[PATCH] can: mcp251xfd: fix infinite loop when xmit fails

[PATCH] can: mcp251xfd: fix infinite loop when xmit fails

[Vitor Soares]

From: Vitor Soares <vitor.soares@toradex.com>

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().

This patch resolves the issue by decreasing tx_ring->head if
mcp251xfd_start_xmit() fails. With the fix, if we attempt to trigger
the issue again, the driver prints an error and discard the message.

Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Cc: stable@vger.kernel.org
Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
---
 drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c | 27 ++++++++++----------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
index 160528d3cc26..a8eb941c1b95 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
@@ -181,25 +181,26 @@ netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb,
 	tx_obj = mcp251xfd_get_tx_obj_next(tx_ring);
 	mcp251xfd_tx_obj_from_skb(priv, tx_obj, skb, tx_ring->head);
 
-	/* Stop queue if we occupy the complete TX FIFO */
 	tx_head = mcp251xfd_get_tx_head(tx_ring);
-	tx_ring->head++;
-	if (mcp251xfd_get_tx_free(tx_ring) == 0)
-		netif_stop_queue(ndev);
-
 	frame_len = can_skb_get_frame_len(skb);
-	err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
-	if (!err)
-		netdev_sent_queue(priv->ndev, frame_len);
+	can_put_echo_skb(skb, ndev, tx_head, frame_len);
+
+	tx_ring->head++;
 
 	err = mcp251xfd_tx_obj_write(priv, tx_obj);
-	if (err)
-		goto out_err;
+	if (err) {
+		can_free_echo_skb(ndev, tx_head, NULL);
 
-	return NETDEV_TX_OK;
+		tx_ring->head--;
+
+		netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
+	} else {
+		/* Stop queue if we occupy the complete TX FIFO */
+		if (mcp251xfd_get_tx_free(tx_ring) == 0)
+			netif_stop_queue(ndev);
 
- out_err:
-	netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
+		netdev_sent_queue(priv->ndev, frame_len);
+	}
 
 	return NETDEV_TX_OK;
 }
-- 
2.34.1

Re: [PATCH] can: mcp251xfd: fix infinite loop when xmit fails

[Marc Kleine-Budde]

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On 07.03.2024 12:04:42, Vitor Soares wrote:
> From: Vitor Soares <vitor.soares@toradex.com>
> 
> 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().
> 
> This patch resolves the issue by decreasing tx_ring->head if
> mcp251xfd_start_xmit() fails. With the fix, if we attempt to trigger
> the issue again, the driver prints an error and discard the message.

What about returning NETDEV_TX_BUSY, then the networking stack will
retry.

> Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
> Cc: stable@vger.kernel.org
> Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
> ---
>  drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c | 27 ++++++++++----------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> index 160528d3cc26..a8eb941c1b95 100644
> --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> @@ -181,25 +181,26 @@ netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb,
>  	tx_obj = mcp251xfd_get_tx_obj_next(tx_ring);
>  	mcp251xfd_tx_obj_from_skb(priv, tx_obj, skb, tx_ring->head);
>  
> -	/* Stop queue if we occupy the complete TX FIFO */
>  	tx_head = mcp251xfd_get_tx_head(tx_ring);
> -	tx_ring->head++;
> -	if (mcp251xfd_get_tx_free(tx_ring) == 0)
> -		netif_stop_queue(ndev);
> -
>  	frame_len = can_skb_get_frame_len(skb);
> -	err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
> -	if (!err)
> -		netdev_sent_queue(priv->ndev, frame_len);
> +	can_put_echo_skb(skb, ndev, tx_head, frame_len);
> +
> +	tx_ring->head++;
>  
>  	err = mcp251xfd_tx_obj_write(priv, tx_obj);
> -	if (err)
> -		goto out_err;
> +	if (err) {
> +		can_free_echo_skb(ndev, tx_head, NULL);
>  
> -	return NETDEV_TX_OK;
> +		tx_ring->head--;
> +

I'm not sure, if we want an error message for -EBUSY. We could add
proper ethtool statistics.

> +		netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
> +	} else {
> +		/* Stop queue if we occupy the complete TX FIFO */
> +		if (mcp251xfd_get_tx_free(tx_ring) == 0)
> +			netif_stop_queue(ndev);
>  
> - out_err:
> -	netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
> +		netdev_sent_queue(priv->ndev, frame_len);
> +	}
>  
>  	return NETDEV_TX_OK;
>  }

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
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Re: [PATCH] can: mcp251xfd: fix infinite loop when xmit fails

[Marc Kleine-Budde]

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Sorry, resend. I fsck up the linux-can ML's address.

On 07.03.2024 12:04:42, Vitor Soares wrote:
> From: Vitor Soares <vitor.soares@toradex.com>
> 
> 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().
> 
> This patch resolves the issue by decreasing tx_ring->head if
> mcp251xfd_start_xmit() fails. With the fix, if we attempt to trigger
> the issue again, the driver prints an error and discard the message.

What about returning NETDEV_TX_BUSY, then the networking stack will
retry.

> Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
> Cc: stable@vger.kernel.org
> Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
> ---
>  drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c | 27 ++++++++++----------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> index 160528d3cc26..a8eb941c1b95 100644
> --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> @@ -181,25 +181,26 @@ netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb,
>  	tx_obj = mcp251xfd_get_tx_obj_next(tx_ring);
>  	mcp251xfd_tx_obj_from_skb(priv, tx_obj, skb, tx_ring->head);
>  
> -	/* Stop queue if we occupy the complete TX FIFO */
>  	tx_head = mcp251xfd_get_tx_head(tx_ring);
> -	tx_ring->head++;
> -	if (mcp251xfd_get_tx_free(tx_ring) == 0)
> -		netif_stop_queue(ndev);
> -
>  	frame_len = can_skb_get_frame_len(skb);
> -	err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
> -	if (!err)
> -		netdev_sent_queue(priv->ndev, frame_len);
> +	can_put_echo_skb(skb, ndev, tx_head, frame_len);
> +
> +	tx_ring->head++;
>  
>  	err = mcp251xfd_tx_obj_write(priv, tx_obj);
> -	if (err)
> -		goto out_err;
> +	if (err) {
> +		can_free_echo_skb(ndev, tx_head, NULL);
>  
> -	return NETDEV_TX_OK;
> +		tx_ring->head--;
> +

I'm not sure, if we want an error message for -EBUSY. We could add
proper ethtool statistics.

> +		netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
> +	} else {
> +		/* Stop queue if we occupy the complete TX FIFO */
> +		if (mcp251xfd_get_tx_free(tx_ring) == 0)
> +			netif_stop_queue(ndev);
>  
> - out_err:
> -	netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
> +		netdev_sent_queue(priv->ndev, frame_len);
> +	}
>  
>  	return NETDEV_TX_OK;
>  }

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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Re: [PATCH] can: mcp251xfd: fix infinite loop when xmit fails

[vitor]

Hi Marc,

On Thu, 2024-03-07 at 13:23 +0100, Marc Kleine-Budde wrote:
> Sorry, resend. I fsck up the linux-can ML's address.

Thanks for that.
> 
> On 07.03.2024 12:04:42, Vitor Soares wrote:
> > From: Vitor Soares <vitor.soares@toradex.com>
> > 
> > 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().
> > 
> > This patch resolves the issue by decreasing tx_ring->head if
> > mcp251xfd_start_xmit() fails. With the fix, if we attempt to
> > trigger
> > the issue again, the driver prints an error and discard the
> > message.
> 
> What about returning NETDEV_TX_BUSY, then the networking stack will
> retry.

Do you mean when err == -EBUSY?

> 
> > Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip
> > MCP25xxFD SPI CAN")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
> > ---
> >  drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c | 27 ++++++++++------
> > ----
> >  1 file changed, 14 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> > b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> > index 160528d3cc26..a8eb941c1b95 100644
> > --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> > +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> > @@ -181,25 +181,26 @@ netdev_tx_t mcp251xfd_start_xmit(struct
> > sk_buff *skb,
> >         tx_obj = mcp251xfd_get_tx_obj_next(tx_ring);
> >         mcp251xfd_tx_obj_from_skb(priv, tx_obj, skb, tx_ring-
> > >head);
> >  
> > -       /* Stop queue if we occupy the complete TX FIFO */
> >         tx_head = mcp251xfd_get_tx_head(tx_ring);
> > -       tx_ring->head++;
> > -       if (mcp251xfd_get_tx_free(tx_ring) == 0)
> > -               netif_stop_queue(ndev);
> > -
> >         frame_len = can_skb_get_frame_len(skb);
> > -       err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
> > -       if (!err)
> > -               netdev_sent_queue(priv->ndev, frame_len);
> > +       can_put_echo_skb(skb, ndev, tx_head, frame_len);
> > +
> > +       tx_ring->head++;
> >  
> >         err = mcp251xfd_tx_obj_write(priv, tx_obj);
> > -       if (err)
> > -               goto out_err;
> > +       if (err) {
> > +               can_free_echo_skb(ndev, tx_head, NULL);
> >  
> > -       return NETDEV_TX_OK;
> > +               tx_ring->head--;
> > +

I'm testing returning here when err = -EBUSY, but can_put_echo_skb()
should be invoked after mcp251xfd_tx_obj_write(). Otherwise, I get a
Kernel NULL pointer dereference error.


> 
> I'm not sure, if we want an error message for -EBUSY. We could add
> proper ethtool statistics.
> 
> > +               netdev_err(priv->ndev, "ERROR in %s: %d\n",
> > __func__, err);
> > +       } else {
> > +               /* Stop queue if we occupy the complete TX FIFO */
> > +               if (mcp251xfd_get_tx_free(tx_ring) == 0)
> > +                       netif_stop_queue(ndev);
> >  
> > - out_err:
> > -       netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
> > +               netdev_sent_queue(priv->ndev, frame_len);
> > +       }
> >  
> >         return NETDEV_TX_OK;
> >  }
> 
> regards,
> Marc
> 

Best regards,
Vitor Soares

Re: [PATCH] can: mcp251xfd: fix infinite loop when xmit fails

[Marc Kleine-Budde]

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On 07.03.2024 16:54:13, vitor wrote:
> > On 07.03.2024 12:04:42, Vitor Soares wrote:
> > > From: Vitor Soares <vitor.soares@toradex.com>
> > > 
> > > 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().
> > > 
> > > This patch resolves the issue by decreasing tx_ring->head if
> > > mcp251xfd_start_xmit() fails. With the fix, if we attempt to
> > > trigger
> > > the issue again, the driver prints an error and discard the
> > > message.
> > 
> > What about returning NETDEV_TX_BUSY, then the networking stack will
> > retry.
> 
> Do you mean when err == -EBUSY?

ACK

> > 
> > > Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip
> > > MCP25xxFD SPI CAN")
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
> > > ---
> > >  drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c | 27 ++++++++++------
> > > ----
> > >  1 file changed, 14 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> > > b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> > > index 160528d3cc26..a8eb941c1b95 100644
> > > --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> > > +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> > > @@ -181,25 +181,26 @@ netdev_tx_t mcp251xfd_start_xmit(struct
> > > sk_buff *skb,
> > >         tx_obj = mcp251xfd_get_tx_obj_next(tx_ring);
> > >         mcp251xfd_tx_obj_from_skb(priv, tx_obj, skb, tx_ring-
> > > >head);
> > >  
> > > -       /* Stop queue if we occupy the complete TX FIFO */
> > >         tx_head = mcp251xfd_get_tx_head(tx_ring);
> > > -       tx_ring->head++;
> > > -       if (mcp251xfd_get_tx_free(tx_ring) == 0)
> > > -               netif_stop_queue(ndev);
> > > -
> > >         frame_len = can_skb_get_frame_len(skb);
> > > -       err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
> > > -       if (!err)
> > > -               netdev_sent_queue(priv->ndev, frame_len);
> > > +       can_put_echo_skb(skb, ndev, tx_head, frame_len);
> > > +
> > > +       tx_ring->head++;
> > >  
> > >         err = mcp251xfd_tx_obj_write(priv, tx_obj);
> > > -       if (err)
> > > -               goto out_err;
> > > +       if (err) {
> > > +               can_free_echo_skb(ndev, tx_head, NULL);
> > >  
> > > -       return NETDEV_TX_OK;
> > > +               tx_ring->head--;
> > > +
> 
> I'm testing returning here when err = -EBUSY, but can_put_echo_skb()
> should be invoked after mcp251xfd_tx_obj_write(). Otherwise, I get a
> Kernel NULL pointer dereference error.

I mean if mcp251xfd_tx_obj_write() returns -EBUSY don't print an error
message, on any other error it's ok to print the error.

> > 
> > I'm not sure, if we want an error message for -EBUSY. We could add
> > proper ethtool statistics.
> > 
> > > +               netdev_err(priv->ndev, "ERROR in %s: %d\n",
> > > __func__, err);
> > > +       } else {
> > > +               /* Stop queue if we occupy the complete TX FIFO */
> > > +               if (mcp251xfd_get_tx_free(tx_ring) == 0)
> > > +                       netif_stop_queue(ndev);
> > >  
> > > - out_err:
> > > -       netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
> > > +               netdev_sent_queue(priv->ndev, frame_len);
> > > +       }
> > >  
> > >         return NETDEV_TX_OK;
> > >  }

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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[PATCH] can: mcp251xfd: fix infinite loop when xmit fails

[Vitor Soares]

From: Vitor Soares <vitor.soares@toradex.com>

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().

This patch resolves the issue by decreasing tx_ring->head if
mcp251xfd_start_xmit() fails. With the fix, if we trigger the issue and
the err = -EBUSY, the driver returns NETDEV_TX_BUSY. The network stack
retries to transmit the message.
Otherwise, it prints an error and discards the message.

Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Cc: stable@vger.kernel.org
Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
---

V2->V3:
  - Add tx_dropped stats.
  - netdev_sent_queue() only if can_put_echo_skb() succeed.

V1->V2:
  - Return NETDEV_TX_BUSY if mcp251xfd_tx_obj_write() == -EBUSY.
  - Rework the commit message to address the change above.
  - Change can_put_echo_skb() to be called after mcp251xfd_tx_obj_write() succeed.
    Otherwise, we get Kernel NULL pointer dereference error.

 drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c | 34 ++++++++++++--------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
index 160528d3cc26..146c44e47c60 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
@@ -166,6 +166,7 @@ netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb,
 				 struct net_device *ndev)
 {
 	struct mcp251xfd_priv *priv = netdev_priv(ndev);
+	struct net_device_stats *stats = &ndev->stats;
 	struct mcp251xfd_tx_ring *tx_ring = priv->tx;
 	struct mcp251xfd_tx_obj *tx_obj;
 	unsigned int frame_len;
@@ -181,25 +182,32 @@ netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb,
 	tx_obj = mcp251xfd_get_tx_obj_next(tx_ring);
 	mcp251xfd_tx_obj_from_skb(priv, tx_obj, skb, tx_ring->head);
 
-	/* Stop queue if we occupy the complete TX FIFO */
 	tx_head = mcp251xfd_get_tx_head(tx_ring);
-	tx_ring->head++;
-	if (mcp251xfd_get_tx_free(tx_ring) == 0)
-		netif_stop_queue(ndev);
-
 	frame_len = can_skb_get_frame_len(skb);
-	err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
-	if (!err)
-		netdev_sent_queue(priv->ndev, frame_len);
+
+	tx_ring->head++;
 
 	err = mcp251xfd_tx_obj_write(priv, tx_obj);
-	if (err)
-		goto out_err;
+	if (err) {
+		tx_ring->head--;
 
-	return NETDEV_TX_OK;
+		if (err == -EBUSY)
+			return NETDEV_TX_BUSY;
 
- out_err:
-	netdev_err(priv->ndev, "ERROR in %s: %d\n", __func__, err);
+		stats->tx_dropped++;
+
+		if (net_ratelimit())
+			netdev_err(priv->ndev,
+				   "ERROR in %s: %d\n", __func__, err);
+	} else {
+		err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
+		if (!err)
+			netdev_sent_queue(priv->ndev, frame_len);
+
+		/* Stop queue if we occupy the complete TX FIFO */
+		if (mcp251xfd_get_tx_free(tx_ring) == 0)
+			netif_stop_queue(ndev);
+	}
 
 	return NETDEV_TX_OK;
 }
-- 
2.34.1