10  * to the console.  Added hook for sending the console messages
11  * elsewhere, in preparation for a serial line console (someday).
26 #include <linux/console.h>
76 EXPORT_TRACEPOINT_SYMBOL_GPL(console);
86  * console_mutex protects console_list updates and console->flags updates.
88  * accessible via the console list.
93  * console_sem protects updates to console->seq
94  * and also provides serialization for console printing.
243  * console_list_lock - Lock the console list
245  * For console list or console->flags updates
267  * console_list_unlock - Unlock the console list
279  *	SRCU-protected console list
281  * Use for_each_console_srcu() to iterate the console list
295  *	the SRCU-protected console list
323 	 * because spindump/WARN/etc from under console ->lock will  in __down_trylock_console_sem()
351  * keeping track if we have the console semaphore held. It's
354  * paths in the console code where we end up in places I want
355  * locked without the console semaphore held).
360  *	Array of consoles built from command line options (console=)
371 /* Flag: console code may call schedule() */
441  * Specifies if a legacy console is registered. If legacy consoles are
442  * present, it is necessary to perform the console lock/unlock dance
443  * whenever console flushing should occur.
448  * Specifies if an nbcon console is registered. If nbcon consoles are present,
455  * Specifies if a boot console is registered. If boot consoles are present,
457  * the console lock. This is because boot consoles and nbcon consoles may
1280 		 "ignore loglevel setting (prints all kernel messages to the console)");
1778 	/* Disable logging to console */  in do_syslog()
1784 	/* Enable logging to console */  in do_syslog()
1791 	/* Set level of messages printed to console */  in do_syslog()
1798 		/* Implicitly re-enable logging to console */  in do_syslog()
2029 	 * The owner passed the console lock to us.  in console_trylock_spinning()
2030 	 * Since we did not spin on console lock, annotate  in console_trylock_spinning()
2417 		 * Try to acquire and then immediately release the console  in vprintk_emit()
2455 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
2467 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }  in __pr_flush()
2472 struct console *early_console;
2497 	 * @c console was defined by the user on the command line.  in set_user_specified()
2501 	/* At least one console defined by the user on the command line. */  in set_user_specified()
2516 	 * We use a signed short index for struct console for device drivers to  in __add_preferred_console()
2518 	 * value is not valid when the console name and index are defined on  in __add_preferred_console()
2566  * Set up a console.  Called via do_early_param() in init/main.c
2567  * for each "console=" parameter in the boot command line.
2581 	 * console="" or console=null have been suggested as a way to  in console_setup()
2582 	 * disable console output. Use ttynull that has been created  in console_setup()
2593 	/* For a DEVNAME:0.0 style console the character device is unknown early */  in console_setup()
2633 __setup("console=", console_setup);
2639  * @options: options for this console
2641  * The last preferred console added will be used for kernel messages
2643  * above to handle user-supplied console arguments; however it can also
2645  * commonly to provide a default console (ie from PROM variables) when
2654  * match_devname_and_update_preferred_console - Update a preferred console
2657  * @name: Name of the corresponding console driver, e.g. "ttyS"
2658  * @idx: Console index, e.g. port number.
2661  * preferred via the console=DEVNAME:0.0 command line option.
2662  * It fills the missing console driver name and console index
2668  * could predict which console driver name and index this device
2686 			pr_info("associate the preferred console \"%s\" with \"%s%d\"\n",  in match_devname_and_update_preferred_console()
2709 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2722 MODULE_PARM_DESC(console_no_auto_verbose, "Disable console loglevel raise to highest on oops/panic/…
2725  * console_suspend_all - suspend the console subsystem
2731 	struct console *con;  in console_suspend_all()
2735 	pr_info("Suspending console(s) (use no_console_suspend to debug)\n");  in console_suspend_all()
2755 	struct console *con;  in console_resume_all()
2782  * console_cpu_notify - print deferred console messages after CPU hotplug
2786  * will be printed on the console only if there are CON_ANYTIME consoles.
2807  * console_lock - block the console subsystem from printing
2829  * console_trylock - try to block the console subsystem from printing
2945  * console output.
2987 	 * has level above the console loglevel.  in printk_get_next_message()
3005  * Legacy console printing from printk() caller context does not respect
3011  * console write() callback when legacy printing to avoid false positive
3033  * Used as the printk buffers for non-panic, serialized console printing.
3040  * Print one record for the given console. The record printed is whatever
3041  * record is the next available record for the given console.
3049  * Returns false if the given console has no next record to print, otherwise
3054 static bool console_emit_next_record(struct console *con, bool *handover, int cookie)  in console_emit_next_record()
3127 static bool console_emit_next_record(struct console *con, bool *handover, int cookie)  in console_emit_next_record()
3151  * Returns true when there was at least one usable console and all messages
3164 	struct console *con;  in console_flush_all()
3243 	 * Console drivers are called with interrupts disabled, so  in __console_flush_and_unlock()
3246 	 * console registration path, and should invoke cond_resched()  in __console_flush_and_unlock()
3248 	 * scheduling stall on a slow console leading to RCU stall and  in __console_flush_and_unlock()
3273 		 * console_flush_all() but before unlocking the console.  in __console_flush_and_unlock()
3281  * console_unlock - unblock the legacy console subsystem from printing
3284  * the legacy console subsystem.
3286  * While the console_lock was held, console output may have been buffered
3307  * If the console code is currently allowed to sleep, and
3323 	struct console *c;  in console_unblank()
3329 	 * console lock, which in particular can be dangerous if  in console_unblank()
3349 	 * Stop console printing because the unblank() callback may  in console_unblank()
3350 	 * assume the console is not within its write() callback.  in console_unblank()
3361 		 * Attempting to trylock the console lock can deadlock  in console_unblank()
3401 	struct console *c;  in __console_rewind_all()
3427  * console_flush_on_panic - flush console content on panic
3439 	 * Ignore the console lock and flush out the messages. Attempting a  in console_flush_on_panic()
3449 	 * If another context is holding the console lock,  in console_flush_on_panic()
3468  * Return the console tty driver structure and its associated index
3472 	struct console *c;  in console_device()
3478 	 * other console operations. For example, fg_console is  in console_device()
3498  * Prevent further output on the passed console device so that (for example)
3499  * serial drivers can suspend console output before suspending a port, and can
3502 void console_suspend(struct console *console)  in console_suspend()  argument
3504 	__pr_flush(console, 1000, true);  in console_suspend()
3506 	console_srcu_write_flags(console, console->flags & ~CON_ENABLED);  in console_suspend()
3511 	 * be able to see that this console is disabled so that (for example)  in console_suspend()
3519 void console_resume(struct console *console)  in console_resume()  argument
3525 	console_srcu_write_flags(console, console->flags | CON_ENABLED);  in console_resume()
3526 	is_nbcon = console->flags & CON_NBCON;  in console_resume()
3538 		nbcon_kthread_wake(console);  in console_resume()
3542 	__pr_flush(console, 1000, true);  in console_resume()
3547 static int unregister_console_locked(struct console *console);
3557 	struct console *con;  in legacy_kthread_should_wakeup()
3632 	 * It is important that console printing threads are scheduled  in legacy_kthread_create()
3649 	struct console *con;  in printk_kthreads_shutdown()
3682 	struct console *con;  in printk_kthreads_check_locked()
3712 	 * Printer threads cannot be started as long as any boot console is  in printk_kthreads_check_locked()
3714 	 * registers between boot console code and regular console code.  in printk_kthreads_check_locked()
3716 	 * an nbcon console is registered.  in printk_kthreads_check_locked()
3757 	pr_info("debug: skip boot console de-registration.\n");  in keep_bootcon_setup()
3764 static int console_call_setup(struct console *newcon, char *options)  in console_call_setup()
3771 	/* Synchronize with possible boot console. */  in console_call_setup()
3781  * the newly registered console with any of the ones selected
3788 static int try_enable_preferred_console(struct console *newcon,  in try_enable_preferred_console()
3797 		/* Console not yet initialized? */  in try_enable_preferred_console()
3838 /* Try to enable the console unconditionally */
3839 static void try_enable_default_console(struct console *newcon)  in try_enable_default_console()
3853 /* Return the starting sequence number for a newly registered console. */
3854 static u64 get_init_console_seq(struct console *newcon, bool bootcon_registered)  in get_init_console_seq()
3856 	struct console *con;  in get_init_console_seq()
3872 		 * device as @newcon. Since it is not known which boot console  in get_init_console_seq()
3874 		 * start with the message of the enabled boot console that is  in get_init_console_seq()
3879 			 * Hold the console_lock to stop console printing and  in get_init_console_seq()
3880 			 * guarantee safe access to console->seq.  in get_init_console_seq()
3885 			 * Flush all consoles and set the console to start at  in get_init_console_seq()
3928 	hlist_entry(console_list.first, struct console, node)
3930 static int unregister_console_locked(struct console *console);
3933  * The console driver calls this routine during kernel initialization
3934  * to register the console printing procedure with printk() and to
3936  * console driver was initialized.
3946  *  - As soon as a "real" console is registered, all bootconsoles
3948  *  - Once a "real" console is registered, any attempt to register a
3951 void register_console(struct console *newcon)  in register_console()
3956 	struct console *con;  in register_console()
3964 		if (WARN(con == newcon, "console '%s%d' already registered\n",  in register_console()
3984 		 * Ensure the nbcon console buffers can be allocated  in register_console()
3992 	 * See if we want to enable this console driver by default.  in register_console()
3994 	 * Nope when a console is preferred by the command line, device  in register_console()
3997 	 * The first real console with tty binding (driver) wins. More  in register_console()
4000 	 * Note that a console with tty binding will have CON_CONSDEV  in register_console()
4010 	/* See if this console matches one we selected on the command line */  in register_console()
4017 	/* printk() messages are not printed to the Braille console. */  in register_console()
4025 	 * If we have a bootconsole, and are switching to a real console,  in register_console()
4026 	 * don't print everything out again, since when the boot console, and  in register_console()
4027 	 * the real console are the same physical device, it's annoying to  in register_console()
4051 	 * console, it will not be aware of the nbcon synchronization. This  in register_console()
4053 	 * simultaneously if this new console is used for atomic printing  in register_console()
4057 	 * in use while this new console transitions to being registered.  in register_console()
4063 	 * Put this console in the list - keep the  in register_console()
4082 	 * on all contexts being able to see the new console before  in register_console()
4086 	/* This new console is now registered. */  in register_console()
4093 	 * By unregistering the bootconsoles after we enable the real console  in register_console()
4094 	 * we get the "console xxx enabled" message on all the consoles -  in register_console()
4097 	 * went to the bootconsole (that they do not see on the real console)  in register_console()
4111 	/* Changed console list, may require printer threads to start/stop. */  in register_console()
4119 static int unregister_console_locked(struct console *console)  in unregister_console_locked()  argument
4121 	bool use_device_lock = (console->flags & CON_NBCON) && console->write_atomic;  in unregister_console_locked()
4126 	struct console *c;  in unregister_console_locked()
4131 	con_printk(KERN_INFO, console, "disabled\n");  in unregister_console_locked()
4133 	res = _braille_unregister_console(console);  in unregister_console_locked()
4139 	if (!console_is_registered_locked(console))  in unregister_console_locked()
4141 	else if (console_is_usable(console, console->flags, true))  in unregister_console_locked()
4142 		__pr_flush(console, 1000, true);  in unregister_console_locked()
4145 	console_srcu_write_flags(console, console->flags & ~CON_ENABLED);  in unregister_console_locked()
4152 	 * in use while this console transitions to being unregistered.  in unregister_console_locked()
4155 		console->device_lock(console, &flags);  in unregister_console_locked()
4157 	hlist_del_init_rcu(&console->node);  in unregister_console_locked()
4160 		console->device_unlock(console, flags);  in unregister_console_locked()
4164 	 * If this isn't the last console and it has CON_CONSDEV set, we  in unregister_console_locked()
4165 	 * need to set it on the next preferred console.  in unregister_console_locked()
4169 	 * console has any device attached. Oh well....  in unregister_console_locked()
4171 	if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV)  in unregister_console_locked()
4176 	 * must not be able to see this console in the list so that any  in unregister_console_locked()
4182 	 * With this console gone, the global flags tracking registered  in unregister_console_locked()
4183 	 * console types may have changed. Update them.  in unregister_console_locked()
4202 	if (console->flags & CON_NBCON)  in unregister_console_locked()
4203 		nbcon_free(console);  in unregister_console_locked()
4207 	if (console->exit)  in unregister_console_locked()
4208 		res = console->exit(console);  in unregister_console_locked()
4210 	/* Changed console list, may require printer threads to start/stop. */  in unregister_console_locked()
4216 int unregister_console(struct console *console)  in unregister_console()  argument
4221 	res = unregister_console_locked(console);  in unregister_console()
4228  * console_force_preferred_locked - force a registered console preferred
4229  * @con: The registered console to force preferred.
4233 void console_force_preferred_locked(struct console *con)  in console_force_preferred_locked()
4235 	struct console *cur_pref_con;  in console_force_preferred_locked()
4247 	 * Delete, but do not re-initialize the entry. This allows the console  in console_force_preferred_locked()
4249 	 * checks), even though it was briefly removed from the console list.  in console_force_preferred_locked()
4254 	 * Ensure that all SRCU list walks have completed so that the console  in console_force_preferred_locked()
4255 	 * can be added to the beginning of the console list and its forward  in console_force_preferred_locked()
4270  * Initialize the console device. This is called *early*, so
4290 	 * set up the console device so that later boot sequences can  in console_init()
4294 	trace_initcall_level("console");  in console_init()
4310  * module, the real console hasn't registered yet at this point, there will
4311  * be a brief interval in which no messages are logged to the console, which
4316  * get unregistered when the real preferred console is registered.
4321 	struct console *con;  in printk_late_init()
4359 /* If @con is specified, only wait for that console. Otherwise wait for all. */
4360 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress)  in __pr_flush()
4365 	struct console *c;  in __pr_flush()
4398 		 * console->seq. Releasing console_lock flushes more  in __pr_flush()
4404 		 * console could register at any time. Always hold the  in __pr_flush()
4472  * Context: Process context. May sleep while acquiring console lock.
4538  * and the console printing of those records has already occurred or is
4551  *	console printing in a deferred context
4554  * this context is responsible for console printing those records, but
4555  * the current context is not allowed to perform the console printing.
4556  * Trigger an irq_work context to perform the console printing. This
4902  * Try to obtain lock on console subsystem and replay all