From d22f8f10683c8c0f2675d9fd411a06facaf07c1b Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sun, 10 Jan 2016 14:39:32 -0800 Subject: [PATCH] serial: 8250: Fix lost rx state When max_count is reached, the rx loop exits. However, UART_LSR has already been read so those char flags are lost, and subsequent rx status will be for the wrong byte until the rx fifo drains. Reported-by: George Spelvin Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 7580d713cde5..48680565c991 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1478,16 +1478,17 @@ static void serial8250_read_char(struct uart_8250_port *up, unsigned char lsr) * value, and returns the remaining LSR bits not handled * by this Rx routine. */ -unsigned char -serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr) +unsigned char serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr) { struct uart_port *port = &up->port; int max_count = 256; do { serial8250_read_char(up, lsr); + if (--max_count == 0) + break; lsr = serial_in(up, UART_LSR); - } while ((lsr & (UART_LSR_DR | UART_LSR_BI)) && (--max_count > 0)); + } while (lsr & (UART_LSR_DR | UART_LSR_BI)); spin_unlock(&port->lock); tty_flip_buffer_push(&port->state->port); spin_lock(&port->lock);