@@ -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>
@@ -112,6 +113,13 @@ static void dw8250_force_idle(struct uart_port *p)
struct uart_8250_port *up = up_to_u8250p(p);
unsigned int lsr;
+ /*
+ * The serial_in(p, UART_RX) should be under port->lock, but we can't add
+ * it to avoid AA deadlock as we're unsure if serial_out*(...UART_LCR)
+ * is under port->lock.
+ */
+ lockdep_assert_held_once(&p->lock);
+
serial8250_clear_and_reinit_fifos(up);
/*
Read UART_RX and check UART_LSR_DR in critical section. Unsure if caller of dw8250_force_idle() holds port->lock. Don't acquire it directly to avoid deadlock. Use lockdep_assert_held_once for warning. Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com> --- drivers/tty/serial/8250/8250_dw.c | 8 ++++++++ 1 file changed, 8 insertions(+)