This is the same game as with the
generichash construction. We want
to protect it with a mutex so
different processes can safely do
work on the same resource.
While here, also move the _update
function onto the dirty scheduler.
It is by far the most expensive
operation, and why it wasn't there
in the first place is odd. This should
unblock the scheduler on long
sign-checks. It also move the
possible mutex block onto the
dirty scheduler thread, away from
the core schedulers, improving
latency in the system as a result.
While sodium is thread-safe, our
resources are not. Furthermore,
we might have an update call going
when someone decides to call
finalize and so on. It is not clever
to do so, but on the other hand
I want to protect against this.
While here, mark the mutexed
calls as dirty CPU. This avoids them
blocking the main scheduler and
only messes with the background
dirty threads, which is somewhat
more safe.
The consequence is that order
access to the resource is now
serialized. I don't think you should
do it, but it is now possible.
