整理

include/boost/atomic/detail/wait_ops_generic.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_generic.hpp
+ *
+ * This header contains generic (lock-based) implementation of the waiting/notifying atomic operations.
+ *
+ * This backend is used when lock-free atomic operations are available but native waiting/notifying operations are not.
+ */
+
+#ifndef BOOST_ATOMIC_DETAIL_WAIT_OPS_GENERIC_HPP_INCLUDED_
+#define BOOST_ATOMIC_DETAIL_WAIT_OPS_GENERIC_HPP_INCLUDED_
+
+#include <cstddef>
+#include <chrono>
+#include <boost/memory_order.hpp>
+#include <boost/atomic/thread_pause.hpp>
+#include <boost/atomic/detail/config.hpp>
+#if !defined(BOOST_WINDOWS)
+#include <time.h>
+#include <type_traits>
+#include <boost/atomic/posix_clock_traits_fwd.hpp>
+#include <boost/atomic/detail/has_posix_clock_traits.hpp>
+#endif
+#include <boost/atomic/detail/chrono.hpp>
+#include <boost/atomic/detail/lock_pool.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 {
+
+//! Generic implementation of waiting/notifying operations
+template< typename Base, bool Interprocess >
+struct wait_operations_generic;
+
+template< typename Base >
+struct wait_operations_generic< Base, false > :
+    public Base
+{
+    using base_type = Base;
+    using storage_type = typename base_type::storage_type;
+    using scoped_lock = lock_pool::scoped_lock< base_type::storage_alignment, true >;
+    using scoped_wait_state = lock_pool::scoped_wait_state< base_type::storage_alignment >;
+
+    static constexpr bool always_has_native_wait_notify = false;
+
+    static BOOST_FORCEINLINE bool has_native_wait_notify(storage_type const volatile&) noexcept
+    {
+        return false;
+    }
+
+    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);
+        if (new_val == old_val)
+        {
+            scoped_wait_state wait_state(&storage);
+            new_val = base_type::load(storage, order);
+            while (new_val == old_val)
+            {
+                wait_state.wait();
+                new_val = base_type::load(storage, order);
+            }
+        }
+
+        return new_val;
+    }
+
+private:
+    template< typename Clock >
+    static BOOST_FORCEINLINE storage_type wait_until_fallback
+    (
+        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);
+        if (new_val == old_val)
+        {
+            scoped_wait_state wait_state(&storage);
+            while (new_val == old_val)
+            {
+                const std::chrono::nanoseconds nsec = atomics::detail::chrono::ceil< std::chrono::nanoseconds >(timeout - now);
+                if (nsec.count() <= 0)
+                {
+                    timed_out = true;
+                    break;
+                }
+
+                wait_state.wait_for(nsec);
+
+                now = Clock::now();
+                new_val = base_type::load(storage, order);
+            }
+        }
+
+        return new_val;
+    }
+
+#if !defined(BOOST_WINDOWS)
+
+    template< typename Clock >
+    static BOOST_FORCEINLINE storage_type wait_until_abs_timeout
+    (
+        storage_type const volatile& storage,
+        storage_type old_val,
+        typename Clock::time_point timeout,
+        memory_order order,
+        bool& timed_out
+    ) noexcept
+    {
+        storage_type new_val = base_type::load(storage, order);
+        if (new_val == old_val)
+        {
+            scoped_wait_state wait_state(&storage);
+            const timespec abs_timeout(posix_clock_traits< Clock >::to_timespec(timeout));
+            if (BOOST_LIKELY(abs_timeout.tv_sec >= 0))
+            {
+                while (new_val == old_val)
+                {
+                    const bool wait_timed_out = wait_state.wait_until(posix_clock_traits< Clock >::clock_id, abs_timeout);
+                    new_val = base_type::load(storage, order);
+
+                    if (wait_timed_out)
+                        goto timeout_expired;
+                }
+            }
+            else
+            {
+            timeout_expired:
+                timed_out = new_val == old_val;
+            }
+        }
+
+        return new_val;
+    }
+
+    template< typename Clock >
+    static BOOST_FORCEINLINE storage_type wait_until_dispatch
+    (
+        storage_type const volatile& storage,
+        storage_type old_val,
+        typename Clock::time_point timeout,
+        memory_order order,
+        bool& timed_out,
+        std::true_type
+    ) noexcept
+    {
+        return wait_until_abs_timeout< Clock >(storage, old_val, timeout, order, timed_out);
+    }
+
+    template< typename Clock >
+    static BOOST_FORCEINLINE storage_type wait_until_dispatch
+    (
+        storage_type const volatile& storage,
+        storage_type old_val,
+        typename Clock::time_point timeout,
+        memory_order order,
+        bool& timed_out,
+        std::false_type
+    ) noexcept(noexcept(Clock::now()))
+    {
+        return wait_until_fallback< Clock >(storage, old_val, timeout, Clock::now(), order, timed_out);
+    }
+
+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(wait_until_dispatch< Clock >(
+        storage, old_val, timeout, order, timed_out, std::integral_constant< bool, has_posix_clock_traits< Clock >::value >())))
+    {
+        return wait_until_dispatch< Clock >(storage, old_val, timeout, order, timed_out, std::integral_constant< bool, has_posix_clock_traits< Clock >::value >());
+    }
+
+#else // !defined(BOOST_WINDOWS)
+
+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(wait_until_fallback< Clock >(storage, old_val, timeout, Clock::now(), order, timed_out)))
+    {
+        return wait_until_fallback< Clock >(storage, old_val, timeout, Clock::now(), order, timed_out);
+    }
+
+#endif // !defined(BOOST_WINDOWS)
+
+    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_fallback< std::chrono::steady_clock >(storage, old_val, now + timeout, now, order, timed_out);
+    }
+
+    static BOOST_FORCEINLINE void notify_one(storage_type volatile& storage) noexcept
+    {
+        scoped_lock lock(&storage);
+        lock_pool::notify_one(lock.get_lock_state(), &storage);
+    }
+
+    static BOOST_FORCEINLINE void notify_all(storage_type volatile& storage) noexcept
+    {
+        scoped_lock lock(&storage);
+        lock_pool::notify_all(lock.get_lock_state(), &storage);
+    }
+};
+
+template< typename Base >
+struct wait_operations_generic< Base, true > :
+    public Base
+{
+    using base_type = Base;
+    using storage_type = typename base_type::storage_type;
+
+    static constexpr bool always_has_native_wait_notify = false;
+
+private:
+    static constexpr unsigned int fast_loop_count = 16u;
+
+public:
+    static BOOST_FORCEINLINE bool has_native_wait_notify(storage_type const volatile&) noexcept
+    {
+        return false;
+    }
+
+    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);
+        if (new_val == old_val)
+        {
+            for (unsigned int i = 0u; i < fast_loop_count; ++i)
+            {
+                atomics::thread_pause();
+                new_val = base_type::load(storage, order);
+                if (new_val != old_val)
+                    goto finish;
+            }
+
+            do
+            {
+                atomics::detail::wait_some();
+                new_val = base_type::load(storage, order);
+            }
+            while (new_val == old_val);
+        }
+
+    finish:
+        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);
+        if (new_val == old_val)
+        {
+            for (unsigned int i = 0u; i < fast_loop_count; ++i)
+            {
+                if ((now - timeout).count() >= 0)
+                {
+                    timed_out = true;
+                    goto finish;
+                }
+
+                atomics::thread_pause();
+                now = Clock::now();
+
+                new_val = base_type::load(storage, order);
+                if (new_val != old_val)
+                    goto finish;
+            }
+
+            do
+            {
+                if ((now - timeout).count() >= 0)
+                {
+                    timed_out = true;
+                    goto finish;
+                }
+
+                atomics::detail::wait_some();
+                now = Clock::now();
+                new_val = base_type::load(storage, order);
+            }
+            while (new_val == old_val);
+        }
+
+    finish:
+        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(wait_until_impl< Clock >(storage, old_val, timeout, Clock::now(), order, timed_out)))
+    {
+        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&) noexcept
+    {
+    }
+
+    static BOOST_FORCEINLINE void notify_all(storage_type volatile&) noexcept
+    {
+    }
+};
+
+template< typename Base, std::size_t Size, bool Interprocess >
+struct wait_operations< Base, Size, true, Interprocess > :
+    public wait_operations_generic< Base, Interprocess >
+{
+};
+
+} // namespace detail
+} // namespace atomics
+} // namespace boost
+
+#include <boost/atomic/detail/footer.hpp>
+
+#endif // BOOST_ATOMIC_DETAIL_WAIT_OPS_GENERIC_HPP_INCLUDED_