1// <thread> -*- C++ -*-
2
3// Copyright (C) 2008-2019 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)
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    // 3039. Unnecessary decay in thread and packaged_task
108    template<typename _Tp>
109      using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
110
111  public:
112    thread() noexcept = default;
113
114    template<typename _Callable, typename... _Args,
115	     typename = _Require<__not_same<_Callable>>>
116      explicit
117      thread(_Callable&& __f, _Args&&... __args)
118      {
119	static_assert( __is_invocable<typename decay<_Callable>::type,
120				      typename decay<_Args>::type...>::value,
121	  "std::thread arguments must be invocable after conversion to rvalues"
122	  );
123
124#ifdef GTHR_ACTIVE_PROXY
125	// Create a reference to pthread_create, not just the gthr weak symbol.
126	auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
127#else
128	auto __depend = nullptr;
129#endif
130        _M_start_thread(_S_make_state(
131	      __make_invoker(std::forward<_Callable>(__f),
132			     std::forward<_Args>(__args)...)),
133	    __depend);
134      }
135
136    ~thread()
137    {
138      if (joinable())
139	std::terminate();
140    }
141
142    thread(const thread&) = delete;
143
144    thread(thread&& __t) noexcept
145    { swap(__t); }
146
147    thread& operator=(const thread&) = delete;
148
149    thread& operator=(thread&& __t) noexcept
150    {
151      if (joinable())
152	std::terminate();
153      swap(__t);
154      return *this;
155    }
156
157    void
158    swap(thread& __t) noexcept
159    { std::swap(_M_id, __t._M_id); }
160
161    bool
162    joinable() const noexcept
163    { return !(_M_id == id()); }
164
165    void
166    join();
167
168    void
169    detach();
170
171    thread::id
172    get_id() const noexcept
173    { return _M_id; }
174
175    /** @pre thread is joinable
176     */
177    native_handle_type
178    native_handle()
179    { return _M_id._M_thread; }
180
181    // Returns a value that hints at the number of hardware thread contexts.
182    static unsigned int
183    hardware_concurrency() noexcept;
184
185  private:
186    template<typename _Callable>
187      struct _State_impl : public _State
188      {
189	_Callable		_M_func;
190
191	_State_impl(_Callable&& __f) : _M_func(std::forward<_Callable>(__f))
192	{ }
193
194	void
195	_M_run() { _M_func(); }
196      };
197
198    void
199    _M_start_thread(_State_ptr, void (*)());
200
201    template<typename _Callable>
202      static _State_ptr
203      _S_make_state(_Callable&& __f)
204      {
205	using _Impl = _State_impl<_Callable>;
206	return _State_ptr{new _Impl{std::forward<_Callable>(__f)}};
207      }
208#if _GLIBCXX_THREAD_ABI_COMPAT
209  public:
210    struct _Impl_base;
211    typedef shared_ptr<_Impl_base>	__shared_base_type;
212    struct _Impl_base
213    {
214      __shared_base_type	_M_this_ptr;
215      virtual ~_Impl_base() = default;
216      virtual void _M_run() = 0;
217    };
218
219  private:
220    void
221    _M_start_thread(__shared_base_type, void (*)());
222
223    void
224    _M_start_thread(__shared_base_type);
225#endif
226
227  private:
228    // A call wrapper that does INVOKE(forwarded tuple elements...)
229    template<typename _Tuple>
230      struct _Invoker
231      {
232	_Tuple _M_t;
233
234	template<typename>
235	  struct __result;
236	template<typename _Fn, typename... _Args>
237	  struct __result<tuple<_Fn, _Args...>>
238	  : __invoke_result<_Fn, _Args...>
239	  { };
240
241	template<size_t... _Ind>
242	  typename __result<_Tuple>::type
243	  _M_invoke(_Index_tuple<_Ind...>)
244	  { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
245
246	typename __result<_Tuple>::type
247	operator()()
248	{
249	  using _Indices
250	    = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
251	  return _M_invoke(_Indices());
252	}
253      };
254
255    template<typename... _Tp>
256      using __decayed_tuple = tuple<typename decay<_Tp>::type...>;
257
258  public:
259    // Returns a call wrapper that stores
260    // tuple{DECAY_COPY(__callable), DECAY_COPY(__args)...}.
261    template<typename _Callable, typename... _Args>
262      static _Invoker<__decayed_tuple<_Callable, _Args...>>
263      __make_invoker(_Callable&& __callable, _Args&&... __args)
264      {
265	return { __decayed_tuple<_Callable, _Args...>{
266	    std::forward<_Callable>(__callable), std::forward<_Args>(__args)...
267	} };
268      }
269  };
270
271  inline void
272  swap(thread& __x, thread& __y) noexcept
273  { __x.swap(__y); }
274
275  inline bool
276  operator==(thread::id __x, thread::id __y) noexcept
277  {
278    // pthread_equal is undefined if either thread ID is not valid, so we
279    // can't safely use __gthread_equal on default-constructed values (nor
280    // the non-zero value returned by this_thread::get_id() for
281    // single-threaded programs using GNU libc). Assume EqualityComparable.
282    return __x._M_thread == __y._M_thread;
283  }
284
285  inline bool
286  operator!=(thread::id __x, thread::id __y) noexcept
287  { return !(__x == __y); }
288
289  inline bool
290  operator<(thread::id __x, thread::id __y) noexcept
291  {
292    // Pthreads doesn't define any way to do this, so we just have to
293    // assume native_handle_type is LessThanComparable.
294    return __x._M_thread < __y._M_thread;
295  }
296
297  inline bool
298  operator<=(thread::id __x, thread::id __y) noexcept
299  { return !(__y < __x); }
300
301  inline bool
302  operator>(thread::id __x, thread::id __y) noexcept
303  { return __y < __x; }
304
305  inline bool
306  operator>=(thread::id __x, thread::id __y) noexcept
307  { return !(__x < __y); }
308
309  // DR 889.
310  /// std::hash specialization for thread::id.
311  template<>
312    struct hash<thread::id>
313    : public __hash_base<size_t, thread::id>
314    {
315      size_t
316      operator()(const thread::id& __id) const noexcept
317      { return std::_Hash_impl::hash(__id._M_thread); }
318    };
319
320  template<class _CharT, class _Traits>
321    inline basic_ostream<_CharT, _Traits>&
322    operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
323    {
324      if (__id == thread::id())
325	return __out << "thread::id of a non-executing thread";
326      else
327	return __out << __id._M_thread;
328    }
329
330  /** @namespace std::this_thread
331   *  @brief ISO C++ 2011 entities sub-namespace for thread.
332   *  30.3.2 Namespace this_thread.
333   */
334  namespace this_thread
335  {
336    /// get_id
337    inline thread::id
338    get_id() noexcept
339    {
340/* L4Re added: "&& !defined(__UCLIBC__)" although it's rather an L4 issue */
341#if defined(__GLIBC__) && !defined(__UCLIBC__)
342      // For the GNU C library pthread_self() is usable without linking to
343      // libpthread.so but returns 0, so we cannot use it in single-threaded
344      // programs, because this_thread::get_id() != thread::id{} must be true.
345      // We know that pthread_t is an integral type in the GNU C library.
346      if (!__gthread_active_p())
347	return thread::id(1);
348#endif
349      return thread::id(__gthread_self());
350    }
351
352    /// yield
353    inline void
354    yield() noexcept
355    {
356#ifdef _GLIBCXX_USE_SCHED_YIELD
357      __gthread_yield();
358#endif
359    }
360
361    void
362    __sleep_for(chrono::seconds, chrono::nanoseconds);
363
364    /// sleep_for
365    template<typename _Rep, typename _Period>
366      inline void
367      sleep_for(const chrono::duration<_Rep, _Period>& __rtime)
368      {
369	if (__rtime <= __rtime.zero())
370	  return;
371	auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
372	auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
373#ifdef _GLIBCXX_USE_NANOSLEEP
374	__gthread_time_t __ts =
375	  {
376	    static_cast<std::time_t>(__s.count()),
377	    static_cast<long>(__ns.count())
378	  };
379	while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
380	  { }
381#else
382	__sleep_for(__s, __ns);
383#endif
384      }
385
386    /// sleep_until
387    template<typename _Clock, typename _Duration>
388      inline void
389      sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
390      {
391	auto __now = _Clock::now();
392	if (_Clock::is_steady)
393	  {
394	    if (__now < __atime)
395	      sleep_for(__atime - __now);
396	    return;
397	  }
398	while (__now < __atime)
399	  {
400	    sleep_for(__atime - __now);
401	    __now = _Clock::now();
402	  }
403      }
404  }
405
406  /// @} group threads
407
408_GLIBCXX_END_NAMESPACE_VERSION
409} // namespace
410
411#endif // _GLIBCXX_HAS_GTHREADS
412
413#endif // C++11
414
415#endif // _GLIBCXX_THREAD
416