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// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <map>
#include <vector>
#include <boost/range/algorithm_ext/erase.hpp>
#include "common/assert.h"
#include "core/core.h"
#include "core/hle/kernel/errors.h"
#include "core/hle/kernel/handle_table.h"
#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/mutex.h"
#include "core/hle/kernel/object_address_table.h"
#include "core/hle/kernel/thread.h"
namespace Kernel {
/// Returns the number of threads that are waiting for a mutex, and the highest priority one among
/// those.
static std::pair<SharedPtr<Thread>, u32> GetHighestPriorityMutexWaitingThread(VAddr mutex_addr) {
auto& thread_list = Core::System::GetInstance().Scheduler().GetThreadList();
SharedPtr<Thread> highest_priority_thread;
u32 num_waiters = 0;
for (auto& thread : thread_list) {
if (thread->mutex_wait_address != mutex_addr)
continue;
ASSERT(thread->status == THREADSTATUS_WAIT_MUTEX);
++num_waiters;
if (highest_priority_thread == nullptr ||
thread->GetPriority() < highest_priority_thread->GetPriority()) {
highest_priority_thread = thread;
}
}
return {highest_priority_thread, num_waiters};
}
ResultCode Mutex::TryAcquire(VAddr address, Handle holding_thread_handle,
Handle requesting_thread_handle) {
// The mutex address must be 4-byte aligned
if ((address % sizeof(u32)) != 0) {
return ResultCode(ErrorModule::Kernel, ErrCodes::MisalignedAddress);
}
SharedPtr<Thread> holding_thread = g_handle_table.Get<Thread>(holding_thread_handle);
SharedPtr<Thread> requesting_thread = g_handle_table.Get<Thread>(requesting_thread_handle);
// TODO(Subv): It is currently unknown if it is possible to lock a mutex in behalf of another
// thread.
ASSERT(requesting_thread == GetCurrentThread());
u32 addr_value = Memory::Read32(address);
// If the mutex isn't being held, just return success.
if (addr_value != (holding_thread_handle | Mutex::MutexHasWaitersFlag)) {
return RESULT_SUCCESS;
}
if (holding_thread == nullptr)
return ERR_INVALID_HANDLE;
// Wait until the mutex is released
requesting_thread->mutex_wait_address = address;
requesting_thread->wait_handle = requesting_thread_handle;
requesting_thread->status = THREADSTATUS_WAIT_MUTEX;
requesting_thread->wakeup_callback = nullptr;
Core::System::GetInstance().PrepareReschedule();
return RESULT_SUCCESS;
}
ResultCode Mutex::Release(VAddr address) {
// The mutex address must be 4-byte aligned
if ((address % sizeof(u32)) != 0) {
return ResultCode(ErrorModule::Kernel, ErrCodes::MisalignedAddress);
}
auto [thread, num_waiters] = GetHighestPriorityMutexWaitingThread(address);
// There are no more threads waiting for the mutex, release it completely.
if (thread == nullptr) {
Memory::Write32(address, 0);
return RESULT_SUCCESS;
}
u32 mutex_value = thread->wait_handle;
if (num_waiters >= 2) {
// Notify the guest that there are still some threads waiting for the mutex
mutex_value |= Mutex::MutexHasWaitersFlag;
}
// Grant the mutex to the next waiting thread and resume it.
Memory::Write32(address, mutex_value);
ASSERT(thread->status == THREADSTATUS_WAIT_MUTEX);
thread->ResumeFromWait();
thread->condvar_wait_address = 0;
thread->mutex_wait_address = 0;
thread->wait_handle = 0;
return RESULT_SUCCESS;
}
} // namespace Kernel
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