Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v4 07/39] tty: serial: kgdboc: document console_lock usage | Date | Mon, 14 Nov 2022 17:35:00 +0106 |
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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 <john.ogness@linutronix.de> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> Reviewed-by: Petr Mladek <pmladek@suse.com> --- drivers/tty/serial/kgdboc.c | 8 ++++++++ 1 file changed, 8 insertions(+)
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 && -- 2.30.2
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