[FEATURE, BUG] Busy Waiting for Worker Threads

[DeveloperPaul123]

Currently, the thread pool will eventually deadlock if a user launches a tasks that recursively creates new tasks on the thread pool wait for a result.

Sample code:

// see
// https://github.com/DevShiftTeam/AppShift-MemoryPool/commit/ea5908cbbd1c9163e9bc700d102e97b53e737fe5
int fib_thread_loop(int n, dp::thread_pool<>& pool) {
    if (n <= 1) return n;
    auto a = pool.enqueue(fib_thread_loop, n - 1, std::ref(pool));
    auto b = pool.enqueue(fib_thread_loop, n - 2, std::ref(pool));
    return a.get() + b.get();
}

TEST_CASE("Recursive fibonacci sequence") {
    dp::thread_pool pool{};
    auto result = fib_thread_loop(4, pool);
    CHECK(result == 3);
}

This is also discussed in #56 .

We could possible get around this with a custom promise and future, or we could potentially use coroutines internally to allow for busy waiting.