Instead of joining on the scheduler threads, instead keep a count of active
schedulers. When there are no more schedulers raise a signal for the main
thread to continue.
This will be required once schedulers can be added and removed from the
running kernel.
At the moment there's not really any reason to be raising this signal,
since they schedulers wake up periodically anyway, but once we remove
the timer this will be how the schedulers know to exit.
When the kernel fails, kill all tasks and wait for the schedulers to stop
instead of just exiting. I'm sure there are tons of lurking issues here but
this is enough to fail without leaking (at least in the absence of cleanups).
This is the new way to refer to tasks in rust-land. Currently all they
do is serve as a key to look up the old rust_task structure. Ideally
they won't be ref counted, but baby steps.
getenv is not threadsafe and (maybe as a result) it's randomly crashing with
CFLAGS=-g and RUST_THREADS=32. Calls from rust code are still on their
own.
Tasks are spawned on a random thread. Currently they stay there, but
we should add task migration and load balancing in the future. This
should drammatically improve our task performance benchmarks.
