Luna/kernel/src/lib/KMutex.h

#pragma once
#include "Log.h"
#include "arch/CPU.h"
#include "thread/Scheduler.h"
#include "thread/Thread.h"
#include <luna/CircularQueue.h>

template <usize ConcurrentThreads> class KMutex
{
  public:
    void lock()
    {
        int expected = 0;
        while (!m_lock.compare_exchange_strong(expected, 1))
        {
            expected = 0;
            auto* current = Scheduler::current();

            // We cannot be interrupted between these functions, otherwise we might never exit the loop
            CPU::disable_interrupts();
            bool ok = m_blocked_threads.try_push(current);
            if (!ok) kernel_sleep(10);
            else
                kernel_wait_for_event();
            CPU::enable_interrupts();
        }
    };

    void unlock()
    {
        int expected = 1;
        if (!m_lock.compare_exchange_strong(expected, 0))
        {
            kwarnln("KMutex::unlock() called on an unlocked lock with value %d", expected);
        }

        Thread* blocked;
        if (m_blocked_threads.try_pop(blocked)) blocked->wake_up();
    }

    bool try_lock()
    {
        int expected = 0;
        return m_lock.compare_exchange_strong(expected, 1);
    }

  private:
    CircularQueue<Thread*, ConcurrentThreads> m_blocked_threads;
    Atomic<int> m_lock;
};

template <usize ConcurrentThreads> class ScopedKMutexLock
{
  public:
    ScopedKMutexLock(KMutex<ConcurrentThreads>& lock) : m_lock(lock)
    {
        m_lock.lock();
    }

    ~ScopedKMutexLock()
    {
        if (!m_taken_over) m_lock.unlock();
    }

    ScopedKMutexLock(const ScopedKMutexLock&) = delete;
    ScopedKMutexLock(ScopedKMutexLock&&) = delete;

    KMutex<ConcurrentThreads>& take_over()
    {
        m_taken_over = true;
        return m_lock;
    }

  private:
    KMutex<ConcurrentThreads>& m_lock;
    bool m_taken_over { false };
};