Messages in this thread | | | Subject | Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read | From | Eric Dumazet <> | Date | Thu, 22 Jan 2015 14:50:50 -0800 |
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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 <isubramanian@apm.com> > Signed-off-by: Keyur Chudgar <kchudgar@apm.com> > Tested-by: Mark Langsdorf <mlangsdo@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.
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