nve(4) patch - please test!

David G. Lawrence dg at dglawrence.com
Wed Jan 4 16:21:16 PST 2006

> Since I sent the mail below I had to discover that the new driver
> has a problem when no cable is plugged in, at least on my Asus board.
> It doesn't only run into timeouts, during some of these timeout the
> machine or at least the keyboard hangs for about a minute.
> Is there anything I can do to help debug this?

   I ran into this problem recently as well and spent some time diagnosing
it. It's not that the cable isn't plugged in - rather it happens whenever
the traffic levels are low.
   The problem is that the nvidia-supplied portion of the driver is defering
the releasing of the completed transmit buffers and this occasionally
results in if_timer expiring, causing the driver watchdog routine to be
called ("device timeout"). The watchdog routine resets the card and the
nvidia-supplied code sits in a high-priority loop waiting for the card
to reset. This can take many seconds and your system will be hung until
it completes.
   I have a work-around patch for the problem that I've attached to this
email. It simply disables the watchdog. A real fix would involve accounting
for the outstanding transmit buffers differently (or perhaps not at all -
e.g. always attempt to call the nvidia-supplied code and if a queue-full
error occurs, then wait for an interrupt before trying to queue more
transmit packets).


David G. Lawrence
Download Technologies, Inc. - http://www.downloadtech.com - (866) 399 8500
The FreeBSD Project - http://www.freebsd.org
Pave the road of life with opportunities.
-------------- next part --------------
Index: if_nve.c
RCS file: /home/ncvs/src/sys/dev/nve/if_nve.c,v
retrieving revision
diff -c -r1.7.2.8 if_nve.c
*** if_nve.c	25 Dec 2005 21:57:03 -0000
--- if_nve.c	5 Jan 2006 00:12:45 -0000
*** 943,949 ****
  		/* Set watchdog timer. */
! 		ifp->if_timer = 8;
  		/* Copy packet to BPF tap */
  		BPF_MTAP(ifp, m0);
--- 943,949 ----
  		/* Set watchdog timer. */
! 		ifp->if_timer = 0;
  		/* Copy packet to BPF tap */
  		BPF_MTAP(ifp, m0);

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