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Edit File: mutex
// <mutex> -*- C++ -*- // Copyright (C) 2003-2021 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 include/mutex * This is a Standard C++ Library header. */ #ifndef _GLIBCXX_MUTEX #define _GLIBCXX_MUTEX 1 #pragma GCC system_header #if __cplusplus < 201103L # include <bits/c++0x_warning.h> #else #include <tuple> #include <chrono> #include <exception> #include <type_traits> #include <system_error> #include <bits/std_mutex.h> #include <bits/unique_lock.h> #if ! _GTHREAD_USE_MUTEX_TIMEDLOCK # include <condition_variable> # include <thread> #endif #include <ext/atomicity.h> // __gnu_cxx::__is_single_threaded #if defined _GLIBCXX_HAS_GTHREADS && ! defined _GLIBCXX_HAVE_TLS # include <bits/std_function.h> // std::function #endif namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION /** * @addtogroup mutexes * @{ */ #ifdef _GLIBCXX_HAS_GTHREADS // Common base class for std::recursive_mutex and std::recursive_timed_mutex class __recursive_mutex_base { protected: typedef __gthread_recursive_mutex_t __native_type; __recursive_mutex_base(const __recursive_mutex_base&) = delete; __recursive_mutex_base& operator=(const __recursive_mutex_base&) = delete; #ifdef __GTHREAD_RECURSIVE_MUTEX_INIT __native_type _M_mutex = __GTHREAD_RECURSIVE_MUTEX_INIT; __recursive_mutex_base() = default; #else __native_type _M_mutex; __recursive_mutex_base() { // XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may) __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION(&_M_mutex); } ~__recursive_mutex_base() { __gthread_recursive_mutex_destroy(&_M_mutex); } #endif }; /// The standard recursive mutex type. class recursive_mutex : private __recursive_mutex_base { public: typedef __native_type* native_handle_type; recursive_mutex() = default; ~recursive_mutex() = default; recursive_mutex(const recursive_mutex&) = delete; recursive_mutex& operator=(const recursive_mutex&) = delete; void lock() { int __e = __gthread_recursive_mutex_lock(&_M_mutex); // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may) if (__e) __throw_system_error(__e); } bool try_lock() noexcept { // XXX EINVAL, EAGAIN, EBUSY return !__gthread_recursive_mutex_trylock(&_M_mutex); } void unlock() { // XXX EINVAL, EAGAIN, EBUSY __gthread_recursive_mutex_unlock(&_M_mutex); } native_handle_type native_handle() noexcept { return &_M_mutex; } }; #if _GTHREAD_USE_MUTEX_TIMEDLOCK template<typename _Derived> class __timed_mutex_impl { protected: template<typename _Rep, typename _Period> bool _M_try_lock_for(const chrono::duration<_Rep, _Period>& __rtime) { #if _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK using __clock = chrono::steady_clock; #else using __clock = chrono::system_clock; #endif auto __rt = chrono::duration_cast<__clock::duration>(__rtime); if (ratio_greater<__clock::period, _Period>()) ++__rt; return _M_try_lock_until(__clock::now() + __rt); } template<typename _Duration> bool _M_try_lock_until(const chrono::time_point<chrono::system_clock, _Duration>& __atime) { auto __s = chrono::time_point_cast<chrono::seconds>(__atime); auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s); __gthread_time_t __ts = { static_cast<std::time_t>(__s.time_since_epoch().count()), static_cast<long>(__ns.count()) }; return static_cast<_Derived*>(this)->_M_timedlock(__ts); } #ifdef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK template<typename _Duration> bool _M_try_lock_until(const chrono::time_point<chrono::steady_clock, _Duration>& __atime) { auto __s = chrono::time_point_cast<chrono::seconds>(__atime); auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s); __gthread_time_t __ts = { static_cast<std::time_t>(__s.time_since_epoch().count()), static_cast<long>(__ns.count()) }; return static_cast<_Derived*>(this)->_M_clocklock(CLOCK_MONOTONIC, __ts); } #endif template<typename _Clock, typename _Duration> bool _M_try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime) { #if __cplusplus > 201703L static_assert(chrono::is_clock_v<_Clock>); #endif // The user-supplied clock may not tick at the same rate as // steady_clock, so we must loop in order to guarantee that // the timeout has expired before returning false. auto __now = _Clock::now(); do { auto __rtime = __atime - __now; if (_M_try_lock_for(__rtime)) return true; __now = _Clock::now(); } while (__atime > __now); return false; } }; /// The standard timed mutex type. class timed_mutex : private __mutex_base, public __timed_mutex_impl<timed_mutex> { public: typedef __native_type* native_handle_type; timed_mutex() = default; ~timed_mutex() = default; timed_mutex(const timed_mutex&) = delete; timed_mutex& operator=(const timed_mutex&) = delete; void lock() { int __e = __gthread_mutex_lock(&_M_mutex); // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may) if (__e) __throw_system_error(__e); } bool try_lock() noexcept { // XXX EINVAL, EAGAIN, EBUSY return !__gthread_mutex_trylock(&_M_mutex); } template <class _Rep, class _Period> bool try_lock_for(const chrono::duration<_Rep, _Period>& __rtime) { return _M_try_lock_for(__rtime); } template <class _Clock, class _Duration> bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime) { return _M_try_lock_until(__atime); } void unlock() { // XXX EINVAL, EAGAIN, EBUSY __gthread_mutex_unlock(&_M_mutex); } native_handle_type native_handle() noexcept { return &_M_mutex; } private: friend class __timed_mutex_impl<timed_mutex>; bool _M_timedlock(const __gthread_time_t& __ts) { return !__gthread_mutex_timedlock(&_M_mutex, &__ts); } #if _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK bool _M_clocklock(clockid_t clockid, const __gthread_time_t& __ts) { return !pthread_mutex_clocklock(&_M_mutex, clockid, &__ts); } #endif }; /// recursive_timed_mutex class recursive_timed_mutex : private __recursive_mutex_base, public __timed_mutex_impl<recursive_timed_mutex> { public: typedef __native_type* native_handle_type; recursive_timed_mutex() = default; ~recursive_timed_mutex() = default; recursive_timed_mutex(const recursive_timed_mutex&) = delete; recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete; void lock() { int __e = __gthread_recursive_mutex_lock(&_M_mutex); // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may) if (__e) __throw_system_error(__e); } bool try_lock() noexcept { // XXX EINVAL, EAGAIN, EBUSY return !__gthread_recursive_mutex_trylock(&_M_mutex); } template <class _Rep, class _Period> bool try_lock_for(const chrono::duration<_Rep, _Period>& __rtime) { return _M_try_lock_for(__rtime); } template <class _Clock, class _Duration> bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime) { return _M_try_lock_until(__atime); } void unlock() { // XXX EINVAL, EAGAIN, EBUSY __gthread_recursive_mutex_unlock(&_M_mutex); } native_handle_type native_handle() noexcept { return &_M_mutex; } private: friend class __timed_mutex_impl<recursive_timed_mutex>; bool _M_timedlock(const __gthread_time_t& __ts) { return !__gthread_recursive_mutex_timedlock(&_M_mutex, &__ts); } #ifdef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK bool _M_clocklock(clockid_t clockid, const __gthread_time_t& __ts) { return !pthread_mutex_clocklock(&_M_mutex, clockid, &__ts); } #endif }; #else // !_GTHREAD_USE_MUTEX_TIMEDLOCK /// timed_mutex class timed_mutex { mutex _M_mut; condition_variable _M_cv; bool _M_locked = false; public: timed_mutex() = default; ~timed_mutex() { __glibcxx_assert( !_M_locked ); } timed_mutex(const timed_mutex&) = delete; timed_mutex& operator=(const timed_mutex&) = delete; void lock() { unique_lock<mutex> __lk(_M_mut); _M_cv.wait(__lk, [&]{ return !_M_locked; }); _M_locked = true; } bool try_lock() { lock_guard<mutex> __lk(_M_mut); if (_M_locked) return false; _M_locked = true; return true; } template<typename _Rep, typename _Period> bool try_lock_for(const chrono::duration<_Rep, _Period>& __rtime) { unique_lock<mutex> __lk(_M_mut); if (!_M_cv.wait_for(__lk, __rtime, [&]{ return !_M_locked; })) return false; _M_locked = true; return true; } template<typename _Clock, typename _Duration> bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime) { unique_lock<mutex> __lk(_M_mut); if (!_M_cv.wait_until(__lk, __atime, [&]{ return !_M_locked; })) return false; _M_locked = true; return true; } void unlock() { lock_guard<mutex> __lk(_M_mut); __glibcxx_assert( _M_locked ); _M_locked = false; _M_cv.notify_one(); } }; /// recursive_timed_mutex class recursive_timed_mutex { mutex _M_mut; condition_variable _M_cv; thread::id _M_owner; unsigned _M_count = 0; // Predicate type that tests whether the current thread can lock a mutex. struct _Can_lock { // Returns true if the mutex is unlocked or is locked by _M_caller. bool operator()() const noexcept { return _M_mx->_M_count == 0 || _M_mx->_M_owner == _M_caller; } const recursive_timed_mutex* _M_mx; thread::id _M_caller; }; public: recursive_timed_mutex() = default; ~recursive_timed_mutex() { __glibcxx_assert( _M_count == 0 ); } recursive_timed_mutex(const recursive_timed_mutex&) = delete; recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete; void lock() { auto __id = this_thread::get_id(); _Can_lock __can_lock{this, __id}; unique_lock<mutex> __lk(_M_mut); _M_cv.wait(__lk, __can_lock); if (_M_count == -1u) __throw_system_error(EAGAIN); // [thread.timedmutex.recursive]/3 _M_owner = __id; ++_M_count; } bool try_lock() { auto __id = this_thread::get_id(); _Can_lock __can_lock{this, __id}; lock_guard<mutex> __lk(_M_mut); if (!__can_lock()) return false; if (_M_count == -1u) return false; _M_owner = __id; ++_M_count; return true; } template<typename _Rep, typename _Period> bool try_lock_for(const chrono::duration<_Rep, _Period>& __rtime) { auto __id = this_thread::get_id(); _Can_lock __can_lock{this, __id}; unique_lock<mutex> __lk(_M_mut); if (!_M_cv.wait_for(__lk, __rtime, __can_lock)) return false; if (_M_count == -1u) return false; _M_owner = __id; ++_M_count; return true; } template<typename _Clock, typename _Duration> bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime) { auto __id = this_thread::get_id(); _Can_lock __can_lock{this, __id}; unique_lock<mutex> __lk(_M_mut); if (!_M_cv.wait_until(__lk, __atime, __can_lock)) return false; if (_M_count == -1u) return false; _M_owner = __id; ++_M_count; return true; } void unlock() { lock_guard<mutex> __lk(_M_mut); __glibcxx_assert( _M_owner == this_thread::get_id() ); __glibcxx_assert( _M_count > 0 ); if (--_M_count == 0) { _M_owner = {}; _M_cv.notify_one(); } } }; #endif #endif // _GLIBCXX_HAS_GTHREADS /// @cond undocumented template<typename _Lock> inline unique_lock<_Lock> __try_to_lock(_Lock& __l) { return unique_lock<_Lock>{__l, try_to_lock}; } template<int _Idx, bool _Continue = true> struct __try_lock_impl { template<typename... _Lock> static void __do_try_lock(tuple<_Lock&...>& __locks, int& __idx) { __idx = _Idx; auto __lock = std::__try_to_lock(std::get<_Idx>(__locks)); if (__lock.owns_lock()) { constexpr bool __cont = _Idx + 2 < sizeof...(_Lock); using __try_locker = __try_lock_impl<_Idx + 1, __cont>; __try_locker::__do_try_lock(__locks, __idx); if (__idx == -1) __lock.release(); } } }; template<int _Idx> struct __try_lock_impl<_Idx, false> { template<typename... _Lock> static void __do_try_lock(tuple<_Lock&...>& __locks, int& __idx) { __idx = _Idx; auto __lock = std::__try_to_lock(std::get<_Idx>(__locks)); if (__lock.owns_lock()) { __idx = -1; __lock.release(); } } }; /// @endcond /** @brief Generic try_lock. * @param __l1 Meets Lockable requirements (try_lock() may throw). * @param __l2 Meets Lockable requirements (try_lock() may throw). * @param __l3 Meets Lockable requirements (try_lock() may throw). * @return Returns -1 if all try_lock() calls return true. Otherwise returns * a 0-based index corresponding to the argument that returned false. * @post Either all arguments are locked, or none will be. * * Sequentially calls try_lock() on each argument. */ template<typename _Lock1, typename _Lock2, typename... _Lock3> int try_lock(_Lock1& __l1, _Lock2& __l2, _Lock3&... __l3) { int __idx; auto __locks = std::tie(__l1, __l2, __l3...); __try_lock_impl<0>::__do_try_lock(__locks, __idx); return __idx; } /** @brief Generic lock. * @param __l1 Meets Lockable requirements (try_lock() may throw). * @param __l2 Meets Lockable requirements (try_lock() may throw). * @param __l3 Meets Lockable requirements (try_lock() may throw). * @throw An exception thrown by an argument's lock() or try_lock() member. * @post All arguments are locked. * * All arguments are locked via a sequence of calls to lock(), try_lock() * and unlock(). If the call exits via an exception any locks that were * obtained will be released. */ template<typename _L1, typename _L2, typename... _L3> void lock(_L1& __l1, _L2& __l2, _L3&... __l3) { while (true) { using __try_locker = __try_lock_impl<0, sizeof...(_L3) != 0>; unique_lock<_L1> __first(__l1); int __idx; auto __locks = std::tie(__l2, __l3...); __try_locker::__do_try_lock(__locks, __idx); if (__idx == -1) { __first.release(); return; } } } #if __cplusplus >= 201703L #define __cpp_lib_scoped_lock 201703 /** @brief A scoped lock type for multiple lockable objects. * * A scoped_lock controls mutex ownership within a scope, releasing * ownership in the destructor. */ template<typename... _MutexTypes> class scoped_lock { public: explicit scoped_lock(_MutexTypes&... __m) : _M_devices(std::tie(__m...)) { std::lock(__m...); } explicit scoped_lock(adopt_lock_t, _MutexTypes&... __m) noexcept : _M_devices(std::tie(__m...)) { } // calling thread owns mutex ~scoped_lock() { std::apply([](auto&... __m) { (__m.unlock(), ...); }, _M_devices); } scoped_lock(const scoped_lock&) = delete; scoped_lock& operator=(const scoped_lock&) = delete; private: tuple<_MutexTypes&...> _M_devices; }; template<> class scoped_lock<> { public: explicit scoped_lock() = default; explicit scoped_lock(adopt_lock_t) noexcept { } ~scoped_lock() = default; scoped_lock(const scoped_lock&) = delete; scoped_lock& operator=(const scoped_lock&) = delete; }; template<typename _Mutex> class scoped_lock<_Mutex> { public: using mutex_type = _Mutex; explicit scoped_lock(mutex_type& __m) : _M_device(__m) { _M_device.lock(); } explicit scoped_lock(adopt_lock_t, mutex_type& __m) noexcept : _M_device(__m) { } // calling thread owns mutex ~scoped_lock() { _M_device.unlock(); } scoped_lock(const scoped_lock&) = delete; scoped_lock& operator=(const scoped_lock&) = delete; private: mutex_type& _M_device; }; #endif // C++17 #ifdef _GLIBCXX_HAS_GTHREADS /// Flag type used by std::call_once struct once_flag { constexpr once_flag() noexcept = default; /// Deleted copy constructor once_flag(const once_flag&) = delete; /// Deleted assignment operator once_flag& operator=(const once_flag&) = delete; private: // For gthreads targets a pthread_once_t is used with pthread_once, but // for most targets this doesn't work correctly for exceptional executions. __gthread_once_t _M_once = __GTHREAD_ONCE_INIT; struct _Prepare_execution; template<typename _Callable, typename... _Args> friend void call_once(once_flag& __once, _Callable&& __f, _Args&&... __args); }; /// @cond undocumented # ifdef _GLIBCXX_HAVE_TLS // If TLS is available use thread-local state for the type-erased callable // that is being run by std::call_once in the current thread. extern __thread void* __once_callable; extern __thread void (*__once_call)(); // RAII type to set up state for pthread_once call. struct once_flag::_Prepare_execution { template<typename _Callable> explicit _Prepare_execution(_Callable& __c) { // Store address in thread-local pointer: __once_callable = std::__addressof(__c); // Trampoline function to invoke the closure via thread-local pointer: __once_call = [] { (*static_cast<_Callable*>(__once_callable))(); }; } ~_Prepare_execution() { // PR libstdc++/82481 __once_callable = nullptr; __once_call = nullptr; } _Prepare_execution(const _Prepare_execution&) = delete; _Prepare_execution& operator=(const _Prepare_execution&) = delete; }; # else // Without TLS use a global std::mutex and store the callable in a // global std::function. extern function<void()> __once_functor; extern void __set_once_functor_lock_ptr(unique_lock<mutex>*); extern mutex& __get_once_mutex(); // RAII type to set up state for pthread_once call. struct once_flag::_Prepare_execution { template<typename _Callable> explicit _Prepare_execution(_Callable& __c) { // Store the callable in the global std::function __once_functor = __c; __set_once_functor_lock_ptr(&_M_functor_lock); } ~_Prepare_execution() { if (_M_functor_lock) __set_once_functor_lock_ptr(nullptr); } private: // XXX This deadlocks if used recursively (PR 97949) unique_lock<mutex> _M_functor_lock{__get_once_mutex()}; _Prepare_execution(const _Prepare_execution&) = delete; _Prepare_execution& operator=(const _Prepare_execution&) = delete; }; # endif /// @endcond // This function is passed to pthread_once by std::call_once. // It runs __once_call() or __once_functor(). extern "C" void __once_proxy(void); /// Invoke a callable and synchronize with other calls using the same flag template<typename _Callable, typename... _Args> void call_once(once_flag& __once, _Callable&& __f, _Args&&... __args) { // Closure type that runs the function auto __callable = [&] { std::__invoke(std::forward<_Callable>(__f), std::forward<_Args>(__args)...); }; once_flag::_Prepare_execution __exec(__callable); // XXX pthread_once does not reset the flag if an exception is thrown. if (int __e = __gthread_once(&__once._M_once, &__once_proxy)) __throw_system_error(__e); } #else // _GLIBCXX_HAS_GTHREADS /// Flag type used by std::call_once struct once_flag { constexpr once_flag() noexcept = default; /// Deleted copy constructor once_flag(const once_flag&) = delete; /// Deleted assignment operator once_flag& operator=(const once_flag&) = delete; private: // There are two different std::once_flag interfaces, abstracting four // different implementations. // The single-threaded interface uses the _M_activate() and _M_finish(bool) // functions, which start and finish an active execution respectively. // See [thread.once.callonce] in C++11 for the definition of // active/passive/returning/exceptional executions. enum _Bits : int { _Init = 0, _Active = 1, _Done = 2 }; int _M_once = _Bits::_Init; // Check to see if all executions will be passive now. bool _M_passive() const noexcept; // Attempts to begin an active execution. bool _M_activate(); // Must be called to complete an active execution. // The argument is true if the active execution was a returning execution, // false if it was an exceptional execution. void _M_finish(bool __returning) noexcept; // RAII helper to call _M_finish. struct _Active_execution { explicit _Active_execution(once_flag& __flag) : _M_flag(__flag) { } ~_Active_execution() { _M_flag._M_finish(_M_returning); } _Active_execution(const _Active_execution&) = delete; _Active_execution& operator=(const _Active_execution&) = delete; once_flag& _M_flag; bool _M_returning = false; }; template<typename _Callable, typename... _Args> friend void call_once(once_flag& __once, _Callable&& __f, _Args&&... __args); }; // Inline definitions of std::once_flag members for single-threaded targets. inline bool once_flag::_M_passive() const noexcept { return _M_once == _Bits::_Done; } inline bool once_flag::_M_activate() { if (_M_once == _Bits::_Init) [[__likely__]] { _M_once = _Bits::_Active; return true; } else if (_M_passive()) // Caller should have checked this already. return false; else __throw_system_error(EDEADLK); } inline void once_flag::_M_finish(bool __returning) noexcept { _M_once = __returning ? _Bits::_Done : _Bits::_Init; } /// Invoke a callable and synchronize with other calls using the same flag template<typename _Callable, typename... _Args> inline void call_once(once_flag& __once, _Callable&& __f, _Args&&... __args) { if (__once._M_passive()) return; else if (__once._M_activate()) { once_flag::_Active_execution __exec(__once); // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2442. call_once() shouldn't DECAY_COPY() std::__invoke(std::forward<_Callable>(__f), std::forward<_Args>(__args)...); // __f(__args...) did not throw __exec._M_returning = true; } } #endif // _GLIBCXX_HAS_GTHREADS /// @} group mutexes _GLIBCXX_END_NAMESPACE_VERSION } // namespace #endif // C++11 #endif // _GLIBCXX_MUTEX