[ECOS] eth_drv_send() called recursively

[Xiaochen Zhou <zhouxiaochen at h3c dot com>]

Hi,everyone:

Here is ethernet packet sending flow in our ecos application:

1. eth_drv_send() call my_eth_driver_send()
2. my_eth_driver_send() call eth_drv_tx_done()
3. eth_drv_tx_done() call eth_drv_send()

eth_drv_send() and eth_drv_tx_done() are implemented in
io/eth/current/src/net/eth_drv.c

eth_drv_tx_done(struct eth_drv_sc *sc, CYG_ADDRESS key, int status)
{
    ....
    eth_drv_send(ifp);
    ....

eth_drv_send(struct ifnet *ifp)
{
    ....
    while ((sc->funs->can_send)(sc) > 0) {
        IF_DEQUEUE(&ifp->if_snd, m0);
        if (m0 == 0) {
            break;
        }
    ....
}

If sending queue has many mbufs (we using queue for QOS application),
sending thread will call eth_drv_send() recursively, the stack of packet
sending thread will overflow.

Can anyone tell me why call eth_drv_send() in eth_drv_tx_done()? In
eth_drv_send(), there are a loop to call IF_DEQUEUE(), so I think it is
useless and harmful. Can I delete "eth_drv_send(ifp)" line in
eth_drv_tx_done()?

Thanks!

Xiaochen Zhou

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