From: Marc Kleine-Budde <mkl@pengutronix.de>
To: vitor <ivitro@gmail.com>
Cc: manivannan.sadhasivam@linaro.org, thomas.kopp@microchip.com,
wg@grandegger.com, linux-can@vger.kernel.org,
linux-kernel@vger.kernel.org, vitor.soares@toradex.com,
stable@vger.kernel.org
Subject: Re: [PATCH] can: mcp251xfd: fix infinite loop when xmit fails
Date: Thu, 7 Mar 2024 21:40:33 +0100 [thread overview]
Message-ID: <20240307-sturdy-cringe-fa9b095b25ab-mkl@pengutronix.de> (raw)
In-Reply-To: <75fa2711c1aace90a831f95a00b8ba41abf1c883.camel@gmail.com>
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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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next prev parent reply other threads:[~2024-03-07 20:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240307120442.12262-1-ivitro@gmail.com>
2024-03-07 12:23 ` [PATCH] can: mcp251xfd: fix infinite loop when xmit fails Marc Kleine-Budde
2024-03-07 16:54 ` vitor
2024-03-07 20:40 ` Marc Kleine-Budde [this message]
2024-03-11 11:37 Vitor Soares
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