diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index ce948b6..27f34a9 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1874,7 +1874,9 @@
 		 * the interrupt is enabled.  Delays are necessary to
 		 * allow register changes to become visible.
 		 */
-		spin_lock_irqsave(&up->port.lock, flags);
+		spin_lock(&up->port.lock);
+		if (up->port.flags & UPF_SHARE_IRQ)
+			disable_irq_nosync(up->port.irq);
 
 		wait_for_xmitr(up, UART_LSR_THRE);
 		serial_out_sync(up, UART_IER, UART_IER_THRI);
@@ -1886,7 +1888,9 @@
 		iir = serial_in(up, UART_IIR);
 		serial_out(up, UART_IER, 0);
 
-		spin_unlock_irqrestore(&up->port.lock, flags);
+		if (up->port.flags & UPF_SHARE_IRQ)
+			enable_irq(up->port.irq);
+		spin_unlock(&up->port.lock);
 
 		/*
 		 * If the interrupt is not reasserted, setup a timer to