MBUF Cluster Network freeze problem

bob bobwis at ascweb.co.uk
Fri Dec 15 13:32:37 UTC 2000

Hello Eric / RTEMS users
I have been testing again this morning (snapshot 20001201) and it is all
looking very positive. I can now confirm that we don't need the recv before
a close, to empty the data to save MBUFs.  I am fairly certain this was not
always the case, but I could be wrong. The MBUF pool also seems to cope with
the cable being pulled - that is, it recovers the used MBUFs all by itself
after the timeout has occurred.
The only problem we are seeing now is not a BSD stack problem as such, its
when the task servicing the open socket stops calling read (because it has
frozen). The open socket still allows incoming data into free MBUFs, fills
the clusters and locks up the lot after a while. The only recovery seems to
be a system reset. While the MBUF clusters are filling, the master
application task still allows accept(), to spawn new tasks and sockets, and
so the "big lockup" comes quite a while after this. This had us going for a
while ;-)

To conclude, the TCP Stack looks very solid again, now that we have isolated
the problems to our application.
Thanks again for all your help.
Bob Wisdom

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