4.2 hangs with locked root inode

[Joe Kelsey]

Index:	Probably sys/{ufs,sys}_inode.c

Description:
	We occaisionally have systems hang in such a state that no
	useful work seems to be getting done.  When we force a crash,
	the dump reveals several interesting facts:
	1) Almost no runnable processes.  If there are any runnable 
	   processes, it's usually something inoccuous like rwhod.
	2) LOTS of processes stuck in disk wait, with WCHAN pointing
	   to the ROOT INODE!  Also, the root inode has ILOCK|IWANT
	   set, indicating someone locked it and lots of people want
	   it (count is large).
Repeat-By:
	I really don't know how to repeat this.  It seems to occur
	randomly enough that I can't seem to pin down the cause.
	How do you tell which process has set a lock on an inode that
	others want to access?

/Joe Kelsey