On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote: > This patch fixes the following kernel crash, > > WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 > tcp_clean_rtx_queue+0x658/0x80c() > Call trace:
> > Software writes poison data into the descriptor bytes[15:8] and upon > receiving the interrupt, if those bytes are overwritten by the hardware with > the valid data, software also reads bytes[7:0] and executes receive/tx > completion logic. > > If the CPU executes the above two reads in out of order fashion, then the > bytes[7:0] will have older data and causing the kernel panic. We have to > force the order of the reads and thus this patch introduces read memory > barrier between these reads. > > Signed-off-by: Iyappan Subramanian <isubraman...@apm.com> > Signed-off-by: Keyur Chudgar <kchud...@apm.com> > Tested-by: Mark Langsdorf <mlang...@redhat.com> > --- > drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c > b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c > index 83a5028..3622cdb 100644 > --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c > +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c > @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct > xgene_enet_desc_ring *ring, > if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc))) > break; > > + /* read fpqnum field after dataaddr field */ > + smp_rmb(); > if (is_rx_desc(raw_desc)) > ret = xgene_enet_rx_frame(ring, raw_desc); > else Reading your changelog, it looks like you need a plain rmb() here. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
