modified webserver - application crash under load

Hi again,

while debugging noticed a certain flow: at some point the Nios stops servicing HTTP requests, the PC asks for TCP retransmissions and than sends ARP packets for a while. After a number of ARPs the Nios starts sending flow control messages (in my understanding resume messages).

Now if it sends resume messages I should understand it initially sent a pause request, which I don't see in the trace...

I have attached a Wireshark trace of the session, from OK to failure...

60    6.778055000    Altera_1c:12:34    Spanning-tree-(for-bridges)_01    MAC CTRL    60    MAC PAUSE: pause_time: 0 quanta    203
0000  01 80 c2 00 00 01 00 07  ed 1c 12 34 88 08 00 01   ........ ...4....
0010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........
0020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........
0030  00 00 00 00 00 00 00 00  00 00 00 00               ........ ....

==============

In a Qsys design without TSE MAC flow control the Nios also "hangs" but with the difference that the flow control message never gets sent.

In both cases, while the Nios is in the complete silence state, 3 interrupts are continuously high: SGDMA RX, SGDMA TX and JTAG UART.

==============

EDIT: I was able to capture the following exception:

panic: unlock NET
dtrap - needs breakpoint
ip_exit: calling func 0xa028e88
netclose: closing iface Altera TSE MAC ethernet
ip_exit: calling func 0xa02da20
panic: unlock NET
dtrap - needs breakpoint
ip_exit: calling func 0x0
ip_exit: calling func 0x0

in Objdump I have the following mapping:

* 0xa02da20 - clock_c

* 0xa028e88 - netclose

Can anyone help me understand what's happening in this scenario?