On Wed, Jan 30, 2008 at 02:41:34PM +0300, Denis V. Lunev wrote:
> The pid of the locking daemon can be substituted with a task struct
> without a problem. Namely, the value if filled in the context of the lockd
> thread and used in lockd_up/lockd_down.
> 
> It is possible to save task struct instead and use it to kill the process.
> The safety of this operation is guaranteed by the RCU, i.e. task can't
> disappear without passing a quiscent state.

We have a patch series pending on the nfs list that does this plus a lot
more in the area.