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// Copyright 2020 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
// This file references various implementation details from Atmosphere, an open-source firmware for
// the Nintendo Switch. Copyright 2018-2020 Atmosphere-NX.
#pragma once
#include <atomic>
#include "common/common_types.h"
#include "common/spin_lock.h"
#include "core/hle/kernel/global_scheduler_context.h"
#include "core/hle/kernel/k_priority_queue.h"
#include "core/hle/kernel/k_scheduler_lock.h"
#include "core/hle/kernel/k_scoped_lock.h"
namespace Common {
class Fiber;
}
namespace Core {
class System;
}
namespace Kernel {
class KernelCore;
class Process;
class SchedulerLock;
class KThread;
class KScheduler final {
public:
explicit KScheduler(Core::System& system, s32 core_id);
~KScheduler();
/// Reschedules to the next available thread (call after current thread is suspended)
void RescheduleCurrentCore();
/// Reschedules cores pending reschedule, to be called on EnableScheduling.
static void RescheduleCores(KernelCore& kernel, u64 cores_pending_reschedule);
/// The next two are for SingleCore Only.
/// Unload current thread before preempting core.
void Unload(KThread* thread);
/// Reload current thread after core preemption.
void Reload(KThread* thread);
/// Gets the current running thread
[[nodiscard]] KThread* GetCurrentThread() const;
/// Returns true if the scheduler is idle
[[nodiscard]] bool IsIdle() const {
return GetCurrentThread() == idle_thread;
}
/// Gets the timestamp for the last context switch in ticks.
[[nodiscard]] u64 GetLastContextSwitchTicks() const;
[[nodiscard]] bool ContextSwitchPending() const {
return state.needs_scheduling.load(std::memory_order_relaxed);
}
void Initialize();
void OnThreadStart();
[[nodiscard]] std::shared_ptr<Common::Fiber>& ControlContext() {
return switch_fiber;
}
[[nodiscard]] const std::shared_ptr<Common::Fiber>& ControlContext() const {
return switch_fiber;
}
[[nodiscard]] u64 UpdateHighestPriorityThread(KThread* highest_thread);
/**
* Takes a thread and moves it to the back of the it's priority list.
*
* @note This operation can be redundant and no scheduling is changed if marked as so.
*/
static void YieldWithoutCoreMigration(KernelCore& kernel);
/**
* 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.
*
* @note This operation can be redundant and no scheduling is changed if marked as so.
*/
static void YieldWithCoreMigration(KernelCore& kernel);
/**
* Takes a thread and moves it out of the scheduling queue.
* and into the suggested queue. If no thread can be scheduled afterwards in that core,
* a suggested thread is obtained instead.
*
* @note This operation can be redundant and no scheduling is changed if marked as so.
*/
static void YieldToAnyThread(KernelCore& kernel);
static void ClearPreviousThread(KernelCore& kernel, KThread* thread);
/// Notify the scheduler a thread's status has changed.
static void OnThreadStateChanged(KernelCore& kernel, KThread* thread, ThreadState old_state);
/// Notify the scheduler a thread's priority has changed.
static void OnThreadPriorityChanged(KernelCore& kernel, KThread* thread, s32 old_priority);
/// Notify the scheduler a thread's core and/or affinity mask has changed.
static void OnThreadAffinityMaskChanged(KernelCore& kernel, KThread* thread,
const KAffinityMask& old_affinity, s32 old_core);
static bool CanSchedule(KernelCore& kernel);
static bool IsSchedulerUpdateNeeded(const KernelCore& kernel);
static void SetSchedulerUpdateNeeded(KernelCore& kernel);
static void ClearSchedulerUpdateNeeded(KernelCore& kernel);
static void DisableScheduling(KernelCore& kernel);
static void EnableScheduling(KernelCore& kernel, u64 cores_needing_scheduling);
[[nodiscard]] static u64 UpdateHighestPriorityThreads(KernelCore& kernel);
private:
friend class GlobalSchedulerContext;
/**
* Takes care of selecting the new scheduled threads in three steps:
*
* 1. 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.
*
* 2. 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.
*
* 3. 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.
*
* returns the cores needing scheduling.
*/
[[nodiscard]] static u64 UpdateHighestPriorityThreadsImpl(KernelCore& kernel);
[[nodiscard]] static KSchedulerPriorityQueue& GetPriorityQueue(KernelCore& kernel);
void RotateScheduledQueue(s32 core_id, s32 priority);
void Schedule() {
ASSERT(GetCurrentThread()->GetDisableDispatchCount() == 1);
this->ScheduleImpl();
}
/// Switches the CPU's active thread context to that of the specified thread
void ScheduleImpl();
/// When a thread wakes up, it must run this through it's new scheduler
void SwitchContextStep2();
/**
* Called on every context switch to update the internal timestamp
* This also updates the running time ticks for the given thread and
* process using the following difference:
*
* ticks += most_recent_ticks - last_context_switch_ticks
*
* The internal tick timestamp for the scheduler is simply the
* most recent tick count retrieved. No special arithmetic is
* applied to it.
*/
void UpdateLastContextSwitchTime(KThread* thread, Process* process);
static void OnSwitch(void* this_scheduler);
void SwitchToCurrent();
KThread* prev_thread{};
std::atomic<KThread*> current_thread{};
KThread* idle_thread;
std::shared_ptr<Common::Fiber> switch_fiber{};
struct SchedulingState {
std::atomic<bool> needs_scheduling;
bool interrupt_task_thread_runnable{};
bool should_count_idle{};
u64 idle_count{};
KThread* highest_priority_thread{};
void* idle_thread_stack{};
};
SchedulingState state;
Core::System& system;
u64 last_context_switch_time{};
const s32 core_id;
Common::SpinLock guard{};
};
class KScopedSchedulerLock : KScopedLock<GlobalSchedulerContext::LockType> {
public:
explicit KScopedSchedulerLock(KernelCore& kernel);
~KScopedSchedulerLock();
};
} // namespace Kernel
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