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Subject[PATCH 4.20 182/352] serial: sh-sci: Fix locking in sci_submit_rx()
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit dd1f2250da95e87cb3e612858f94b14f99445a7c ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 cc56cb3b3eca..613007d7165e 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 */
--
2.19.1


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