diff --git a/drivers/char/mxser.c b/drivers/char/mxser.c
index 95c9f54f3d302ea52ed8cb0f59850ddf0ea72f14..47023053ee85973a80c31bc0117b7f027257b5fb 100644
--- a/drivers/char/mxser.c
+++ b/drivers/char/mxser.c
@@ -1768,7 +1768,7 @@ static int mxser_ioctl(struct tty_struct *tty, struct file *file,
 		int len, lsr;
 
 		len = mxser_chars_in_buffer(tty);
-		spin_lock(&info->slock);
+		spin_lock_irq(&info->slock);
 		lsr = inb(info->ioaddr + UART_LSR) & UART_LSR_THRE;
 		spin_unlock_irq(&info->slock);
 		len += (lsr ? 0 : 1);
@@ -1778,12 +1778,12 @@ static int mxser_ioctl(struct tty_struct *tty, struct file *file,
 	case MOXA_ASPP_MON: {
 		int mcr, status;
 
-		spin_lock(&info->slock);
+		spin_lock_irq(&info->slock);
 		status = mxser_get_msr(info->ioaddr, 1, tty->index);
 		mxser_check_modem_status(tty, info, status);
 
 		mcr = inb(info->ioaddr + UART_MCR);
-		spin_unlock(&info->slock);
+		spin_unlock_irq(&info->slock);
 
 		if (mcr & MOXA_MUST_MCR_XON_FLAG)
 			info->mon_data.hold_reason &= ~NPPI_NOTIFY_XOFFHOLD;