Kernel: Make WaitObjects share ownership of Threads waiting on them

During normal operation, a thread waiting on an WaitObject and the
object hold mutual references to each other for the duration of the
wait.

If a process is forcefully terminated (The CTR kernel has a SVC to do
this, TerminateProcess, though no equivalent exists for threads.) its
threads would also be stopped and destroyed, leaving dangling pointers
in the WaitObjects.

The solution is to simply have the Thread remove itself from WaitObjects
when it is stopped. The vector of Threads in WaitObject has also been
changed to hold SharedPtrs, just in case. (Better to have a reference
cycle than a crash.)

src/core/hle/kernel/kernel.cpp

@@ -20,10 +20,10 @@ SharedPtr<Thread> g_main_thread = nullptr;
 HandleTable g_handle_table;
 u64 g_program_id = 0;
 
-void WaitObject::AddWaitingThread(Thread* thread) {
+void WaitObject::AddWaitingThread(SharedPtr<Thread> thread) {
     auto itr = std::find(waiting_threads.begin(), waiting_threads.end(), thread);
     if (itr == waiting_threads.end())
-        waiting_threads.push_back(thread);
+        waiting_threads.push_back(std::move(thread));
 }
 
 void WaitObject::RemoveWaitingThread(Thread* thread) {
@@ -32,11 +32,11 @@ void WaitObject::RemoveWaitingThread(Thread* thread) {
         waiting_threads.erase(itr);
 }
 
-Thread* WaitObject::WakeupNextThread() {
+SharedPtr<Thread> WaitObject::WakeupNextThread() {
     if (waiting_threads.empty())
         return nullptr;
 
-    auto next_thread = waiting_threads.front();
+    auto next_thread = std::move(waiting_threads.front());
     waiting_threads.erase(waiting_threads.begin());
 
     next_thread->ReleaseWaitObject(this);

src/core/hle/kernel/kernel.h

@@ -136,25 +136,26 @@ public:
      * Add a thread to wait on this object
      * @param thread Pointer to thread to add
      */
-    void AddWaitingThread(Thread* thread);
+    void AddWaitingThread(SharedPtr<Thread> thread);
 
     /**
      * Removes a thread from waiting on this object (e.g. if it was resumed already)
      * @param thread Pointer to thread to remove
      */
-    void RemoveWaitingThread(Thread* thead);
+    void RemoveWaitingThread(Thread* thread);
 
     /**
      * Wake up the next thread waiting on this object
      * @return Pointer to the thread that was resumed, nullptr if no threads are waiting
      */
-    Thread* WakeupNextThread();
+    SharedPtr<Thread> WakeupNextThread();
 
     /// Wake up all threads waiting on this object
     void WakeupAllWaitingThreads();
 
 private:
-    std::vector<Thread*> waiting_threads; ///< Threads waiting for this object to become available
+    /// Threads waiting for this object to become available
+    std::vector<SharedPtr<Thread>> waiting_threads;
 };
 
 /**
@@ -275,7 +276,6 @@ private:
 };
 
 extern HandleTable g_handle_table;
-extern SharedPtr<Thread> g_main_thread;
 
 /// The ID code of the currently running game
 /// TODO(Subv): This variable should not be here, 

src/core/hle/kernel/mutex.cpp

@@ -66,7 +66,7 @@ void Mutex::Acquire() {
     Acquire(GetCurrentThread());
 }
 
-void Mutex::Acquire(Thread* thread) {
+void Mutex::Acquire(SharedPtr<Thread> thread) {
     _assert_msg_(Kernel, !ShouldWait(), "object unavailable!");
     if (locked)
         return;
@@ -74,7 +74,7 @@ void Mutex::Acquire(Thread* thread) {
     locked = true;
 
     thread->held_mutexes.insert(this);
-    holding_thread = thread;
+    holding_thread = std::move(thread);
 }
 
 void Mutex::Release() {

src/core/hle/kernel/mutex.h

@@ -43,7 +43,7 @@ public:
     * @param mutex Mutex that is to be acquired
     * @param thread Thread that will acquire the mutex
     */
-    void Acquire(Thread* thread);
+    void Acquire(SharedPtr<Thread> thread);
     void Release();
 
 private:

src/core/hle/kernel/thread.cpp

@@ -110,6 +110,9 @@ void Thread::Stop(const char* reason) {
     WakeupAllWaitingThreads();
 
     // Stopped threads are never waiting.
+    for (auto& wait_object : wait_objects) {
+        wait_object->RemoveWaitingThread(this);
+    }
     wait_objects.clear();
     wait_address = 0;
 }

src/core/hle/kernel/thread.h

@@ -134,6 +134,8 @@ private:
     Handle callback_handle;
 };
 
+extern SharedPtr<Thread> g_main_thread;
+
 /// Sets up the primary application thread
 SharedPtr<Thread> SetupMainThread(s32 priority, u32 stack_size);