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Subject[PATCH printk v3 19/40] printk: console_device: use srcu console list iterator
Date
Use srcu console list iteration for console list traversal.

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>
---
kernel/printk/printk.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index de86a502b50b..ec50777d0301 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3029,15 +3029,25 @@ 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;
}
--
2.30.2
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