2022-09-10 22:31:37

by Thomas Gleixner

Subject: [patch RFC 07/29] printk: Convert console list walks for readers to list lock

Facilities which expose console information to sysfs or procfs can use the
new list protection to keep the list stable. No need to hold console lock.

Signed-off-by: Thomas Gleixner <[email protected]>
---
drivers/tty/tty_io.c | 6 +++---
fs/proc/consoles.c | 6 +++---
kernel/printk/printk.c | 8 ++++----
3 files changed, 10 insertions(+), 10 deletions(-)

--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3535,8 +3535,8 @@ static ssize_t show_cons_active(struct d
struct console *c;
ssize_t count = 0;

- console_lock();
- for_each_console(c) {
+ console_list_lock();
+ for_each_registered_console(c) {
if (!c->device)
continue;
if (!c->write)
@@ -3560,7 +3560,7 @@ static ssize_t show_cons_active(struct d

count += sprintf(buf + count, "%c", i ? ' ':'\n');
}
- console_unlock();
+ console_list_unlock();

return count;
}
--- a/fs/proc/consoles.c
+++ b/fs/proc/consoles.c
@@ -63,8 +63,8 @@ static void *c_start(struct seq_file *m,
struct console *con;
loff_t off = 0;

- console_lock();
- for_each_console(con)
+ console_list_lock();
+ for_each_registered_console(con)
if (off++ == *pos)
break;

@@ -80,7 +80,7 @@ static void *c_next(struct seq_file *m,

static void c_stop(struct seq_file *m, void *v)
{
- console_unlock();
+ console_list_unlock();
}

static const struct seq_operations consoles_op = {
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2985,18 +2985,18 @@ void console_flush_on_panic(enum con_flu
*/
struct tty_driver *console_device(int *index)
{
- struct console *c;
struct tty_driver *driver = NULL;
+ struct console *c;

- console_lock();
- for_each_console(c) {
+ console_list_lock();
+ for_each_registered_console(c) {
if (!c->device)
continue;
driver = c->device(c, index);
if (driver)
break;
}
- console_unlock();
+ console_list_unlock();
return driver;
}

2022-09-14 13:21:56

by Sergey Senozhatsky

Subject: Re: [patch RFC 07/29] printk: Convert console list walks for readers to list lock

On (22/09/11 00:27), Thomas Gleixner wrote:
> Facilities which expose console information to sysfs or procfs can use the
> new list protection to keep the list stable. No need to hold console lock.

Yeah I guess it makes sense to take the list lock in console stop/start then.
(I wonder if it'll be better to do it in this patch.)

> Signed-off-by: Thomas Gleixner <[email protected]>

Reviewed-by: Sergey Senozhatsky <[email protected]>