Prepare for separate methods of preventing unsafe uart port access when sending xchar; claim port mutex for the tty ops method (which might sleep) and rcu for the throttle/unthrottle uses.
The implied limitation is that uart drivers which support AUTOXOFF flow control cannot define a send_xchar() method that sleeps. Signed-off-by: Peter Hurley <pe...@hurleysoftware.com> --- drivers/tty/serial/serial_core.c | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 4430518..806eba81 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -610,23 +610,31 @@ static void uart_flush_buffer(struct tty_struct *tty) * This function is used to send a high-priority XON/XOFF character to * the device */ -static void uart_send_xchar(struct tty_struct *tty, char ch) +static void __uart_send_xchar(struct uart_port *uport, char ch) { - struct uart_state *state = tty->driver_data; - struct uart_port *port = state->uart_port; unsigned long flags; - if (port->ops->send_xchar) - port->ops->send_xchar(port, ch); + if (uport->ops->send_xchar) + uport->ops->send_xchar(uport, ch); else { - spin_lock_irqsave(&port->lock, flags); - port->x_char = ch; + spin_lock_irqsave(&uport->lock, flags); + uport->x_char = ch; if (ch) - port->ops->start_tx(port); - spin_unlock_irqrestore(&port->lock, flags); + uport->ops->start_tx(port); + spin_unlock_irqrestore(&uport->lock, flags); } } +static void uart_send_xchar(struct tty_struct *tty, char ch) +{ + struct uart_state *state = tty->driver_data; + struct uart_port *uport = state->uart_port; + + mutex_lock(&state->port.mutex); + __uart_send_xchar(uport, ch); + mutex_unlock(&state->port.mutex); +} + static void uart_throttle(struct tty_struct *tty) { struct uart_state *state = tty->driver_data; @@ -644,7 +652,7 @@ static void uart_throttle(struct tty_struct *tty) } if (mask & UPSTAT_AUTOXOFF) - uart_send_xchar(tty, STOP_CHAR(tty)); + __uart_send_xchar(port, STOP_CHAR(tty)); if (mask & UPSTAT_AUTORTS) uart_clear_mctrl(port, TIOCM_RTS); @@ -667,7 +675,7 @@ static void uart_unthrottle(struct tty_struct *tty) } if (mask & UPSTAT_AUTOXOFF) - uart_send_xchar(tty, START_CHAR(tty)); + __uart_send_xchar(port, START_CHAR(tty)); if (mask & UPSTAT_AUTORTS) uart_set_mctrl(port, TIOCM_RTS); -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/