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

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// Copyright 2014 Citra Emulator Project
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// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
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#include <map>
#include <vector>
#include <boost/range/algorithm_ext/erase.hpp>
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#include "common/assert.h"
#include "core/core.h"
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#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/mutex.h"
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#include "core/hle/kernel/thread.h"
namespace Kernel {
/**
* Boost's a thread's priority to the best priority among the thread's held mutexes.
* This prevents priority inversion via priority inheritance.
*/
static void UpdateThreadPriority(Thread* thread) {
s32 best_priority = THREADPRIO_LOWEST;
for (auto& mutex : thread->held_mutexes) {
if (mutex->priority < best_priority)
best_priority = mutex->priority;
}
best_priority = std::min(best_priority, thread->nominal_priority);
thread->SetPriority(best_priority);
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}
void ReleaseThreadMutexes(Thread* thread) {
for (auto& mtx : thread->held_mutexes) {
mtx->lock_count = 0;
mtx->holding_thread = nullptr;
mtx->WakeupAllWaitingThreads();
}
thread->held_mutexes.clear();
}
Mutex::Mutex() {}
Mutex::~Mutex() {}
SharedPtr<Mutex> Mutex::Create(bool initial_locked, std::string name) {
SharedPtr<Mutex> mutex(new Mutex);
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mutex->lock_count = 0;
mutex->name = std::move(name);
mutex->holding_thread = nullptr;
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// Acquire mutex with current thread if initialized as locked
if (initial_locked)
mutex->Acquire(GetCurrentThread());
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return mutex;
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}
bool Mutex::ShouldWait(Thread* thread) const {
return lock_count > 0 && thread != holding_thread;
}
void Mutex::Acquire(Thread* thread) {
ASSERT_MSG(!ShouldWait(thread), "object unavailable!");
// Actually "acquire" the mutex only if we don't already have it
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if (lock_count == 0) {
priority = thread->current_priority;
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thread->held_mutexes.insert(this);
holding_thread = thread;
UpdateThreadPriority(thread);
Core::System::GetInstance().PrepareReschedule();
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}
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lock_count++;
}
void Mutex::Release() {
// Only release if the mutex is held
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if (lock_count > 0) {
lock_count--;
// Yield to the next thread only if we've fully released the mutex
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if (lock_count == 0) {
holding_thread->held_mutexes.erase(this);
UpdateThreadPriority(holding_thread.get());
holding_thread = nullptr;
WakeupAllWaitingThreads();
Core::System::GetInstance().PrepareReschedule();
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}
}
}
void Mutex::AddWaitingThread(SharedPtr<Thread> thread) {
WaitObject::AddWaitingThread(thread);
// Elevate the mutex priority to the best priority
// among the priorities of all its waiting threads.
s32 best_priority = THREADPRIO_LOWEST;
for (auto& waiter : GetWaitingThreads()) {
if (waiter->current_priority < best_priority)
best_priority = waiter->current_priority;
}
if (best_priority != priority) {
priority = best_priority;
UpdateThreadPriority(holding_thread.get());
}
}
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} // namespace