2022-10-19 15:11:34

by John Ogness

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

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 <[email protected]>
---
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)
{
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

2022-10-25 14:00:33

by Petr Mladek

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

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 <[email protected]>

Reviewed-by: Petr Mladek <[email protected]>

> ---
> 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