// shared_ptr atomic access -*- C++ -*- // Copyright (C) 2014-2020 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file bits/shared_ptr_atomic.h * This is an internal header file, included by other library headers. * Do not attempt to use it directly. @headername{memory} */ #ifndef _SHARED_PTR_ATOMIC_H #define _SHARED_PTR_ATOMIC_H 1 #include <bits/atomic_base.h> namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION /** * @addtogroup pointer_abstractions * @{ */ /// @relates shared_ptr @{ /// @cond undocumented struct _Sp_locker { _Sp_locker(const _Sp_locker&) = delete; _Sp_locker& operator=(const _Sp_locker&) = delete; #ifdef __GTHREADS explicit _Sp_locker(const void*) noexcept; _Sp_locker(const void*, const void*) noexcept; ~_Sp_locker(); private: unsigned char _M_key1; unsigned char _M_key2; #else explicit _Sp_locker(const void*, const void* = nullptr) { } #endif }; /// @endcond /** * @brief Report whether shared_ptr atomic operations are lock-free. * @param __p A non-null pointer to a shared_ptr object. * @return True if atomic access to @c *__p is lock-free, false otherwise. * @{ */ template<typename _Tp, _Lock_policy _Lp> inline bool atomic_is_lock_free(const __shared_ptr<_Tp, _Lp>* __p) { #ifdef __GTHREADS return __gthread_active_p() == 0; #else return true; #endif } template<typename _Tp> inline bool atomic_is_lock_free(const shared_ptr<_Tp>* __p) { return std::atomic_is_lock_free<_Tp, __default_lock_policy>(__p); } // @} /** * @brief Atomic load for shared_ptr objects. * @param __p A non-null pointer to a shared_ptr object. * @return @c *__p * * The memory order shall not be @c memory_order_release or * @c memory_order_acq_rel. * @{ */ template<typename _Tp> inline shared_ptr<_Tp> atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order) { _Sp_locker __lock{__p}; return *__p; } template<typename _Tp> inline shared_ptr<_Tp> atomic_load(const shared_ptr<_Tp>* __p) { return std::atomic_load_explicit(__p, memory_order_seq_cst); } template<typename _Tp, _Lock_policy _Lp> inline __shared_ptr<_Tp, _Lp> atomic_load_explicit(const __shared_ptr<_Tp, _Lp>* __p, memory_order) { _Sp_locker __lock{__p}; return *__p; } template<typename _Tp, _Lock_policy _Lp> inline __shared_ptr<_Tp, _Lp> atomic_load(const __shared_ptr<_Tp, _Lp>* __p) { return std::atomic_load_explicit(__p, memory_order_seq_cst); } // @} /** * @brief Atomic store for shared_ptr objects. * @param __p A non-null pointer to a shared_ptr object. * @param __r The value to store. * * The memory order shall not be @c memory_order_acquire or * @c memory_order_acq_rel. * @{ */ template<typename _Tp> inline void atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order) { _Sp_locker __lock{__p}; __p->swap(__r); // use swap so that **__p not destroyed while lock held } template<typename _Tp> inline void atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) { std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); } template<typename _Tp, _Lock_policy _Lp> inline void atomic_store_explicit(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r, memory_order) { _Sp_locker __lock{__p}; __p->swap(__r); // use swap so that **__p not destroyed while lock held } template<typename _Tp, _Lock_policy _Lp> inline void atomic_store(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r) { std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); } // @} /** * @brief Atomic exchange for shared_ptr objects. * @param __p A non-null pointer to a shared_ptr object. * @param __r New value to store in @c *__p. * @return The original value of @c *__p * @{ */ template<typename _Tp> inline shared_ptr<_Tp> atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order) { _Sp_locker __lock{__p}; __p->swap(__r); return __r; } template<typename _Tp> inline shared_ptr<_Tp> atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) { return std::atomic_exchange_explicit(__p, std::move(__r), memory_order_seq_cst); } template<typename _Tp, _Lock_policy _Lp> inline __shared_ptr<_Tp, _Lp> atomic_exchange_explicit(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r, memory_order) { _Sp_locker __lock{__p}; __p->swap(__r); return __r; } template<typename _Tp, _Lock_policy _Lp> inline __shared_ptr<_Tp, _Lp> atomic_exchange(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r) { return std::atomic_exchange_explicit(__p, std::move(__r), memory_order_seq_cst); } // @} /** * @brief Atomic compare-and-swap for shared_ptr objects. * @param __p A non-null pointer to a shared_ptr object. * @param __v A non-null pointer to a shared_ptr object. * @param __w A non-null pointer to a shared_ptr object. * @return True if @c *__p was equivalent to @c *__v, false otherwise. * * The memory order for failure shall not be @c memory_order_release or * @c memory_order_acq_rel, or stronger than the memory order for success. * @{ */ template<typename _Tp> bool atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w, memory_order, memory_order) { shared_ptr<_Tp> __x; // goes out of scope after __lock _Sp_locker __lock{__p, __v}; owner_less<shared_ptr<_Tp>> __less; if (*__p == *__v && !__less(*__p, *__v) && !__less(*__v, *__p)) { __x = std::move(*__p); *__p = std::move(__w); return true; } __x = std::move(*__v); *__v = *__p; return false; } template<typename _Tp> inline bool atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w) { return std::atomic_compare_exchange_strong_explicit(__p, __v, std::move(__w), memory_order_seq_cst, memory_order_seq_cst); } template<typename _Tp> inline bool atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w, memory_order __success, memory_order __failure) { return std::atomic_compare_exchange_strong_explicit(__p, __v, std::move(__w), __success, __failure); } template<typename _Tp> inline bool atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w) { return std::atomic_compare_exchange_weak_explicit(__p, __v, std::move(__w), memory_order_seq_cst, memory_order_seq_cst); } template<typename _Tp, _Lock_policy _Lp> bool atomic_compare_exchange_strong_explicit(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp>* __v, __shared_ptr<_Tp, _Lp> __w, memory_order, memory_order) { __shared_ptr<_Tp, _Lp> __x; // goes out of scope after __lock _Sp_locker __lock{__p, __v}; owner_less<__shared_ptr<_Tp, _Lp>> __less; if (*__p == *__v && !__less(*__p, *__v) && !__less(*__v, *__p)) { __x = std::move(*__p); *__p = std::move(__w); return true; } __x = std::move(*__v); *__v = *__p; return false; } template<typename _Tp, _Lock_policy _Lp> inline bool atomic_compare_exchange_strong(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp>* __v, __shared_ptr<_Tp, _Lp> __w) { return std::atomic_compare_exchange_strong_explicit(__p, __v, std::move(__w), memory_order_seq_cst, memory_order_seq_cst); } template<typename _Tp, _Lock_policy _Lp> inline bool atomic_compare_exchange_weak_explicit(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp>* __v, __shared_ptr<_Tp, _Lp> __w, memory_order __success, memory_order __failure) { return std::atomic_compare_exchange_strong_explicit(__p, __v, std::move(__w), __success, __failure); } template<typename _Tp, _Lock_policy _Lp> inline bool atomic_compare_exchange_weak(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp>* __v, __shared_ptr<_Tp, _Lp> __w) { return std::atomic_compare_exchange_weak_explicit(__p, __v, std::move(__w), memory_order_seq_cst, memory_order_seq_cst); } // @} // @} relates shared_ptr // @} group pointer_abstractions _GLIBCXX_END_NAMESPACE_VERSION } // namespace #endif // _SHARED_PTR_ATOMIC_H