netdev - RE: [PATCH net-next v14 06/13] rtase: Implement .ndo_start

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Date: Thu, 14 Dec 2023 13:00:29 +0000
From: JustinLai0215 <justinlai0215@...ltek.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com"
	<edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "andrew@...n.ch"
	<andrew@...n.ch>, Ping-Ke Shih <pkshih@...ltek.com>,
        Larry Chiu
	<larry.chiu@...ltek.com>
Subject: RE: [PATCH net-next v14 06/13] rtase: Implement .ndo_start_xmit function

> 
> On Fri, 8 Dec 2023 17:47:26 +0800 Justin Lai wrote:
> > +static int tx_handler(struct rtase_ring *ring, int budget)
> 
> I don't see how this is called, the way you split the submission makes it a bit
> hard to review, oh well. Anyway - if you pass the NAPI budget here - that's not
> right, it may be 0, and you'd loop forever.
> For Tx - you should try to reap some fixed number of packets, say 128, the
> budget is for Rx, not for Tx.

Even if the budget is 0, this function will not loop forever, it will just run all tx_left.
Or what changes would you like us to make?
> 
> > +     const struct rtase_private *tp = ring->ivec->tp;
> > +     struct net_device *dev = tp->dev;
> > +     int workdone = 0;
> > +     u32 dirty_tx;
> > +     u32 tx_left;
> > +
> > +     dirty_tx = ring->dirty_idx;
> > +     tx_left = READ_ONCE(ring->cur_idx) - dirty_tx;
> > +
> > +     while (tx_left > 0) {
> > +             u32 entry = dirty_tx % NUM_DESC;
> > +             struct tx_desc *desc = ring->desc +
> > +                                    sizeof(struct tx_desc) * entry;
> > +             u32 len = ring->mis.len[entry];
> > +             u32 status;
> > +
> > +             status = le32_to_cpu(desc->opts1);
> > +
> > +             if (status & DESC_OWN)
> > +                     break;
> > +
> > +             rtase_unmap_tx_skb(tp->pdev, len, desc);
> > +             ring->mis.len[entry] = 0;
> > +             if (ring->skbuff[entry]) {
> > +                     dev_consume_skb_any(ring->skbuff[entry]);
> 
> napi_consume_skb, assuming you call this from NAPI

Ok, I will modify it.
> 
> > +                     ring->skbuff[entry] = NULL;
> > +             }
> > +
> > +             dev->stats.tx_bytes += len;
> > +             dev->stats.tx_packets++;
> > +             dirty_tx++;
> > +             tx_left--;
> > +             workdone++;
> > +
> > +             if (workdone == budget)
> > +                     break;
> > +     }
> > +
> > +     if (ring->dirty_idx != dirty_tx) {
> > +             WRITE_ONCE(ring->dirty_idx, dirty_tx);
> > +
> > +             if (__netif_subqueue_stopped(dev, ring->index) &&
> > +                 rtase_tx_avail(ring))
> > +                     netif_start_subqueue(dev, ring->index);
> 
> Please use the start / stop macros from include/net/netdev_queues.h I'm
> pretty sure the current code is racy.
> 

Ok, I will use the macros from include/net/netdev_queues.h.