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/platform/windows_runtime.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) ) && !defined(__c2__)
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
64#if defined(__clang__) && defined(__x86_64__)
65// clang x64 warns that __stdcall is ignored
66# define BOOST_SP_STDCALL
67#else
68# define BOOST_SP_STDCALL __stdcall
69#endif
70
71#if defined(__LP64__) // Cygwin 64
72 extern "C" __declspec(dllimport) void BOOST_SP_STDCALL Sleep( unsigned int ms );
73#else
74 extern "C" __declspec(dllimport) void BOOST_SP_STDCALL Sleep( unsigned long ms );
75#endif
76
77#undef BOOST_SP_STDCALL
78
79#endif // !defined( BOOST_USE_WINDOWS_H ) && !BOOST_PLAT_WINDOWS_RUNTIME
80
81inline void yield( unsigned k ) BOOST_NOEXCEPT
82{
83 if( k < 4 )
84 {
85 }
86#if defined( BOOST_SMT_PAUSE )
87 else if( k < 16 )
88 {
89 BOOST_SMT_PAUSE
90 }
91#endif
92#if !BOOST_PLAT_WINDOWS_RUNTIME
93 else if( k < 32 )
94 {
95 Sleep( 0 );
96 }
97 else
98 {
99 Sleep( 1 );
100 }
101#else
102 else
103 {
104 // Sleep isn't supported on the Windows Runtime.
105 std::this_thread::yield();
106 }
107#endif
108}
109
110} // namespace detail
111
112} // namespace boost
113
114#elif defined( BOOST_HAS_PTHREADS )
115
116#ifndef _AIX
117#include <sched.h>
118#else
119 // AIX's sched.h defines ::var which sometimes conflicts with Lambda's var
120 extern "C" int sched_yield(void);
121#endif
122
123#include <time.h>
124
125namespace boost
126{
127
128namespace detail
129{
130
131inline void yield( unsigned k )
132{
133 if( k < 4 )
134 {
135 }
136#if defined( BOOST_SMT_PAUSE )
137 else if( k < 16 )
138 {
139 BOOST_SMT_PAUSE
140 }
141#endif
142 else if( k < 32 || k & 1 )
143 {
144 sched_yield();
145 }
146 else
147 {
148 // g++ -Wextra warns on {} or {0}
149 struct timespec rqtp = { 0, 0 };
150
151 // POSIX says that timespec has tv_sec and tv_nsec
152 // But it doesn't guarantee order or placement
153
154 rqtp.tv_sec = 0;
155 rqtp.tv_nsec = 1000;
156
157 nanosleep( &rqtp, 0 );
158 }
159}
160
161} // namespace detail
162
163} // namespace boost
164
165#else
166
167namespace boost
168{
169
170namespace detail
171{
172
173inline void yield( unsigned )
174{
175}
176
177} // namespace detail
178
179} // namespace boost
180
181#endif
182
183#endif // #ifndef BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED
184