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Commit dd1f2250 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Greg Kroah-Hartman
Browse files

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: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: default avatarSimon Horman <horms+renesas@verge.net.au>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9c96f401

drivers/tty/serial/sh-sci.c

+9 −7
Original line number Diff line number Diff line
@@ -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;
@@ -1362,15 +1362,17 @@ 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);

	if (!port_lock_held)

		spin_unlock_irqrestore(&port->lock, flags);

}
@@ -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 */