kernel: fix single-core preemption points

src/core/cpu_manager.cpp

@@ -144,11 +144,8 @@ void CpuManager::SingleCoreRunIdleThread() {
 }
 
 void CpuManager::PreemptSingleCore(bool from_running_environment) {
-    {
     auto& kernel = system.Kernel();
-        auto& scheduler = kernel.Scheduler(current_core);
 
-        Kernel::KThread* current_thread = scheduler.GetSchedulerCurrentThread();
     if (idle_count >= 4 || from_running_environment) {
         if (!from_running_environment) {
             system.CoreTiming().Idle();
@@ -160,24 +157,13 @@ void CpuManager::PreemptSingleCore(bool from_running_environment) {
     }
     current_core.store((current_core + 1) % Core::Hardware::NUM_CPU_CORES);
     system.CoreTiming().ResetTicks();
-        scheduler.Unload(scheduler.GetSchedulerCurrentThread());
-
-        auto& next_scheduler = kernel.Scheduler(current_core);
-
-        // Disable dispatch. We're about to preempt this thread.
-        Kernel::KScopedDisableDispatch dd{kernel};
-        Common::Fiber::YieldTo(current_thread->GetHostContext(), *next_scheduler.GetSwitchFiber());
-    }
+    kernel.Scheduler(current_core).PreemptSingleCore();
 
     // We've now been scheduled again, and we may have exchanged schedulers.
     // Reload the scheduler in case it's different.
-    {
-        auto& scheduler = system.Kernel().Scheduler(current_core);
-        scheduler.Reload(scheduler.GetSchedulerCurrentThread());
-        if (!scheduler.IsIdle()) {
+    if (!kernel.Scheduler(current_core).IsIdle()) {
         idle_count = 0;
     }
-    }
 }
 
 void CpuManager::GuestActivate() {

src/core/cpu_manager.h

@@ -5,7 +5,6 @@
 
 #include <array>
 #include <atomic>
-#include <csetjmp>
 #include <functional>
 #include <memory>
 #include <thread>

src/core/hle/kernel/k_scheduler.cpp

@@ -103,7 +103,20 @@ void KScheduler::ScheduleOnInterrupt() {
     GetCurrentThread(kernel).EnableDispatch();
 }
 
+void KScheduler::PreemptSingleCore() {
+    GetCurrentThread(kernel).DisableDispatch();
+
+    auto* thread = GetCurrentThreadPointer(kernel);
+    auto& previous_scheduler = kernel.Scheduler(thread->GetCurrentCore());
+    previous_scheduler.Unload(thread);
+
+    Common::Fiber::YieldTo(thread->GetHostContext(), *m_switch_fiber);
+
+    GetCurrentThread(kernel).EnableDispatch();
+}
+
 void KScheduler::RescheduleCurrentCore() {
+    ASSERT(!kernel.IsPhantomModeForSingleCore());
     ASSERT(GetCurrentThread(kernel).GetDisableDispatchCount() == 1);
 
     GetCurrentThread(kernel).EnableDispatch();

src/core/hle/kernel/k_scheduler.h

@@ -49,6 +49,7 @@ public:
 
     void SetInterruptTaskRunnable();
     void RequestScheduleOnInterrupt();
+    void PreemptSingleCore();
 
     u64 GetIdleCount() {
         return m_state.idle_count;
@@ -62,10 +63,6 @@ public:
         return m_current_thread.load() == m_idle_thread;
     }
 
-    std::shared_ptr<Common::Fiber> GetSwitchFiber() {
-        return m_switch_fiber;
-    }
-
     KThread* GetPreviousThread() const {
         return m_state.prev_thread;
     }

src/core/hle/kernel/k_thread.cpp

@@ -1204,12 +1204,6 @@ KScopedDisableDispatch::~KScopedDisableDispatch() {
         return;
     }
 
-    // Skip the reschedule if single-core.
-    if (!Settings::values.use_multi_core.GetValue()) {
-        GetCurrentThread(kernel).EnableDispatch();
-        return;
-    }
-
     if (GetCurrentThread(kernel).GetDisableDispatchCount() <= 1) {
         auto scheduler = kernel.CurrentScheduler();
 

src/core/hle/kernel/k_thread.h

@@ -110,7 +110,6 @@ void SetCurrentThread(KernelCore& kernel, KThread* thread);
 [[nodiscard]] KThread* GetCurrentThreadPointer(KernelCore& kernel);
 [[nodiscard]] KThread& GetCurrentThread(KernelCore& kernel);
 [[nodiscard]] s32 GetCurrentCoreId(KernelCore& kernel);
-size_t CaptureBacktrace(void** buffer, size_t max);
 
 class KThread final : public KAutoObjectWithSlabHeapAndContainer<KThread, KWorkerTask>,
                       public boost::intrusive::list_base_hook<> {