libstdc++
thread
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00001 // <thread> -*- C++ -*-
00002 
00003 // Copyright (C) 2008-2019 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file include/thread
00026  *  This is a Standard C++ Library header.
00027  */
00028 
00029 #ifndef _GLIBCXX_THREAD
00030 #define _GLIBCXX_THREAD 1
00031 
00032 #pragma GCC system_header
00033 
00034 #if __cplusplus < 201103L
00035 # include <bits/c++0x_warning.h>
00036 #else
00037 
00038 #include <chrono>
00039 #include <memory>
00040 #include <tuple>
00041 #include <cerrno>
00042 #include <bits/functexcept.h>
00043 #include <bits/functional_hash.h>
00044 #include <bits/invoke.h>
00045 #include <bits/gthr.h>
00046 
00047 #if defined(_GLIBCXX_HAS_GTHREADS)
00048 
00049 namespace std _GLIBCXX_VISIBILITY(default)
00050 {
00051 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00052 
00053   /**
00054    * @defgroup threads Threads
00055    * @ingroup concurrency
00056    *
00057    * Classes for thread support.
00058    * @{
00059    */
00060 
00061   /// thread
00062   class thread
00063   {
00064   public:
00065     // Abstract base class for types that wrap arbitrary functors to be
00066     // invoked in the new thread of execution.
00067     struct _State
00068     {
00069       virtual ~_State();
00070       virtual void _M_run() = 0;
00071     };
00072     using _State_ptr = unique_ptr<_State>;
00073 
00074     typedef __gthread_t                 native_handle_type;
00075 
00076     /// thread::id
00077     class id
00078     {
00079       native_handle_type        _M_thread;
00080 
00081     public:
00082       id() noexcept : _M_thread() { }
00083 
00084       explicit
00085       id(native_handle_type __id) : _M_thread(__id) { }
00086 
00087     private:
00088       friend class thread;
00089       friend class hash<thread::id>;
00090 
00091       friend bool
00092       operator==(thread::id __x, thread::id __y) noexcept;
00093 
00094       friend bool
00095       operator<(thread::id __x, thread::id __y) noexcept;
00096 
00097       template<class _CharT, class _Traits>
00098         friend basic_ostream<_CharT, _Traits>&
00099         operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id);
00100     };
00101 
00102   private:
00103     id                          _M_id;
00104 
00105     // _GLIBCXX_RESOLVE_LIB_DEFECTS
00106     // 2097.  packaged_task constructors should be constrained
00107     // 3039. Unnecessary decay in thread and packaged_task
00108     template<typename _Tp>
00109       using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
00110 
00111   public:
00112     thread() noexcept = default;
00113 
00114     template<typename _Callable, typename... _Args,
00115              typename = _Require<__not_same<_Callable>>>
00116       explicit
00117       thread(_Callable&& __f, _Args&&... __args)
00118       {
00119         static_assert( __is_invocable<typename decay<_Callable>::type,
00120                                       typename decay<_Args>::type...>::value,
00121           "std::thread arguments must be invocable after conversion to rvalues"
00122           );
00123 
00124 #ifdef GTHR_ACTIVE_PROXY
00125         // Create a reference to pthread_create, not just the gthr weak symbol.
00126         auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
00127 #else
00128         auto __depend = nullptr;
00129 #endif
00130         _M_start_thread(_S_make_state(
00131               __make_invoker(std::forward<_Callable>(__f),
00132                              std::forward<_Args>(__args)...)),
00133             __depend);
00134       }
00135 
00136     ~thread()
00137     {
00138       if (joinable())
00139         std::terminate();
00140     }
00141 
00142     thread(const thread&) = delete;
00143 
00144     thread(thread&& __t) noexcept
00145     { swap(__t); }
00146 
00147     thread& operator=(const thread&) = delete;
00148 
00149     thread& operator=(thread&& __t) noexcept
00150     {
00151       if (joinable())
00152         std::terminate();
00153       swap(__t);
00154       return *this;
00155     }
00156 
00157     void
00158     swap(thread& __t) noexcept
00159     { std::swap(_M_id, __t._M_id); }
00160 
00161     bool
00162     joinable() const noexcept
00163     { return !(_M_id == id()); }
00164 
00165     void
00166     join();
00167 
00168     void
00169     detach();
00170 
00171     thread::id
00172     get_id() const noexcept
00173     { return _M_id; }
00174 
00175     /** @pre thread is joinable
00176      */
00177     native_handle_type
00178     native_handle()
00179     { return _M_id._M_thread; }
00180 
00181     // Returns a value that hints at the number of hardware thread contexts.
00182     static unsigned int
00183     hardware_concurrency() noexcept;
00184 
00185   private:
00186     template<typename _Callable>
00187       struct _State_impl : public _State
00188       {
00189         _Callable               _M_func;
00190 
00191         _State_impl(_Callable&& __f) : _M_func(std::forward<_Callable>(__f))
00192         { }
00193 
00194         void
00195         _M_run() { _M_func(); }
00196       };
00197 
00198     void
00199     _M_start_thread(_State_ptr, void (*)());
00200 
00201     template<typename _Callable>
00202       static _State_ptr
00203       _S_make_state(_Callable&& __f)
00204       {
00205         using _Impl = _State_impl<_Callable>;
00206         return _State_ptr{new _Impl{std::forward<_Callable>(__f)}};
00207       }
00208 #if _GLIBCXX_THREAD_ABI_COMPAT
00209   public:
00210     struct _Impl_base;
00211     typedef shared_ptr<_Impl_base>      __shared_base_type;
00212     struct _Impl_base
00213     {
00214       __shared_base_type        _M_this_ptr;
00215       virtual ~_Impl_base() = default;
00216       virtual void _M_run() = 0;
00217     };
00218 
00219   private:
00220     void
00221     _M_start_thread(__shared_base_type, void (*)());
00222 
00223     void
00224     _M_start_thread(__shared_base_type);
00225 #endif
00226 
00227   private:
00228     // A call wrapper that does INVOKE(forwarded tuple elements...)
00229     template<typename _Tuple>
00230       struct _Invoker
00231       {
00232         _Tuple _M_t;
00233 
00234         template<typename>
00235           struct __result;
00236         template<typename _Fn, typename... _Args>
00237           struct __result<tuple<_Fn, _Args...>>
00238           : __invoke_result<_Fn, _Args...>
00239           { };
00240 
00241         template<size_t... _Ind>
00242           typename __result<_Tuple>::type
00243           _M_invoke(_Index_tuple<_Ind...>)
00244           { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
00245 
00246         typename __result<_Tuple>::type
00247         operator()()
00248         {
00249           using _Indices
00250             = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
00251           return _M_invoke(_Indices());
00252         }
00253       };
00254 
00255     template<typename... _Tp>
00256       using __decayed_tuple = tuple<typename decay<_Tp>::type...>;
00257 
00258   public:
00259     // Returns a call wrapper that stores
00260     // tuple{DECAY_COPY(__callable), DECAY_COPY(__args)...}.
00261     template<typename _Callable, typename... _Args>
00262       static _Invoker<__decayed_tuple<_Callable, _Args...>>
00263       __make_invoker(_Callable&& __callable, _Args&&... __args)
00264       {
00265         return { __decayed_tuple<_Callable, _Args...>{
00266             std::forward<_Callable>(__callable), std::forward<_Args>(__args)...
00267         } };
00268       }
00269   };
00270 
00271   inline void
00272   swap(thread& __x, thread& __y) noexcept
00273   { __x.swap(__y); }
00274 
00275   inline bool
00276   operator==(thread::id __x, thread::id __y) noexcept
00277   {
00278     // pthread_equal is undefined if either thread ID is not valid, so we
00279     // can't safely use __gthread_equal on default-constructed values (nor
00280     // the non-zero value returned by this_thread::get_id() for
00281     // single-threaded programs using GNU libc). Assume EqualityComparable.
00282     return __x._M_thread == __y._M_thread;
00283   }
00284 
00285   inline bool
00286   operator!=(thread::id __x, thread::id __y) noexcept
00287   { return !(__x == __y); }
00288 
00289   inline bool
00290   operator<(thread::id __x, thread::id __y) noexcept
00291   {
00292     // Pthreads doesn't define any way to do this, so we just have to
00293     // assume native_handle_type is LessThanComparable.
00294     return __x._M_thread < __y._M_thread;
00295   }
00296 
00297   inline bool
00298   operator<=(thread::id __x, thread::id __y) noexcept
00299   { return !(__y < __x); }
00300 
00301   inline bool
00302   operator>(thread::id __x, thread::id __y) noexcept
00303   { return __y < __x; }
00304 
00305   inline bool
00306   operator>=(thread::id __x, thread::id __y) noexcept
00307   { return !(__x < __y); }
00308 
00309   // DR 889.
00310   /// std::hash specialization for thread::id.
00311   template<>
00312     struct hash<thread::id>
00313     : public __hash_base<size_t, thread::id>
00314     {
00315       size_t
00316       operator()(const thread::id& __id) const noexcept
00317       { return std::_Hash_impl::hash(__id._M_thread); }
00318     };
00319 
00320   template<class _CharT, class _Traits>
00321     inline basic_ostream<_CharT, _Traits>&
00322     operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
00323     {
00324       if (__id == thread::id())
00325         return __out << "thread::id of a non-executing thread";
00326       else
00327         return __out << __id._M_thread;
00328     }
00329 
00330   /** @namespace std::this_thread
00331    *  @brief ISO C++ 2011 entities sub-namespace for thread.
00332    *  30.3.2 Namespace this_thread.
00333    */
00334   namespace this_thread
00335   {
00336     /// get_id
00337     inline thread::id
00338     get_id() noexcept
00339     {
00340 #ifdef __GLIBC__
00341       // For the GNU C library pthread_self() is usable without linking to
00342       // libpthread.so but returns 0, so we cannot use it in single-threaded
00343       // programs, because this_thread::get_id() != thread::id{} must be true.
00344       // We know that pthread_t is an integral type in the GNU C library.
00345       if (!__gthread_active_p())
00346         return thread::id(1);
00347 #endif
00348       return thread::id(__gthread_self());
00349     }
00350 
00351     /// yield
00352     inline void
00353     yield() noexcept
00354     {
00355 #ifdef _GLIBCXX_USE_SCHED_YIELD
00356       __gthread_yield();
00357 #endif
00358     }
00359 
00360     void
00361     __sleep_for(chrono::seconds, chrono::nanoseconds);
00362 
00363     /// sleep_for
00364     template<typename _Rep, typename _Period>
00365       inline void
00366       sleep_for(const chrono::duration<_Rep, _Period>& __rtime)
00367       {
00368         if (__rtime <= __rtime.zero())
00369           return;
00370         auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
00371         auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
00372 #ifdef _GLIBCXX_USE_NANOSLEEP
00373         __gthread_time_t __ts =
00374           {
00375             static_cast<std::time_t>(__s.count()),
00376             static_cast<long>(__ns.count())
00377           };
00378         while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
00379           { }
00380 #else
00381         __sleep_for(__s, __ns);
00382 #endif
00383       }
00384 
00385     /// sleep_until
00386     template<typename _Clock, typename _Duration>
00387       inline void
00388       sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
00389       {
00390         auto __now = _Clock::now();
00391         if (_Clock::is_steady)
00392           {
00393             if (__now < __atime)
00394               sleep_for(__atime - __now);
00395             return;
00396           }
00397         while (__now < __atime)
00398           {
00399             sleep_for(__atime - __now);
00400             __now = _Clock::now();
00401           }
00402       }
00403   }
00404 
00405   // @} group threads
00406 
00407 _GLIBCXX_END_NAMESPACE_VERSION
00408 } // namespace
00409 
00410 #endif // _GLIBCXX_HAS_GTHREADS
00411 
00412 #endif // C++11
00413 
00414 #endif // _GLIBCXX_THREAD