Commit d8fb63e4 authored by Vitor Soares's avatar Vitor Soares Committed by Marc Kleine-Budde
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can: mcp251xfd: fix infinite loop when xmit fails 



When the mcp251xfd_start_xmit() function fails, the driver stops
processing messages, and the interrupt routine does not return,
running indefinitely even after killing the running application.

Error messages:
[  441.298819] mcp251xfd spi2.0 can0: ERROR in mcp251xfd_start_xmit: -16
[  441.306498] mcp251xfd spi2.0 can0: Transmit Event FIFO buffer not empty. (seq=0x000017c7, tef_tail=0x000017cf, tef_head=0x000017d0, tx_head=0x000017d3).
... and repeat forever.

The issue can be triggered when multiple devices share the same SPI
interface. And there is concurrent access to the bus.

The problem occurs because tx_ring->head increments even if
mcp251xfd_start_xmit() fails. Consequently, the driver skips one TX
package while still expecting a response in
mcp251xfd_handle_tefif_one().

Resolve the issue by starting a workqueue to write the tx obj
synchronously if err = -EBUSY. In case of another error, decrement
tx_ring->head, remove skb from the echo stack, and drop the message.

Fixes: 55e5b97f ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarVitor Soares <vitor.soares@toradex.com>
Link: https://lore.kernel.org/all/20240517134355.770777-1-ivitro@gmail.com


[mkl: use more imperative wording in patch description]
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent 0d34d816

drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c

+13 −1
Original line number Diff line number Diff line
@@ -1618,11 +1618,20 @@ static int mcp251xfd_open(struct net_device *ndev) 
	clear_bit(MCP251XFD_FLAGS_DOWN, priv->flags);

	can_rx_offload_enable(&priv->offload);



	priv->wq = alloc_ordered_workqueue("%s-mcp251xfd_wq",

					   WQ_FREEZABLE | WQ_MEM_RECLAIM,

					   dev_name(&spi->dev));

	if (!priv->wq) {

		err = -ENOMEM;

		goto out_can_rx_offload_disable;

	}

	INIT_WORK(&priv->tx_work, mcp251xfd_tx_obj_write_sync);



	err = request_threaded_irq(spi->irq, NULL, mcp251xfd_irq,

				   IRQF_SHARED | IRQF_ONESHOT,

				   dev_name(&spi->dev), priv);

	if (err)

		goto out_can_rx_offload_disable;

		goto out_destroy_workqueue;



	err = mcp251xfd_chip_interrupts_enable(priv);

	if (err)
@@ -1634,6 +1643,8 @@ static int mcp251xfd_open(struct net_device *ndev) 


 out_free_irq:

	free_irq(spi->irq, priv);

 out_destroy_workqueue:

	destroy_workqueue(priv->wq);

 out_can_rx_offload_disable:

	can_rx_offload_disable(&priv->offload);

	set_bit(MCP251XFD_FLAGS_DOWN, priv->flags);
@@ -1661,6 +1672,7 @@ static int mcp251xfd_stop(struct net_device *ndev) 
	hrtimer_cancel(&priv->tx_irq_timer);

	mcp251xfd_chip_interrupts_disable(priv);

	free_irq(ndev->irq, priv);

	destroy_workqueue(priv->wq);

	can_rx_offload_disable(&priv->offload);

	mcp251xfd_timestamp_stop(priv);

	mcp251xfd_chip_stop(priv, CAN_STATE_STOPPED);

drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c

+47 −8
Original line number Diff line number Diff line
@@ -131,6 +131,39 @@ mcp251xfd_tx_obj_from_skb(const struct mcp251xfd_priv *priv, 
	tx_obj->xfer[0].len = len;

}



static void mcp251xfd_tx_failure_drop(const struct mcp251xfd_priv *priv,

				      struct mcp251xfd_tx_ring *tx_ring,

				      int err)

{

	struct net_device *ndev = priv->ndev;

	struct net_device_stats *stats = &ndev->stats;

	unsigned int frame_len = 0;

	u8 tx_head;



	tx_ring->head--;

	stats->tx_dropped++;

	tx_head = mcp251xfd_get_tx_head(tx_ring);

	can_free_echo_skb(ndev, tx_head, &frame_len);

	netdev_completed_queue(ndev, 1, frame_len);

	netif_wake_queue(ndev);



	if (net_ratelimit())

		netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);

}



void mcp251xfd_tx_obj_write_sync(struct work_struct *work)

{

	struct mcp251xfd_priv *priv = container_of(work, struct mcp251xfd_priv,

						   tx_work);

	struct mcp251xfd_tx_obj *tx_obj = priv->tx_work_obj;

	struct mcp251xfd_tx_ring *tx_ring = priv->tx;

	int err;



	err = spi_sync(priv->spi, &tx_obj->msg);

	if (err)

		mcp251xfd_tx_failure_drop(priv, tx_ring, err);

}



static int mcp251xfd_tx_obj_write(const struct mcp251xfd_priv *priv,

				  struct mcp251xfd_tx_obj *tx_obj)

{
@@ -162,6 +195,11 @@ static bool mcp251xfd_tx_busy(const struct mcp251xfd_priv *priv, 
	return false;

}



static bool mcp251xfd_work_busy(struct work_struct *work)

{

	return work_busy(work);

}



netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb,

				 struct net_device *ndev)

{
@@ -175,7 +213,8 @@ netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb, 
	if (can_dev_dropped_skb(ndev, skb))

		return NETDEV_TX_OK;



	if (mcp251xfd_tx_busy(priv, tx_ring))

	if (mcp251xfd_tx_busy(priv, tx_ring) ||

	    mcp251xfd_work_busy(&priv->tx_work))

		return NETDEV_TX_BUSY;



	tx_obj = mcp251xfd_get_tx_obj_next(tx_ring);
@@ -193,13 +232,13 @@ netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb, 
		netdev_sent_queue(priv->ndev, frame_len);



	err = mcp251xfd_tx_obj_write(priv, tx_obj);

	if (err)

		goto out_err;



	return NETDEV_TX_OK;



 out_err:

	netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);

	if (err == -EBUSY) {

		netif_stop_queue(ndev);

		priv->tx_work_obj = tx_obj;

		queue_work(priv->wq, &priv->tx_work);

	} else if (err) {

		mcp251xfd_tx_failure_drop(priv, tx_ring, err);

	}



	return NETDEV_TX_OK;

}

drivers/net/can/spi/mcp251xfd/mcp251xfd.h

+5 −0
Original line number Diff line number Diff line
@@ -633,6 +633,10 @@ struct mcp251xfd_priv { 
	struct mcp251xfd_rx_ring *rx[MCP251XFD_FIFO_RX_NUM];

	struct mcp251xfd_tx_ring tx[MCP251XFD_FIFO_TX_NUM];



	struct workqueue_struct *wq;

	struct work_struct tx_work;

	struct mcp251xfd_tx_obj *tx_work_obj;



	DECLARE_BITMAP(flags, __MCP251XFD_FLAGS_SIZE__);



	u8 rx_ring_num;
@@ -952,6 +956,7 @@ void mcp251xfd_skb_set_timestamp(const struct mcp251xfd_priv *priv, 
void mcp251xfd_timestamp_init(struct mcp251xfd_priv *priv);

void mcp251xfd_timestamp_stop(struct mcp251xfd_priv *priv);



void mcp251xfd_tx_obj_write_sync(struct work_struct *work);

netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb,

				 struct net_device *ndev);