Re: [PATCH printk v2 24/38] xen: fbfront: use srcu console list iterator

[Petr Mladek]

On Wed 2022-10-19 17:01:46, John Ogness wrote:
> Since the console_lock is not being used for anything other than
> safe console list traversal, use srcu console list iteration instead.
> 
> Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx>

Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>

> ---
>  drivers/video/fbdev/xen-fbfront.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/video/fbdev/xen-fbfront.c b/drivers/video/fbdev/xen-fbfront.c
> index 4d2694d904aa..2552c853c6c2 100644
> --- a/drivers/video/fbdev/xen-fbfront.c
> +++ b/drivers/video/fbdev/xen-fbfront.c
> @@ -500,16 +500,18 @@ static int xenfb_probe(struct xenbus_device *dev,
>  static void xenfb_make_preferred_console(void)

Just for record. This function is a dirty hack how to associate "ttyX"
console with /dev/console.

A clean solution would be to just reshuffle console_drivers list. I
have a patch for this in my bottom drawer. It is part of a bigger
clean up that it not ready for upstreaming yet.

Best Regards,
Petr

>  {
>  	struct console *c;
> +	int cookie;
>  
>  	if (console_set_on_cmdline)
>  		return;
>  
> -	console_lock();
> -	for_each_console(c) {
> +	cookie = console_srcu_read_lock();
> +	for_each_console_srcu(c) {
>  		if (!strcmp(c->name, "tty") && c->index == 0)
>  			break;
>  	}
> -	console_unlock();
> +	console_srcu_read_unlock(cookie);
> +
>  	if (c) {
>  		unregister_console(c);
>  		c->flags |= CON_CONSDEV;
> -- 
> 2.30.2