userland and a dedicated system call to get replies.
The vnode-bypass of fifos broke this into a panic.
Ditch all the magic and create a device /dev/nfslock instead, and
use that for both directions apart from the shorter path, this is
also faster because the device driver runs Giant free using the
vnode bypass.
Noticed by: marcel
reference: with td->td_ucred, it will be desirable to authorize
based on td->td_ucred, rather than p->p_ucred.
o Since the same variable 'p' was later used with pfind() on the target
process for the wakeup, introduce a new local variable 'targetp'
to use instead.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
