On Thu, Aug 4, 2022 at 10:42 AM Sebastian Würl
<sebastian.wuerl@xxxxxxxxxxxxx> wrote:
>
> The mcp251x driver uses both receiving mailboxes of the CAN controller
> chips. For retrieving the CAN frames from the controller via SPI, it checks
> once per interrupt which mailboxes have been filled and will retrieve the
> messages accordingly.
>
> This introduces a race condition, as another CAN frame can enter mailbox 1
> while mailbox 0 is emptied. If now another CAN frame enters mailbox 0 until
> the interrupt handler is called next, mailbox 0 is emptied before
> mailbox 1, leading to out-of-order CAN frames in the network device.
>
> This is fixed by checking the interrupt flags once again after freeing
> mailbox 0, to correctly also empty mailbox 1 before leaving the handler.
>
> For reproducing the bug I created the following setup:
> - Two CAN devices, one Raspberry Pi with MCP2515, the other can be any.
> - Setup CAN to 1 MHz
> - Spam bursts of 5 CAN-messages with increasing CAN-ids
> - Continue sending the bursts while sleeping a second between the bursts
> - Check on the RPi whether the received messages have increasing CAN-ids
> - Without this patch, every burst of messages will contain a flipped pair
For future submissions...
> Fixes: bf66f3736a94 ("can: mcp251x: Move to threaded interrupts instead of workqueues.")
> Signed-off-by: Sebastian Würl <sebastian.wuerl@xxxxxxxxxxxxx>
> ---
When you send the new version of a single patch, use --annotate to put
a changelog here (after the cutter '---' line) so people will know how
v4 differes to v3 to v2 and to v1.
Also you mentioned some issues with the mail program. Use `git
send-email` for patch submission. Also you may consider my "smart"
(no) script [1] for that.
[1]: https://github.com/andy-shev/home-bin-tools/blob/master/ge2maintainer.sh
--
With Best Regards,
Andy Shevchenko
