1// <thread> -*- C++ -*-
2
3// Copyright (C) 2008-2020 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 <bits/c++config.h>
39
40#if defined(_GLIBCXX_HAS_GTHREADS)
41#include <bits/gthr.h>
42
43#include <chrono> // std::chrono::*
44#include <memory> // std::unique_ptr
45#include <tuple>  // std::tuple
46
47#if __cplusplus > 201703L
48# include <compare>	// std::strong_ordering
49# include <stop_token>	// std::stop_source, std::stop_token, std::nostopstate
50#endif
51
52#ifdef _GLIBCXX_USE_NANOSLEEP
53# include <cerrno>  // errno, EINTR
54# include <time.h>  // nanosleep
55#endif
56
57#include <bits/functional_hash.h> // std::hash
58#include <bits/invoke.h>	  // std::__invoke
59
60namespace std _GLIBCXX_VISIBILITY(default)
61{
62_GLIBCXX_BEGIN_NAMESPACE_VERSION
63
64  /**
65   * @defgroup threads Threads
66   * @ingroup concurrency
67   *
68   * Classes for thread support.
69   * @{
70   */
71
72  /// thread
73  class thread
74  {
75  public:
76    // Abstract base class for types that wrap arbitrary functors to be
77    // invoked in the new thread of execution.
78    struct _State
79    {
80      virtual ~_State();
81      virtual void _M_run() = 0;
82    };
83    using _State_ptr = unique_ptr<_State>;
84
85    typedef __gthread_t			native_handle_type;
86
87    /// thread::id
88    class id
89    {
90      native_handle_type	_M_thread;
91
92    public:
93      id() noexcept : _M_thread() { }
94
95      explicit
96      id(native_handle_type __id) : _M_thread(__id) { }
97
98    private:
99      friend class thread;
100      friend class hash<id>;
101
102      friend bool
103      operator==(id __x, id __y) noexcept;
104
105#if __cpp_lib_three_way_comparison
106      friend strong_ordering
107      operator<=>(id __x, id __y) noexcept;
108#else
109      friend bool
110      operator<(id __x, id __y) noexcept;
111#endif
112
113      template<class _CharT, class _Traits>
114	friend basic_ostream<_CharT, _Traits>&
115	operator<<(basic_ostream<_CharT, _Traits>& __out, id __id);
116    };
117
118  private:
119    id				_M_id;
120
121    // _GLIBCXX_RESOLVE_LIB_DEFECTS
122    // 2097.  packaged_task constructors should be constrained
123    // 3039. Unnecessary decay in thread and packaged_task
124    template<typename _Tp>
125      using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
126
127  public:
128    thread() noexcept = default;
129
130    template<typename _Callable, typename... _Args,
131	     typename = _Require<__not_same<_Callable>>>
132      explicit
133      thread(_Callable&& __f, _Args&&... __args)
134      {
135	static_assert( __is_invocable<typename decay<_Callable>::type,
136				      typename decay<_Args>::type...>::value,
137	  "std::thread arguments must be invocable after conversion to rvalues"
138	  );
139
140#ifdef GTHR_ACTIVE_PROXY
141	// Create a reference to pthread_create, not just the gthr weak symbol.
142	auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
143#else
144	auto __depend = nullptr;
145#endif
146	// A call wrapper holding tuple{DECAY_COPY(__f), DECAY_COPY(__args)...}
147	using _Invoker_type = _Invoker<__decayed_tuple<_Callable, _Args...>>;
148
149	_M_start_thread(_S_make_state<_Invoker_type>(
150	      std::forward<_Callable>(__f), std::forward<_Args>(__args)...),
151	    __depend);
152      }
153
154    ~thread()
155    {
156      if (joinable())
157	std::terminate();
158    }
159
160    thread(const thread&) = delete;
161
162    thread(thread&& __t) noexcept
163    { swap(__t); }
164
165    thread& operator=(const thread&) = delete;
166
167    thread& operator=(thread&& __t) noexcept
168    {
169      if (joinable())
170	std::terminate();
171      swap(__t);
172      return *this;
173    }
174
175    void
176    swap(thread& __t) noexcept
177    { std::swap(_M_id, __t._M_id); }
178
179    bool
180    joinable() const noexcept
181    { return !(_M_id == id()); }
182
183    void
184    join();
185
186    void
187    detach();
188
189    id
190    get_id() const noexcept
191    { return _M_id; }
192
193    /** @pre thread is joinable
194     */
195    native_handle_type
196    native_handle()
197    { return _M_id._M_thread; }
198
199    // Returns a value that hints at the number of hardware thread contexts.
200    static unsigned int
201    hardware_concurrency() noexcept;
202
203  private:
204    template<typename _Callable>
205      struct _State_impl : public _State
206      {
207	_Callable		_M_func;
208
209	template<typename... _Args>
210	  _State_impl(_Args&&... __args)
211	  : _M_func{{std::forward<_Args>(__args)...}}
212	  { }
213
214	void
215	_M_run() { _M_func(); }
216      };
217
218    void
219    _M_start_thread(_State_ptr, void (*)());
220
221    template<typename _Callable, typename... _Args>
222      static _State_ptr
223      _S_make_state(_Args&&... __args)
224      {
225	using _Impl = _State_impl<_Callable>;
226	return _State_ptr{new _Impl{std::forward<_Args>(__args)...}};
227      }
228#if _GLIBCXX_THREAD_ABI_COMPAT
229  public:
230    struct _Impl_base;
231    typedef shared_ptr<_Impl_base>	__shared_base_type;
232    struct _Impl_base
233    {
234      __shared_base_type	_M_this_ptr;
235      virtual ~_Impl_base() = default;
236      virtual void _M_run() = 0;
237    };
238
239  private:
240    void
241    _M_start_thread(__shared_base_type, void (*)());
242
243    void
244    _M_start_thread(__shared_base_type);
245#endif
246
247  private:
248    // A call wrapper that does INVOKE(forwarded tuple elements...)
249    template<typename _Tuple>
250      struct _Invoker
251      {
252	_Tuple _M_t;
253
254	template<typename>
255	  struct __result;
256	template<typename _Fn, typename... _Args>
257	  struct __result<tuple<_Fn, _Args...>>
258	  : __invoke_result<_Fn, _Args...>
259	  { };
260
261	template<size_t... _Ind>
262	  typename __result<_Tuple>::type
263	  _M_invoke(_Index_tuple<_Ind...>)
264	  { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
265
266	typename __result<_Tuple>::type
267	operator()()
268	{
269	  using _Indices
270	    = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
271	  return _M_invoke(_Indices());
272	}
273      };
274
275    template<typename... _Tp>
276      using __decayed_tuple = tuple<typename decay<_Tp>::type...>;
277
278  public:
279    // Returns a call wrapper that stores
280    // tuple{DECAY_COPY(__callable), DECAY_COPY(__args)...}.
281    template<typename _Callable, typename... _Args>
282      static _Invoker<__decayed_tuple<_Callable, _Args...>>
283      __make_invoker(_Callable&& __callable, _Args&&... __args)
284      {
285	return { __decayed_tuple<_Callable, _Args...>{
286	    std::forward<_Callable>(__callable), std::forward<_Args>(__args)...
287	} };
288      }
289  };
290
291  inline void
292  swap(thread& __x, thread& __y) noexcept
293  { __x.swap(__y); }
294
295  inline bool
296  operator==(thread::id __x, thread::id __y) noexcept
297  {
298    // pthread_equal is undefined if either thread ID is not valid, so we
299    // can't safely use __gthread_equal on default-constructed values (nor
300    // the non-zero value returned by this_thread::get_id() for
301    // single-threaded programs using GNU libc). Assume EqualityComparable.
302    return __x._M_thread == __y._M_thread;
303  }
304
305#if __cpp_lib_three_way_comparison
306  inline strong_ordering
307  operator<=>(thread::id __x, thread::id __y) noexcept
308  { return __x._M_thread <=> __y._M_thread; }
309#else
310  inline bool
311  operator!=(thread::id __x, thread::id __y) noexcept
312  { return !(__x == __y); }
313
314  inline bool
315  operator<(thread::id __x, thread::id __y) noexcept
316  {
317    // Pthreads doesn't define any way to do this, so we just have to
318    // assume native_handle_type is LessThanComparable.
319    return __x._M_thread < __y._M_thread;
320  }
321
322  inline bool
323  operator<=(thread::id __x, thread::id __y) noexcept
324  { return !(__y < __x); }
325
326  inline bool
327  operator>(thread::id __x, thread::id __y) noexcept
328  { return __y < __x; }
329
330  inline bool
331  operator>=(thread::id __x, thread::id __y) noexcept
332  { return !(__x < __y); }
333#endif // __cpp_lib_three_way_comparison
334
335  // DR 889.
336  /// std::hash specialization for thread::id.
337  template<>
338    struct hash<thread::id>
339    : public __hash_base<size_t, thread::id>
340    {
341      size_t
342      operator()(const thread::id& __id) const noexcept
343      { return std::_Hash_impl::hash(__id._M_thread); }
344    };
345
346  template<class _CharT, class _Traits>
347    inline basic_ostream<_CharT, _Traits>&
348    operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
349    {
350      if (__id == thread::id())
351	return __out << "thread::id of a non-executing thread";
352      else
353	return __out << __id._M_thread;
354    }
355
356  /** @namespace std::this_thread
357   *  @brief ISO C++ 2011 namespace for interacting with the current thread
358   *
359   *  C++11 30.3.2 [thread.thread.this] Namespace this_thread.
360   */
361  namespace this_thread
362  {
363    /// get_id
364    inline thread::id
365    get_id() noexcept
366    {
367#ifdef _GLIBCXX_NATIVE_THREAD_ID
368      return thread::id(_GLIBCXX_NATIVE_THREAD_ID);
369#else
370      return thread::id(__gthread_self());
371#endif
372    }
373
374    /// yield
375    inline void
376    yield() noexcept
377    {
378#ifdef _GLIBCXX_USE_SCHED_YIELD
379      __gthread_yield();
380#endif
381    }
382
383    void
384    __sleep_for(chrono::seconds, chrono::nanoseconds);
385
386    /// sleep_for
387    template<typename _Rep, typename _Period>
388      inline void
389      sleep_for(const chrono::duration<_Rep, _Period>& __rtime)
390      {
391	if (__rtime <= __rtime.zero())
392	  return;
393	auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
394	auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
395#ifdef _GLIBCXX_USE_NANOSLEEP
396	__gthread_time_t __ts =
397	  {
398	    static_cast<std::time_t>(__s.count()),
399	    static_cast<long>(__ns.count())
400	  };
401	while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
402	  { }
403#else
404	__sleep_for(__s, __ns);
405#endif
406      }
407
408    /// sleep_until
409    template<typename _Clock, typename _Duration>
410      inline void
411      sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
412      {
413#if __cplusplus > 201703L
414	static_assert(chrono::is_clock_v<_Clock>);
415#endif
416	auto __now = _Clock::now();
417	if (_Clock::is_steady)
418	  {
419	    if (__now < __atime)
420	      sleep_for(__atime - __now);
421	    return;
422	  }
423	while (__now < __atime)
424	  {
425	    sleep_for(__atime - __now);
426	    __now = _Clock::now();
427	  }
428      }
429  }
430
431  /// @} group threads
432
433#ifdef __cpp_lib_jthread
434
435  class jthread
436  {
437  public:
438    using id = thread::id;
439    using native_handle_type = thread::native_handle_type;
440
441    jthread() noexcept
442    : _M_stop_source{nostopstate}
443    { }
444
445    template<typename _Callable, typename... _Args,
446	     typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
447					       jthread>>>
448      explicit
449      jthread(_Callable&& __f, _Args&&... __args)
450      : _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
451			    std::forward<_Args>(__args)...)}
452      { }
453
454    jthread(const jthread&) = delete;
455    jthread(jthread&&) noexcept = default;
456
457    ~jthread()
458    {
459      if (joinable())
460        {
461          request_stop();
462          join();
463        }
464    }
465
466    jthread&
467    operator=(const jthread&) = delete;
468
469    jthread&
470    operator=(jthread&& __other) noexcept
471    {
472      std::jthread(std::move(__other)).swap(*this);
473      return *this;
474    }
475
476    void
477    swap(jthread& __other) noexcept
478    {
479      std::swap(_M_stop_source, __other._M_stop_source);
480      std::swap(_M_thread, __other._M_thread);
481    }
482
483    [[nodiscard]] bool
484    joinable() const noexcept
485    {
486      return _M_thread.joinable();
487    }
488
489    void
490    join()
491    {
492      _M_thread.join();
493    }
494
495    void
496    detach()
497    {
498      _M_thread.detach();
499    }
500
501    [[nodiscard]] id
502    get_id() const noexcept
503    {
504      return _M_thread.get_id();
505    }
506
507    [[nodiscard]] native_handle_type
508    native_handle()
509    {
510      return _M_thread.native_handle();
511    }
512
513    [[nodiscard]] static unsigned
514    hardware_concurrency() noexcept
515    {
516      return thread::hardware_concurrency();
517    }
518
519    [[nodiscard]] stop_source
520    get_stop_source() noexcept
521    {
522      return _M_stop_source;
523    }
524
525    [[nodiscard]] stop_token
526    get_stop_token() const noexcept
527    {
528      return _M_stop_source.get_token();
529    }
530
531    bool request_stop() noexcept
532    {
533      return _M_stop_source.request_stop();
534    }
535
536    friend void swap(jthread& __lhs, jthread& __rhs) noexcept
537    {
538      __lhs.swap(__rhs);
539    }
540
541  private:
542    template<typename _Callable, typename... _Args>
543      static thread
544      _S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
545      {
546	if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
547				    decay_t<_Args>...>)
548	  return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
549			std::forward<_Args>(__args)...};
550	else
551	  {
552	    static_assert(is_invocable_v<decay_t<_Callable>,
553					 decay_t<_Args>...>,
554			  "std::thread arguments must be invocable after"
555			  " conversion to rvalues");
556	    return thread{std::forward<_Callable>(__f),
557			  std::forward<_Args>(__args)...};
558	  }
559      }
560
561    stop_source _M_stop_source;
562    thread _M_thread;
563  };
564#endif // __cpp_lib_jthread
565_GLIBCXX_END_NAMESPACE_VERSION
566} // namespace
567#endif // _GLIBCXX_HAS_GTHREADS
568#endif // C++11
569#endif // _GLIBCXX_THREAD
570