Xiaochen Zhou <[EMAIL PROTECTED]> writes:
> 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()?
No!
In general eth_drv_tx_done() is not called from the driver's send
routine, it is usually called from the deliver/poll routine once the
packet has actually been transmitted. Usually in response to an
interrupt.
The only situation in which eth_drv_tx_done() may be called from the
send routine is if you have copied the packet out to an internal
buffer, in the driver or hardware. In this case the can_send routine
will fend off susequent send attempts until the packet is sent and a
buffer is available.
So I suspect that either your driver is calling eth_drv_tx_done() in
the wrong place, or your can_send routine is not working correctly.
Whatever the problem, deleting lines from generic code that has been
working corretly for many years is not the correct solution.
--
Nick Garnett eCos Kernel Architect
eCosCentric Limited http://www.eCosCentric.com/ The eCos experts
Barnwell House, Barnwell Drive, Cambridge, UK. Tel: +44 1223 245571
Registered in England and Wales: Reg No 4422071.
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