bf1666fb0b
When we initially implemented the C++20 synchronization library, we reluctantly accepted for the implementation to be backported to C++03 upon request from the person who provided the patch. This was when we were only starting to have experience with the issues this can create, so we flinched. Nowadays, we have a much stricter stance about not backporting features to previous standards. We have recently started fixing several bugs (and near bugs) in our implementation of the synchronization library. A recurring theme during these reviews has been how difficult to understand the current code is, and upon inspection it becomes clear that being able to use a few recent C++ features (in particular lambdas) would help a great deal. The code would still be pretty intricate, but it would be a lot easier to reason about the flow of callbacks through things like __thread_poll_with_backoff. As a result, this patch drops support for the synchronization library before C++20. This makes us more strictly conforming and opens the door to major simplifications, in particular around atomic_wait which was supported all the way to C++03. This change will probably have some impact on downstream users, however since the C++20 synchronization library was added only in LLVM 10 (~3 years ago) and it's quite a niche feature, the set of people trying to use this part of the library before C++20 should be reasonably small.
188 lines
6.9 KiB
C++
188 lines
6.9 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ATOMIC_ATOMIC_FLAG_H
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#define _LIBCPP___ATOMIC_ATOMIC_FLAG_H
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#include <__atomic/atomic_sync.h>
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#include <__atomic/contention_t.h>
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#include <__atomic/cxx_atomic_impl.h>
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#include <__atomic/memory_order.h>
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#include <__chrono/duration.h>
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#include <__config>
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#include <__memory/addressof.h>
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#include <__thread/support.h>
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#include <cstdint>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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struct atomic_flag {
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__cxx_atomic_impl<_LIBCPP_ATOMIC_FLAG_TYPE> __a_;
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_LIBCPP_HIDE_FROM_ABI bool test(memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT {
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return _LIBCPP_ATOMIC_FLAG_TYPE(true) == __cxx_atomic_load(&__a_, __m);
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}
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_LIBCPP_HIDE_FROM_ABI bool test(memory_order __m = memory_order_seq_cst) const _NOEXCEPT {
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return _LIBCPP_ATOMIC_FLAG_TYPE(true) == __cxx_atomic_load(&__a_, __m);
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}
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_LIBCPP_HIDE_FROM_ABI bool test_and_set(memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT {
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return __cxx_atomic_exchange(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(true), __m);
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}
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_LIBCPP_HIDE_FROM_ABI bool test_and_set(memory_order __m = memory_order_seq_cst) _NOEXCEPT {
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return __cxx_atomic_exchange(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(true), __m);
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}
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_LIBCPP_HIDE_FROM_ABI void clear(memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT {
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__cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), __m);
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}
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_LIBCPP_HIDE_FROM_ABI void clear(memory_order __m = memory_order_seq_cst) _NOEXCEPT {
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__cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), __m);
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}
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#if _LIBCPP_STD_VER >= 20
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_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void wait(bool __v, memory_order __m = memory_order_seq_cst) const
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volatile _NOEXCEPT {
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std::__atomic_wait(*this, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
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}
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_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
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wait(bool __v, memory_order __m = memory_order_seq_cst) const _NOEXCEPT {
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std::__atomic_wait(*this, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
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}
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_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() volatile _NOEXCEPT {
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std::__atomic_notify_one(*this);
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}
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_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() _NOEXCEPT { std::__atomic_notify_one(*this); }
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_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() volatile _NOEXCEPT {
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std::__atomic_notify_all(*this);
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}
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_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() _NOEXCEPT { std::__atomic_notify_all(*this); }
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#endif
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#if _LIBCPP_STD_VER >= 20
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_LIBCPP_HIDE_FROM_ABI constexpr atomic_flag() _NOEXCEPT : __a_(false) {}
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#else
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atomic_flag() _NOEXCEPT = default;
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#endif
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR atomic_flag(bool __b) _NOEXCEPT : __a_(__b) {} // EXTENSION
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atomic_flag(const atomic_flag&) = delete;
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atomic_flag& operator=(const atomic_flag&) = delete;
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atomic_flag& operator=(const atomic_flag&) volatile = delete;
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};
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template <>
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struct __atomic_waitable_traits<atomic_flag> {
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static _LIBCPP_HIDE_FROM_ABI _LIBCPP_ATOMIC_FLAG_TYPE __atomic_load(const atomic_flag& __a, memory_order __order) {
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return std::__cxx_atomic_load(&__a.__a_, __order);
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}
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static _LIBCPP_HIDE_FROM_ABI _LIBCPP_ATOMIC_FLAG_TYPE
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__atomic_load(const volatile atomic_flag& __a, memory_order __order) {
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return std::__cxx_atomic_load(&__a.__a_, __order);
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}
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static _LIBCPP_HIDE_FROM_ABI const __cxx_atomic_impl<_LIBCPP_ATOMIC_FLAG_TYPE>*
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__atomic_contention_address(const atomic_flag& __a) {
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return std::addressof(__a.__a_);
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}
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static _LIBCPP_HIDE_FROM_ABI const volatile __cxx_atomic_impl<_LIBCPP_ATOMIC_FLAG_TYPE>*
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__atomic_contention_address(const volatile atomic_flag& __a) {
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return std::addressof(__a.__a_);
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}
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};
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inline _LIBCPP_HIDE_FROM_ABI bool atomic_flag_test(const volatile atomic_flag* __o) _NOEXCEPT { return __o->test(); }
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inline _LIBCPP_HIDE_FROM_ABI bool atomic_flag_test(const atomic_flag* __o) _NOEXCEPT { return __o->test(); }
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inline _LIBCPP_HIDE_FROM_ABI bool
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atomic_flag_test_explicit(const volatile atomic_flag* __o, memory_order __m) _NOEXCEPT {
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return __o->test(__m);
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}
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inline _LIBCPP_HIDE_FROM_ABI bool atomic_flag_test_explicit(const atomic_flag* __o, memory_order __m) _NOEXCEPT {
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return __o->test(__m);
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}
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inline _LIBCPP_HIDE_FROM_ABI bool atomic_flag_test_and_set(volatile atomic_flag* __o) _NOEXCEPT {
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return __o->test_and_set();
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}
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inline _LIBCPP_HIDE_FROM_ABI bool atomic_flag_test_and_set(atomic_flag* __o) _NOEXCEPT { return __o->test_and_set(); }
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inline _LIBCPP_HIDE_FROM_ABI bool
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atomic_flag_test_and_set_explicit(volatile atomic_flag* __o, memory_order __m) _NOEXCEPT {
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return __o->test_and_set(__m);
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}
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inline _LIBCPP_HIDE_FROM_ABI bool atomic_flag_test_and_set_explicit(atomic_flag* __o, memory_order __m) _NOEXCEPT {
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return __o->test_and_set(__m);
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}
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inline _LIBCPP_HIDE_FROM_ABI void atomic_flag_clear(volatile atomic_flag* __o) _NOEXCEPT { __o->clear(); }
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inline _LIBCPP_HIDE_FROM_ABI void atomic_flag_clear(atomic_flag* __o) _NOEXCEPT { __o->clear(); }
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inline _LIBCPP_HIDE_FROM_ABI void atomic_flag_clear_explicit(volatile atomic_flag* __o, memory_order __m) _NOEXCEPT {
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__o->clear(__m);
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}
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inline _LIBCPP_HIDE_FROM_ABI void atomic_flag_clear_explicit(atomic_flag* __o, memory_order __m) _NOEXCEPT {
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__o->clear(__m);
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}
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#if _LIBCPP_STD_VER >= 20
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
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atomic_flag_wait(const volatile atomic_flag* __o, bool __v) _NOEXCEPT {
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__o->wait(__v);
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}
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
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atomic_flag_wait(const atomic_flag* __o, bool __v) _NOEXCEPT {
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__o->wait(__v);
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}
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
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atomic_flag_wait_explicit(const volatile atomic_flag* __o, bool __v, memory_order __m) _NOEXCEPT {
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__o->wait(__v, __m);
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}
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
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atomic_flag_wait_explicit(const atomic_flag* __o, bool __v, memory_order __m) _NOEXCEPT {
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__o->wait(__v, __m);
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}
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
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atomic_flag_notify_one(volatile atomic_flag* __o) _NOEXCEPT {
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__o->notify_one();
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}
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void atomic_flag_notify_one(atomic_flag* __o) _NOEXCEPT {
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__o->notify_one();
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}
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
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atomic_flag_notify_all(volatile atomic_flag* __o) _NOEXCEPT {
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__o->notify_all();
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}
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void atomic_flag_notify_all(atomic_flag* __o) _NOEXCEPT {
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__o->notify_all();
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}
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#endif // _LIBCPP_STD_VER >= 20
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___ATOMIC_ATOMIC_FLAG_H
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