preparation for threaded/atomic printing

[PATCH printk 09/18] serial: kgdboc: Lock console list in probe function

Posted by John Ogness 3 years, 6 months ago

From: Thomas Gleixner <tglx@linutronix.de>

Unprotected list walks are not necessarily safe.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/tty/serial/kgdboc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index 79b7db8580e0..af2aa76bae15 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -193,7 +193,8 @@ static int configure_kgdboc(void)
 	if (!p)
 		goto noconfig;
 
-	for_each_console(cons) {
+	console_list_lock();
+	for_each_registered_console(cons) {
 		int idx;
 		if (cons->device && cons->device(cons, &idx) == p &&
 		    idx == tty_line) {
@@ -201,6 +202,7 @@ static int configure_kgdboc(void)
 			break;
 		}
 	}
+	console_list_unlock();
 
 	kgdb_tty_driver = p;
 	kgdb_tty_line = tty_line;
-- 
2.30.2

Re: [PATCH printk 09/18] serial: kgdboc: Lock console list in probe function

Posted by Petr Mladek 3 years, 6 months ago

On Sat 2022-09-24 02:10:45, John Ogness wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> Unprotected list walks are not necessarily safe.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>

It looks correct in principle. There is still a discussion [1] whether
to introduce console_list_lock() or use the existing console_lock(),
see https://lore.kernel.org/r/20220924000454.3319186-7-john.ogness@linutronix.de

Depending on the result of the discussion, with either
console_list_lock() or console_lock():

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

Best Regards,
Petr

Re: [PATCH printk 09/18] serial: kgdboc: Lock console list in probe function

Posted by Doug Anderson 3 years, 6 months ago

Hi,

On Fri, Sep 23, 2022 at 5:05 PM John Ogness <john.ogness@linutronix.de> wrote:
>
> From: Thomas Gleixner <tglx@linutronix.de>
>
> Unprotected list walks are not necessarily safe.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  drivers/tty/serial/kgdboc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
> index 79b7db8580e0..af2aa76bae15 100644
> --- a/drivers/tty/serial/kgdboc.c
> +++ b/drivers/tty/serial/kgdboc.c
> @@ -193,7 +193,8 @@ static int configure_kgdboc(void)
>         if (!p)
>                 goto noconfig;
>
> -       for_each_console(cons) {
> +       console_list_lock();
> +       for_each_registered_console(cons) {
>                 int idx;
>                 if (cons->device && cons->device(cons, &idx) == p &&
>                     idx == tty_line) {
> @@ -201,6 +202,7 @@ static int configure_kgdboc(void)
>                         break;
>                 }
>         }
> +       console_list_unlock();

Seems right to me, thanks!

Reviewed-by: Douglas Anderson <dianders@chromium.org>