diff options
Diffstat (limited to 'drivers/net/ethernet/sfc/ptp.c')
| -rw-r--r-- | drivers/net/ethernet/sfc/ptp.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/net/ethernet/sfc/ptp.c b/drivers/net/ethernet/sfc/ptp.c index 4625f85acab2..10ad0b93d283 100644 --- a/drivers/net/ethernet/sfc/ptp.c +++ b/drivers/net/ethernet/sfc/ptp.c @@ -1100,7 +1100,29 @@ static void efx_ptp_xmit_skb_queue(struct efx_nic *efx, struct sk_buff *skb) tx_queue = efx_channel_get_tx_queue(ptp_data->channel, type); if (tx_queue && tx_queue->timestamping) { + /* This code invokes normal driver TX code which is always + * protected from softirqs when called from generic TX code, + * which in turn disables preemption. Look at __dev_queue_xmit + * which uses rcu_read_lock_bh disabling preemption for RCU + * plus disabling softirqs. We do not need RCU reader + * protection here. + * + * Although it is theoretically safe for current PTP TX/RX code + * running without disabling softirqs, there are three good + * reasond for doing so: + * + * 1) The code invoked is mainly implemented for non-PTP + * packets and it is always executed with softirqs + * disabled. + * 2) This being a single PTP packet, better to not + * interrupt its processing by softirqs which can lead + * to high latencies. + * 3) netdev_xmit_more checks preemption is disabled and + * triggers a BUG_ON if not. + */ + local_bh_disable(); efx_enqueue_skb(tx_queue, skb); + local_bh_enable(); } else { WARN_ONCE(1, "PTP channel has no timestamped tx queue\n"); dev_kfree_skb_any(skb); |