Merge pull request #2971 from FernandoS27/new-scheduler-v2

Kernel: Implement a New Thread Scheduler V2

src/common/multi_level_queue.h

@@ -304,6 +304,13 @@ public:
         return levels[priority == Depth ? 63 : priority].back();
     }
 
+    void clear() {
+        used_priorities = 0;
+        for (std::size_t i = 0; i < Depth; i++) {
+            levels[i].clear();
+        }
+    }
+
 private:
     using const_list_iterator = typename std::list<T>::const_iterator;
 

src/core/core.cpp

@@ -409,6 +409,12 @@ void System::PrepareReschedule() {
     CurrentCpuCore().PrepareReschedule();
 }
 
+void System::PrepareReschedule(const u32 core_index) {
+    if (core_index < GlobalScheduler().CpuCoresCount()) {
+        CpuCore(core_index).PrepareReschedule();
+    }
+}
+
 PerfStatsResults System::GetAndResetPerfStats() {
     return impl->GetAndResetPerfStats();
 }
@@ -449,6 +455,16 @@ const Kernel::Scheduler& System::Scheduler(std::size_t core_index) const {
     return CpuCore(core_index).Scheduler();
 }
 
+/// Gets the global scheduler
+Kernel::GlobalScheduler& System::GlobalScheduler() {
+    return impl->kernel.GlobalScheduler();
+}
+
+/// Gets the global scheduler
+const Kernel::GlobalScheduler& System::GlobalScheduler() const {
+    return impl->kernel.GlobalScheduler();
+}
+
 Kernel::Process* System::CurrentProcess() {
     return impl->kernel.CurrentProcess();
 }

src/core/core.h

@@ -24,6 +24,7 @@ class VfsFilesystem;
 } // namespace FileSys
 
 namespace Kernel {
+class GlobalScheduler;
 class KernelCore;
 class Process;
 class Scheduler;
@@ -184,6 +185,9 @@ public:
     /// Prepare the core emulation for a reschedule
     void PrepareReschedule();
 
+    /// Prepare the core emulation for a reschedule
+    void PrepareReschedule(u32 core_index);
+
     /// Gets and resets core performance statistics
     PerfStatsResults GetAndResetPerfStats();
 
@@ -238,6 +242,12 @@ public:
     /// Gets the scheduler for the CPU core with the specified index
     const Kernel::Scheduler& Scheduler(std::size_t core_index) const;
 
+    /// Gets the global scheduler
+    Kernel::GlobalScheduler& GlobalScheduler();
+
+    /// Gets the global scheduler
+    const Kernel::GlobalScheduler& GlobalScheduler() const;
+
     /// Provides a pointer to the current process
     Kernel::Process* CurrentProcess();
 

src/core/core_cpu.cpp

@@ -52,7 +52,8 @@ bool CpuBarrier::Rendezvous() {
 
 Cpu::Cpu(System& system, ExclusiveMonitor& exclusive_monitor, CpuBarrier& cpu_barrier,
          std::size_t core_index)
-    : cpu_barrier{cpu_barrier}, core_timing{system.CoreTiming()}, core_index{core_index} {
+    : cpu_barrier{cpu_barrier}, global_scheduler{system.GlobalScheduler()},
+      core_timing{system.CoreTiming()}, core_index{core_index} {
 #ifdef ARCHITECTURE_x86_64
     arm_interface = std::make_unique<ARM_Dynarmic>(system, exclusive_monitor, core_index);
 #else
@@ -60,7 +61,7 @@ Cpu::Cpu(System& system, ExclusiveMonitor& exclusive_monitor, CpuBarrier& cpu_ba
     LOG_WARNING(Core, "CPU JIT requested, but Dynarmic not available");
 #endif
 
-    scheduler = std::make_unique<Kernel::Scheduler>(system, *arm_interface);
+    scheduler = std::make_unique<Kernel::Scheduler>(system, *arm_interface, core_index);
 }
 
 Cpu::~Cpu() = default;
@@ -81,21 +82,21 @@ void Cpu::RunLoop(bool tight_loop) {
         return;
     }
 
+    Reschedule();
+
     // If we don't have a currently active thread then don't execute instructions,
     // instead advance to the next event and try to yield to the next thread
     if (Kernel::GetCurrentThread() == nullptr) {
         LOG_TRACE(Core, "Core-{} idling", core_index);
         core_timing.Idle();
-        core_timing.Advance();
-        PrepareReschedule();
     } else {
         if (tight_loop) {
             arm_interface->Run();
         } else {
             arm_interface->Step();
         }
-        core_timing.Advance();
     }
+    core_timing.Advance();
 
     Reschedule();
 }
@@ -106,18 +107,18 @@ void Cpu::SingleStep() {
 
 void Cpu::PrepareReschedule() {
     arm_interface->PrepareReschedule();
-    reschedule_pending = true;
 }
 
 void Cpu::Reschedule() {
-    if (!reschedule_pending) {
+    // Lock the global kernel mutex when we manipulate the HLE state
-        return;
+    std::lock_guard lock(HLE::g_hle_lock);
+
+    global_scheduler.SelectThread(core_index);
+    scheduler->TryDoContextSwitch();
 }
 
-    reschedule_pending = false;
+void Cpu::Shutdown() {
-    // Lock the global kernel mutex when we manipulate the HLE state
+    scheduler->Shutdown();
-    std::lock_guard lock{HLE::g_hle_lock};
-    scheduler->Reschedule();
 }
 
 } // namespace Core

src/core/core_cpu.h

@@ -12,8 +12,9 @@
 #include "common/common_types.h"
 
 namespace Kernel {
+class GlobalScheduler;
 class Scheduler;
-}
+} // namespace Kernel
 
 namespace Core {
 class System;
@@ -83,6 +84,8 @@ public:
         return core_index;
     }
 
+    void Shutdown();
+
     static std::unique_ptr<ExclusiveMonitor> MakeExclusiveMonitor(std::size_t num_cores);
 
 private:
@@ -90,6 +93,7 @@ private:
 
     std::unique_ptr<ARM_Interface> arm_interface;
     CpuBarrier& cpu_barrier;
+    Kernel::GlobalScheduler& global_scheduler;
     std::unique_ptr<Kernel::Scheduler> scheduler;
     Timing::CoreTiming& core_timing;
 

src/core/cpu_core_manager.cpp

@@ -58,6 +58,7 @@ void CpuCoreManager::Shutdown() {
 
     thread_to_cpu.clear();
     for (auto& cpu_core : cores) {
+        cpu_core->Shutdown();
         cpu_core.reset();
     }
 

src/core/gdbstub/gdbstub.cpp

@@ -202,15 +202,13 @@ void RegisterModule(std::string name, VAddr beg, VAddr end, bool add_elf_ext) {
 }
 
 static Kernel::Thread* FindThreadById(s64 id) {
-    for (u32 core = 0; core < Core::NUM_CPU_CORES; core++) {
+    const auto& threads = Core::System::GetInstance().GlobalScheduler().GetThreadList();
-        const auto& threads = Core::System::GetInstance().Scheduler(core).GetThreadList();
     for (auto& thread : threads) {
         if (thread->GetThreadID() == static_cast<u64>(id)) {
-                current_core = core;
+            current_core = thread->GetProcessorID();
             return thread.get();
         }
     }
-    }
     return nullptr;
 }
 
@@ -647,12 +645,10 @@ static void HandleQuery() {
         SendReply(buffer.c_str());
     } else if (strncmp(query, "fThreadInfo", strlen("fThreadInfo")) == 0) {
         std::string val = "m";
-        for (u32 core = 0; core < Core::NUM_CPU_CORES; core++) {
+        const auto& threads = Core::System::GetInstance().GlobalScheduler().GetThreadList();
-            const auto& threads = Core::System::GetInstance().Scheduler(core).GetThreadList();
         for (const auto& thread : threads) {
             val += fmt::format("{:x},", thread->GetThreadID());
         }
-        }
         val.pop_back();
         SendReply(val.c_str());
     } else if (strncmp(query, "sThreadInfo", strlen("sThreadInfo")) == 0) {
@@ -661,13 +657,11 @@ static void HandleQuery() {
         std::string buffer;
         buffer += "l<?xml version=\"1.0\"?>";
         buffer += "<threads>";
-        for (u32 core = 0; core < Core::NUM_CPU_CORES; core++) {
+        const auto& threads = Core::System::GetInstance().GlobalScheduler().GetThreadList();
-            const auto& threads = Core::System::GetInstance().Scheduler(core).GetThreadList();
         for (const auto& thread : threads) {
             buffer +=
                 fmt::format(R"*(<thread id="{:x}" core="{:d}" name="Thread {:x}"></thread>)*",
-                                thread->GetThreadID(), core, thread->GetThreadID());
+                            thread->GetThreadID(), thread->GetProcessorID(), thread->GetThreadID());
-            }
         }
         buffer += "</threads>";
         SendReply(buffer.c_str());

src/core/hle/kernel/address_arbiter.cpp

@@ -22,6 +22,7 @@ namespace Kernel {
 namespace {
 // Wake up num_to_wake (or all) threads in a vector.
 void WakeThreads(const std::vector<SharedPtr<Thread>>& waiting_threads, s32 num_to_wake) {
+    auto& system = Core::System::GetInstance();
     // Only process up to 'target' threads, unless 'target' is <= 0, in which case process
     // them all.
     std::size_t last = waiting_threads.size();
@@ -35,6 +36,7 @@ void WakeThreads(const std::vector<SharedPtr<Thread>>& waiting_threads, s32 num_
         waiting_threads[i]->SetWaitSynchronizationResult(RESULT_SUCCESS);
         waiting_threads[i]->SetArbiterWaitAddress(0);
         waiting_threads[i]->ResumeFromWait();
+        system.PrepareReschedule(waiting_threads[i]->GetProcessorID());
     }
 }
 } // Anonymous namespace
@@ -89,13 +91,21 @@ ResultCode AddressArbiter::ModifyByWaitingCountAndSignalToAddressIfEqual(VAddr a
 
     // Determine the modified value depending on the waiting count.
     s32 updated_value;
+    if (num_to_wake <= 0) {
         if (waiting_threads.empty()) {
             updated_value = value + 1;
-    } else if (num_to_wake <= 0 || waiting_threads.size() <= static_cast<u32>(num_to_wake)) {
+        } else {
+            updated_value = value - 1;
+        }
+    } else {
+        if (waiting_threads.empty()) {
+            updated_value = value + 1;
+        } else if (waiting_threads.size() <= static_cast<u32>(num_to_wake)) {
             updated_value = value - 1;
         } else {
             updated_value = value;
         }
+    }
 
     if (static_cast<s32>(Memory::Read32(address)) != value) {
         return ERR_INVALID_STATE;
@@ -169,30 +179,22 @@ ResultCode AddressArbiter::WaitForAddressImpl(VAddr address, s64 timeout) {
 
     current_thread->WakeAfterDelay(timeout);
 
-    system.CpuCore(current_thread->GetProcessorID()).PrepareReschedule();
+    system.PrepareReschedule(current_thread->GetProcessorID());
     return RESULT_TIMEOUT;
 }
 
 std::vector<SharedPtr<Thread>> AddressArbiter::GetThreadsWaitingOnAddress(VAddr address) const {
-    const auto RetrieveWaitingThreads = [this](std::size_t core_index,
-                                               std::vector<SharedPtr<Thread>>& waiting_threads,
-                                               VAddr arb_addr) {
-        const auto& scheduler = system.Scheduler(core_index);
-        const auto& thread_list = scheduler.GetThreadList();
-
-        for (const auto& thread : thread_list) {
-            if (thread->GetArbiterWaitAddress() == arb_addr) {
-                waiting_threads.push_back(thread);
-            }
-        }
-    };
 
     // Retrieve all threads that are waiting for this address.
     std::vector<SharedPtr<Thread>> threads;
-    RetrieveWaitingThreads(0, threads, address);
+    const auto& scheduler = system.GlobalScheduler();
-    RetrieveWaitingThreads(1, threads, address);
+    const auto& thread_list = scheduler.GetThreadList();
-    RetrieveWaitingThreads(2, threads, address);
+
-    RetrieveWaitingThreads(3, threads, address);
+    for (const auto& thread : thread_list) {
+        if (thread->GetArbiterWaitAddress() == address) {
+            threads.push_back(thread);
+        }
+    }
 
     // Sort them by priority, such that the highest priority ones come first.
     std::sort(threads.begin(), threads.end(),

src/core/hle/kernel/kernel.cpp

@@ -12,12 +12,15 @@
 
 #include "core/core.h"
 #include "core/core_timing.h"
+#include "core/core_timing_util.h"
 #include "core/hle/kernel/address_arbiter.h"
 #include "core/hle/kernel/client_port.h"
+#include "core/hle/kernel/errors.h"
 #include "core/hle/kernel/handle_table.h"
 #include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/process.h"
 #include "core/hle/kernel/resource_limit.h"
+#include "core/hle/kernel/scheduler.h"
 #include "core/hle/kernel/thread.h"
 #include "core/hle/lock.h"
 #include "core/hle/result.h"
@@ -58,12 +61,8 @@ static void ThreadWakeupCallback(u64 thread_handle, [[maybe_unused]] s64 cycles_
         if (thread->HasWakeupCallback()) {
             resume = thread->InvokeWakeupCallback(ThreadWakeupReason::Timeout, thread, nullptr, 0);
         }
-    }
+    } else if (thread->GetStatus() == ThreadStatus::WaitMutex ||
-
+               thread->GetStatus() == ThreadStatus::WaitCondVar) {
-    if (thread->GetMutexWaitAddress() != 0 || thread->GetCondVarWaitAddress() != 0 ||
-        thread->GetWaitHandle() != 0) {
-        ASSERT(thread->GetStatus() == ThreadStatus::WaitMutex ||
-               thread->GetStatus() == ThreadStatus::WaitCondVar);
         thread->SetMutexWaitAddress(0);
         thread->SetCondVarWaitAddress(0);
         thread->SetWaitHandle(0);
@@ -83,18 +82,23 @@ static void ThreadWakeupCallback(u64 thread_handle, [[maybe_unused]] s64 cycles_
     }
 
     if (resume) {
+        if (thread->GetStatus() == ThreadStatus::WaitCondVar ||
+            thread->GetStatus() == ThreadStatus::WaitArb) {
+            thread->SetWaitSynchronizationResult(RESULT_TIMEOUT);
+        }
         thread->ResumeFromWait();
     }
 }
 
 struct KernelCore::Impl {
-    explicit Impl(Core::System& system) : system{system} {}
+    explicit Impl(Core::System& system) : system{system}, global_scheduler{system} {}
 
     void Initialize(KernelCore& kernel) {
         Shutdown();
 
         InitializeSystemResourceLimit(kernel);
         InitializeThreads();
+        InitializePreemption();
     }
 
     void Shutdown() {
@@ -110,6 +114,9 @@ struct KernelCore::Impl {
 
         thread_wakeup_callback_handle_table.Clear();
         thread_wakeup_event_type = nullptr;
+        preemption_event = nullptr;
+
+        global_scheduler.Shutdown();
 
         named_ports.clear();
     }
@@ -132,6 +139,18 @@ struct KernelCore::Impl {
             system.CoreTiming().RegisterEvent("ThreadWakeupCallback", ThreadWakeupCallback);
     }
 
+    void InitializePreemption() {
+        preemption_event = system.CoreTiming().RegisterEvent(
+            "PreemptionCallback", [this](u64 userdata, s64 cycles_late) {
+                global_scheduler.PreemptThreads();
+                s64 time_interval = Core::Timing::msToCycles(std::chrono::milliseconds(10));
+                system.CoreTiming().ScheduleEvent(time_interval, preemption_event);
+            });
+
+        s64 time_interval = Core::Timing::msToCycles(std::chrono::milliseconds(10));
+        system.CoreTiming().ScheduleEvent(time_interval, preemption_event);
+    }
+
     std::atomic<u32> next_object_id{0};
     std::atomic<u64> next_kernel_process_id{Process::InitialKIPIDMin};
     std::atomic<u64> next_user_process_id{Process::ProcessIDMin};
@@ -140,10 +159,12 @@ struct KernelCore::Impl {
     // Lists all processes that exist in the current session.
     std::vector<SharedPtr<Process>> process_list;
     Process* current_process = nullptr;
+    Kernel::GlobalScheduler global_scheduler;
 
     SharedPtr<ResourceLimit> system_resource_limit;
 
     Core::Timing::EventType* thread_wakeup_event_type = nullptr;
+    Core::Timing::EventType* preemption_event = nullptr;
     // TODO(yuriks): This can be removed if Thread objects are explicitly pooled in the future,
     // allowing us to simply use a pool index or similar.
     Kernel::HandleTable thread_wakeup_callback_handle_table;
@@ -203,6 +224,14 @@ const std::vector<SharedPtr<Process>>& KernelCore::GetProcessList() const {
     return impl->process_list;
 }
 
+Kernel::GlobalScheduler& KernelCore::GlobalScheduler() {
+    return impl->global_scheduler;
+}
+
+const Kernel::GlobalScheduler& KernelCore::GlobalScheduler() const {
+    return impl->global_scheduler;
+}
+
 void KernelCore::AddNamedPort(std::string name, SharedPtr<ClientPort> port) {
     impl->named_ports.emplace(std::move(name), std::move(port));
 }

src/core/hle/kernel/kernel.h

@@ -21,6 +21,7 @@ namespace Kernel {
 
 class AddressArbiter;
 class ClientPort;
+class GlobalScheduler;
 class HandleTable;
 class Process;
 class ResourceLimit;
@@ -75,6 +76,12 @@ public:
     /// Retrieves the list of processes.
     const std::vector<SharedPtr<Process>>& GetProcessList() const;
 
+    /// Gets the sole instance of the global scheduler
+    Kernel::GlobalScheduler& GlobalScheduler();
+
+    /// Gets the sole instance of the global scheduler
+    const Kernel::GlobalScheduler& GlobalScheduler() const;
+
     /// Adds a port to the named port table
     void AddNamedPort(std::string name, SharedPtr<ClientPort> port);
 

src/core/hle/kernel/mutex.cpp

@@ -139,6 +139,9 @@ ResultCode Mutex::Release(VAddr address) {
     thread->SetCondVarWaitAddress(0);
     thread->SetMutexWaitAddress(0);
     thread->SetWaitHandle(0);
+    thread->SetWaitSynchronizationResult(RESULT_SUCCESS);
+
+    system.PrepareReschedule();
 
     return RESULT_SUCCESS;
 }

src/core/hle/kernel/process.cpp

@@ -213,10 +213,7 @@ void Process::PrepareForTermination() {
         }
     };
 
-    stop_threads(system.Scheduler(0).GetThreadList());
+    stop_threads(system.GlobalScheduler().GetThreadList());
-    stop_threads(system.Scheduler(1).GetThreadList());
-    stop_threads(system.Scheduler(2).GetThreadList());
-    stop_threads(system.Scheduler(3).GetThreadList());
 
     FreeTLSRegion(tls_region_address);
     tls_region_address = 0;

src/core/hle/kernel/scheduler.cpp

@@ -1,8 +1,13 @@
 // Copyright 2018 yuzu emulator team
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
+//
+// SelectThreads, Yield functions originally by TuxSH.
+// licensed under GPLv2 or later under exception provided by the author.
 
 #include <algorithm>
+#include <set>
+#include <unordered_set>
 #include <utility>
 
 #include "common/assert.h"
@@ -17,56 +22,405 @@
 
 namespace Kernel {
 
-std::mutex Scheduler::scheduler_mutex;
+GlobalScheduler::GlobalScheduler(Core::System& system) : system{system} {
+    is_reselection_pending = false;
+}
 
-Scheduler::Scheduler(Core::System& system, Core::ARM_Interface& cpu_core)
+void GlobalScheduler::AddThread(SharedPtr<Thread> thread) {
-    : cpu_core{cpu_core}, system{system} {}
+    thread_list.push_back(std::move(thread));
+}
 
-Scheduler::~Scheduler() {
+void GlobalScheduler::RemoveThread(const Thread* thread) {
-    for (auto& thread : thread_list) {
+    thread_list.erase(std::remove(thread_list.begin(), thread_list.end(), thread),
-        thread->Stop();
+                      thread_list.end());
+}
+
+/*
+ * UnloadThread selects a core and forces it to unload its current thread's context
+ */
+void GlobalScheduler::UnloadThread(s32 core) {
+    Scheduler& sched = system.Scheduler(core);
+    sched.UnloadThread();
+}
+
+/*
+ * SelectThread takes care of selecting the new scheduled thread.
+ * It does it in 3 steps:
+ * - First a thread is selected from the top of the priority queue. If no thread
+ * is obtained then we move to step two, else we are done.
+ * - Second we try to get a suggested thread that's not assigned to any core or
+ * that is not the top thread in that core.
+ * - Third is no suggested thread is found, we do a second pass and pick a running
+ * thread in another core and swap it with its current thread.
+ */
+void GlobalScheduler::SelectThread(u32 core) {
+    const auto update_thread = [](Thread* thread, Scheduler& sched) {
+        if (thread != sched.selected_thread) {
+            if (thread == nullptr) {
+                ++sched.idle_selection_count;
+            }
+            sched.selected_thread = thread;
+        }
+        sched.is_context_switch_pending = sched.selected_thread != sched.current_thread;
+        std::atomic_thread_fence(std::memory_order_seq_cst);
+    };
+    Scheduler& sched = system.Scheduler(core);
+    Thread* current_thread = nullptr;
+    // Step 1: Get top thread in schedule queue.
+    current_thread = scheduled_queue[core].empty() ? nullptr : scheduled_queue[core].front();
+    if (current_thread) {
+        update_thread(current_thread, sched);
+        return;
+    }
+    // Step 2: Try selecting a suggested thread.
+    Thread* winner = nullptr;
+    std::set<s32> sug_cores;
+    for (auto thread : suggested_queue[core]) {
+        s32 this_core = thread->GetProcessorID();
+        Thread* thread_on_core = nullptr;
+        if (this_core >= 0) {
+            thread_on_core = scheduled_queue[this_core].front();
+        }
+        if (this_core < 0 || thread != thread_on_core) {
+            winner = thread;
+            break;
+        }
+        sug_cores.insert(this_core);
+    }
+    // if we got a suggested thread, select it, else do a second pass.
+    if (winner && winner->GetPriority() > 2) {
+        if (winner->IsRunning()) {
+            UnloadThread(winner->GetProcessorID());
+        }
+        TransferToCore(winner->GetPriority(), core, winner);
+        update_thread(winner, sched);
+        return;
+    }
+    // Step 3: Select a suggested thread from another core
+    for (auto& src_core : sug_cores) {
+        auto it = scheduled_queue[src_core].begin();
+        it++;
+        if (it != scheduled_queue[src_core].end()) {
+            Thread* thread_on_core = scheduled_queue[src_core].front();
+            Thread* to_change = *it;
+            if (thread_on_core->IsRunning() || to_change->IsRunning()) {
+                UnloadThread(src_core);
+            }
+            TransferToCore(thread_on_core->GetPriority(), core, thread_on_core);
+            current_thread = thread_on_core;
+            break;
         }
     }
+    update_thread(current_thread, sched);
+}
+
+/*
+ * YieldThread takes a thread and moves it to the back of the it's priority list
+ * This operation can be redundant and no scheduling is changed if marked as so.
+ */
+bool GlobalScheduler::YieldThread(Thread* yielding_thread) {
+    // Note: caller should use critical section, etc.
+    const u32 core_id = static_cast<u32>(yielding_thread->GetProcessorID());
+    const u32 priority = yielding_thread->GetPriority();
+
+    // Yield the thread
+    ASSERT_MSG(yielding_thread == scheduled_queue[core_id].front(priority),
+               "Thread yielding without being in front");
+    scheduled_queue[core_id].yield(priority);
+
+    Thread* winner = scheduled_queue[core_id].front(priority);
+    return AskForReselectionOrMarkRedundant(yielding_thread, winner);
+}
+
+/*
+ * YieldThreadAndBalanceLoad takes a thread and moves it to the back of the it's priority list.
+ * Afterwards, tries to pick a suggested thread from the suggested queue that has worse time or
+ * a better priority than the next thread in the core.
+ * This operation can be redundant and no scheduling is changed if marked as so.
+ */
+bool GlobalScheduler::YieldThreadAndBalanceLoad(Thread* yielding_thread) {
+    // Note: caller should check if !thread.IsSchedulerOperationRedundant and use critical section,
+    // etc.
+    const u32 core_id = static_cast<u32>(yielding_thread->GetProcessorID());
+    const u32 priority = yielding_thread->GetPriority();
+
+    // Yield the thread
+    ASSERT_MSG(yielding_thread == scheduled_queue[core_id].front(priority),
+               "Thread yielding without being in front");
+    scheduled_queue[core_id].yield(priority);
+
+    std::array<Thread*, NUM_CPU_CORES> current_threads;
+    for (u32 i = 0; i < NUM_CPU_CORES; i++) {
+        current_threads[i] = scheduled_queue[i].empty() ? nullptr : scheduled_queue[i].front();
+    }
+
+    Thread* next_thread = scheduled_queue[core_id].front(priority);
+    Thread* winner = nullptr;
+    for (auto& thread : suggested_queue[core_id]) {
+        const s32 source_core = thread->GetProcessorID();
+        if (source_core >= 0) {
+            if (current_threads[source_core] != nullptr) {
+                if (thread == current_threads[source_core] ||
+                    current_threads[source_core]->GetPriority() < min_regular_priority) {
+                    continue;
+                }
+            }
+        }
+        if (next_thread->GetLastRunningTicks() >= thread->GetLastRunningTicks() ||
+            next_thread->GetPriority() < thread->GetPriority()) {
+            if (thread->GetPriority() <= priority) {
+                winner = thread;
+                break;
+            }
+        }
+    }
+
+    if (winner != nullptr) {
+        if (winner != yielding_thread) {
+            if (winner->IsRunning()) {
+                UnloadThread(winner->GetProcessorID());
+            }
+            TransferToCore(winner->GetPriority(), core_id, winner);
+        }
+    } else {
+        winner = next_thread;
+    }
+
+    return AskForReselectionOrMarkRedundant(yielding_thread, winner);
+}
+
+/*
+ * YieldThreadAndWaitForLoadBalancing takes a thread and moves it out of the scheduling queue
+ * and into the suggested queue. If no thread can be squeduled afterwards in that core,
+ * a suggested thread is obtained instead.
+ * This operation can be redundant and no scheduling is changed if marked as so.
+ */
+bool GlobalScheduler::YieldThreadAndWaitForLoadBalancing(Thread* yielding_thread) {
+    // Note: caller should check if !thread.IsSchedulerOperationRedundant and use critical section,
+    // etc.
+    Thread* winner = nullptr;
+    const u32 core_id = static_cast<u32>(yielding_thread->GetProcessorID());
+
+    // Remove the thread from its scheduled mlq, put it on the corresponding "suggested" one instead
+    TransferToCore(yielding_thread->GetPriority(), -1, yielding_thread);
+
+    // If the core is idle, perform load balancing, excluding the threads that have just used this
+    // function...
+    if (scheduled_queue[core_id].empty()) {
+        // Here, "current_threads" is calculated after the ""yield"", unlike yield -1
+        std::array<Thread*, NUM_CPU_CORES> current_threads;
+        for (u32 i = 0; i < NUM_CPU_CORES; i++) {
+            current_threads[i] = scheduled_queue[i].empty() ? nullptr : scheduled_queue[i].front();
+        }
+        for (auto& thread : suggested_queue[core_id]) {
+            const s32 source_core = thread->GetProcessorID();
+            if (source_core < 0 || thread == current_threads[source_core]) {
+                continue;
+            }
+            if (current_threads[source_core] == nullptr ||
+                current_threads[source_core]->GetPriority() >= min_regular_priority) {
+                winner = thread;
+            }
+            break;
+        }
+        if (winner != nullptr) {
+            if (winner != yielding_thread) {
+                if (winner->IsRunning()) {
+                    UnloadThread(winner->GetProcessorID());
+                }
+                TransferToCore(winner->GetPriority(), core_id, winner);
+            }
+        } else {
+            winner = yielding_thread;
+        }
+    }
+
+    return AskForReselectionOrMarkRedundant(yielding_thread, winner);
+}
+
+void GlobalScheduler::PreemptThreads() {
+    for (std::size_t core_id = 0; core_id < NUM_CPU_CORES; core_id++) {
+        const u32 priority = preemption_priorities[core_id];
+
+        if (scheduled_queue[core_id].size(priority) > 0) {
+            scheduled_queue[core_id].front(priority)->IncrementYieldCount();
+            scheduled_queue[core_id].yield(priority);
+            if (scheduled_queue[core_id].size(priority) > 1) {
+                scheduled_queue[core_id].front(priority)->IncrementYieldCount();
+            }
+        }
+
+        Thread* current_thread =
+            scheduled_queue[core_id].empty() ? nullptr : scheduled_queue[core_id].front();
+        Thread* winner = nullptr;
+        for (auto& thread : suggested_queue[core_id]) {
+            const s32 source_core = thread->GetProcessorID();
+            if (thread->GetPriority() != priority) {
+                continue;
+            }
+            if (source_core >= 0) {
+                Thread* next_thread = scheduled_queue[source_core].empty()
+                                          ? nullptr
+                                          : scheduled_queue[source_core].front();
+                if (next_thread != nullptr && next_thread->GetPriority() < 2) {
+                    break;
+                }
+                if (next_thread == thread) {
+                    continue;
+                }
+            }
+            if (current_thread != nullptr &&
+                current_thread->GetLastRunningTicks() >= thread->GetLastRunningTicks()) {
+                winner = thread;
+                break;
+            }
+        }
+
+        if (winner != nullptr) {
+            if (winner->IsRunning()) {
+                UnloadThread(winner->GetProcessorID());
+            }
+            TransferToCore(winner->GetPriority(), core_id, winner);
+            current_thread =
+                winner->GetPriority() <= current_thread->GetPriority() ? winner : current_thread;
+        }
+
+        if (current_thread != nullptr && current_thread->GetPriority() > priority) {
+            for (auto& thread : suggested_queue[core_id]) {
+                const s32 source_core = thread->GetProcessorID();
+                if (thread->GetPriority() < priority) {
+                    continue;
+                }
+                if (source_core >= 0) {
+                    Thread* next_thread = scheduled_queue[source_core].empty()
+                                              ? nullptr
+                                              : scheduled_queue[source_core].front();
+                    if (next_thread != nullptr && next_thread->GetPriority() < 2) {
+                        break;
+                    }
+                    if (next_thread == thread) {
+                        continue;
+                    }
+                }
+                if (current_thread != nullptr &&
+                    current_thread->GetLastRunningTicks() >= thread->GetLastRunningTicks()) {
+                    winner = thread;
+                    break;
+                }
+            }
+
+            if (winner != nullptr) {
+                if (winner->IsRunning()) {
+                    UnloadThread(winner->GetProcessorID());
+                }
+                TransferToCore(winner->GetPriority(), core_id, winner);
+                current_thread = winner;
+            }
+        }
+
+        is_reselection_pending.store(true, std::memory_order_release);
+    }
+}
+
+void GlobalScheduler::Suggest(u32 priority, u32 core, Thread* thread) {
+    suggested_queue[core].add(thread, priority);
+}
+
+void GlobalScheduler::Unsuggest(u32 priority, u32 core, Thread* thread) {
+    suggested_queue[core].remove(thread, priority);
+}
+
+void GlobalScheduler::Schedule(u32 priority, u32 core, Thread* thread) {
+    ASSERT_MSG(thread->GetProcessorID() == core, "Thread must be assigned to this core.");
+    scheduled_queue[core].add(thread, priority);
+}
+
+void GlobalScheduler::SchedulePrepend(u32 priority, u32 core, Thread* thread) {
+    ASSERT_MSG(thread->GetProcessorID() == core, "Thread must be assigned to this core.");
+    scheduled_queue[core].add(thread, priority, false);
+}
+
+void GlobalScheduler::Reschedule(u32 priority, u32 core, Thread* thread) {
+    scheduled_queue[core].remove(thread, priority);
+    scheduled_queue[core].add(thread, priority);
+}
+
+void GlobalScheduler::Unschedule(u32 priority, u32 core, Thread* thread) {
+    scheduled_queue[core].remove(thread, priority);
+}
+
+void GlobalScheduler::TransferToCore(u32 priority, s32 destination_core, Thread* thread) {
+    const bool schedulable = thread->GetPriority() < THREADPRIO_COUNT;
+    const s32 source_core = thread->GetProcessorID();
+    if (source_core == destination_core || !schedulable) {
+        return;
+    }
+    thread->SetProcessorID(destination_core);
+    if (source_core >= 0) {
+        Unschedule(priority, source_core, thread);
+    }
+    if (destination_core >= 0) {
+        Unsuggest(priority, destination_core, thread);
+        Schedule(priority, destination_core, thread);
+    }
+    if (source_core >= 0) {
+        Suggest(priority, source_core, thread);
+    }
+}
+
+bool GlobalScheduler::AskForReselectionOrMarkRedundant(Thread* current_thread, Thread* winner) {
+    if (current_thread == winner) {
+        current_thread->IncrementYieldCount();
+        return true;
+    } else {
+        is_reselection_pending.store(true, std::memory_order_release);
+        return false;
+    }
+}
+
+void GlobalScheduler::Shutdown() {
+    for (std::size_t core = 0; core < NUM_CPU_CORES; core++) {
+        scheduled_queue[core].clear();
+        suggested_queue[core].clear();
+    }
+    thread_list.clear();
+}
+
+GlobalScheduler::~GlobalScheduler() = default;
+
+Scheduler::Scheduler(Core::System& system, Core::ARM_Interface& cpu_core, u32 core_id)
+    : system(system), cpu_core(cpu_core), core_id(core_id) {}
+
+Scheduler::~Scheduler() = default;
 
 bool Scheduler::HaveReadyThreads() const {
-    std::lock_guard lock{scheduler_mutex};
+    return system.GlobalScheduler().HaveReadyThreads(core_id);
-    return !ready_queue.empty();
 }
 
 Thread* Scheduler::GetCurrentThread() const {
     return current_thread.get();
 }
 
+Thread* Scheduler::GetSelectedThread() const {
+    return selected_thread.get();
+}
+
+void Scheduler::SelectThreads() {
+    system.GlobalScheduler().SelectThread(core_id);
+}
+
 u64 Scheduler::GetLastContextSwitchTicks() const {
     return last_context_switch_time;
 }
 
-Thread* Scheduler::PopNextReadyThread() {
+void Scheduler::TryDoContextSwitch() {
-    Thread* next = nullptr;
+    if (is_context_switch_pending) {
-    Thread* thread = GetCurrentThread();
+        SwitchContext();
-
-    if (thread && thread->GetStatus() == ThreadStatus::Running) {
-        if (ready_queue.empty()) {
-            return thread;
     }
-        // We have to do better than the current thread.
-        // This call returns null when that's not possible.
-        next = ready_queue.front();
-        if (next == nullptr || next->GetPriority() >= thread->GetPriority()) {
-            next = thread;
-        }
-    } else {
-        if (ready_queue.empty()) {
-            return nullptr;
-        }
-        next = ready_queue.front();
 }
 
-    return next;
+void Scheduler::UnloadThread() {
-}
+    Thread* const previous_thread = GetCurrentThread();
-
-void Scheduler::SwitchContext(Thread* new_thread) {
-    Thread* previous_thread = GetCurrentThread();
     Process* const previous_process = system.Kernel().CurrentProcess();
 
     UpdateLastContextSwitchTime(previous_thread, previous_process);
@@ -80,23 +434,52 @@ void Scheduler::SwitchContext(Thread* new_thread) {
         if (previous_thread->GetStatus() == ThreadStatus::Running) {
             // This is only the case when a reschedule is triggered without the current thread
             // yielding execution (i.e. an event triggered, system core time-sliced, etc)
-            ready_queue.add(previous_thread, previous_thread->GetPriority(), false);
             previous_thread->SetStatus(ThreadStatus::Ready);
         }
+        previous_thread->SetIsRunning(false);
+    }
+    current_thread = nullptr;
+}
+
+void Scheduler::SwitchContext() {
+    Thread* const previous_thread = GetCurrentThread();
+    Thread* const new_thread = GetSelectedThread();
+
+    is_context_switch_pending = false;
+    if (new_thread == previous_thread) {
+        return;
+    }
+
+    Process* const previous_process = system.Kernel().CurrentProcess();
+
+    UpdateLastContextSwitchTime(previous_thread, previous_process);
+
+    // Save context for previous thread
+    if (previous_thread) {
+        cpu_core.SaveContext(previous_thread->GetContext());
+        // Save the TPIDR_EL0 system register in case it was modified.
+        previous_thread->SetTPIDR_EL0(cpu_core.GetTPIDR_EL0());
+
+        if (previous_thread->GetStatus() == ThreadStatus::Running) {
+            // This is only the case when a reschedule is triggered without the current thread
+            // yielding execution (i.e. an event triggered, system core time-sliced, etc)
+            previous_thread->SetStatus(ThreadStatus::Ready);
+        }
+        previous_thread->SetIsRunning(false);
     }
 
     // Load context of new thread
     if (new_thread) {
+        ASSERT_MSG(new_thread->GetProcessorID() == this->core_id,
+                   "Thread must be assigned to this core.");
         ASSERT_MSG(new_thread->GetStatus() == ThreadStatus::Ready,
                    "Thread must be ready to become running.");
 
         // Cancel any outstanding wakeup events for this thread
         new_thread->CancelWakeupTimer();
-
         current_thread = new_thread;
-
-        ready_queue.remove(new_thread, new_thread->GetPriority());
         new_thread->SetStatus(ThreadStatus::Running);
+        new_thread->SetIsRunning(true);
 
         auto* const thread_owner_process = current_thread->GetOwnerProcess();
         if (previous_process != thread_owner_process) {
@@ -130,124 +513,9 @@ void Scheduler::UpdateLastContextSwitchTime(Thread* thread, Process* process) {
     last_context_switch_time = most_recent_switch_ticks;
 }
 
-void Scheduler::Reschedule() {
+void Scheduler::Shutdown() {
-    std::lock_guard lock{scheduler_mutex};
+    current_thread = nullptr;
-
+    selected_thread = nullptr;
-    Thread* cur = GetCurrentThread();
-    Thread* next = PopNextReadyThread();
-
-    if (cur && next) {
-        LOG_TRACE(Kernel, "context switch {} -> {}", cur->GetObjectId(), next->GetObjectId());
-    } else if (cur) {
-        LOG_TRACE(Kernel, "context switch {} -> idle", cur->GetObjectId());
-    } else if (next) {
-        LOG_TRACE(Kernel, "context switch idle -> {}", next->GetObjectId());
-    }
-
-    SwitchContext(next);
-}
-
-void Scheduler::AddThread(SharedPtr<Thread> thread) {
-    std::lock_guard lock{scheduler_mutex};
-
-    thread_list.push_back(std::move(thread));
-}
-
-void Scheduler::RemoveThread(Thread* thread) {
-    std::lock_guard lock{scheduler_mutex};
-
-    thread_list.erase(std::remove(thread_list.begin(), thread_list.end(), thread),
-                      thread_list.end());
-}
-
-void Scheduler::ScheduleThread(Thread* thread, u32 priority) {
-    std::lock_guard lock{scheduler_mutex};
-
-    ASSERT(thread->GetStatus() == ThreadStatus::Ready);
-    ready_queue.add(thread, priority);
-}
-
-void Scheduler::UnscheduleThread(Thread* thread, u32 priority) {
-    std::lock_guard lock{scheduler_mutex};
-
-    ASSERT(thread->GetStatus() == ThreadStatus::Ready);
-    ready_queue.remove(thread, priority);
-}
-
-void Scheduler::SetThreadPriority(Thread* thread, u32 priority) {
-    std::lock_guard lock{scheduler_mutex};
-    if (thread->GetPriority() == priority) {
-        return;
-    }
-
-    // If thread was ready, adjust queues
-    if (thread->GetStatus() == ThreadStatus::Ready)
-        ready_queue.adjust(thread, thread->GetPriority(), priority);
-}
-
-Thread* Scheduler::GetNextSuggestedThread(u32 core, u32 maximum_priority) const {
-    std::lock_guard lock{scheduler_mutex};
-
-    const u32 mask = 1U << core;
-    for (auto* thread : ready_queue) {
-        if ((thread->GetAffinityMask() & mask) != 0 && thread->GetPriority() < maximum_priority) {
-            return thread;
-        }
-    }
-    return nullptr;
-}
-
-void Scheduler::YieldWithoutLoadBalancing(Thread* thread) {
-    ASSERT(thread != nullptr);
-    // Avoid yielding if the thread isn't even running.
-    ASSERT(thread->GetStatus() == ThreadStatus::Running);
-
-    // Sanity check that the priority is valid
-    ASSERT(thread->GetPriority() < THREADPRIO_COUNT);
-
-    // Yield this thread -- sleep for zero time and force reschedule to different thread
-    GetCurrentThread()->Sleep(0);
-}
-
-void Scheduler::YieldWithLoadBalancing(Thread* thread) {
-    ASSERT(thread != nullptr);
-    const auto priority = thread->GetPriority();
-    const auto core = static_cast<u32>(thread->GetProcessorID());
-
-    // Avoid yielding if the thread isn't even running.
-    ASSERT(thread->GetStatus() == ThreadStatus::Running);
-
-    // Sanity check that the priority is valid
-    ASSERT(priority < THREADPRIO_COUNT);
-
-    // Sleep for zero time to be able to force reschedule to different thread
-    GetCurrentThread()->Sleep(0);
-
-    Thread* suggested_thread = nullptr;
-
-    // Search through all of the cpu cores (except this one) for a suggested thread.
-    // Take the first non-nullptr one
-    for (unsigned cur_core = 0; cur_core < Core::NUM_CPU_CORES; ++cur_core) {
-        const auto res =
-            system.CpuCore(cur_core).Scheduler().GetNextSuggestedThread(core, priority);
-
-        // If scheduler provides a suggested thread
-        if (res != nullptr) {
-            // And its better than the current suggested thread (or is the first valid one)
-            if (suggested_thread == nullptr ||
-                suggested_thread->GetPriority() > res->GetPriority()) {
-                suggested_thread = res;
-            }
-        }
-    }
-
-    // If a suggested thread was found, queue that for this core
-    if (suggested_thread != nullptr)
-        suggested_thread->ChangeCore(core, suggested_thread->GetAffinityMask());
-}
-
-void Scheduler::YieldAndWaitForLoadBalancing(Thread* thread) {
-    UNIMPLEMENTED_MSG("Wait for load balancing thread yield type is not implemented!");
 }
 
 } // namespace Kernel

src/core/hle/kernel/scheduler.h

@@ -20,124 +20,172 @@ namespace Kernel {
 
 class Process;
 
-class Scheduler final {
+class GlobalScheduler final {
 public:
-    explicit Scheduler(Core::System& system, Core::ARM_Interface& cpu_core);
+    static constexpr u32 NUM_CPU_CORES = 4;
-    ~Scheduler();
-
-    /// Returns whether there are any threads that are ready to run.
-    bool HaveReadyThreads() const;
-
-    /// Reschedules to the next available thread (call after current thread is suspended)
-    void Reschedule();
-
-    /// Gets the current running thread
-    Thread* GetCurrentThread() const;
-
-    /// Gets the timestamp for the last context switch in ticks.
-    u64 GetLastContextSwitchTicks() const;
 
+    explicit GlobalScheduler(Core::System& system);
+    ~GlobalScheduler();
     /// Adds a new thread to the scheduler
     void AddThread(SharedPtr<Thread> thread);
 
     /// Removes a thread from the scheduler
-    void RemoveThread(Thread* thread);
+    void RemoveThread(const Thread* thread);
-
-    /// Schedules a thread that has become "ready"
-    void ScheduleThread(Thread* thread, u32 priority);
-
-    /// Unschedules a thread that was already scheduled
-    void UnscheduleThread(Thread* thread, u32 priority);
-
-    /// Sets the priority of a thread in the scheduler
-    void SetThreadPriority(Thread* thread, u32 priority);
-
-    /// Gets the next suggested thread for load balancing
-    Thread* GetNextSuggestedThread(u32 core, u32 minimum_priority) const;
-
-    /**
-     * YieldWithoutLoadBalancing -- analogous to normal yield on a system
-     * Moves the thread to the end of the ready queue for its priority, and then reschedules the
-     * system to the new head of the queue.
-     *
-     * Example (Single Core -- but can be extrapolated to multi):
-     * ready_queue[prio=0]: ThreadA, ThreadB, ThreadC (->exec order->)
-     * Currently Running: ThreadR
-     *
-     * ThreadR calls YieldWithoutLoadBalancing
-     *
-     * ThreadR is moved to the end of ready_queue[prio=0]:
-     * ready_queue[prio=0]: ThreadA, ThreadB, ThreadC, ThreadR (->exec order->)
-     * Currently Running: Nothing
-     *
-     * System is rescheduled (ThreadA is popped off of queue):
-     * ready_queue[prio=0]: ThreadB, ThreadC, ThreadR (->exec order->)
-     * Currently Running: ThreadA
-     *
-     * If the queue is empty at time of call, no yielding occurs. This does not cross between cores
-     * or priorities at all.
-     */
-    void YieldWithoutLoadBalancing(Thread* thread);
-
-    /**
-     * YieldWithLoadBalancing -- yield but with better selection of the new running thread
-     * Moves the current thread to the end of the ready queue for its priority, then selects a
-     * 'suggested thread' (a thread on a different core that could run on this core) from the
-     * scheduler, changes its core, and reschedules the current core to that thread.
-     *
-     * Example (Dual Core -- can be extrapolated to Quad Core, this is just normal yield if it were
-     * single core):
-     * ready_queue[core=0][prio=0]: ThreadA, ThreadB (affinities not pictured as irrelevant
-     * ready_queue[core=1][prio=0]: ThreadC[affinity=both], ThreadD[affinity=core1only]
-     * Currently Running: ThreadQ on Core 0 || ThreadP on Core 1
-     *
-     * ThreadQ calls YieldWithLoadBalancing
-     *
-     * ThreadQ is moved to the end of ready_queue[core=0][prio=0]:
-     * ready_queue[core=0][prio=0]: ThreadA, ThreadB
-     * ready_queue[core=1][prio=0]: ThreadC[affinity=both], ThreadD[affinity=core1only]
-     * Currently Running: ThreadQ on Core 0 || ThreadP on Core 1
-     *
-     * A list of suggested threads for each core is compiled
-     * Suggested Threads: {ThreadC on Core 1}
-     * If this were quad core (as the switch is), there could be between 0 and 3 threads in this
-     * list. If there are more than one, the thread is selected by highest prio.
-     *
-     * ThreadC is core changed to Core 0:
-     * ready_queue[core=0][prio=0]: ThreadC, ThreadA, ThreadB, ThreadQ
-     * ready_queue[core=1][prio=0]: ThreadD
-     * Currently Running: None on Core 0 || ThreadP on Core 1
-     *
-     * System is rescheduled (ThreadC is popped off of queue):
-     * ready_queue[core=0][prio=0]: ThreadA, ThreadB, ThreadQ
-     * ready_queue[core=1][prio=0]: ThreadD
-     * Currently Running: ThreadC on Core 0 || ThreadP on Core 1
-     *
-     * If no suggested threads can be found this will behave just as normal yield. If there are
-     * multiple candidates for the suggested thread on a core, the highest prio is taken.
-     */
-    void YieldWithLoadBalancing(Thread* thread);
-
-    /// Currently unknown -- asserts as unimplemented on call
-    void YieldAndWaitForLoadBalancing(Thread* thread);
 
     /// Returns a list of all threads managed by the scheduler
     const std::vector<SharedPtr<Thread>>& GetThreadList() const {
         return thread_list;
     }
 
-private:
+    // Add a thread to the suggested queue of a cpu core. Suggested threads may be
-    /**
+    // picked if no thread is scheduled to run on the core.
-     * Pops and returns the next thread from the thread queue
+    void Suggest(u32 priority, u32 core, Thread* thread);
-     * @return A pointer to the next ready thread
-     */
-    Thread* PopNextReadyThread();
 
+    // Remove a thread to the suggested queue of a cpu core. Suggested threads may be
+    // picked if no thread is scheduled to run on the core.
+    void Unsuggest(u32 priority, u32 core, Thread* thread);
+
+    // Add a thread to the scheduling queue of a cpu core. The thread is added at the
+    // back the queue in its priority level
+    void Schedule(u32 priority, u32 core, Thread* thread);
+
+    // Add a thread to the scheduling queue of a cpu core. The thread is added at the
+    // front the queue in its priority level
+    void SchedulePrepend(u32 priority, u32 core, Thread* thread);
+
+    // Reschedule an already scheduled thread based on a new priority
+    void Reschedule(u32 priority, u32 core, Thread* thread);
+
+    // Unschedule a thread.
+    void Unschedule(u32 priority, u32 core, Thread* thread);
+
+    // Transfers a thread into an specific core. If the destination_core is -1
+    // it will be unscheduled from its source code and added into its suggested
+    // queue.
+    void TransferToCore(u32 priority, s32 destination_core, Thread* thread);
+
+    /*
+     * UnloadThread selects a core and forces it to unload its current thread's context
+     */
+    void UnloadThread(s32 core);
+
+    /*
+     * SelectThread takes care of selecting the new scheduled thread.
+     * It does it in 3 steps:
+     * - First a thread is selected from the top of the priority queue. If no thread
+     * is obtained then we move to step two, else we are done.
+     * - Second we try to get a suggested thread that's not assigned to any core or
+     * that is not the top thread in that core.
+     * - Third is no suggested thread is found, we do a second pass and pick a running
+     * thread in another core and swap it with its current thread.
+     */
+    void SelectThread(u32 core);
+
+    bool HaveReadyThreads(u32 core_id) const {
+        return !scheduled_queue[core_id].empty();
+    }
+
+    /*
+     * YieldThread takes a thread and moves it to the back of the it's priority list
+     * This operation can be redundant and no scheduling is changed if marked as so.
+     */
+    bool YieldThread(Thread* thread);
+
+    /*
+     * YieldThreadAndBalanceLoad takes a thread and moves it to the back of the it's priority list.
+     * Afterwards, tries to pick a suggested thread from the suggested queue that has worse time or
+     * a better priority than the next thread in the core.
+     * This operation can be redundant and no scheduling is changed if marked as so.
+     */
+    bool YieldThreadAndBalanceLoad(Thread* thread);
+
+    /*
+     * YieldThreadAndWaitForLoadBalancing takes a thread and moves it out of the scheduling queue
+     * and into the suggested queue. If no thread can be squeduled afterwards in that core,
+     * a suggested thread is obtained instead.
+     * This operation can be redundant and no scheduling is changed if marked as so.
+     */
+    bool YieldThreadAndWaitForLoadBalancing(Thread* thread);
+
+    /*
+     * PreemptThreads this operation rotates the scheduling queues of threads at
+     * a preemption priority and then does some core rebalancing. Preemption priorities
+     * can be found in the array 'preemption_priorities'. This operation happens
+     * every 10ms.
+     */
+    void PreemptThreads();
+
+    u32 CpuCoresCount() const {
+        return NUM_CPU_CORES;
+    }
+
+    void SetReselectionPending() {
+        is_reselection_pending.store(true, std::memory_order_release);
+    }
+
+    bool IsReselectionPending() const {
+        return is_reselection_pending.load(std::memory_order_acquire);
+    }
+
+    void Shutdown();
+
+private:
+    bool AskForReselectionOrMarkRedundant(Thread* current_thread, Thread* winner);
+
+    static constexpr u32 min_regular_priority = 2;
+    std::array<Common::MultiLevelQueue<Thread*, THREADPRIO_COUNT>, NUM_CPU_CORES> scheduled_queue;
+    std::array<Common::MultiLevelQueue<Thread*, THREADPRIO_COUNT>, NUM_CPU_CORES> suggested_queue;
+    std::atomic<bool> is_reselection_pending;
+
+    // `preemption_priorities` are the priority levels at which the global scheduler
+    // preempts threads every 10 ms. They are ordered from Core 0 to Core 3
+    std::array<u32, NUM_CPU_CORES> preemption_priorities = {59, 59, 59, 62};
+
+    /// Lists all thread ids that aren't deleted/etc.
+    std::vector<SharedPtr<Thread>> thread_list;
+    Core::System& system;
+};
+
+class Scheduler final {
+public:
+    explicit Scheduler(Core::System& system, Core::ARM_Interface& cpu_core, u32 core_id);
+    ~Scheduler();
+
+    /// Returns whether there are any threads that are ready to run.
+    bool HaveReadyThreads() const;
+
+    /// Reschedules to the next available thread (call after current thread is suspended)
+    void TryDoContextSwitch();
+
+    /// Unloads currently running thread
+    void UnloadThread();
+
+    /// Select the threads in top of the scheduling multilist.
+    void SelectThreads();
+
+    /// Gets the current running thread
+    Thread* GetCurrentThread() const;
+
+    /// Gets the currently selected thread from the top of the multilevel queue
+    Thread* GetSelectedThread() const;
+
+    /// Gets the timestamp for the last context switch in ticks.
+    u64 GetLastContextSwitchTicks() const;
+
+    bool ContextSwitchPending() const {
+        return is_context_switch_pending;
+    }
+
+    /// Shutdowns the scheduler.
+    void Shutdown();
+
+private:
+    friend class GlobalScheduler;
     /**
      * Switches the CPU's active thread context to that of the specified thread
      * @param new_thread The thread to switch to
      */
-    void SwitchContext(Thread* new_thread);
+    void SwitchContext();
 
     /**
      * Called on every context switch to update the internal timestamp
@@ -152,19 +200,16 @@ private:
      */
     void UpdateLastContextSwitchTime(Thread* thread, Process* process);
 
-    /// Lists all thread ids that aren't deleted/etc.
-    std::vector<SharedPtr<Thread>> thread_list;
-
-    /// Lists only ready thread ids.
-    Common::MultiLevelQueue<Thread*, THREADPRIO_LOWEST + 1> ready_queue;
-
     SharedPtr<Thread> current_thread = nullptr;
-
+    SharedPtr<Thread> selected_thread = nullptr;
-    Core::ARM_Interface& cpu_core;
-    u64 last_context_switch_time = 0;
 
     Core::System& system;
-    static std::mutex scheduler_mutex;
+    Core::ARM_Interface& cpu_core;
+    u64 last_context_switch_time = 0;
+    u64 idle_selection_count = 0;
+    const u32 core_id;
+
+    bool is_context_switch_pending = false;
 };
 
 } // namespace Kernel

src/core/hle/kernel/svc.cpp

@@ -516,7 +516,7 @@ static ResultCode WaitSynchronization(Core::System& system, Handle* index, VAddr
     thread->WakeAfterDelay(nano_seconds);
     thread->SetWakeupCallback(DefaultThreadWakeupCallback);
 
-    system.CpuCore(thread->GetProcessorID()).PrepareReschedule();
+    system.PrepareReschedule(thread->GetProcessorID());
 
     return RESULT_TIMEOUT;
 }
@@ -534,6 +534,7 @@ static ResultCode CancelSynchronization(Core::System& system, Handle thread_hand
     }
 
     thread->CancelWait();
+    system.PrepareReschedule(thread->GetProcessorID());
     return RESULT_SUCCESS;
 }
 
@@ -1066,6 +1067,8 @@ static ResultCode SetThreadActivity(Core::System& system, Handle handle, u32 act
     }
 
     thread->SetActivity(static_cast<ThreadActivity>(activity));
+
+    system.PrepareReschedule(thread->GetProcessorID());
     return RESULT_SUCCESS;
 }
 
@@ -1147,7 +1150,7 @@ static ResultCode SetThreadPriority(Core::System& system, Handle handle, u32 pri
 
     thread->SetPriority(priority);
 
-    system.CpuCore(thread->GetProcessorID()).PrepareReschedule();
+    system.PrepareReschedule(thread->GetProcessorID());
     return RESULT_SUCCESS;
 }
 
@@ -1503,7 +1506,7 @@ static ResultCode CreateThread(Core::System& system, Handle* out_handle, VAddr e
     thread->SetName(
         fmt::format("thread[entry_point={:X}, handle={:X}]", entry_point, *new_thread_handle));
 
-    system.CpuCore(thread->GetProcessorID()).PrepareReschedule();
+    system.PrepareReschedule(thread->GetProcessorID());
 
     return RESULT_SUCCESS;
 }
@@ -1525,7 +1528,7 @@ static ResultCode StartThread(Core::System& system, Handle thread_handle) {
     thread->ResumeFromWait();
 
     if (thread->GetStatus() == ThreadStatus::Ready) {
-        system.CpuCore(thread->GetProcessorID()).PrepareReschedule();
+        system.PrepareReschedule(thread->GetProcessorID());
     }
 
     return RESULT_SUCCESS;
@@ -1537,7 +1540,7 @@ static void ExitThread(Core::System& system) {
 
     auto* const current_thread = system.CurrentScheduler().GetCurrentThread();
     current_thread->Stop();
-    system.CurrentScheduler().RemoveThread(current_thread);
+    system.GlobalScheduler().RemoveThread(current_thread);
     system.PrepareReschedule();
 }
 
@@ -1553,17 +1556,18 @@ static void SleepThread(Core::System& system, s64 nanoseconds) {
 
     auto& scheduler = system.CurrentScheduler();
     auto* const current_thread = scheduler.GetCurrentThread();
+    bool is_redundant = false;
 
     if (nanoseconds <= 0) {
         switch (static_cast<SleepType>(nanoseconds)) {
         case SleepType::YieldWithoutLoadBalancing:
-            scheduler.YieldWithoutLoadBalancing(current_thread);
+            is_redundant = current_thread->YieldSimple();
             break;
         case SleepType::YieldWithLoadBalancing:
-            scheduler.YieldWithLoadBalancing(current_thread);
+            is_redundant = current_thread->YieldAndBalanceLoad();
             break;
         case SleepType::YieldAndWaitForLoadBalancing:
-            scheduler.YieldAndWaitForLoadBalancing(current_thread);
+            is_redundant = current_thread->YieldAndWaitForLoadBalancing();
             break;
         default:
             UNREACHABLE_MSG("Unimplemented sleep yield type '{:016X}'!", nanoseconds);
@@ -1572,10 +1576,13 @@ static void SleepThread(Core::System& system, s64 nanoseconds) {
         current_thread->Sleep(nanoseconds);
     }
 
-    // Reschedule all CPU cores
+    if (is_redundant) {
-    for (std::size_t i = 0; i < Core::NUM_CPU_CORES; ++i) {
+        // If it's redundant, the core is pretty much idle. Some games keep idling
-        system.CpuCore(i).PrepareReschedule();
+        // a core while it's doing nothing, we advance timing to avoid costly continuous
+        // calls.
+        system.CoreTiming().AddTicks(2000);
     }
+    system.PrepareReschedule(current_thread->GetProcessorID());
 }
 
 /// Wait process wide key atomic
@@ -1601,6 +1608,8 @@ static ResultCode WaitProcessWideKeyAtomic(Core::System& system, VAddr mutex_add
         return ERR_INVALID_ADDRESS;
     }
 
+    ASSERT(condition_variable_addr == Common::AlignDown(condition_variable_addr, 4));
+
     auto* const current_process = system.Kernel().CurrentProcess();
     const auto& handle_table = current_process->GetHandleTable();
     SharedPtr<Thread> thread = handle_table.Get<Thread>(thread_handle);
@@ -1622,7 +1631,7 @@ static ResultCode WaitProcessWideKeyAtomic(Core::System& system, VAddr mutex_add
 
     // Note: Deliberately don't attempt to inherit the lock owner's priority.
 
-    system.CpuCore(current_thread->GetProcessorID()).PrepareReschedule();
+    system.PrepareReschedule(current_thread->GetProcessorID());
     return RESULT_SUCCESS;
 }
 
@@ -1632,24 +1641,19 @@ static ResultCode SignalProcessWideKey(Core::System& system, VAddr condition_var
     LOG_TRACE(Kernel_SVC, "called, condition_variable_addr=0x{:X}, target=0x{:08X}",
               condition_variable_addr, target);
 
-    const auto RetrieveWaitingThreads = [&system](std::size_t core_index,
+    ASSERT(condition_variable_addr == Common::AlignDown(condition_variable_addr, 4));
-                                                  std::vector<SharedPtr<Thread>>& waiting_threads,
-                                                  VAddr condvar_addr) {
-        const auto& scheduler = system.Scheduler(core_index);
-        const auto& thread_list = scheduler.GetThreadList();
-
-        for (const auto& thread : thread_list) {
-            if (thread->GetCondVarWaitAddress() == condvar_addr)
-                waiting_threads.push_back(thread);
-        }
-    };
 
     // Retrieve a list of all threads that are waiting for this condition variable.
     std::vector<SharedPtr<Thread>> waiting_threads;
-    RetrieveWaitingThreads(0, waiting_threads, condition_variable_addr);
+    const auto& scheduler = system.GlobalScheduler();
-    RetrieveWaitingThreads(1, waiting_threads, condition_variable_addr);
+    const auto& thread_list = scheduler.GetThreadList();
-    RetrieveWaitingThreads(2, waiting_threads, condition_variable_addr);
+
-    RetrieveWaitingThreads(3, waiting_threads, condition_variable_addr);
+    for (const auto& thread : thread_list) {
+        if (thread->GetCondVarWaitAddress() == condition_variable_addr) {
+            waiting_threads.push_back(thread);
+        }
+    }
+
     // Sort them by priority, such that the highest priority ones come first.
     std::sort(waiting_threads.begin(), waiting_threads.end(),
               [](const SharedPtr<Thread>& lhs, const SharedPtr<Thread>& rhs) {
@@ -1679,18 +1683,20 @@ static ResultCode SignalProcessWideKey(Core::System& system, VAddr condition_var
 
         // Atomically read the value of the mutex.
         u32 mutex_val = 0;
+        u32 update_val = 0;
+        const VAddr mutex_address = thread->GetMutexWaitAddress();
         do {
-            monitor.SetExclusive(current_core, thread->GetMutexWaitAddress());
+            monitor.SetExclusive(current_core, mutex_address);
 
             // If the mutex is not yet acquired, acquire it.
-            mutex_val = Memory::Read32(thread->GetMutexWaitAddress());
+            mutex_val = Memory::Read32(mutex_address);
 
             if (mutex_val != 0) {
-                monitor.ClearExclusive();
+                update_val = mutex_val | Mutex::MutexHasWaitersFlag;
-                break;
+            } else {
+                update_val = thread->GetWaitHandle();
             }
-        } while (!monitor.ExclusiveWrite32(current_core, thread->GetMutexWaitAddress(),
+        } while (!monitor.ExclusiveWrite32(current_core, mutex_address, update_val));
-                                           thread->GetWaitHandle()));
         if (mutex_val == 0) {
             // We were able to acquire the mutex, resume this thread.
             ASSERT(thread->GetStatus() == ThreadStatus::WaitCondVar);
@@ -1704,20 +1710,9 @@ static ResultCode SignalProcessWideKey(Core::System& system, VAddr condition_var
             thread->SetLockOwner(nullptr);
             thread->SetMutexWaitAddress(0);
             thread->SetWaitHandle(0);
-            system.CpuCore(thread->GetProcessorID()).PrepareReschedule();
+            thread->SetWaitSynchronizationResult(RESULT_SUCCESS);
+            system.PrepareReschedule(thread->GetProcessorID());
         } else {
-            // Atomically signal that the mutex now has a waiting thread.
-            do {
-                monitor.SetExclusive(current_core, thread->GetMutexWaitAddress());
-
-                // Ensure that the mutex value is still what we expect.
-                u32 value = Memory::Read32(thread->GetMutexWaitAddress());
-                // TODO(Subv): When this happens, the kernel just clears the exclusive state and
-                // retries the initial read for this thread.
-                ASSERT_MSG(mutex_val == value, "Unhandled synchronization primitive case");
-            } while (!monitor.ExclusiveWrite32(current_core, thread->GetMutexWaitAddress(),
-                                               mutex_val | Mutex::MutexHasWaitersFlag));
-
             // The mutex is already owned by some other thread, make this thread wait on it.
             const Handle owner_handle = static_cast<Handle>(mutex_val & Mutex::MutexOwnerMask);
             const auto& handle_table = system.Kernel().CurrentProcess()->GetHandleTable();
@@ -1728,6 +1723,7 @@ static ResultCode SignalProcessWideKey(Core::System& system, VAddr condition_var
             thread->SetStatus(ThreadStatus::WaitMutex);
 
             owner->AddMutexWaiter(thread);
+            system.PrepareReschedule(thread->GetProcessorID());
         }
     }
 
@@ -1754,7 +1750,12 @@ static ResultCode WaitForAddress(Core::System& system, VAddr address, u32 type,
 
     const auto arbitration_type = static_cast<AddressArbiter::ArbitrationType>(type);
     auto& address_arbiter = system.Kernel().CurrentProcess()->GetAddressArbiter();
-    return address_arbiter.WaitForAddress(address, arbitration_type, value, timeout);
+    const ResultCode result =
+        address_arbiter.WaitForAddress(address, arbitration_type, value, timeout);
+    if (result == RESULT_SUCCESS) {
+        system.PrepareReschedule();
+    }
+    return result;
 }
 
 // Signals to an address (via Address Arbiter)
@@ -2040,7 +2041,10 @@ static ResultCode SetThreadCoreMask(Core::System& system, Handle thread_handle,
         return ERR_INVALID_HANDLE;
     }
 
+    system.PrepareReschedule(thread->GetProcessorID());
     thread->ChangeCore(core, affinity_mask);
+    system.PrepareReschedule(thread->GetProcessorID());
+
     return RESULT_SUCCESS;
 }
 
@@ -2151,6 +2155,7 @@ static ResultCode SignalEvent(Core::System& system, Handle handle) {
     }
 
     writable_event->Signal();
+    system.PrepareReschedule();
     return RESULT_SUCCESS;
 }
 

src/core/hle/kernel/thread.cpp

@@ -45,15 +45,7 @@ void Thread::Stop() {
                                                              callback_handle);
     kernel.ThreadWakeupCallbackHandleTable().Close(callback_handle);
     callback_handle = 0;
-
+    SetStatus(ThreadStatus::Dead);
-    // Clean up thread from ready queue
-    // This is only needed when the thread is terminated forcefully (SVC TerminateProcess)
-    if (status == ThreadStatus::Ready || status == ThreadStatus::Paused) {
-        scheduler->UnscheduleThread(this, current_priority);
-    }
-
-    status = ThreadStatus::Dead;
-
     WakeupAllWaitingThreads();
 
     // Clean up any dangling references in objects that this thread was waiting for
@@ -132,17 +124,16 @@ void Thread::ResumeFromWait() {
     wakeup_callback = nullptr;
 
     if (activity == ThreadActivity::Paused) {
-        status = ThreadStatus::Paused;
+        SetStatus(ThreadStatus::Paused);
         return;
     }
 
-    status = ThreadStatus::Ready;
+    SetStatus(ThreadStatus::Ready);
-
-    ChangeScheduler();
 }
 
 void Thread::CancelWait() {
     ASSERT(GetStatus() == ThreadStatus::WaitSynch);
+    ClearWaitObjects();
     SetWaitSynchronizationResult(ERR_SYNCHRONIZATION_CANCELED);
     ResumeFromWait();
 }
@@ -205,9 +196,9 @@ ResultVal<SharedPtr<Thread>> Thread::Create(KernelCore& kernel, std::string name
     thread->name = std::move(name);
     thread->callback_handle = kernel.ThreadWakeupCallbackHandleTable().Create(thread).Unwrap();
     thread->owner_process = &owner_process;
+    auto& scheduler = kernel.GlobalScheduler();
+    scheduler.AddThread(thread);
     thread->tls_address = thread->owner_process->CreateTLSRegion();
-    thread->scheduler = &system.Scheduler(processor_id);
-    thread->scheduler->AddThread(thread);
 
     thread->owner_process->RegisterThread(thread.get());
 
@@ -250,6 +241,22 @@ void Thread::SetStatus(ThreadStatus new_status) {
         return;
     }
 
+    switch (new_status) {
+    case ThreadStatus::Ready:
+    case ThreadStatus::Running:
+        SetSchedulingStatus(ThreadSchedStatus::Runnable);
+        break;
+    case ThreadStatus::Dormant:
+        SetSchedulingStatus(ThreadSchedStatus::None);
+        break;
+    case ThreadStatus::Dead:
+        SetSchedulingStatus(ThreadSchedStatus::Exited);
+        break;
+    default:
+        SetSchedulingStatus(ThreadSchedStatus::Paused);
+        break;
+    }
+
     if (status == ThreadStatus::Running) {
         last_running_ticks = Core::System::GetInstance().CoreTiming().GetTicks();
     }
@@ -311,8 +318,7 @@ void Thread::UpdatePriority() {
         return;
     }
 
-    scheduler->SetThreadPriority(this, new_priority);
+    SetCurrentPriority(new_priority);
-    current_priority = new_priority;
 
     if (!lock_owner) {
         return;
@@ -328,47 +334,7 @@ void Thread::UpdatePriority() {
 }
 
 void Thread::ChangeCore(u32 core, u64 mask) {
-    ideal_core = core;
+    SetCoreAndAffinityMask(core, mask);
-    affinity_mask = mask;
-    ChangeScheduler();
-}
-
-void Thread::ChangeScheduler() {
-    if (status != ThreadStatus::Ready) {
-        return;
-    }
-
-    auto& system = Core::System::GetInstance();
-    std::optional<s32> new_processor_id{GetNextProcessorId(affinity_mask)};
-
-    if (!new_processor_id) {
-        new_processor_id = processor_id;
-    }
-    if (ideal_core != -1 && system.Scheduler(ideal_core).GetCurrentThread() == nullptr) {
-        new_processor_id = ideal_core;
-    }
-
-    ASSERT(*new_processor_id < 4);
-
-    // Add thread to new core's scheduler
-    auto& next_scheduler = system.Scheduler(*new_processor_id);
-
-    if (*new_processor_id != processor_id) {
-        // Remove thread from previous core's scheduler
-        scheduler->RemoveThread(this);
-        next_scheduler.AddThread(this);
-    }
-
-    processor_id = *new_processor_id;
-
-    // If the thread was ready, unschedule from the previous core and schedule on the new core
-    scheduler->UnscheduleThread(this, current_priority);
-    next_scheduler.ScheduleThread(this, current_priority);
-
-    // Change thread's scheduler
-    scheduler = &next_scheduler;
-
-    system.CpuCore(processor_id).PrepareReschedule();
 }
 
 bool Thread::AllWaitObjectsReady() const {
@@ -388,10 +354,8 @@ void Thread::SetActivity(ThreadActivity value) {
 
     if (value == ThreadActivity::Paused) {
         // Set status if not waiting
-        if (status == ThreadStatus::Ready) {
+        if (status == ThreadStatus::Ready || status == ThreadStatus::Running) {
-            status = ThreadStatus::Paused;
+            SetStatus(ThreadStatus::Paused);
-        } else if (status == ThreadStatus::Running) {
-            status = ThreadStatus::Paused;
             Core::System::GetInstance().CpuCore(processor_id).PrepareReschedule();
         }
     } else if (status == ThreadStatus::Paused) {
@@ -408,6 +372,170 @@ void Thread::Sleep(s64 nanoseconds) {
     WakeAfterDelay(nanoseconds);
 }
 
+bool Thread::YieldSimple() {
+    auto& scheduler = kernel.GlobalScheduler();
+    return scheduler.YieldThread(this);
+}
+
+bool Thread::YieldAndBalanceLoad() {
+    auto& scheduler = kernel.GlobalScheduler();
+    return scheduler.YieldThreadAndBalanceLoad(this);
+}
+
+bool Thread::YieldAndWaitForLoadBalancing() {
+    auto& scheduler = kernel.GlobalScheduler();
+    return scheduler.YieldThreadAndWaitForLoadBalancing(this);
+}
+
+void Thread::SetSchedulingStatus(ThreadSchedStatus new_status) {
+    const u32 old_flags = scheduling_state;
+    scheduling_state = (scheduling_state & static_cast<u32>(ThreadSchedMasks::HighMask)) |
+                       static_cast<u32>(new_status);
+    AdjustSchedulingOnStatus(old_flags);
+}
+
+void Thread::SetCurrentPriority(u32 new_priority) {
+    const u32 old_priority = std::exchange(current_priority, new_priority);
+    AdjustSchedulingOnPriority(old_priority);
+}
+
+ResultCode Thread::SetCoreAndAffinityMask(s32 new_core, u64 new_affinity_mask) {
+    const auto HighestSetCore = [](u64 mask, u32 max_cores) {
+        for (s32 core = max_cores - 1; core >= 0; core--) {
+            if (((mask >> core) & 1) != 0) {
+                return core;
+            }
+        }
+        return -1;
+    };
+
+    const bool use_override = affinity_override_count != 0;
+    if (new_core == THREADPROCESSORID_DONT_UPDATE) {
+        new_core = use_override ? ideal_core_override : ideal_core;
+        if ((new_affinity_mask & (1ULL << new_core)) == 0) {
+            return ERR_INVALID_COMBINATION;
+        }
+    }
+    if (use_override) {
+        ideal_core_override = new_core;
+        affinity_mask_override = new_affinity_mask;
+    } else {
+        const u64 old_affinity_mask = std::exchange(affinity_mask, new_affinity_mask);
+        ideal_core = new_core;
+        if (old_affinity_mask != new_affinity_mask) {
+            const s32 old_core = processor_id;
+            if (processor_id >= 0 && ((affinity_mask >> processor_id) & 1) == 0) {
+                if (ideal_core < 0) {
+                    processor_id = HighestSetCore(affinity_mask, GlobalScheduler::NUM_CPU_CORES);
+                } else {
+                    processor_id = ideal_core;
+                }
+            }
+            AdjustSchedulingOnAffinity(old_affinity_mask, old_core);
+        }
+    }
+    return RESULT_SUCCESS;
+}
+
+void Thread::AdjustSchedulingOnStatus(u32 old_flags) {
+    if (old_flags == scheduling_state) {
+        return;
+    }
+
+    auto& scheduler = kernel.GlobalScheduler();
+    if (static_cast<ThreadSchedStatus>(old_flags & static_cast<u32>(ThreadSchedMasks::LowMask)) ==
+        ThreadSchedStatus::Runnable) {
+        // In this case the thread was running, now it's pausing/exitting
+        if (processor_id >= 0) {
+            scheduler.Unschedule(current_priority, processor_id, this);
+        }
+
+        for (s32 core = 0; core < GlobalScheduler::NUM_CPU_CORES; core++) {
+            if (core != processor_id && ((affinity_mask >> core) & 1) != 0) {
+                scheduler.Unsuggest(current_priority, static_cast<u32>(core), this);
+            }
+        }
+    } else if (GetSchedulingStatus() == ThreadSchedStatus::Runnable) {
+        // The thread is now set to running from being stopped
+        if (processor_id >= 0) {
+            scheduler.Schedule(current_priority, processor_id, this);
+        }
+
+        for (s32 core = 0; core < GlobalScheduler::NUM_CPU_CORES; core++) {
+            if (core != processor_id && ((affinity_mask >> core) & 1) != 0) {
+                scheduler.Suggest(current_priority, static_cast<u32>(core), this);
+            }
+        }
+    }
+
+    scheduler.SetReselectionPending();
+}
+
+void Thread::AdjustSchedulingOnPriority(u32 old_priority) {
+    if (GetSchedulingStatus() != ThreadSchedStatus::Runnable) {
+        return;
+    }
+    auto& scheduler = Core::System::GetInstance().GlobalScheduler();
+    if (processor_id >= 0) {
+        scheduler.Unschedule(old_priority, processor_id, this);
+    }
+
+    for (u32 core = 0; core < GlobalScheduler::NUM_CPU_CORES; core++) {
+        if (core != processor_id && ((affinity_mask >> core) & 1) != 0) {
+            scheduler.Unsuggest(old_priority, core, this);
+        }
+    }
+
+    // Add thread to the new priority queues.
+    Thread* current_thread = GetCurrentThread();
+
+    if (processor_id >= 0) {
+        if (current_thread == this) {
+            scheduler.SchedulePrepend(current_priority, processor_id, this);
+        } else {
+            scheduler.Schedule(current_priority, processor_id, this);
+        }
+    }
+
+    for (u32 core = 0; core < GlobalScheduler::NUM_CPU_CORES; core++) {
+        if (core != processor_id && ((affinity_mask >> core) & 1) != 0) {
+            scheduler.Suggest(current_priority, core, this);
+        }
+    }
+
+    scheduler.SetReselectionPending();
+}
+
+void Thread::AdjustSchedulingOnAffinity(u64 old_affinity_mask, s32 old_core) {
+    auto& scheduler = Core::System::GetInstance().GlobalScheduler();
+    if (GetSchedulingStatus() != ThreadSchedStatus::Runnable ||
+        current_priority >= THREADPRIO_COUNT) {
+        return;
+    }
+
+    for (u32 core = 0; core < GlobalScheduler::NUM_CPU_CORES; core++) {
+        if (((old_affinity_mask >> core) & 1) != 0) {
+            if (core == old_core) {
+                scheduler.Unschedule(current_priority, core, this);
+            } else {
+                scheduler.Unsuggest(current_priority, core, this);
+            }
+        }
+    }
+
+    for (u32 core = 0; core < GlobalScheduler::NUM_CPU_CORES; core++) {
+        if (((affinity_mask >> core) & 1) != 0) {
+            if (core == processor_id) {
+                scheduler.Schedule(current_priority, core, this);
+            } else {
+                scheduler.Suggest(current_priority, core, this);
+            }
+        }
+    }
+
+    scheduler.SetReselectionPending();
+}
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 /**

src/core/hle/kernel/thread.h

@@ -75,6 +75,26 @@ enum class ThreadActivity : u32 {
     Paused = 1,
 };
 
+enum class ThreadSchedStatus : u32 {
+    None = 0,
+    Paused = 1,
+    Runnable = 2,
+    Exited = 3,
+};
+
+enum class ThreadSchedFlags : u32 {
+    ProcessPauseFlag = 1 << 4,
+    ThreadPauseFlag = 1 << 5,
+    ProcessDebugPauseFlag = 1 << 6,
+    KernelInitPauseFlag = 1 << 8,
+};
+
+enum class ThreadSchedMasks : u32 {
+    LowMask = 0x000f,
+    HighMask = 0xfff0,
+    ForcePauseMask = 0x0070,
+};
+
 class Thread final : public WaitObject {
 public:
     using MutexWaitingThreads = std::vector<SharedPtr<Thread>>;
@@ -278,6 +298,10 @@ public:
         return processor_id;
     }
 
+    void SetProcessorID(s32 new_core) {
+        processor_id = new_core;
+    }
+
     Process* GetOwnerProcess() {
         return owner_process;
     }
@@ -295,6 +319,9 @@ public:
     }
 
     void ClearWaitObjects() {
+        for (const auto& waiting_object : wait_objects) {
+            waiting_object->RemoveWaitingThread(this);
+        }
         wait_objects.clear();
     }
 
@@ -383,11 +410,47 @@ public:
     /// Sleeps this thread for the given amount of nanoseconds.
     void Sleep(s64 nanoseconds);
 
+    /// Yields this thread without rebalancing loads.
+    bool YieldSimple();
+
+    /// Yields this thread and does a load rebalancing.
+    bool YieldAndBalanceLoad();
+
+    /// Yields this thread and if the core is left idle, loads are rebalanced
+    bool YieldAndWaitForLoadBalancing();
+
+    void IncrementYieldCount() {
+        yield_count++;
+    }
+
+    u64 GetYieldCount() const {
+        return yield_count;
+    }
+
+    ThreadSchedStatus GetSchedulingStatus() const {
+        return static_cast<ThreadSchedStatus>(scheduling_state &
+                                              static_cast<u32>(ThreadSchedMasks::LowMask));
+    }
+
+    bool IsRunning() const {
+        return is_running;
+    }
+
+    void SetIsRunning(bool value) {
+        is_running = value;
+    }
+
 private:
     explicit Thread(KernelCore& kernel);
     ~Thread() override;
 
-    void ChangeScheduler();
+    void SetSchedulingStatus(ThreadSchedStatus new_status);
+    void SetCurrentPriority(u32 new_priority);
+    ResultCode SetCoreAndAffinityMask(s32 new_core, u64 new_affinity_mask);
+
+    void AdjustSchedulingOnStatus(u32 old_flags);
+    void AdjustSchedulingOnPriority(u32 old_priority);
+    void AdjustSchedulingOnAffinity(u64 old_affinity_mask, s32 old_core);
 
     Core::ARM_Interface::ThreadContext context{};
 
@@ -409,6 +472,8 @@ private:
 
     u64 total_cpu_time_ticks = 0; ///< Total CPU running ticks.
     u64 last_running_ticks = 0;   ///< CPU tick when thread was last running
+    u64 yield_count = 0;          ///< Number of redundant yields carried by this thread.
+                                  ///< a redundant yield is one where no scheduling is changed
 
     s32 processor_id = 0;
 
@@ -453,6 +518,13 @@ private:
 
     ThreadActivity activity = ThreadActivity::Normal;
 
+    s32 ideal_core_override = -1;
+    u64 affinity_mask_override = 0x1;
+    u32 affinity_override_count = 0;
+
+    u32 scheduling_state = 0;
+    bool is_running = false;
+
     std::string name;
 };
 

src/core/hle/kernel/wait_object.cpp

@@ -6,6 +6,9 @@
 #include "common/assert.h"
 #include "common/common_types.h"
 #include "common/logging/log.h"
+#include "core/core.h"
+#include "core/core_cpu.h"
+#include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/object.h"
 #include "core/hle/kernel/process.h"
 #include "core/hle/kernel/thread.h"
@@ -82,9 +85,6 @@ void WaitObject::WakeupWaitingThread(SharedPtr<Thread> thread) {
 
     const std::size_t index = thread->GetWaitObjectIndex(this);
 
-    for (const auto& object : thread->GetWaitObjects()) {
-        object->RemoveWaitingThread(thread.get());
-    }
     thread->ClearWaitObjects();
 
     thread->CancelWakeupTimer();
@@ -95,6 +95,7 @@ void WaitObject::WakeupWaitingThread(SharedPtr<Thread> thread) {
     }
     if (resume) {
         thread->ResumeFromWait();
+        Core::System::GetInstance().PrepareReschedule(thread->GetProcessorID());
     }
 }
 

src/yuzu/debugger/wait_tree.cpp

@@ -66,10 +66,7 @@ std::vector<std::unique_ptr<WaitTreeThread>> WaitTreeItem::MakeThreadItemList()
     };
 
     const auto& system = Core::System::GetInstance();
-    add_threads(system.Scheduler(0).GetThreadList());
+    add_threads(system.GlobalScheduler().GetThreadList());
-    add_threads(system.Scheduler(1).GetThreadList());
-    add_threads(system.Scheduler(2).GetThreadList());
-    add_threads(system.Scheduler(3).GetThreadList());
 
     return item_list;
 }