On 03.08.2022 18:48:57, Andy Shevchenko wrote: > On Wed, Aug 3, 2022 at 5:36 PM Sebastian Würl > wrote: > > > > The mcp251x driver uses both receiving mailboxes of the can controller > > CAN > > > chips. For retrieving the CAN frames from the controller via SPI, it checks > > once per interrupt which mailboxes have been filled, an 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 > > Fixes tag? Should be: Fixes: bf66f3736a94 ("can: mcp251x: Move to threaded interrupts instead of workqueues.") 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 |