1#ifndef BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED
2#define BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED
3
4// MS compatible compilers support #pragma once
5
6#if defined(_MSC_VER) && (_MSC_VER >= 1020)
7# pragma once
8#endif
9
10//
11// yield_k.hpp
12//
13// Copyright (c) 2008 Peter Dimov
14// Copyright (c) Microsoft Corporation 2014
15//
16// void yield( unsigned k );
17//
18// Typical use:
19//
20// for( unsigned k = 0; !try_lock(); ++k ) yield( k );
21//
22// Distributed under the Boost Software License, Version 1.0.
23// See accompanying file LICENSE_1_0.txt or copy at
24// http://www.boost.org/LICENSE_1_0.txt
25//
26
27#include <boost/config.hpp>
28#include <boost/predef.h>
29
30#if BOOST_PLAT_WINDOWS_RUNTIME
31#include <thread>
32#endif
33
34// BOOST_SMT_PAUSE
35
36#if defined(_MSC_VER) && _MSC_VER >= 1310 && ( defined(_M_IX86) || defined(_M_X64) )
37
38extern "C" void _mm_pause();
39
40#define BOOST_SMT_PAUSE _mm_pause();
41
42#elif defined(__GNUC__) && ( defined(__i386__) || defined(__x86_64__) )
43
44#define BOOST_SMT_PAUSE __asm__ __volatile__( "rep; nop" : : : "memory" );
45
46#endif
47
48//
49
50#if defined( WIN32 ) || defined( _WIN32 ) || defined( __WIN32__ ) || defined( __CYGWIN__ )
51
52#if defined( BOOST_USE_WINDOWS_H )
53# include <windows.h>
54#endif
55
56namespace boost
57{
58
59namespace detail
60{
61
62#if !defined( BOOST_USE_WINDOWS_H ) && !BOOST_PLAT_WINDOWS_RUNTIME
63#if !BOOST_COMP_CLANG || !defined __MINGW32__
64 extern "C" void __stdcall Sleep( unsigned long ms );
65#else
66#include <_mingw.h>
67#if !defined __MINGW64_VERSION_MAJOR
68 extern "C" void __stdcall Sleep( unsigned long ms );
69#else
70 extern "C" __declspec(dllimport) void __stdcall Sleep( unsigned long ms );
71#endif
72#endif
73#endif
74
75inline void yield( unsigned k )
76{
77 if( k < 4 )
78 {
79 }
80#if defined( BOOST_SMT_PAUSE )
81 else if( k < 16 )
82 {
83 BOOST_SMT_PAUSE
84 }
85#endif
86#if !BOOST_PLAT_WINDOWS_RUNTIME
87 else if( k < 32 )
88 {
89 Sleep( 0 );
90 }
91 else
92 {
93 Sleep( 1 );
94 }
95#else
96 else
97 {
98 // Sleep isn't supported on the Windows Runtime.
99 std::this_thread::yield();
100 }
101#endif
102}
103
104} // namespace detail
105
106} // namespace boost
107
108#elif defined( BOOST_HAS_PTHREADS )
109
110#ifndef _AIX
111#include <sched.h>
112#else
113 // AIX's sched.h defines ::var which sometimes conflicts with Lambda's var
114 extern "C" int sched_yield(void);
115#endif
116
117#include <time.h>
118
119namespace boost
120{
121
122namespace detail
123{
124
125inline void yield( unsigned k )
126{
127 if( k < 4 )
128 {
129 }
130#if defined( BOOST_SMT_PAUSE )
131 else if( k < 16 )
132 {
133 BOOST_SMT_PAUSE
134 }
135#endif
136 else if( k < 32 || k & 1 )
137 {
138 sched_yield();
139 }
140 else
141 {
142 // g++ -Wextra warns on {} or {0}
143 struct timespec rqtp = { .tv_sec: 0, .tv_nsec: 0 };
144
145 // POSIX says that timespec has tv_sec and tv_nsec
146 // But it doesn't guarantee order or placement
147
148 rqtp.tv_sec = 0;
149 rqtp.tv_nsec = 1000;
150
151 nanosleep( requested_time: &rqtp, remaining: 0 );
152 }
153}
154
155} // namespace detail
156
157} // namespace boost
158
159#else
160
161namespace boost
162{
163
164namespace detail
165{
166
167inline void yield( unsigned )
168{
169}
170
171} // namespace detail
172
173} // namespace boost
174
175#endif
176
177#endif // #ifndef BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED
178

source code of boost/boost/smart_ptr/detail/yield_k.hpp