//! Spinner half of init's SMP self-test: one thread per hart, each
//! incrementing its own counter in the page given in slot 0.

#![no_std]
#![no_main]
#![forbid(unsafe_code)]

extern crate libkos;

use core::sync::atomic::{AtomicUsize, Ordering};
use libkos::syscall;
use types::address::VirtualAddress;
use types::bounded::CapSlot;
use types::mapping::PagePerms;

/// Counter page layout (words): 0 next free counter index, 1..=THREADS counters.
const COUNTERS_VA: VirtualAddress = VirtualAddress::from_raw(0x0100_0000);
const THREADS: usize = 4;

fn main() {
    let page = CapSlot::const_new(0);
    let Ok(window) = libkos::window::map(page, COUNTERS_VA, PagePerms::ReadWrite) else {
        libkos::println!("smptest: cannot map the counter page");
        syscall::exit();
    };
    let words = window.atomics(types::address::ByteOffset::ZERO, 1 + THREADS);
    for _ in 1..THREADS {
        if !libkos::thread::spawn(words, spin) {
            break;
        }
    }
    spin(words);
}

libkos::entry!(main);

fn spin(word: &'static [AtomicUsize]) -> ! {
    let mine = 1 + word[0].fetch_add(1, Ordering::Relaxed) % THREADS;
    loop {
        // Yield so a spinner sharing init's hart cannot starve it.
        for _ in 0..1024 {
            word[mine].fetch_add(1, Ordering::Relaxed);
        }
        syscall::yield_now();
    }
}