The proposal in this patch is to add a system_reset caller that only
resets state related to the cpu. This will guarantee that does functions
are called from the cpu-threads, not the I/O thread.
In principle, it might seem close to the remote execution mechanism, but:
* It does not involve any extra signalling, so it should be faster.
* The cpu is guaranteed to be stopped, so it is much less racy.
* What runs where becomes more explicit.
* This is much, much less racy
The previous implementation was giving me races on reset. This one makes
it work flawlesly w.r.t reset.