Suspend some host threads that make guest callbacks.

src/xenia/kernel/kernel_state.cc

@@ -263,6 +263,8 @@ void KernelState::SetExecutableModule(object_ref<UserModule> module) {
           }
           return 0;
         }));
+    // As we run guest callbacks the debugger must be able to suspend us.
+    dispatch_thread_->set_can_debugger_suspend(true);
     dispatch_thread_->set_name("Kernel Dispatch Thread");
     dispatch_thread_->Create();
   }

src/xenia/kernel/xthread.cc

@@ -702,7 +702,11 @@ X_STATUS XThread::Delay(uint32_t processor_mode, uint32_t alertable,
 XHostThread::XHostThread(KernelState* kernel_state, uint32_t stack_size,
                          uint32_t creation_flags, std::function<int()> host_fn)
     : XThread(kernel_state, stack_size, 0, 0, 0, creation_flags, false),
-      host_fn_(host_fn) {}
+      host_fn_(host_fn) {
+  // By default host threads are not debugger suspendable. If the thread runs
+  // any guest code this must be overridden.
+  can_debugger_suspend_ = false;
+}
 
 void XHostThread::Execute() {
   XELOGKERNEL(

src/xenia/kernel/xthread.h

@@ -125,7 +125,13 @@ class XThread : public XObject {
   const CreationParams* creation_params() const { return &creation_params_; }
   uint32_t tls_ptr() const { return tls_address_; }
   uint32_t pcr_ptr() const { return pcr_address_; }
+  // True if the thread is created by the guest app.
   bool is_guest_thread() const { return guest_thread_; }
+  // True if the thread should be paused by the debugger.
+  // All threads that can run guest code must be stopped for the debugger to
+  // work properly.
+  bool can_debugger_suspend() const { return can_debugger_suspend_; }
+  void set_can_debugger_suspend(bool value) { can_debugger_suspend_ = value; }
   bool is_running() const { return running_; }
 
   cpu::ThreadState* thread_state() const { return thread_state_; }
@@ -182,7 +188,8 @@ class XThread : public XObject {
   uint32_t tls_address_ = 0;
   uint32_t pcr_address_ = 0;
   cpu::ThreadState* thread_state_ = nullptr;
-  bool guest_thread_ = false;  // Launched into guest code?
+  bool guest_thread_ = false;
+  bool can_debugger_suspend_ = true;
   bool running_ = false;
 
   std::string name_;