Poor network connection causes lockup with V4.6.0pre5

[Steve Strobel]

I hate to ask a question about an old version, but it has been 
working well for years and we haven't tried to stay current.  We are 
running RTEMS V4.6.0pre5 on a MCF5272.  The network is used mostly to 
provide telnet connections to a command-line interface.  One of the 
commands causes a relatively large response consisting of about 200KB 
of text.  When that command is executed over a good (LAN or Internet) 
network connection, it works fine.  We recently started testing it 
over a wireless network connection (a D-Link mobile router with a 
Sierra Wireless AirCard 595 over Verizon's EV-DO network) which has 
occasional dropouts, pauses, etc.  A packet sniffer (WireShark) shows 
frequent retries when sending the 200KB chunk.  That wouldn't be a 
problem except that our whole application (running on RTEMS) often 
seems to hang at those times and never recovers.  I am trying to 
track down the cause of the hangups and would welcome any suggestions.

At the risk of narrowing the focus too much...I seem to remember a 
lot of discussion on this mailing list about mbufs:  how many were 
needed, the algorithm used to free them, what should happen when they 
are exhausted, race conditions, etc.  I can't remember if or how 
those issues were resolved nor if they caused symptoms similar to 
what I am seeing.  Does anyone remember the short answer, or should I 
dig through the archives?  My network configuration just uses the defaults:

   0,      /* Default network task priority */
   0,      /* Default mbuf capacity */
   0,      /* Default mbuf cluster capacity */

Thanks for any suggestions,

Steve



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Steve Strobel
Link Communications, Inc.
1035 Cerise Rd
Billings, MT 59101-7378
(406) 245-5002 ext 102
(406) 245-4889 (fax)
WWW: http://www.link-comm.com
MailTo:steve.strobel at link-comm.com