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 and removing the skb from the echo stack if mcp251xfd_start_xmit() fails. Consequently, the package is dropped not been possible to re-transmit.
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 --- With this approach, some packages get lost in concurrent SPI bus access due to can_put_echo_skb() being called before mcp251xfd_tx_obj_write(). The can_put_echo_skb() calls can_create_echo_skb() that consumes the original skb resulting in a Kernel NULL pointer dereference error if return NETDEV_TX_BUSY on mcp251xfd_tx_obj_write() failure. A potential solution would be to change the code to use spi_sync(), which would wait for SPI bus to be unlocked. Any thoughts about this?
V3->V4: - Leave can_put_echo_skb() and stop the queue if needed, before mcp251xfd_tx_obj_write(). - Re-sync head and remove echo skb if mcp251xfd_tx_obj_write() fails. - Revert -> return NETDEV_TX_BUSY if mcp251xfd_tx_obj_write() == -EBUSY.
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 | 26 ++++++++++++++------ 1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c index 160528d3cc26..9909e23de7b9 100644 --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c @@ -166,11 +166,12 @@ 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; + int err, echo_err; u8 tx_head; - int err;
if (can_dev_dropped_skb(ndev, skb)) return NETDEV_TX_OK; @@ -188,18 +189,27 @@ netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb, 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) + echo_err = can_put_echo_skb(skb, ndev, tx_head, frame_len); + if (!echo_err) netdev_sent_queue(priv->ndev, frame_len);
err = mcp251xfd_tx_obj_write(priv, tx_obj); - if (err) - goto out_err; + if (err) { + tx_ring->head--;
- return NETDEV_TX_OK; + if (!echo_err) { + can_free_echo_skb(ndev, tx_head, &frame_len); + netdev_completed_queue(ndev, 1, frame_len); + } + + if (mcp251xfd_get_tx_free(tx_ring)) + netif_wake_queue(ndev);
- 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); + }
return NETDEV_TX_OK; }