3 files changed, 210 insertions, 0 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 2f1fd7880..76f70a844 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -53,6 +53,8 @@ add_library(core STATIC
     hle/kernel/process.h
     hle/kernel/resource_limit.cpp
     hle/kernel/resource_limit.h
+    hle/kernel/scheduler.cpp
+    hle/kernel/scheduler.h
     hle/kernel/server_port.cpp
     hle/kernel/server_port.h
     hle/kernel/server_session.cpp
diff --git a/src/core/hle/kernel/scheduler.cpp b/src/core/hle/kernel/scheduler.cpp
new file mode 100644
index 000000000..2fe0d5a38
--- /dev/null
+++ b/src/core/hle/kernel/scheduler.cpp
@@ -0,0 +1,134 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "core/core_timing.h"
+#include "core/hle/kernel/process.h"
+#include "core/hle/kernel/scheduler.h"
+
+namespace Kernel {
+
+Scheduler::Scheduler(std::shared_ptr<ARM_Interface> cpu_core) : cpu_core(cpu_core) {}
+
+Scheduler::~Scheduler() {
+    for (auto& thread : thread_list) {
+        thread->Stop();
+    }
+}
+
+bool Scheduler::HaveReadyThreads() {
+    return ready_queue.get_first() != nullptr;
+}
+
+Thread* Scheduler::GetCurrentThread() const {
+    return current_thread.get();
+}
+
+Thread* Scheduler::PopNextReadyThread() {
+    Thread* next = nullptr;
+    Thread* thread = GetCurrentThread();
+
+    if (thread && thread->status == THREADSTATUS_RUNNING) {
+        // We have to do better than the current thread.
+        // This call returns null when that's not possible.
+        next = ready_queue.pop_first_better(thread->current_priority);
+        if (!next) {
+            // Otherwise just keep going with the current thread
+            next = thread;
+        }
+    } else {
+        next = ready_queue.pop_first();
+    }
+
+    return next;
+}
+
+void Scheduler::SwitchContext(Thread* new_thread) {
+    Thread* previous_thread = GetCurrentThread();
+
+    // Save context for previous thread
+    if (previous_thread) {
+        previous_thread->last_running_ticks = CoreTiming::GetTicks();
+        cpu_core->SaveContext(previous_thread->context);
+
+        if (previous_thread->status == 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.push_front(previous_thread->current_priority, previous_thread);
+            previous_thread->status = THREADSTATUS_READY;
+        }
+    }
+
+    // Load context of new thread
+    if (new_thread) {
+        ASSERT_MSG(new_thread->status == THREADSTATUS_READY,
+                   "Thread must be ready to become running.");
+
+        // Cancel any outstanding wakeup events for this thread
+        new_thread->CancelWakeupTimer();
+
+        auto previous_process = Kernel::g_current_process;
+
+        current_thread = new_thread;
+
+        ready_queue.remove(new_thread->current_priority, new_thread);
+        new_thread->status = THREADSTATUS_RUNNING;
+
+        if (previous_process != current_thread->owner_process) {
+            Kernel::g_current_process = current_thread->owner_process;
+            SetCurrentPageTable(&Kernel::g_current_process->vm_manager.page_table);
+        }
+
+        cpu_core->LoadContext(new_thread->context);
+        cpu_core->SetTlsAddress(new_thread->GetTLSAddress());
+    } else {
+        current_thread = nullptr;
+        // Note: We do not reset the current process and current page table when idling because
+        // technically we haven't changed processes, our threads are just paused.
+    }
+}
+
+void Scheduler::Reschedule() {
+    Thread* cur = GetCurrentThread();
+    Thread* next = PopNextReadyThread();
+
+    if (cur && next) {
+        LOG_TRACE(Kernel, "context switch %u -> %u", cur->GetObjectId(), next->GetObjectId());
+    } else if (cur) {
+        LOG_TRACE(Kernel, "context switch %u -> idle", cur->GetObjectId());
+    } else if (next) {
+        LOG_TRACE(Kernel, "context switch idle -> %u", next->GetObjectId());
+    }
+
+    SwitchContext(next);
+}
+
+void Scheduler::AddThread(SharedPtr<Thread> thread, u32 priority) {
+    thread_list.push_back(thread);
+    ready_queue.prepare(priority);
+}
+
+void Scheduler::RemoveThread(Thread* thread) {
+    thread_list.erase(std::remove(thread_list.begin(), thread_list.end(), thread),
+                      thread_list.end());
+}
+
+void Scheduler::ScheduleThread(Thread* thread, u32 priority) {
+    ASSERT(thread->status == THREADSTATUS_READY);
+    ready_queue.push_back(priority, thread);
+}
+
+void Scheduler::UnscheduleThread(Thread* thread, u32 priority) {
+    ASSERT(thread->status == THREADSTATUS_READY);
+    ready_queue.remove(priority, thread);
+}
+
+void Scheduler::SetThreadPriority(Thread* thread, u32 priority) {
+    // If thread was ready, adjust queues
+    if (thread->status == THREADSTATUS_READY)
+        ready_queue.move(thread, thread->current_priority, priority);
+    else
+        ready_queue.prepare(priority);
+}
+
+} // namespace Kernel
diff --git a/src/core/hle/kernel/scheduler.h b/src/core/hle/kernel/scheduler.h
new file mode 100644
index 000000000..72e658ec6
--- /dev/null
+++ b/src/core/hle/kernel/scheduler.h
@@ -0,0 +1,74 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <vector>
+#include "common/common_types.h"
+#include "common/thread_queue_list.h"
+#include "core/arm/arm_interface.h"
+#include "core/hle/kernel/thread.h"
+
+namespace Kernel {
+
+class Scheduler final {
+public:
+    Scheduler(std::shared_ptr<ARM_Interface> cpu_core);
+    ~Scheduler();
+
+    /// Returns whether there are any threads that are ready to run.
+    bool HaveReadyThreads();
+
+    /// Reschedules to the next available thread (call after current thread is suspended)
+    void Reschedule();
+
+    /// Gets the current running thread
+    Thread* GetCurrentThread() const;
+
+    /// Adds a new thread to the scheduler
+    void AddThread(SharedPtr<Thread> thread, u32 priority);
+
+    /// Removes a thread from the scheduler
+    void RemoveThread(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);
+
+    /// Returns a list of all threads managed by the scheduler
+    const std::vector<SharedPtr<Thread>>& GetThreadList() const {
+        return thread_list;
+    }
+
+private:
+    /**
+     * Pops and returns the next thread from the thread queue
+     * @return A pointer to the next ready thread
+     */
+    Thread* PopNextReadyThread();
+
+    /**
+     * 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);
+
+    /// Lists all thread ids that aren't deleted/etc.
+    std::vector<SharedPtr<Thread>> thread_list;
+
+    /// Lists only ready thread ids.
+    Common::ThreadQueueList<Thread*, THREADPRIO_LOWEST + 1> ready_queue;
+
+    SharedPtr<Thread> current_thread = nullptr;
+
+    std::shared_ptr<ARM_Interface> cpu_core;
+};
+
+} // namespace Kernel