pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n");

		register_ttynull_console();



		file = filp_open("/dev/console", O_RDWR, 0);

		if (IS_ERR(file)) {

			pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n");

			return;

		}

	}

	init_dup(file);

	init_dup(file);

	init_dup(file);

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