Possible solution to lockups on FreeBSD 6?

[Luke Dean]

In my ongoing quest to figure out why my machine keeps locking up since I 
upgraded from 5.4 to 6.0, I came across this interesting passage in man 
(5) pf.conf:

BUGS
   Due to a lock order reversal (LOR) with the socket layer, the use of the
   group and user filter parameter in conjuction with a Giant-free netstack
   can result in a deadlock.  If you have to use group or user you must set
   debug.mpsafenet to ``0'' from the loader(8), for the moment.  This work-
   around will still produce the LOR, but Giant will protect from the dead-
   lock.

In the release notes for FreeBSD 6, I found:

   Fine-grained locking has been applied to many of the data structures in
   the IPX/SPX protocol stack. While not fully MPSAFE at this point, it is
   generally safe to use IPX/SPX without the Giant lock (in other words,
   the debug.mpsafenet sysctl variable may be set to 1).

While I don't fully understand what this passage is talking about, I take 
it to mean that the default value of debug.mpsafenet is now 1, and that 
this is a new feature of FreeBSD version 6.

I use pf.  I use the user filter parameter on some oft-evaluated rules. 
I discovered that my debug.mpsafenet is indeed "1" .  My system is 
deadlocking occasionally under 6 where it never did so under 5.4.

I think I'm going to attempt to set debug.mpsafenet to "0" in my 
loader.conf and see how many days I can go without a lockup this time. 
I've seen several threads lately from people having lockup troubles after 
upgrading to version 6, and at least one of them mentioned pf 
specifically, so I bet some of the rest of you may want to try this too.