1// <thread> -*- C++ -*-
2
3// Copyright (C) 2008-2018 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file include/thread
26 *  This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_THREAD
30#define _GLIBCXX_THREAD 1
31
32#pragma GCC system_header
33
34#if __cplusplus < 201103L
35# include <bits/c++0x_warning.h>
36#else
37
38#include <chrono>
39#include <memory>
40#include <tuple>
41#include <cerrno>
42#include <bits/functexcept.h>
43#include <bits/functional_hash.h>
44#include <bits/invoke.h>
45#include <bits/gthr.h>
46
47#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
48
49namespace std _GLIBCXX_VISIBILITY(default)
50{
51_GLIBCXX_BEGIN_NAMESPACE_VERSION
52
53  /**
54   * @defgroup threads Threads
55   * @ingroup concurrency
56   *
57   * Classes for thread support.
58   * @{
59   */
60
61  /// thread
62  class thread
63  {
64  public:
65    // Abstract base class for types that wrap arbitrary functors to be
66    // invoked in the new thread of execution.
67    struct _State
68    {
69      virtual ~_State();
70      virtual void _M_run() = 0;
71    };
72    using _State_ptr = unique_ptr<_State>;
73
74    typedef __gthread_t			native_handle_type;
75
76    /// thread::id
77    class id
78    {
79      native_handle_type	_M_thread;
80
81    public:
82      id() noexcept : _M_thread() { }
83
84      explicit
85      id(native_handle_type __id) : _M_thread(__id) { }
86
87    private:
88      friend class thread;
89      friend class hash<thread::id>;
90
91      friend bool
92      operator==(thread::id __x, thread::id __y) noexcept;
93
94      friend bool
95      operator<(thread::id __x, thread::id __y) noexcept;
96
97      template<class _CharT, class _Traits>
98	friend basic_ostream<_CharT, _Traits>&
99	operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id);
100    };
101
102  private:
103    id				_M_id;
104
105    // _GLIBCXX_RESOLVE_LIB_DEFECTS
106    // 2097.  packaged_task constructors should be constrained
107    template<typename _Tp>
108      using __not_same = __not_<is_same<
109	typename remove_cv<typename remove_reference<_Tp>::type>::type,
110	thread>>;
111
112  public:
113    thread() noexcept = default;
114
115    template<typename _Callable, typename... _Args,
116	     typename = _Require<__not_same<_Callable>>>
117      explicit
118      thread(_Callable&& __f, _Args&&... __args)
119      {
120	static_assert( __is_invocable<typename decay<_Callable>::type,
121				      typename decay<_Args>::type...>::value,
122	  "std::thread arguments must be invocable after conversion to rvalues"
123	  );
124
125#ifdef GTHR_ACTIVE_PROXY
126	// Create a reference to pthread_create, not just the gthr weak symbol.
127	auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
128#else
129	auto __depend = nullptr;
130#endif
131        _M_start_thread(_S_make_state(
132	      __make_invoker(std::forward<_Callable>(__f),
133			     std::forward<_Args>(__args)...)),
134	    __depend);
135      }
136
137    ~thread()
138    {
139      if (joinable())
140	std::terminate();
141    }
142
143    thread(const thread&) = delete;
144
145    thread(thread&& __t) noexcept
146    { swap(__t); }
147
148    thread& operator=(const thread&) = delete;
149
150    thread& operator=(thread&& __t) noexcept
151    {
152      if (joinable())
153	std::terminate();
154      swap(__t);
155      return *this;
156    }
157
158    void
159    swap(thread& __t) noexcept
160    { std::swap(_M_id, __t._M_id); }
161
162    bool
163    joinable() const noexcept
164    { return !(_M_id == id()); }
165
166    void
167    join();
168
169    void
170    detach();
171
172    thread::id
173    get_id() const noexcept
174    { return _M_id; }
175
176    /** @pre thread is joinable
177     */
178    native_handle_type
179    native_handle()
180    { return _M_id._M_thread; }
181
182    // Returns a value that hints at the number of hardware thread contexts.
183    static unsigned int
184    hardware_concurrency() noexcept;
185
186  private:
187    template<typename _Callable>
188      struct _State_impl : public _State
189      {
190	_Callable		_M_func;
191
192	_State_impl(_Callable&& __f) : _M_func(std::forward<_Callable>(__f))
193	{ }
194
195	void
196	_M_run() { _M_func(); }
197      };
198
199    void
200    _M_start_thread(_State_ptr, void (*)());
201
202    template<typename _Callable>
203      static _State_ptr
204      _S_make_state(_Callable&& __f)
205      {
206	using _Impl = _State_impl<_Callable>;
207	return _State_ptr{new _Impl{std::forward<_Callable>(__f)}};
208      }
209#if _GLIBCXX_THREAD_ABI_COMPAT
210  public:
211    struct _Impl_base;
212    typedef shared_ptr<_Impl_base>	__shared_base_type;
213    struct _Impl_base
214    {
215      __shared_base_type	_M_this_ptr;
216      virtual ~_Impl_base() = default;
217      virtual void _M_run() = 0;
218    };
219
220  private:
221    void
222    _M_start_thread(__shared_base_type, void (*)());
223
224    void
225    _M_start_thread(__shared_base_type);
226#endif
227
228  private:
229    // A call wrapper that does INVOKE(forwarded tuple elements...)
230    template<typename _Tuple>
231      struct _Invoker
232      {
233	_Tuple _M_t;
234
235	template<size_t _Index>
236	  static __tuple_element_t<_Index, _Tuple>&&
237	  _S_declval();
238
239	template<size_t... _Ind>
240	  auto
241	  _M_invoke(_Index_tuple<_Ind...>)
242	  noexcept(noexcept(std::__invoke(_S_declval<_Ind>()...)))
243	  -> decltype(std::__invoke(_S_declval<_Ind>()...))
244	  { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
245
246	using _Indices
247	  = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
248
249	auto
250	operator()()
251	noexcept(noexcept(std::declval<_Invoker&>()._M_invoke(_Indices())))
252	-> decltype(std::declval<_Invoker&>()._M_invoke(_Indices()))
253	{ return _M_invoke(_Indices()); }
254      };
255
256    template<typename... _Tp>
257      using __decayed_tuple = tuple<typename std::decay<_Tp>::type...>;
258
259  public:
260    // Returns a call wrapper that stores
261    // tuple{DECAY_COPY(__callable), DECAY_COPY(__args)...}.
262    template<typename _Callable, typename... _Args>
263      static _Invoker<__decayed_tuple<_Callable, _Args...>>
264      __make_invoker(_Callable&& __callable, _Args&&... __args)
265      {
266	return { __decayed_tuple<_Callable, _Args...>{
267	    std::forward<_Callable>(__callable), std::forward<_Args>(__args)...
268	} };
269      }
270  };
271
272  inline void
273  swap(thread& __x, thread& __y) noexcept
274  { __x.swap(__y); }
275
276  inline bool
277  operator==(thread::id __x, thread::id __y) noexcept
278  {
279    // pthread_equal is undefined if either thread ID is not valid, so we
280    // can't safely use __gthread_equal on default-constructed values (nor
281    // the non-zero value returned by this_thread::get_id() for
282    // single-threaded programs using GNU libc). Assume EqualityComparable.
283    return __x._M_thread == __y._M_thread;
284  }
285
286  inline bool
287  operator!=(thread::id __x, thread::id __y) noexcept
288  { return !(__x == __y); }
289
290  inline bool
291  operator<(thread::id __x, thread::id __y) noexcept
292  {
293    // Pthreads doesn't define any way to do this, so we just have to
294    // assume native_handle_type is LessThanComparable.
295    return __x._M_thread < __y._M_thread;
296  }
297
298  inline bool
299  operator<=(thread::id __x, thread::id __y) noexcept
300  { return !(__y < __x); }
301
302  inline bool
303  operator>(thread::id __x, thread::id __y) noexcept
304  { return __y < __x; }
305
306  inline bool
307  operator>=(thread::id __x, thread::id __y) noexcept
308  { return !(__x < __y); }
309
310  // DR 889.
311  /// std::hash specialization for thread::id.
312  template<>
313    struct hash<thread::id>
314    : public __hash_base<size_t, thread::id>
315    {
316      size_t
317      operator()(const thread::id& __id) const noexcept
318      { return std::_Hash_impl::hash(__id._M_thread); }
319    };
320
321  template<class _CharT, class _Traits>
322    inline basic_ostream<_CharT, _Traits>&
323    operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
324    {
325      if (__id == thread::id())
326	return __out << "thread::id of a non-executing thread";
327      else
328	return __out << __id._M_thread;
329    }
330
331  /** @namespace std::this_thread
332   *  @brief ISO C++ 2011 entities sub-namespace for thread.
333   *  30.3.2 Namespace this_thread.
334   */
335  namespace this_thread
336  {
337    /// get_id
338    inline thread::id
339    get_id() noexcept
340    {
341#ifdef L4__pthread_t_IS_NOT_AN_INT
342#ifdef __GLIBC__
343      // For the GNU C library pthread_self() is usable without linking to
344      // libpthread.so but returns 0, so we cannot use it in single-threaded
345      // programs, because this_thread::get_id() != thread::id{} must be true.
346      // We know that pthread_t is an integral type in the GNU C library.
347      if (!__gthread_active_p())
348	return thread::id(1);
349#endif
350#endif
351      return thread::id(__gthread_self());
352    }
353
354    /// yield
355    inline void
356    yield() noexcept
357    {
358#ifdef _GLIBCXX_USE_SCHED_YIELD
359      __gthread_yield();
360#endif
361    }
362
363    void
364    __sleep_for(chrono::seconds, chrono::nanoseconds);
365
366    /// sleep_for
367    template<typename _Rep, typename _Period>
368      inline void
369      sleep_for(const chrono::duration<_Rep, _Period>& __rtime)
370      {
371	if (__rtime <= __rtime.zero())
372	  return;
373	auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
374	auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
375#ifdef _GLIBCXX_USE_NANOSLEEP
376	__gthread_time_t __ts =
377	  {
378	    static_cast<std::time_t>(__s.count()),
379	    static_cast<long>(__ns.count())
380	  };
381	while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
382	  { }
383#else
384	__sleep_for(__s, __ns);
385#endif
386      }
387
388    /// sleep_until
389    template<typename _Clock, typename _Duration>
390      inline void
391      sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
392      {
393	auto __now = _Clock::now();
394	if (_Clock::is_steady)
395	  {
396	    if (__now < __atime)
397	      sleep_for(__atime - __now);
398	    return;
399	  }
400	while (__now < __atime)
401	  {
402	    sleep_for(__atime - __now);
403	    __now = _Clock::now();
404	  }
405      }
406  }
407
408  // @} group threads
409
410_GLIBCXX_END_NAMESPACE_VERSION
411} // namespace
412
413#endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
414
415#endif // C++11
416
417#endif // _GLIBCXX_THREAD
418