More syscall messaging commits, and some testing code as well.

[Eric J. Chet]

On Tue, 12 Aug 2003, Matthew Dillon wrote:

>     Hysteresis would definitely be desireable.  The userland scheduler cannot
>     just stop, though, because that could deadlock the program.   It would
>     have to revert to polling until the concurrent syscall count drops below
>     the hysteresis point.

Once the userland scheduler polls and can't execute the current thread
wouldn't it schedule another thread?  If there arn't any other threads to
schedule, I guess it would continue to poll.

Eric