diff mbox series

[printk,v4,35/39] tty: serial: kgdboc: use console_list_lock for list traversal

Message ID 20221114162932.141883-36-john.ogness@linutronix.de
State New
Headers
Series reduce console_lock scope |

Commit Message

John Ogness Nov. 14, 2022, 4:29 p.m. UTC 
  configure_kgdboc() uses the console_lock for console list iteration. Use
the console_list_lock instead because list synchronization responsibility
will be removed from the console_lock in a later change.

The SRCU iterator could have been used here, but a later change will
relocate the locking of the console_list_lock to also provide
synchronization against register_console().

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

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 drivers/tty/serial/kgdboc.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

Petr Mladek Nov. 15, 2022, 3:18 p.m. UTC | #1 
On Mon 2022-11-14 17:35:28, John Ogness wrote:
> configure_kgdboc() uses the console_lock for console list iteration. Use
> the console_list_lock instead because list synchronization responsibility
> will be removed from the console_lock in a later change.
> 
> The SRCU iterator could have been used here, but a later change will
> relocate the locking of the console_list_lock to also provide
> synchronization against register_console().
> 
> Note, the console_lock is still needed to serialize the device()
> callback with other console operations.
> 
> Signed-off-by: John Ogness <john.ogness@linutronix.de>

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

Best Regards,
Petr
diff mbox series

Patch

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index c6df9ef34099..82b4b4d67823 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -193,7 +193,16 @@  static int configure_kgdboc(void)
 	if (!p)
 		goto noconfig;
 
+	/* For safe traversal of the console list. */
+	console_list_lock();
+
+	/*
+	 * 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();
+
 	for_each_console(cons) {
 		int idx;
 		if (cons->device && cons->device(cons, &idx) == p &&
@@ -202,8 +211,11 @@  static int configure_kgdboc(void)
 			break;
 		}
 	}
+
 	console_unlock();
 
+	console_list_unlock();
+
 	kgdb_tty_driver = p;
 	kgdb_tty_line = tty_line;