整理

include/boost/atomic/detail/wait_ops_dragonfly_umtx.hpp

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+/*
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * Copyright (c) 2020-2025 Andrey Semashev
+ */
+/*!
+ * \file   atomic/detail/wait_ops_dragonfly_umtx.hpp
+ *
+ * This header contains implementation of the waiting/notifying atomic operations based on DragonFly BSD umtx.
+ * https://man.dragonflybsd.org/?command=umtx&section=2
+ */
+
+#ifndef BOOST_ATOMIC_DETAIL_WAIT_OPS_DRAGONFLY_UMTX_HPP_INCLUDED_
+#define BOOST_ATOMIC_DETAIL_WAIT_OPS_DRAGONFLY_UMTX_HPP_INCLUDED_
+
+#include <unistd.h>
+#include <cstdint>
+#include <limits>
+#include <chrono>
+#include <boost/memory_order.hpp>
+#include <boost/atomic/detail/config.hpp>
+#include <boost/atomic/detail/chrono.hpp>
+#include <boost/atomic/detail/wait_operations_fwd.hpp>
+#include <boost/atomic/detail/header.hpp>
+
+#ifdef BOOST_HAS_PRAGMA_ONCE
+#pragma once
+#endif
+
+namespace boost {
+namespace atomics {
+namespace detail {
+
+template< typename Base, bool Interprocess >
+struct wait_operations< Base, sizeof(int), true, Interprocess > :
+    public Base
+{
+    using base_type = Base;
+    using storage_type = typename base_type::storage_type;
+
+public:
+    static constexpr bool always_has_native_wait_notify = true;
+
+    static BOOST_FORCEINLINE bool has_native_wait_notify(storage_type const volatile&) noexcept
+    {
+        return true;
+    }
+
+    static BOOST_FORCEINLINE storage_type wait(storage_type const volatile& storage, storage_type old_val, memory_order order) noexcept
+    {
+        storage_type new_val = base_type::load(storage, order);
+        while (new_val == old_val)
+        {
+            umtx_sleep(reinterpret_cast< int* >(const_cast< storage_type* >(&storage)), static_cast< int >(old_val), 0);
+            new_val = base_type::load(storage, order);
+        }
+
+        return new_val;
+    }
+
+private:
+    template< typename Clock >
+    static BOOST_FORCEINLINE storage_type wait_until_impl
+    (
+        storage_type const volatile& storage,
+        storage_type old_val,
+        typename Clock::time_point timeout,
+        typename Clock::time_point now,
+        memory_order order,
+        bool& timed_out
+    ) noexcept(noexcept(Clock::now()))
+    {
+        storage_type new_val = base_type::load(storage, order);
+        while (new_val == old_val)
+        {
+            const std::int64_t usec = atomics::detail::chrono::ceil< std::chrono::microseconds >(timeout - now).count();
+            if (usec <= 0)
+            {
+                timed_out = true;
+                break;
+            }
+
+            umtx_sleep
+            (
+                reinterpret_cast< int* >(const_cast< storage_type* >(&storage)),
+                static_cast< int >(old_val),
+                usec <= (std::numeric_limits< int >::max)() ? static_cast< int >(usec) : (std::numeric_limits< int >::max)()
+            );
+
+            now = Clock::now();
+            new_val = base_type::load(storage, order);
+        }
+
+        return new_val;
+    }
+
+public:
+    template< typename Clock, typename Duration >
+    static BOOST_FORCEINLINE storage_type wait_until
+    (
+        storage_type const volatile& storage,
+        storage_type old_val,
+        std::chrono::time_point< Clock, Duration > timeout,
+        memory_order order,
+        bool& timed_out
+    ) noexcept(noexcept(Clock::now()))
+    {
+        return wait_until_impl< Clock >(storage, old_val, timeout, Clock::now(), order, timed_out);
+    }
+
+    template< typename Rep, typename Period >
+    static BOOST_FORCEINLINE storage_type wait_for
+    (
+        storage_type const volatile& storage,
+        storage_type old_val,
+        std::chrono::duration< Rep, Period > timeout,
+        memory_order order,
+        bool& timed_out
+    ) noexcept
+    {
+        const std::chrono::steady_clock::time_point now = std::chrono::steady_clock::now();
+        return wait_until_impl< std::chrono::steady_clock >(storage, old_val, now + timeout, now, order, timed_out);
+    }
+
+    static BOOST_FORCEINLINE void notify_one(storage_type volatile& storage) noexcept
+    {
+        umtx_wakeup(reinterpret_cast< int* >(const_cast< storage_type* >(&storage)), 1);
+    }
+
+    static BOOST_FORCEINLINE void notify_all(storage_type volatile& storage) noexcept
+    {
+        umtx_wakeup(reinterpret_cast< int* >(const_cast< storage_type* >(&storage)), 0);
+    }
+};
+
+} // namespace detail
+} // namespace atomics
+} // namespace boost
+
+#include <boost/atomic/detail/footer.hpp>
+
+#endif // BOOST_ATOMIC_DETAIL_WAIT_OPS_DRAGONFLY_UMTX_HPP_INCLUDED_