wait_object: Refactor to allow waking up a single thread.

src/core/hle/kernel/wait_object.cpp

@@ -67,8 +67,10 @@ SharedPtr<Thread> WaitObject::GetHighestPriorityReadyThread() {
     return candidate;
 }
 
-void WaitObject::WakeupAllWaitingThreads() {
-    while (auto thread = GetHighestPriorityReadyThread()) {
+void WaitObject::WakeupWaitingThread(SharedPtr<Thread> thread) {
+    if (!thread)
+        return;
+
     if (!thread->IsSleepingOnWaitAll()) {
         Acquire(thread.get());
     } else {
@@ -87,6 +89,11 @@ void WaitObject::WakeupAllWaitingThreads() {
 
     thread->ResumeFromWait();
 }
+
+void WaitObject::WakeupAllWaitingThreads() {
+    while (auto thread = GetHighestPriorityReadyThread()) {
+        WakeupWaitingThread(thread);
+    }
 }
 
 const std::vector<SharedPtr<Thread>>& WaitObject::GetWaitingThreads() const {

src/core/hle/kernel/wait_object.h

@@ -44,6 +44,12 @@ public:
      */
     virtual void WakeupAllWaitingThreads();
 
+    /**
+     * Wakes up a single thread waiting on this object.
+     * @param thread Thread that is waiting on this object to wakeup.
+     */
+    void WakeupWaitingThread(SharedPtr<Thread> thread);
+
     /// Obtains the highest priority thread that is ready to run from this object's waiting list.
     SharedPtr<Thread> GetHighestPriorityReadyThread();