From 8cb15f7f492f85d695a6f4d12044c47230f69d96 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Wed, 16 Nov 2022 17:27:32 +0106 Subject: printk: console_device: use srcu console list iterator 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 Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20221116162152.193147-21-john.ogness@linutronix.de --- kernel/printk/printk.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'kernel/printk') diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index b78947077659..101d08d9dc88 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3077,15 +3077,25 @@ 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; } -- cgit v1.2.3