From: Marc Kleine-Budde <mkl@pengutronix.de>
To: Vitor Soares <ivitro@gmail.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
Thomas Kopp <thomas.kopp@microchip.com>,
Vincent Mailhol <mailhol.vincent@wanadoo.fr>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>,
Vitor Soares <vitor.soares@toradex.com>,
linux-can@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v5] can: mcp251xfd: fix infinite loop when xmit fails
Date: Tue, 14 May 2024 14:23:45 +0200 [thread overview]
Message-ID: <20240514-corgi-of-marvelous-peace-968f5c-mkl@pengutronix.de> (raw)
In-Reply-To: <20240514105822.99986-1-ivitro@gmail.com>
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On 14.05.2024 11:58:22, 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 starting a workqueue to write
> the tx obj synchronously if err = -EBUSY. In case of another error,
> it decrements tx_ring->head, removes skb from the echo stack, and
> drops the message.
This looks quite good! Good work!
I think you better move the allocation/destroy of the wq into the open()
and stop() callbacks. You have to destroy the workqueue before putting
the interface to sleep.
>
> 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>
> ---
>
> V4->V5:
> - Start a workqueue to write tx obj with spi_sync() when spi_async() == -EBUSY.
>
> 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.
>
> .../net/can/spi/mcp251xfd/mcp251xfd-core.c | 13 ++++-
> drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c | 51 ++++++++++++++++---
> drivers/net/can/spi/mcp251xfd/mcp251xfd.h | 5 ++
> 3 files changed, 60 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> index 1d9057dc44f2..6cca853f2b1e 100644
> --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> @@ -2141,15 +2141,25 @@ static int mcp251xfd_probe(struct spi_device *spi)
> if (err)
> goto out_free_candev;
>
> + priv->tx_work_obj = NULL;
> + priv->wq = alloc_workqueue("mcp251xfd_wq", WQ_FREEZABLE, 0);
The m_can driver uses a ordered workqueue and you can add the name of
the spi device to the wq's name :)
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_del;
> + }
> + INIT_WORK(&priv->tx_work, mcp251xfd_tx_obj_write_sync);
> +
> err = mcp251xfd_register(priv);
> if (err) {
> dev_err_probe(&spi->dev, err, "Failed to detect %s.\n",
> mcp251xfd_get_model_str(priv));
> - goto out_can_rx_offload_del;
> + goto out_can_free_wq;
nitpick:
out_destroy_workqueue;
to match the function call.
> }
>
> return 0;
>
> + out_can_free_wq:
> + destroy_workqueue(priv->wq);
> out_can_rx_offload_del:
> can_rx_offload_del(&priv->offload);
> out_free_candev:
> @@ -2165,6 +2175,7 @@ static void mcp251xfd_remove(struct spi_device *spi)
> struct mcp251xfd_priv *priv = spi_get_drvdata(spi);
> struct net_device *ndev = priv->ndev;
>
> + destroy_workqueue(priv->wq);
> can_rx_offload_del(&priv->offload);
> mcp251xfd_unregister(priv);
> spi->max_speed_hz = priv->spi_max_speed_hz_orig;
> diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> index 160528d3cc26..1e7ddf316643 100644
> --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
> @@ -131,6 +131,41 @@ 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 *ws)
> +{
> + struct mcp251xfd_priv *priv = container_of(ws, 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);
> +
> + priv->tx_work_obj = NULL;
Race condition:
- after spi_sync() the CAN frame is send
- after the TX complete IRQ the TX queue is restarted
- the xmit handler might get BUSY
- fill the tx_work_obj again
> +}
> +
> static int mcp251xfd_tx_obj_write(const struct mcp251xfd_priv *priv,
> struct mcp251xfd_tx_obj *tx_obj)
> {
> @@ -175,7 +210,7 @@ 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) || priv->tx_work_obj)
This should not happen, but better save than sorry.
> return NETDEV_TX_BUSY;
>
> tx_obj = mcp251xfd_get_tx_obj_next(tx_ring);
> @@ -193,13 +228,13 @@ 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) {
> + priv->tx_work_obj = tx_obj;
> + netif_stop_queue(ndev);
> + queue_work(priv->wq, &priv->tx_work);
nitpick: I would do "netif_stop_queue(ndev);" first.
My mental idea of the code flow is:
- stop the queue
- do everything to start the workqueue.
> + } else if (err) {
> + mcp251xfd_tx_failure_drop(priv, tx_ring, err);
> + }
>
> return NETDEV_TX_OK;
> }
> diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd.h b/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
> index 24510b3b8020..4e27a33f4030 100644
> --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
> +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
> @@ -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 *ws);
> netdev_tx_t mcp251xfd_start_xmit(struct sk_buff *skb,
> struct net_device *ndev);
>
> --
> 2.34.1
>
>
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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next prev parent reply other threads:[~2024-05-14 12:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-14 10:58 [PATCH v5] can: mcp251xfd: fix infinite loop when xmit fails Vitor Soares
2024-05-14 12:23 ` Marc Kleine-Budde [this message]
2024-05-14 14:34 ` Vitor Soares
2024-05-15 11:12 ` Marc Kleine-Budde
2024-05-15 16:29 ` Vitor Soares
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