| Message ID | 20161107095756.15343-1-bpoirier@suse.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Benjamin Poirier <bpoirier@suse.com> Date: Mon, 7 Nov 2016 17:57:56 +0800 > We received two reports of BUG_ON in bnad_txcmpl_process() where > hw_consumer_index appeared to be ahead of producer_index. Out of order > write/read of these variables could explain these reports. > > bnad_start_xmit(), as a producer of tx descriptors, has a few memory > barriers sprinkled around writes to producer_index and the device's > doorbell but they're not paired with anything in bnad_txcmpl_process(), a > consumer. > > Since we are synchronizing with a device, we must use mandatory barriers, > not smp_*. Also, I didn't see the purpose of the last smp_mb() in > bnad_start_xmit(). > > Signed-off-by: Benjamin Poirier <bpoirier@suse.com> Applied.
diff --git a/drivers/net/ethernet/brocade/bna/bnad.c b/drivers/net/ethernet/brocade/bna/bnad.c index f9df4b5a..f42f672 100644 --- a/drivers/net/ethernet/brocade/bna/bnad.c +++ b/drivers/net/ethernet/brocade/bna/bnad.c @@ -177,6 +177,7 @@ bnad_txcmpl_process(struct bnad *bnad, struct bna_tcb *tcb) return 0; hw_cons = *(tcb->hw_consumer_index); + rmb(); cons = tcb->consumer_index; q_depth = tcb->q_depth; @@ -3094,7 +3095,7 @@ bnad_start_xmit(struct sk_buff *skb, struct net_device *netdev) BNA_QE_INDX_INC(prod, q_depth); tcb->producer_index = prod; - smp_mb(); + wmb(); if (unlikely(!test_bit(BNAD_TXQ_TX_STARTED, &tcb->flags))) return NETDEV_TX_OK; @@ -3102,7 +3103,6 @@ bnad_start_xmit(struct sk_buff *skb, struct net_device *netdev) skb_tx_timestamp(skb); bna_txq_prod_indx_doorbell(tcb); - smp_mb(); return NETDEV_TX_OK; }
We received two reports of BUG_ON in bnad_txcmpl_process() where hw_consumer_index appeared to be ahead of producer_index. Out of order write/read of these variables could explain these reports. bnad_start_xmit(), as a producer of tx descriptors, has a few memory barriers sprinkled around writes to producer_index and the device's doorbell but they're not paired with anything in bnad_txcmpl_process(), a consumer. Since we are synchronizing with a device, we must use mandatory barriers, not smp_*. Also, I didn't see the purpose of the last smp_mb() in bnad_start_xmit(). Signed-off-by: Benjamin Poirier <bpoirier@suse.com> --- drivers/net/ethernet/brocade/bna/bnad.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)