From 0fb413ea64603a71e19b4b15a6c5b704e3897d06 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Wed, 16 Nov 2022 17:27:20 +0106 Subject: tty: serial: kgdboc: document console_lock usage kgdboc_earlycon_init() uses the console_lock to ensure that no consoles are unregistered until the kgdboc_earlycon is setup. This is necessary because the trapping of the exit() callback assumes that the exit() callback is not called before the trap is setup. Explicitly document this non-typical console_lock usage. Signed-off-by: John Ogness Reviewed-by: Greg Kroah-Hartman Reviewed-by: Douglas Anderson Reviewed-by: Daniel Thompson Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20221116162152.193147-9-john.ogness@linutronix.de --- drivers/tty/serial/kgdboc.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'drivers/tty/serial') diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c index e76f0186c335..5be381003e58 100644 --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c @@ -530,6 +530,14 @@ static int __init kgdboc_earlycon_init(char *opt) * Look for a matching console, or if the name was left blank just * pick the first one we find. */ + + /* + * Hold the console_lock to guarantee that no consoles are + * unregistered until the kgdboc_earlycon setup is complete. + * Trapping the exit() callback relies on exit() not being + * called until the trap is setup. This also allows safe + * traversal of the console list and race-free reading of @flags. + */ console_lock(); for_each_console(con) { if (con->write && con->read && -- cgit