citra/src/core/hle/kernel/mutex.cpp

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

#include <map>
#include <vector>

#include "common/common.h"

#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/mutex.h"
#include "core/hle/kernel/thread.h"

namespace Kernel {

typedef std::multimap<SharedPtr<Thread>, SharedPtr<Mutex>> MutexMap;
static MutexMap g_mutex_held_locks;

/**
 * Resumes a thread waiting for the specified mutex
 * @param mutex The mutex that some thread is waiting on
 */
static void ResumeWaitingThread(Mutex* mutex) {
    // Reset mutex lock thread handle, nothing is waiting
    mutex->locked = false;
    mutex->holding_thread = nullptr;

    // Find the next waiting thread for the mutex...
    auto next_thread = mutex->WakeupNextThread();
    if (next_thread != nullptr) {
        mutex->Acquire(next_thread);
    }
}

void ReleaseThreadMutexes(Thread* thread) {
    auto locked_range = g_mutex_held_locks.equal_range(thread);
    
    // Release every mutex that the thread holds, and resume execution on the waiting threads
    for (auto iter = locked_range.first; iter != locked_range.second; ++iter) {
        ResumeWaitingThread(iter->second.get());
    }

    // Erase all the locks that this thread holds
    g_mutex_held_locks.erase(thread);
}

ResultVal<SharedPtr<Mutex>> Mutex::Create(bool initial_locked, std::string name) {
    SharedPtr<Mutex> mutex(new Mutex);
    // TOOD(yuriks): Don't create Handle (see Thread::Create())
    CASCADE_RESULT(auto unused, Kernel::g_handle_table.Create(mutex));

    mutex->initial_locked = initial_locked;
    mutex->locked = false;
    mutex->name = std::move(name);
    mutex->holding_thread = nullptr;

    // Acquire mutex with current thread if initialized as locked...
    if (initial_locked)
        mutex->Acquire();

    return MakeResult<SharedPtr<Mutex>>(mutex);
}

bool Mutex::ShouldWait() {
    return locked && holding_thread != GetCurrentThread();
}

void Mutex::Acquire() {
    Acquire(GetCurrentThread());
}

void Mutex::Acquire(Thread* thread) {
    _assert_msg_(Kernel, !ShouldWait(), "object unavailable!");
    if (locked)
        return;

    locked = true;

    g_mutex_held_locks.insert(std::make_pair(thread, this));
    holding_thread = thread;
}

void Mutex::Release() {
    if (!locked)
        return;

    auto locked_range = g_mutex_held_locks.equal_range(holding_thread);

    for (MutexMap::iterator iter = locked_range.first; iter != locked_range.second; ++iter) {
        if (iter->second == this) {
            g_mutex_held_locks.erase(iter);
            break;
        }
    }

    ResumeWaitingThread(this);
}

} // namespace