System hangs with alt0: null mbuf

[David Lesny]

I have a DPW 600 with a DEGPA-TA gigabit card installed in a 64bit slot. The system is running Tru64 5.1B PK3. On occasion the system hangs with the console message

alt0: null mbuf (oldrpp 0x27e haddr 0x4731780200000000 t_f 0x4 c_l 0x1ab00aa)

Is there a patch for this or some tuning that I need to do to prevent this hang.

thanks, dave

[Ralf Puchner]

The DEGPA-TA is not on the supported option list. So it is not supported on this kind of machine.

I don't know this code in detail, but I think alt0 has received some data, but the pointer to the receive buffer is null.

The only fix is to remove the card.

[Vouters]

Hi Dave,

Is, by chance, your gigabit card being cable unplugged ? In such case, make your gigabit interface down using ifconfig.
You should use the
$ netstat -g -p ip
to determine the cause of the null mbuf (watch out the number of lost packets due to resource problems.)
The IP stack being unable to allocate an mbuf can be the cause of a system hang.
Use
$ netstat -is -I alt0
to watch if data goes through your interface.

I had to deal with such a kind of problems using the RPC discovery broadcast code.

Hoping this can help.
Philippe