diff mbox series

[printk,v4,19/39] printk: console_device: use srcu console list iterator

Message ID 20221114162932.141883-20-john.ogness@linutronix.de
State New
Headers
Series reduce console_lock scope |

Commit Message

John Ogness Nov. 14, 2022, 4:29 p.m. UTC 
  Use srcu console list iteration for console list traversal. It is
acceptable because the consoles might come and go at any time.
Strict synchronizing with console registration code would not bring
any advantage over srcu.

Document why the console_lock is still necessary. Note that this
is a preparatory change for when console_lock no longer provides
synchronization for the console list.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
---
 kernel/printk/printk.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index f536233d8234..fb609a19f797 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3076,15 +3076,25 @@  struct tty_driver *console_device(int *index)
 {
 	struct console *c;
 	struct tty_driver *driver = NULL;
+	int cookie;
 
+	/*
+	 * Take console_lock to serialize device() callback with
+	 * other console operations. For example, fg_console is
+	 * modified under console_lock when switching vt.
+	 */
 	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;
 }