131 lines
4 KiB
C++
131 lines
4 KiB
C++
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// Copyright 2021 yuzu Emulator Project
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#include "core/hle/kernel/k_light_lock.h"
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#include "core/hle/kernel/k_scheduler.h"
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#include "core/hle/kernel/k_thread.h"
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#include "core/hle/kernel/kernel.h"
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namespace Kernel {
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void KLightLock::Lock() {
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const uintptr_t cur_thread = reinterpret_cast<uintptr_t>(GetCurrentThreadPointer(kernel));
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const uintptr_t cur_thread_tag = (cur_thread | 1);
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while (true) {
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uintptr_t old_tag = tag.load(std::memory_order_relaxed);
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while (!tag.compare_exchange_weak(old_tag, (old_tag == 0) ? cur_thread : old_tag | 1,
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std::memory_order_acquire)) {
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if ((old_tag | 1) == cur_thread_tag) {
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return;
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}
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}
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if ((old_tag == 0) || ((old_tag | 1) == cur_thread_tag)) {
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break;
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}
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LockSlowPath(old_tag | 1, cur_thread);
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}
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}
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void KLightLock::Unlock() {
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const uintptr_t cur_thread = reinterpret_cast<uintptr_t>(GetCurrentThreadPointer(kernel));
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uintptr_t expected = cur_thread;
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do {
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if (expected != cur_thread) {
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return UnlockSlowPath(cur_thread);
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}
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} while (!tag.compare_exchange_weak(expected, 0, std::memory_order_release));
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}
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void KLightLock::LockSlowPath(uintptr_t _owner, uintptr_t _cur_thread) {
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KThread* cur_thread = reinterpret_cast<KThread*>(_cur_thread);
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// Pend the current thread waiting on the owner thread.
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{
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KScopedSchedulerLock sl{kernel};
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// Ensure we actually have locking to do.
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if (tag.load(std::memory_order_relaxed) != _owner) {
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return;
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}
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// Add the current thread as a waiter on the owner.
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KThread* owner_thread = reinterpret_cast<KThread*>(_owner & ~1ul);
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cur_thread->SetAddressKey(reinterpret_cast<uintptr_t>(std::addressof(tag)));
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owner_thread->AddWaiter(cur_thread);
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// Set thread states.
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if (cur_thread->GetState() == ThreadState::Runnable) {
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cur_thread->SetState(ThreadState::Waiting);
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} else {
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KScheduler::SetSchedulerUpdateNeeded(kernel);
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}
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if (owner_thread->IsSuspended()) {
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owner_thread->ContinueIfHasKernelWaiters();
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KScheduler::SetSchedulerUpdateNeeded(kernel);
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}
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}
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// We're no longer waiting on the lock owner.
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{
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KScopedSchedulerLock sl{kernel};
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KThread* owner_thread = cur_thread->GetLockOwner();
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if (owner_thread) {
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owner_thread->RemoveWaiter(cur_thread);
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}
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}
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}
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void KLightLock::UnlockSlowPath(uintptr_t _cur_thread) {
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KThread* owner_thread = reinterpret_cast<KThread*>(_cur_thread);
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// Unlock.
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{
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KScopedSchedulerLock sl{kernel};
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// Get the next owner.
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s32 num_waiters = 0;
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KThread* next_owner = owner_thread->RemoveWaiterByKey(
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std::addressof(num_waiters), reinterpret_cast<uintptr_t>(std::addressof(tag)));
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// Pass the lock to the next owner.
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uintptr_t next_tag = 0;
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if (next_owner) {
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next_tag = reinterpret_cast<uintptr_t>(next_owner);
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if (num_waiters > 1) {
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next_tag |= 0x1;
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}
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if (next_owner->GetState() == ThreadState::Waiting) {
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next_owner->SetState(ThreadState::Runnable);
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} else {
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KScheduler::SetSchedulerUpdateNeeded(kernel);
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}
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if (next_owner->IsSuspended()) {
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next_owner->ContinueIfHasKernelWaiters();
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}
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}
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// We may have unsuspended in the process of acquiring the lock, so we'll re-suspend now if
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// so.
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if (owner_thread->IsSuspended()) {
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owner_thread->TrySuspend();
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}
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// Write the new tag value.
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tag.store(next_tag);
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}
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}
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bool KLightLock::IsLockedByCurrentThread() const {
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return (tag | 0x1ul) == (reinterpret_cast<uintptr_t>(GetCurrentThreadPointer(kernel)) | 0x1ul);
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}
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} // namespace Kernel
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