[PATCH printk v2 35/38] tty: tty_io: use console_list_lock for list synchronization

John Ogness
2022-10-19T15:06:49Z

show_cons_active() uses the console_lock to gather information
on registered consoles. It requires that no consoles are unregistered
until it is finished. 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 <john.ogness@linutronix.de>
---
drivers/tty/tty_io.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 333579bfa335..46a0e3c5c3a5 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3527,14 +3527,12 @@ static ssize_t show_cons_active(struct device *dev,
ssize_t count = 0;

/*
- * Hold the console_lock to guarantee that no consoles are
+ * Hold the console_list_lock to guarantee that no consoles are
* unregistered until all console processing is complete.
* This also allows safe traversal of the console list.
- *
- * Stop console printing because the device() callback may
- * assume the console is not within its write() callback.
*/
- console_lock();
+ console_list_lock();
+
for_each_console(c) {
if (!c->device)
continue;
@@ -3546,6 +3544,12 @@ static ssize_t show_cons_active(struct device *dev,
if (i >= ARRAY_SIZE(cs))
break;
}
+
+ /*
+ * Stop console printing because the device() callback may
+ * assume the console is not within its write() callback.
+ */
+ console_lock();
while (i--) {
int index = cs[i]->index;
struct tty_driver *drv = cs[i]->device(cs[i], &index);
@@ -3561,6 +3565,8 @@ static ssize_t show_cons_active(struct device *dev,
}
console_unlock();

+ console_list_unlock();
+
return count;
}
static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);
--
2.30.2