On an up-to-date -current system with up-to-date pkgsrc, I can't build 
lsof.  It complains:

In file included from ../dlsof.h:73,
                 from ../lsof.h:190,
                 from dvch.c:43:
/usr/include/sys/buf.h:83:27: sys/workqueue.h: No such file or directory
In file included from ../dlsof.h:73,
                 from ../lsof.h:190,
                 from dvch.c:43:
/usr/include/sys/buf.h:122: error: field `u_work' has incomplete type

I suspect this is due to some changes in buf.h 1.83, but I'm less clear 
on what to do about it, given that this is a pkgsrc problem.

		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb