On 4 September 2015 at 18:20, Richard Purdie <richard.pur...@linuxfoundation.org> wrote: > On Fri, 2015-09-04 at 13:43 +0100, Richard Purdie wrote: >> On Fri, 2015-09-04 at 12:31 +0100, Peter Maydell wrote: >> > On 4 September 2015 at 12:24, Richard Purdie >> > <richard.pur...@linuxfoundation.org> wrote: >> > > So just based on that, yes, seems that the rx_fifo looks to be >> > > overrunning. I can add the asserts but I think it would just confirm >> > > this. >> > >> > Yes, the point of adding assertions is to confirm a hypothesis. >> >> I've now confirmed that it does indeed trigger the assert in >> smc91c111_receive(). > > I just tried an experiment where I put: > > if (s->rx_fifo_len >= NUM_PACKETS) > return -1; > > into smc91c111_receive() and my reproducer stops reproducing the > problem. I also noticed can_receive() could also have a check on buffer > availability. Would one of these changes be the correct fix here?
The interesting question is why smc91c111_allocate_packet() doesn't fail in this situation. We only have NUM_PACKETS worth of storage, shared between the tx and rx buffers, so how could we both have already filled the rx_fifo and have a spare packet for the allocate function to return? -- PMM
