I can't reproduce this. What are you using as the action?
I've tried bottoms, and tight loops whose Core contains no allocations, and not
managed to lock up the prompt, or seen ghci using more threads than I have
cores.
One thing that may give the appearance of locking up the prompt is if
the thread starts reading from the terminal and your commands no longer make it
to the interpreter.
That is not correct - it is "par" that creates sparks may be discarded.
> It is not always a thread. ForkIO creates a spark and then the
> scheduler decides when sparks should be scheduled to threads. Thus
> you get a guarantee of concurrent but not parallel execution.
forkIO always creates new threads, though it is of course up to the scheduler
when the threads are executed, and how many cores are used.
That is, was your ghci compiled with -threaded? This mostly
> Are you running with threads enabled?
depends on the version. what version of ghc are you running, and how did you
install it?