From 423acf53b740ce96ca37988aad79ddf5013645ef Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Tue, 9 Nov 2021 20:51:47 -0800
Subject: [PATCH] hle: kernel: KLightLock: Migrate to updated KThreadQueue.

---
 src/core/hle/kernel/k_light_lock.cpp | 69 ++++++++++++++--------------
 src/core/hle/kernel/k_light_lock.h   |  2 +-
 2 files changed, 36 insertions(+), 35 deletions(-)

diff --git a/src/core/hle/kernel/k_light_lock.cpp b/src/core/hle/kernel/k_light_lock.cpp
index 0896e705fa..5e8f1a5102 100644
--- a/src/core/hle/kernel/k_light_lock.cpp
+++ b/src/core/hle/kernel/k_light_lock.cpp
@@ -5,44 +5,54 @@
 #include "core/hle/kernel/k_light_lock.h"
 #include "core/hle/kernel/k_scheduler.h"
 #include "core/hle/kernel/k_thread.h"
+#include "core/hle/kernel/k_thread_queue.h"
 #include "core/hle/kernel/kernel.h"
 
 namespace Kernel {
 
+namespace {
+
+class ThreadQueueImplForKLightLock final : public KThreadQueue {
+public:
+    explicit ThreadQueueImplForKLightLock(KernelCore& kernel_) : KThreadQueue(kernel_) {}
+
+    virtual void CancelWait([[maybe_unused]] KThread* waiting_thread,
+                            [[maybe_unused]] ResultCode wait_result,
+                            [[maybe_unused]] bool cancel_timer_task) override {
+        // Do nothing, waiting to acquire a light lock cannot be canceled.
+    }
+};
+
+} // namespace
+
 void KLightLock::Lock() {
     const uintptr_t cur_thread = reinterpret_cast<uintptr_t>(GetCurrentThreadPointer(kernel));
-    const uintptr_t cur_thread_tag = (cur_thread | 1);
 
     while (true) {
         uintptr_t old_tag = tag.load(std::memory_order_relaxed);
 
-        while (!tag.compare_exchange_weak(old_tag, (old_tag == 0) ? cur_thread : old_tag | 1,
+        while (!tag.compare_exchange_weak(old_tag, (old_tag == 0) ? cur_thread : (old_tag | 1),
                                           std::memory_order_acquire)) {
-            if ((old_tag | 1) == cur_thread_tag) {
-                return;
-            }
         }
 
-        if ((old_tag == 0) || ((old_tag | 1) == cur_thread_tag)) {
+        if (old_tag == 0 || this->LockSlowPath(old_tag | 1, cur_thread)) {
             break;
         }
-
-        LockSlowPath(old_tag | 1, cur_thread);
     }
 }
 
 void KLightLock::Unlock() {
     const uintptr_t cur_thread = reinterpret_cast<uintptr_t>(GetCurrentThreadPointer(kernel));
+
     uintptr_t expected = cur_thread;
-    do {
-        if (expected != cur_thread) {
-            return UnlockSlowPath(cur_thread);
-        }
-    } while (!tag.compare_exchange_weak(expected, 0, std::memory_order_release));
+    if (!tag.compare_exchange_strong(expected, 0, std::memory_order_release)) {
+        this->UnlockSlowPath(cur_thread);
+    }
 }
 
-void KLightLock::LockSlowPath(uintptr_t _owner, uintptr_t _cur_thread) {
+bool KLightLock::LockSlowPath(uintptr_t _owner, uintptr_t _cur_thread) {
     KThread* cur_thread = reinterpret_cast<KThread*>(_cur_thread);
+    ThreadQueueImplForKLightLock wait_queue(kernel);
 
     // Pend the current thread waiting on the owner thread.
     {
@@ -50,30 +60,23 @@ void KLightLock::LockSlowPath(uintptr_t _owner, uintptr_t _cur_thread) {
 
         // Ensure we actually have locking to do.
         if (tag.load(std::memory_order_relaxed) != _owner) {
-            return;
+            return false;
         }
 
         // Add the current thread as a waiter on the owner.
-        KThread* owner_thread = reinterpret_cast<KThread*>(_owner & ~1ULL);
+        KThread* owner_thread = reinterpret_cast<KThread*>(_owner & ~1ul);
         cur_thread->SetAddressKey(reinterpret_cast<uintptr_t>(std::addressof(tag)));
         owner_thread->AddWaiter(cur_thread);
 
-        // Set thread states.
-        cur_thread->SetState(ThreadState::Waiting);
+        // Begin waiting to hold the lock.
+        cur_thread->BeginWait(std::addressof(wait_queue));
 
         if (owner_thread->IsSuspended()) {
             owner_thread->ContinueIfHasKernelWaiters();
         }
     }
 
-    // We're no longer waiting on the lock owner.
-    {
-        KScopedSchedulerLock sl{kernel};
-
-        if (KThread* owner_thread = cur_thread->GetLockOwner(); owner_thread != nullptr) {
-            owner_thread->RemoveWaiter(cur_thread);
-        }
-    }
+    return true;
 }
 
 void KLightLock::UnlockSlowPath(uintptr_t _cur_thread) {
@@ -81,22 +84,20 @@ void KLightLock::UnlockSlowPath(uintptr_t _cur_thread) {
 
     // Unlock.
     {
-        KScopedSchedulerLock sl{kernel};
+        KScopedSchedulerLock sl(kernel);
 
         // Get the next owner.
-        s32 num_waiters = 0;
+        s32 num_waiters;
         KThread* next_owner = owner_thread->RemoveWaiterByKey(
             std::addressof(num_waiters), reinterpret_cast<uintptr_t>(std::addressof(tag)));
 
         // Pass the lock to the next owner.
         uintptr_t next_tag = 0;
         if (next_owner != nullptr) {
-            next_tag = reinterpret_cast<uintptr_t>(next_owner);
-            if (num_waiters > 1) {
-                next_tag |= 0x1;
-            }
+            next_tag =
+                reinterpret_cast<uintptr_t>(next_owner) | static_cast<uintptr_t>(num_waiters > 1);
 
-            next_owner->SetState(ThreadState::Runnable);
+            next_owner->EndWait(ResultSuccess);
 
             if (next_owner->IsSuspended()) {
                 next_owner->ContinueIfHasKernelWaiters();
@@ -110,7 +111,7 @@ void KLightLock::UnlockSlowPath(uintptr_t _cur_thread) {
         }
 
         // Write the new tag value.
-        tag.store(next_tag);
+        tag.store(next_tag, std::memory_order_release);
     }
 }
 
diff --git a/src/core/hle/kernel/k_light_lock.h b/src/core/hle/kernel/k_light_lock.h
index ad853661d4..4163b8a854 100644
--- a/src/core/hle/kernel/k_light_lock.h
+++ b/src/core/hle/kernel/k_light_lock.h
@@ -20,7 +20,7 @@ public:
 
     void Unlock();
 
-    void LockSlowPath(uintptr_t owner, uintptr_t cur_thread);
+    bool LockSlowPath(uintptr_t owner, uintptr_t cur_thread);
 
     void UnlockSlowPath(uintptr_t cur_thread);