Commit bdfcca65 authored Dec 08, 2025 by Marcos Paulo de Souza Committed by Petr Mladek Dec 15, 2025

printk: nbcon: Check for device_{lock,unlock} callbacks



These callbacks are necessary to synchronize ->write_thread callback
against other operations using the same device.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20251208-nbcon-device-cb-fix-v2-1-36be8d195123@suse.com


Signed-off-by: Petr Mladek <pmladek@suse.com>

parent 4d38b88f

kernel/printk/nbcon.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1760,9 +1760,12 @@ bool nbcon_alloc(struct console *con)
		/* Synchronize the kthread start. */
		lockdep_assert_console_list_lock_held();

		/* The write_thread() callback is mandatory. */
		if (WARN_ON(!con->write_thread))
		/* Check for mandatory nbcon callbacks. */
		if (WARN_ON(!con->write_thread \|\|
		!con->device_lock \|\|
		!con->device_unlock)) {
		return false;
		}

		rcuwait_init(&con->rcuwait);
		init_irq_work(&con->irq_work, nbcon_irq_work);