yuzu/src/core/hle/kernel/mutex.h

// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#pragma once

#include <string>
#include "common/common_types.h"
#include "common/swap.h"
#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/wait_object.h"
#include "core/hle/result.h"

namespace Kernel {

class Thread;

class Mutex final : public WaitObject {
public:
    /**
     * Creates a mutex.
     * @param holding_thread Specifies a thread already holding the mutex. If not nullptr, this
     * thread will acquire the mutex.
     * @param guest_addr Address of the object tracking the mutex in guest memory. If specified,
     * this mutex will update the guest object when its state changes.
     * @param name Optional name of mutex
     * @return Pointer to new Mutex object
     */
    static SharedPtr<Mutex> Create(SharedPtr<Kernel::Thread> holding_thread, VAddr guest_addr = 0,
                                   std::string name = "Unknown");

    std::string GetTypeName() const override {
        return "Mutex";
    }
    std::string GetName() const override {
        return name;
    }

    static const HandleType HANDLE_TYPE = HandleType::Mutex;
    HandleType GetHandleType() const override {
        return HANDLE_TYPE;
    }

    int lock_count;                   ///< Number of times the mutex has been acquired
    u32 priority;                     ///< The priority of the mutex, used for priority inheritance.
    std::string name;                 ///< Name of mutex (optional)
    SharedPtr<Thread> holding_thread; ///< Thread that has acquired the mutex
    VAddr guest_addr;                 ///< Address of the guest mutex value

    /**
     * Elevate the mutex priority to the best priority
     * among the priorities of all its waiting threads.
     */
    void UpdatePriority();

    bool ShouldWait(Thread* thread) const override;
    void Acquire(Thread* thread) override;

    void AddWaitingThread(SharedPtr<Thread> thread) override;
    void RemoveWaitingThread(Thread* thread) override;

    /**
     * Attempts to release the mutex from the specified thread.
     * @param thread Thread that wants to release the mutex.
     * @returns The result code of the operation.
     */
    ResultCode Release(Thread* thread);

private:
    Mutex();
    ~Mutex() override;

    /// Object in guest memory used to track the mutex state
    union GuestState {
        u32_le raw;
        /// Handle of the thread that currently holds the mutex, 0 if available
        BitField<0, 30, u32_le> holding_thread_handle;
        /// 1 when there are threads waiting for this mutex, otherwise 0
        BitField<30, 1, u32_le> has_waiters;
    };
    static_assert(sizeof(GuestState) == 4, "GuestState size is incorrect");

    /// Updates the state of the object tracking this mutex in guest memory
    void UpdateGuestState();

    /// Verifies the state of the object tracking this mutex in guest memory
    void VerifyGuestState();
};

/**
 * Releases all the mutexes held by the specified thread
 * @param thread Thread that is holding the mutexes
 */
void ReleaseThreadMutexes(Thread* thread);

} // namespace Kernel