Commit 7c2af0f6 authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

tty: tty_io: use console_list_lock for list synchronization 



show_cons_active() uses the console_lock to gather information
on registered consoles. It requires that no consoles are unregistered
until it is finished. The console_list_lock should be used because
list synchronization responsibility will be removed from the
console_lock in a later change.

Note, the console_lock is still needed to serialize the device()
callback with other console operations.

Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-34-john.ogness@linutronix.de
parent 6f883675

drivers/tty/tty_io.c

+12 −6
Original line number Diff line number Diff line
@@ -3527,16 +3527,13 @@ static ssize_t show_cons_active(struct device *dev, 
	ssize_t count = 0;



	/*

	 * Hold the console_lock to guarantee that no consoles are

	 * Hold the console_list_lock to guarantee that no consoles are

	 * unregistered until all console processing is complete.

	 * This also allows safe traversal of the console list and

	 * race-free reading of @flags.

	 *

	 * Take console_lock to serialize device() callback with

	 * other console operations. For example, fg_console is

	 * modified under console_lock when switching vt.

	 */

	console_lock();

	console_list_lock();



	for_each_console(c) {

		if (!c->device)

			continue;
@@ -3548,6 +3545,13 @@ static ssize_t show_cons_active(struct device *dev, 
		if (i >= ARRAY_SIZE(cs))

			break;

	}



	/*

	 * Take console_lock to serialize device() callback with

	 * other console operations. For example, fg_console is

	 * modified under console_lock when switching vt.

	 */

	console_lock();

	while (i--) {

		int index = cs[i]->index;

		struct tty_driver *drv = cs[i]->device(cs[i], &index);
@@ -3563,6 +3567,8 @@ static ssize_t show_cons_active(struct device *dev, 
	}

	console_unlock();



	console_list_unlock();



	return count;

}

static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);