tty: serial: samsung: add spin_lock for interrupt and console_write

The console_write and IRQ handler can run concurrently.
Problems may occurs console_write is continuously executed while
the IRQ handler is running.
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com>
Link: https://lore.kernel.org/r/20220407071619.102249-2-jaewon02.kim@samsung.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/samsung_tty.c

@@ -2480,12 +2480,24 @@ s3c24xx_serial_console_write(struct console *co, const char *s,
 			     unsigned int count)
 {
 	unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);
+	unsigned long flags;
+	bool locked = true;
 
 	/* not possible to xmit on unconfigured port */
 	if (!s3c24xx_port_configured(ucon))
 		return;
 
+	if (cons_uart->sysrq)
+		locked = false;
+	else if (oops_in_progress)
+		locked = spin_trylock_irqsave(&cons_uart->lock, flags);
+	else
+		spin_lock_irqsave(&cons_uart->lock, flags);
+
 	uart_console_write(cons_uart, s, count, s3c24xx_serial_console_putchar);
+
+	if (locked)
+		spin_unlock_irqrestore(&cons_uart->lock, flags);
 }
 
 /* Shouldn't be __init, as it can be instantiated from other module */