Commit 28de287a authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

proc: consoles: use console_list_lock for list iteration 



The console_lock is used in part to guarantee safe list iteration.
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 avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-35-john.ogness@linutronix.de
parent 7c2af0f6

fs/proc/consoles.c

+12 −7
Original line number Diff line number Diff line
@@ -33,7 +33,16 @@ static int show_console_dev(struct seq_file *m, void *v) 
	if (con->device) {

		const struct tty_driver *driver;

		int index;



		/*

		 * 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();

		driver = con->device(con, &index);

		console_unlock();



		if (driver) {

			dev = MKDEV(driver->major, driver->minor_start);

			dev += index;
@@ -64,15 +73,11 @@ static void *c_start(struct seq_file *m, loff_t *pos) 
	loff_t off = 0;



	/*

	 * Take console_lock to serialize device() callback with

	 * other console operations. For example, fg_console is

	 * modified under console_lock when switching vt.

	 *

	 * Hold the console_lock to guarantee safe traversal of the

	 * Hold the console_list_lock to guarantee safe traversal of the

	 * console list. SRCU cannot be used because there is no

	 * place to store the SRCU cookie.

	 */

	console_lock();

	console_list_lock();

	for_each_console(con)

		if (off++ == *pos)

			break;
@@ -90,7 +95,7 @@ static void *c_next(struct seq_file *m, void *v, loff_t *pos) 


static void c_stop(struct seq_file *m, void *v)

{

	console_unlock();

	console_list_unlock();

}



static const struct seq_operations consoles_op = {