2022-10-19 15:36:57

by John Ogness

Subject: [PATCH printk v2 36/38] proc: consoles: use console_list_lock for list iteration

The console_lock is used in part to guarantee safe list iteration.
The console_list_lock should be used because list synchronization
repsponsibility will be removed from the console_lock in a later
change.

Note, the console_lock is still needed to stop console printing.

Signed-off-by: John Ogness <[email protected]>
---
fs/proc/consoles.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c
index 32512b477605..77409b176569 100644
--- a/fs/proc/consoles.c
+++ b/fs/proc/consoles.c
@@ -33,7 +33,15 @@ static int show_console_dev(struct seq_file *m, void *v)
if (con->device) {
const struct tty_driver *driver;
int index;
+
+ /*
+ * Stop console printing because the device() callback may
+ * assume the console is not within its write() callback.
+ */
+ console_lock();
driver = con->device(con, &index);
+ console_unlock();
+
if (driver) {
dev = MKDEV(driver->major, driver->minor_start);
dev += index;
@@ -64,14 +72,11 @@ static void *c_start(struct seq_file *m, loff_t *pos)
loff_t off = 0;

/*
- * Stop console printing because the device() callback may
- * assume the console is not within its write() callback.
- *
- * Hold the console_lock to guarantee safe traversal of the
+ * Hold the console_list_lock to guarantee safe traversal of the
* console list. SRCU cannot be used because there is no
* place to store the SRCU cookie.
*/
- console_lock();
+ console_list_lock();
for_each_console(con)
if (off++ == *pos)
break;
@@ -89,7 +94,7 @@ static void *c_next(struct seq_file *m, void *v, loff_t *pos)

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

static const struct seq_operations consoles_op = {
--
2.30.2

2022-10-27 12:39:51

by Petr Mladek

Subject: Re: [PATCH printk v2 36/38] proc: consoles: use console_list_lock for list iteration

On Wed 2022-10-19 17:01:58, John Ogness wrote:
> The console_lock is used in part to guarantee safe list iteration.
> The console_list_lock should be used because list synchronization
> repsponsibility will be removed from the console_lock in a later
> change.
>
> Note, the console_lock is still needed to stop console printing.
>
> Signed-off-by: John Ogness <[email protected]>

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

Best Regards,
Petr