[PATCH v8 3/4] serial: 8250_dw: assert port->lock is held in dw8250_force_idle()

[Yunhui Cui]

Reading UART_RX and checking whether UART_LSR_DR is set should be
atomic. Ensure the caller of dw8250_force_idle() holds port->lock.

Signed-off-by: Yunhui Cui <cuiyunhui@xxxxxxxxxxxxx>
---
 drivers/tty/serial/8250/8250_dw.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 1902f29444a1c..8b0018fadccea 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -13,6 +13,7 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/io.h>
+#include <linux/lockdep.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
@@ -117,6 +118,9 @@ static void dw8250_force_idle(struct uart_port *p)
 	struct uart_8250_port *up = up_to_u8250p(p);
 	unsigned int lsr;
 
+	/* Reading UART_LSR and UART_RX should be atomic. */
+	lockdep_assert_held_once(&p->lock);
+
 	/*
 	 * The following call currently performs serial_out()
 	 * against the FCR register. Because it differs to LCR
-- 
2.39.5