On Wed, Aug 3, 2022 at 6:48 PM Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote: > > On Wed, Aug 3, 2022 at 5:36 PM Sebastian Würl > <sebastian.wuerl@xxxxxxxxxxxxx> 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? Also fix the Subject prefix (you may see the most used ones by running `git log --no-merges --oneline -- drivers/net/can/spi/mcp251x.c`). -- With Best Regards, Andy Shevchenko
