[PATCH] serial: base: do not disable TX on hangup for console ports

[kpursoty]

serial_base_port_shutdown() calls serial_base_port_set_tx(false)
unconditionally. When a TTY hangup occurs on a port that is also a
registered kernel console, this permanently disables the console
transmitter.

uart_hangup() already guards against uart_change_pm(PM_OFF) for console
ports (see the uart_console() check in uart_hangup()). Apply the same
guard in serial_base_port_shutdown(): skip TX-disable if the port is a
registered console.

Without this fix, any path that calls uart_shutdown() on a console port
- including TIOCSCTTY with force=1 (as used by init systems such as
procd) - permanently silences all subsequent kernel console output.

Signed-off-by: Kervin Pursoty <kpursoty@xxxxxxxxx>
---
 drivers/tty/serial/serial_port.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_port.c b/drivers/tty/serial/serial_port.c
--- a/drivers/tty/serial/serial_port.c
+++ b/drivers/tty/serial/serial_port.c
@@ -110,5 +110,14 @@
 {
 	struct serial_port_device *port_dev = port->port_dev;

-	serial_base_port_set_tx(port, port_dev, false);
+	/*
+	 * Do not disable TX on a console port. When an init system calls
+	 * TIOCSCTTY with force=1, the kernel hangs up the previous session,
+	 * triggering uart_hangup() -> uart_shutdown() -> here. Stopping TX
+	 * kills all kernel console output permanently.
+	 * uart_hangup() already skips uart_change_pm(PM_OFF) for consoles
+	 * via uart_console(); apply the same guard here.
+	 */
+	if (!uart_console(port))
+		serial_base_port_set_tx(port, port_dev, false);
 }

 static DEFINE_RUNTIME_DEV_PM_OPS(serial_port_pm,