* [ECOS] eth_drv_send() called recursively
@ 2007-05-24 9:43 Xiaochen Zhou
2007-05-24 12:30 ` Nick Garnett
0 siblings, 1 reply; 2+ messages in thread
From: Xiaochen Zhou @ 2007-05-24 9:43 UTC (permalink / raw)
To: ecos-discuss
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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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [ECOS] eth_drv_send() called recursively
2007-05-24 9:43 [ECOS] eth_drv_send() called recursively Xiaochen Zhou
@ 2007-05-24 12:30 ` Nick Garnett
0 siblings, 0 replies; 2+ messages in thread
From: Nick Garnett @ 2007-05-24 12:30 UTC (permalink / raw)
To: Xiaochen Zhou; +Cc: ecos-discuss
Xiaochen Zhou <zhouxiaochen@h3c.com> 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.
--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
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2007-05-24 9:43 [ECOS] eth_drv_send() called recursively Xiaochen Zhou
2007-05-24 12:30 ` Nick Garnett
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