serial: sh-sci: Fix locking in sci_submit_rx()

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@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 8146d9cef0cbe2d0a52c5f489008aed250ca0cb6..2a08039f792235e520a85a3168f526a1b9e6665d 100644 (file)
--- 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 */