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Date: Wed, 16 Nov 2022 17:27:20 +0106 From: John Ogness <john.ogness@...utronix.de> To: Petr Mladek <pmladek@...e.com> Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, Steven Rostedt <rostedt@...dmis.org>, Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org, Jason Wessel <jason.wessel@...driver.com>, Daniel Thompson <daniel.thompson@...aro.org>, Douglas Anderson <dianders@...omium.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, kgdb-bugreport@...ts.sourceforge.net, linux-serial@...r.kernel.org Subject: [PATCH printk v5 08/40] 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 <john.ogness@...utronix.de> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Reviewed-by: Douglas Anderson <dianders@...omium.org> Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org> Reviewed-by: Petr Mladek <pmladek@...e.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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