panic: sched_priority: invalid priority 3990 on r225375

[John Baldwin]

On Sunday, September 04, 2011 7:21:23 pm Ryan Stone wrote:
> I've gotten the following panic twice while running recent builds of
> head under VirtualBox(FreeBSD 8.2 host).
> 
> panic: sched_priority: invalid priority 3990: nice 0, ticks 1227873280
> ftick 175669871 ltick 175679894 tick pri 3818
> 
> The crashes happened while I was running a stress test of the network
> stack.  I have a client machine and a server machine.  The client is
> running head with a patch that I'm trying to prove out; the server
> should be running with basically stock head as of r225375(I think that
> there's a couple of minor changes in the tree I used to build the
> server with, but I've gotten the crash on the client and the server,
> and neither have any uncommitted patches in common).  The server is
> running several netcat instances in listen mode; the client has a
> script sitting in a loop starting netcat instances that connect to
> instances running on the server and send data from client -> server.
> The client also has a script that changes the routing tables
> periodically.
> 
> Both the client and the server have crashed once so far.  I haven't
> been running any tests on actual hardware so I can't say whether this
> is a FreeBSD problem or a VirtualBox problem.  I'm going to start
> running the same tests against VMs running some version of FreeBSD 8
> to see if I can reproduce the problem there.  In the meantime, I've
> made a core.txt accessible in case anybody wants to take a look.  You
> can find it at:
> 
> http://people.freebsd.org/~rstone/sched_priority/core.txt.0.bz2
> 
> Please let me know if you need any more information.

This is due to ts->ts_ticks being way too large.  I think it needs a cap to 
handle this case, but I'm not sure exactly which bits need to be capped, and 
what the maximum value they should be capped at is.

-- 
John Baldwin