Re: [PATCH tty v1 7/8] serial: 8250: lock port for UART_IER access in omap8250_irq()

Tony Lindgren
2023-05-26T09:01:40Z

* John Ogness <john.ogness@linutronix.de> [230525 09:34]:
> omap8250_irq() accesses UART_IER. This register is modified twice
> by each console write (serial8250_console_write()) under the port
> lock. omap8250_irq() must also take the port lock to guanentee
> synchronized access to UART_IER.
>
> Since the port lock is already being taken for the stop_rx() callback
> and since it is safe to call cancel_delayed_work() while holding the
> port lock, simply extend the port lock region to include UART_IER
> access.
>
> Fixes: 1fe0e1fa3209 ("serial: 8250_omap: Handle optional overrun-throttle-ms property")
> Signed-off-by: John Ogness <john.ogness@linutronix.de>

Reviewed-by: Tony Lindgren <tony@atomide.com>

> ---
> drivers/tty/serial/8250/8250_omap.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
> index 34939462fd69..3225c95fde1d 100644
> --- a/drivers/tty/serial/8250/8250_omap.c
> +++ b/drivers/tty/serial/8250/8250_omap.c
> @@ -659,17 +659,18 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
> if ((lsr & UART_LSR_OE) && up->overrun_backoff_time_ms > 0) {
> unsigned long delay;
>
> + /* Synchronize UART_IER access against the console. */
> + spin_lock(&port->lock);
> up->ier = port->serial_in(port, UART_IER);
> if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
> - spin_lock(&port->lock);
> port->ops->stop_rx(port);
> - spin_unlock(&port->lock);
> } else {
> /* Keep restarting the timer until
> * the input overrun subsides.
> */
> cancel_delayed_work(&up->overrun_backoff);
> }
> + spin_unlock(&port->lock);
>
> delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
> schedule_delayed_work(&up->overrun_backoff, delay);
> --
> 2.30.2
>