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) ) && !defined(__c2__)
37 
38 extern "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 
56 namespace boost
57 {
58 
59 namespace 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 
yield(unsigned k)75 inline 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 
119 namespace boost
120 {
121 
122 namespace detail
123 {
124 
yield(unsigned k)125 inline 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 = { 0, 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( &rqtp, 0 );
152     }
153 }
154 
155 } // namespace detail
156 
157 } // namespace boost
158 
159 #else
160 
161 namespace boost
162 {
163 
164 namespace detail
165 {
166 
yield(unsigned)167 inline 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