patch "serial: core: fix port-lock initialisation" added to tty-linus

This is a note to let you know that I've just added the patch titled

serial: core: fix port-lock initialisation

to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From fe88c6489264eaea23570dfdf03e1d3f5f47f423 Mon Sep 17 00:00:00 2001
From: Johan Hovold <[email protected]>
Date: Wed, 9 Sep 2020 16:31:00 +0200
Subject: 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

---
 drivers/tty/serial/serial_core.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

index f797c971cd82..53b79e1fcbc8 100644
@@ -2378,13 +2378,6 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
 		/* Power up port for set_mctrl() */
 		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()

@@ -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);

2.28.0