The port->console flag is always false, as uart_console() is called
before the serial console has been registered.

Hence for a serial port used as the console, uart_tty_port_shutdown()
will still be called when userspace closes the port, powering it down.
This may lead to a system lock up when the serial console driver writes
to the serial port's registers.

To fix this, move the setting of port->console after the call to
uart_configure_port(), which registers the serial console.

Fixes: 761ed4a94582ab29 ("tty: serial_core: convert uart_close to use 
Reported-by: Niklas Söderlund <>
Signed-off-by: Geert Uytterhoeven <>
Acked-by: Rob Herring <>
  - Add Acked-by,
  - Reworded one-line summary (incl. magic word "fix").

Can easily be reproduced on Renesas boards:
  1. With systemd: hangs during boot,
  2. Without systemd: "telinit n" to switch to a runlevel that doesn't
     run a getty on ttySC0, and trigger kernel console output => hang.
 drivers/tty/serial/serial_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 6e4f63627479db8d..ce8899c13af3d97f 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2746,8 +2746,6 @@ int uart_add_one_port(struct uart_driver *drv, struct 
uart_port *uport)
        uport->cons = drv->cons;
        uport->minor = drv->tty_driver->minor_start + uport->line;
-       port->console = uart_console(uport);
         * If this port is a console, then the spinlock is already
         * initialised.
@@ -2761,6 +2759,8 @@ int uart_add_one_port(struct uart_driver *drv, struct 
uart_port *uport)
        uart_configure_port(drv, state, uport);
+       port->console = uart_console(uport);
        num_groups = 2;
        if (uport->attr_group)

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