[PATCH printk v2 30/38] printk: console_device: use srcu console list iterator

John Ogness
2022-10-19T15:06:16Z

Use srcu console list iteration for console list traversal.

Document why the console_lock is still necessary.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
kernel/printk/printk.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e478cb92e7ba..410ad9d5649c 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3025,15 +3025,24 @@ struct tty_driver *console_device(int *index)
{
struct console *c;
struct tty_driver *driver = NULL;
+ int cookie;

+ /*
+ * Stop console printing because the device() callback may
+ * assume the console is not within its write() callback.
+ */
console_lock();
- for_each_console(c) {
+
+ cookie = console_srcu_read_lock();
+ for_each_console_srcu(c) {
if (!c->device)
continue;
driver = c->device(c, index);
if (driver)
break;
}
+ console_srcu_read_unlock(cookie);
+
console_unlock();
return driver;
}
--
2.30.2