Commit 1fd4224a authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

console: introduce console_is_registered() 



Currently it is not possible for drivers to detect if they have
already successfully registered their console. Several drivers
have multiple paths that lead to console registration. To avoid
attempting a 2nd registration (which leads to a WARN), drivers
are implementing their own solution.

Introduce console_is_registered() so drivers can easily identify
if their console is currently registered. A _locked() variant
is also provided if the caller is already holding the
console_list_lock.

Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-22-john.ogness@linutronix.de
parent 8cb15f7f

include/linux/console.h

+28 −0
Original line number Diff line number Diff line
@@ -228,6 +228,34 @@ static inline void console_srcu_write_flags(struct console *con, short flags) 
	WRITE_ONCE(con->flags, flags);

}



/* Variant of console_is_registered() when the console_list_lock is held. */

static inline bool console_is_registered_locked(const struct console *con)

{

	lockdep_assert_console_list_lock_held();

	return !hlist_unhashed(&con->node);

}



/*

 * console_is_registered - Check if the console is registered

 * @con:	struct console pointer of console to check

 *

 * Context: Process context. May sleep while acquiring console list lock.

 * Return: true if the console is in the console list, otherwise false.

 *

 * If false is returned for a console that was previously registered, it

 * can be assumed that the console's unregistration is fully completed,

 * including the exit() callback after console list removal.

 */

static inline bool console_is_registered(const struct console *con)

{

	bool ret;



	console_list_lock();

	ret = console_is_registered_locked(con);

	console_list_unlock();

	return ret;

}



/**

 * for_each_console_srcu() - Iterator over registered consoles

 * @con:	struct console pointer used as loop cursor

kernel/printk/printk.c

+1 −1
Original line number Diff line number Diff line
@@ -3443,7 +3443,7 @@ static int unregister_console_locked(struct console *console) 
	/* Disable it unconditionally */

	console_srcu_write_flags(console, console->flags & ~CON_ENABLED);



	if (hlist_unhashed(&console->node)) {

	if (!console_is_registered_locked(console)) {

		console_unlock();

		return -ENODEV;

	}