serial: core: fix port-lock initialisation

Commit f743061a85f5 ("serial: core: Initialise spin lock before use in
uart_configure_port()") tried to work around a breakage introduced by
commit a3cb39d258ef ("serial: core: Allow detach and attach serial
device for console") by adding a second initialisation of the port lock
when registering the port.

As reported by the build robots [1], this doesn't really solve the
regression introduced by the console-detach changes and also adds a
second redundant initialisation of the lock for normal ports.

Start cleaning up this mess by removing the redundant initialisation and
making sure that the port lock is again initialised once-only for ports
that aren't already in use as a console.

[1] https://lore.kernel.org/r/20200802054852.GR23458@shao2-debian

Fixes: f743061a85f5 ("serial: core: Initialise spin lock before use in uart_configure_port()")
Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
Cc: stable <stable@vger.kernel.org>     # 5.7
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200909143101.15389-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f797c97..53b79e1 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2379,13 +2379,6 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
                uart_change_pm(state, UART_PM_STATE_ON);
 
                /*
-                * If this driver supports console, and it hasn't been
-                * successfully registered yet, initialise spin lock for it.
-                */
-               if (port->cons && !(port->cons->flags & CON_ENABLED))
-                       __uart_port_spin_lock_init(port);
-
-               /*
                 * Ensure that the modem control lines are de-activated.
                 * keep the DTR setting that is set in uart_set_options()
                 * We probably don't need a spinlock around this, but
@@ -2900,7 +2893,12 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
                goto out;
        }
 
-       uart_port_spin_lock_init(uport);
+       /*
+        * If this port is in use as a console then the spinlock is already
+        * initialised.
+        */
+       if (!uart_console_enabled(uport))
+               __uart_port_spin_lock_init(uport);
 
        if (uport->cons && uport->dev)
                of_console_check(uport->dev->of_node, uport->cons->name, uport->line);