Messages in this thread | | | Subject | Re: [PATCH net v2 3/3] net: nixge: fix tx queue handling | From | Zhang Changzhong <> | Date | Wed, 16 Nov 2022 16:55:58 +0800 |
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On 2022/11/16 7:04, Francois Romieu wrote: > Zhang Changzhong <zhangchangzhong@huawei.com> : >> Currently the driver check for available space at the beginning of >> nixge_start_xmit(), and when there is not enough space for this packet, >> it returns NETDEV_TX_OK, which casues packet loss and memory leak. >> >> Instead the queue should be stopped after the packet is added to the BD >> when there may not be enough space for next packet. In addition, the >> queue should be wakeup only if there is enough space for a packet with >> max frags. >> >> Fixes: 492caffa8a1a ("net: ethernet: nixge: Add support for National Instruments XGE netdev") >> Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> >> --- >> drivers/net/ethernet/ni/nixge.c | 54 +++++++++++++++++++++++++++++------------ >> 1 file changed, 38 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/net/ethernet/ni/nixge.c b/drivers/net/ethernet/ni/nixge.c >> index 91b7ebc..3776a03 100644 >> --- a/drivers/net/ethernet/ni/nixge.c >> +++ b/drivers/net/ethernet/ni/nixge.c > [...] >> static netdev_tx_t nixge_start_xmit(struct sk_buff *skb, >> @@ -518,10 +523,15 @@ static netdev_tx_t nixge_start_xmit(struct sk_buff *skb, >> cur_p = &priv->tx_bd_v[priv->tx_bd_tail]; >> tx_skb = &priv->tx_skb[priv->tx_bd_tail]; >> >> - if (nixge_check_tx_bd_space(priv, num_frag + 1)) { >> - if (!netif_queue_stopped(ndev)) >> - netif_stop_queue(ndev); >> - return NETDEV_TX_OK; >> + if (unlikely(nixge_check_tx_bd_space(priv, num_frag + 1))) { >> + /* Should not happen as last start_xmit call should have >> + * checked for sufficient space and queue should only be >> + * woken when sufficient space is available. >> + */ > > Almost. IRQ triggering after nixge_start_xmit::netif_stop_queue and > before nixge_start_xmit::smp_mb may wrongly wake queue. >
I don't know what you mean by "wronly wake queue". The queue is woken only when there is sufficient for next packet.
> Call me timorous but I would feel more confortable if this code could > be tested on real hardware before being fed into -net. >
I agree with you, hope someone can test and correct it.
Thanks, Changzhong
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