1/*
2 Copyright (c) 2005-2019 Intel Corporation
3
4 Licensed under the Apache License, Version 2.0 (the "License");
5 you may not use this file except in compliance with the License.
6 You may obtain a copy of the License at
7
8 http://www.apache.org/licenses/LICENSE-2.0
9
10 Unless required by applicable law or agreed to in writing, software
11 distributed under the License is distributed on an "AS IS" BASIS,
12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 See the License for the specific language governing permissions and
14 limitations under the License.
15*/
16
17#ifndef __TBB_spin_mutex_H
18#define __TBB_spin_mutex_H
19
20#include <cstddef>
21#include <new>
22#include "aligned_space.h"
23#include "tbb_stddef.h"
24#include "tbb_machine.h"
25#include "tbb_profiling.h"
26#include "internal/_mutex_padding.h"
27
28namespace tbb {
29
30//! A lock that occupies a single byte.
31/** A spin_mutex is a spin mutex that fits in a single byte.
32 It should be used only for locking short critical sections
33 (typically less than 20 instructions) when fairness is not an issue.
34 If zero-initialized, the mutex is considered unheld.
35 @ingroup synchronization */
36class spin_mutex : internal::mutex_copy_deprecated_and_disabled {
37 //! 0 if lock is released, 1 if lock is acquired.
38 __TBB_atomic_flag flag;
39
40public:
41 //! Construct unacquired lock.
42 /** Equivalent to zero-initialization of *this. */
43 spin_mutex() : flag(0) {
44#if TBB_USE_THREADING_TOOLS
45 internal_construct();
46#endif
47 }
48
49 //! Represents acquisition of a mutex.
50 class scoped_lock : internal::no_copy {
51 private:
52 //! Points to currently held mutex, or NULL if no lock is held.
53 spin_mutex* my_mutex;
54
55 //! Value to store into spin_mutex::flag to unlock the mutex.
56 /** This variable is no longer used. Instead, 0 and 1 are used to
57 represent that the lock is free and acquired, respectively.
58 We keep the member variable here to ensure backward compatibility */
59 __TBB_Flag my_unlock_value;
60
61 //! Like acquire, but with ITT instrumentation.
62 void __TBB_EXPORTED_METHOD internal_acquire( spin_mutex& m );
63
64 //! Like try_acquire, but with ITT instrumentation.
65 bool __TBB_EXPORTED_METHOD internal_try_acquire( spin_mutex& m );
66
67 //! Like release, but with ITT instrumentation.
68 void __TBB_EXPORTED_METHOD internal_release();
69
70 friend class spin_mutex;
71
72 public:
73 //! Construct without acquiring a mutex.
74 scoped_lock() : my_mutex(NULL), my_unlock_value(0) {}
75
76 //! Construct and acquire lock on a mutex.
77 scoped_lock( spin_mutex& m ) : my_unlock_value(0) {
78 internal::suppress_unused_warning(my_unlock_value);
79#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
80 my_mutex=NULL;
81 internal_acquire(m);
82#else
83 my_mutex=&m;
84 __TBB_LockByte(m.flag);
85#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
86 }
87
88 //! Acquire lock.
89 void acquire( spin_mutex& m ) {
90#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
91 internal_acquire(m);
92#else
93 my_mutex = &m;
94 __TBB_LockByte(m.flag);
95#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
96 }
97
98 //! Try acquiring lock (non-blocking)
99 /** Return true if lock acquired; false otherwise. */
100 bool try_acquire( spin_mutex& m ) {
101#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
102 return internal_try_acquire(m);
103#else
104 bool result = __TBB_TryLockByte(m.flag);
105 if( result )
106 my_mutex = &m;
107 return result;
108#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
109 }
110
111 //! Release lock
112 void release() {
113#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
114 internal_release();
115#else
116 __TBB_UnlockByte(my_mutex->flag);
117 my_mutex = NULL;
118#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
119 }
120
121 //! Destroy lock. If holding a lock, releases the lock first.
122 ~scoped_lock() {
123 if( my_mutex ) {
124#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
125 internal_release();
126#else
127 __TBB_UnlockByte(my_mutex->flag);
128#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
129 }
130 }
131 };
132
133 //! Internal constructor with ITT instrumentation.
134 void __TBB_EXPORTED_METHOD internal_construct();
135
136 // Mutex traits
137 static const bool is_rw_mutex = false;
138 static const bool is_recursive_mutex = false;
139 static const bool is_fair_mutex = false;
140
141 // ISO C++0x compatibility methods
142
143 //! Acquire lock
144 void lock() {
145#if TBB_USE_THREADING_TOOLS
146 aligned_space<scoped_lock> tmp;
147 new(tmp.begin()) scoped_lock(*this);
148#else
149 __TBB_LockByte(flag);
150#endif /* TBB_USE_THREADING_TOOLS*/
151 }
152
153 //! Try acquiring lock (non-blocking)
154 /** Return true if lock acquired; false otherwise. */
155 bool try_lock() {
156#if TBB_USE_THREADING_TOOLS
157 aligned_space<scoped_lock> tmp;
158 return (new(tmp.begin()) scoped_lock)->internal_try_acquire(*this);
159#else
160 return __TBB_TryLockByte(flag);
161#endif /* TBB_USE_THREADING_TOOLS*/
162 }
163
164 //! Release lock
165 void unlock() {
166#if TBB_USE_THREADING_TOOLS
167 aligned_space<scoped_lock> tmp;
168 scoped_lock& s = *tmp.begin();
169 s.my_mutex = this;
170 s.internal_release();
171#else
172 __TBB_UnlockByte(flag);
173#endif /* TBB_USE_THREADING_TOOLS */
174 }
175
176 friend class scoped_lock;
177}; // end of spin_mutex
178
179__TBB_DEFINE_PROFILING_SET_NAME(spin_mutex)
180
181} // namespace tbb
182
183#if ( __TBB_x86_32 || __TBB_x86_64 )
184#include "internal/_x86_eliding_mutex_impl.h"
185#endif
186
187namespace tbb {
188//! A cross-platform spin mutex with speculative lock acquisition.
189/** On platforms with proper HW support, this lock may speculatively execute
190 its critical sections, using HW mechanisms to detect real data races and
191 ensure atomicity of the critical sections. In particular, it uses
192 Intel(R) Transactional Synchronization Extensions (Intel(R) TSX).
193 Without such HW support, it behaves like a spin_mutex.
194 It should be used for locking short critical sections where the lock is
195 contended but the data it protects are not. If zero-initialized, the
196 mutex is considered unheld.
197 @ingroup synchronization */
198
199#if ( __TBB_x86_32 || __TBB_x86_64 )
200typedef interface7::internal::padded_mutex<interface7::internal::x86_eliding_mutex,false> speculative_spin_mutex;
201#else
202typedef interface7::internal::padded_mutex<spin_mutex,false> speculative_spin_mutex;
203#endif
204__TBB_DEFINE_PROFILING_SET_NAME(speculative_spin_mutex)
205
206} // namespace tbb
207
208#endif /* __TBB_spin_mutex_H */
209