On 11.08.2022 10:30:39, Marc Kleine-Budde wrote:
> On 10.08.2022 16:45:36, Uwe Kleine-König wrote:
> > The following happend on an i.MX25 using flexcan with many packets on
> > the bus:
> >
> > The rx-offload queue reached a length more than skb_queue_len_max. So in
> > can_rx_offload_offload_one() the drop variable was set to true which
> > made the call to .mailbox_read() (here: flexcan_mailbox_read()) just
> > return ERR_PTR(-ENOBUFS) (plus some irrelevant hardware interaction) and
> > so can_rx_offload_offload_one() returned ERR_PTR(-ENOBUFS), too.
> >
> > Now can_rx_offload_irq_offload_fifo() looks as follows:
> >
> > while (1) {
> > skb = can_rx_offload_offload_one(offload, 0);
> > if (IS_ERR(skb))
> > continue;
> > ...
> > }
> >
> > As the i.MX25 is a single core CPU while the rx-offload processing is
> > active there is no thread to process packets from the offload queue and
> > so it doesn't get shorter.
> >
> > The result is a tight loop: can_rx_offload_offload_one() does nothing
> > relevant and returns an error code and so
> > can_rx_offload_irq_offload_fifo() calls can_rx_offload_offload_one()
> > again.
> >
> > To break that loop don't continue calling can_rx_offload_offload_one()
> > after it reported an error.
> >
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> > ---
> > Hello,
> >
> > this patch just implements the obvious change to break the loop. I'm not
> > 100% certain that there is no corner case where the break is wrong. The
> > problem exists at least since v5.6, didn't go back further to check.
> >
> > This fixes a hard hang on said i.MX25.
>
> As Uwe suggested in an IRC conversation, the correct fix for the flexcan
> driver is to return NULL if there is no CAN frame pending.
>
> I'll send a -v2.
https://lore.kernel.org/all/20220811094254.1864367-1-mkl@xxxxxxxxxxxxxx
regards,
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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