1 files changed, 126 insertions, 0 deletions
diff --git a/Kernel/Time/TimerQueue.h b/Kernel/Time/TimerQueue.h
new file mode 100644
index 0000000000..7258c33eca
--- /dev/null
+++ b/Kernel/Time/TimerQueue.h
@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/AtomicRefCounted.h>
+#include <AK/Function.h>
+#include <AK/IntrusiveList.h>
+#include <AK/OwnPtr.h>
+#include <AK/Time.h>
+#include <Kernel/Library/NonnullLockRefPtr.h>
+#include <Kernel/Time/TimeManagement.h>
+
+namespace Kernel {
+
+AK_TYPEDEF_DISTINCT_ORDERED_ID(u64, TimerId);
+
+class Timer final : public AtomicRefCounted<Timer> {
+    friend class TimerQueue;
+
+public:
+    void setup(clockid_t clock_id, Duration expires, Function<void()>&& callback)
+    {
+        VERIFY(!is_queued());
+        m_clock_id = clock_id;
+        m_expires = expires;
+        m_callback = move(callback);
+    }
+
+    ~Timer()
+    {
+        VERIFY(!is_queued());
+    }
+
+    Duration remaining() const;
+
+private:
+    TimerId m_id;
+    clockid_t m_clock_id;
+    Duration m_expires;
+    Duration m_remaining {};
+    Function<void()> m_callback;
+    Atomic<bool> m_cancelled { false };
+    Atomic<bool> m_callback_finished { false };
+    Atomic<bool> m_in_use { false };
+
+    bool operator<(Timer const& rhs) const
+    {
+        return m_expires < rhs.m_expires;
+    }
+    bool operator>(Timer const& rhs) const
+    {
+        return m_expires > rhs.m_expires;
+    }
+    bool operator==(Timer const& rhs) const
+    {
+        return m_id == rhs.m_id;
+    }
+
+    void clear_cancelled() { return m_cancelled.store(false, AK::memory_order_release); }
+    bool set_cancelled() { return m_cancelled.exchange(true, AK::memory_order_acq_rel); }
+
+    bool is_in_use() { return m_in_use.load(AK::memory_order_acquire); };
+    void set_in_use() { m_in_use.store(true, AK::memory_order_release); }
+    void clear_in_use() { return m_in_use.store(false, AK::memory_order_release); }
+
+    bool is_callback_finished() const { return m_callback_finished.load(AK::memory_order_acquire); }
+    void clear_callback_finished() { m_callback_finished.store(false, AK::memory_order_release); }
+    void set_callback_finished() { m_callback_finished.store(true, AK::memory_order_release); }
+
+    Duration now(bool) const;
+
+    bool is_queued() const { return m_list_node.is_in_list(); }
+
+public:
+    IntrusiveListNode<Timer> m_list_node;
+    using List = IntrusiveList<&Timer::m_list_node>;
+};
+
+class TimerQueue {
+    friend class Timer;
+
+public:
+    TimerQueue();
+    static TimerQueue& the();
+
+    TimerId add_timer(NonnullRefPtr<Timer>&&);
+    bool add_timer_without_id(NonnullRefPtr<Timer>, clockid_t, Duration const&, Function<void()>&&);
+    bool cancel_timer(Timer& timer, bool* was_in_use = nullptr);
+    void fire();
+
+private:
+    struct Queue {
+        Timer::List list;
+        Duration next_timer_due {};
+    };
+    void remove_timer_locked(Queue&, Timer&);
+    void update_next_timer_due(Queue&);
+    void add_timer_locked(NonnullRefPtr<Timer>);
+
+    Queue& queue_for_timer(Timer& timer)
+    {
+        switch (timer.m_clock_id) {
+        case CLOCK_MONOTONIC:
+        case CLOCK_MONOTONIC_COARSE:
+        case CLOCK_MONOTONIC_RAW:
+            return m_timer_queue_monotonic;
+        case CLOCK_REALTIME:
+        case CLOCK_REALTIME_COARSE:
+            return m_timer_queue_realtime;
+        default:
+            VERIFY_NOT_REACHED();
+        }
+    }
+
+    u64 m_timer_id_count { 0 };
+    u64 m_ticks_per_second { 0 };
+    Queue m_timer_queue_monotonic;
+    Queue m_timer_queue_realtime;
+    Timer::List m_timers_executing;
+};
+
+}