On 2016-03-31, John Ogness <[email protected]> wrote: > diff --git a/drivers/tty/serial/8250/8250_omap.c > b/drivers/tty/serial/8250/8250_omap.c > index 6f76051..9459b4d 100644 > --- a/drivers/tty/serial/8250/8250_omap.c > +++ b/drivers/tty/serial/8250/8250_omap.c > @@ -460,6 +451,24 @@ static void omap_8250_set_termios(struct uart_port *port, > priv->efr |= OMAP_UART_SW_TX; > } > } > + > + if (dma && dma->tx_running) { > + /* > + * TCSANOW requests the change to occur immediately, however > + * if we have a TX-DMA operation in progress then it has been > + * observed that it might stall and never complete. Therefore > + * we wait until DMA completes to prevent this hang from > + * happening. > + */ > + > + dma->tx_running = 2; > + > + spin_unlock_irq(&up->port.lock); > + wait_event_interruptible(priv->termios_wait, > + dma->tx_running == 3); > + spin_lock_irq(&up->port.lock); > + complete_dma = 1; > + }
Sorry, I just realized that wait_event_interruptible() is used here. IMHO this should be changed to wait_event(), otherwise a signal could trigger the TX-DMA deadlock this code is trying to prevent. If hardware flow control is active, it is possible that wait_event() leads to the caller waiting forever. But allowing interruptible causes too many problems since set_termios() cannot communicate errors. John Ogness
