show_cons_active() uses the console_lock to gather information
on registered consoles. Since the console_lock is being used for
multiple reasons, explicitly document these reasons. This will
be useful when the console_lock is split into fine-grained
locking.
Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
---
drivers/tty/tty_io.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index de06c3c2ff70..ee4da2fec328 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3526,6 +3526,16 @@ static ssize_t show_cons_active(struct device *dev,
struct console *c;
ssize_t count = 0;
+ /*
+ * Hold the console_lock to guarantee that no consoles are
+ * unregistered until all console processing is complete.
+ * This also allows safe traversal of the console list and
+ * race-free reading of @flags.
+ *
+ * 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) {
if (!c->device)
--
2.30.2