On Thu, Dec 13, 2018 at 07:44:41PM +0100, Geert Uytterhoeven wrote:
> Some callers of sci_submit_rx() hold the port spinlock, others don't.
> During fallback to PIO, the driver needs to obtain the port spinlock.
> If the lock was already held, spinlock recursion is detected, causing a
> deadlock: BUG: spinlock recursion on CPU#0.
>
> Fix this by adding a flag parameter to sci_submit_rx() for the caller to
> indicate the port spinlock is already held, so spinlock recursion can be
> avoided.
>
> Move the spin_lock_irqsave() up, so all DMA disable steps are protected,
> which is safe as the recently introduced dmaengine_terminate_async() can
> be called in atomic context.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Reviewed-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
> ---
> v4:
> - No changes,
>
> v3:
> - Split in multiple patches.
> ---
> drivers/tty/serial/sh-sci.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> index 8146d9cef0cbe2d0..2a08039f792235e5 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -1331,7 +1331,7 @@ static void sci_tx_dma_release(struct sci_port *s)
> dma_release_channel(chan);
> }
>
> -static void sci_submit_rx(struct sci_port *s)
> +static void sci_submit_rx(struct sci_port *s, bool port_lock_held)
> {
> struct dma_chan *chan = s->chan_rx;
> struct uart_port *port = &s->port;
> @@ -1362,16 +1362,18 @@ static void sci_submit_rx(struct sci_port *s)
> return;
>
> fail:
> + /* Switch to PIO */
> + if (!port_lock_held)
> + spin_lock_irqsave(&port->lock, flags);
> if (i)
> dmaengine_terminate_async(chan);
> for (i = 0; i < 2; i++)
> s->cookie_rx[i] = -EINVAL;
> s->active_rx = -EINVAL;
> - /* Switch to PIO */
> - spin_lock_irqsave(&port->lock, flags);
> s->chan_rx = NULL;
> sci_start_rx(port);
> - spin_unlock_irqrestore(&port->lock, flags);
> + if (!port_lock_held)
> + spin_unlock_irqrestore(&port->lock, flags);
> }
>
> static void work_fn_tx(struct work_struct *work)
> @@ -1491,7 +1493,7 @@ static enum hrtimer_restart rx_timer_fn(struct hrtimer *t)
> }
>
> if (port->type == PORT_SCIFA || port->type == PORT_SCIFB)
> - sci_submit_rx(s);
> + sci_submit_rx(s, true);
>
> /* Direct new serial port interrupts back to CPU */
> scr = serial_port_in(port, SCSCR);
> @@ -1617,7 +1619,7 @@ static void sci_request_dma(struct uart_port *port)
> s->chan_rx_saved = s->chan_rx = chan;
>
> if (port->type == PORT_SCIFA || port->type == PORT_SCIFB)
> - sci_submit_rx(s);
> + sci_submit_rx(s, false);
> }
> }
>
> @@ -1667,7 +1669,7 @@ static irqreturn_t sci_rx_interrupt(int irq, void *ptr)
> scr |= SCSCR_RDRQE;
> } else {
> scr &= ~SCSCR_RIE;
> - sci_submit_rx(s);
> + sci_submit_rx(s, false);
> }
> serial_port_out(port, SCSCR, scr);
> /* Clear current interrupt */
> --
> 2.17.1
>
