1 /* 2 Copyright (c) 2005-2021 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 "detail/_namespace_injection.h" 21 #include "detail/_mutex_common.h" 22 23 #include "profiling.h" 24 25 #include "detail/_assert.h" 26 #include "detail/_utils.h" 27 #include "detail/_scoped_lock.h" 28 29 #include <atomic> 30 31 namespace tbb { 32 namespace detail { 33 namespace d1 { 34 35 #if __TBB_TSX_INTRINSICS_PRESENT 36 class rtm_mutex; 37 #endif 38 39 /** A spin_mutex is a low-level synchronization primitive. 40 While locked, it causes the waiting threads to spin in a loop until the lock is released. 41 It should be used only for locking short critical sections 42 (typically less than 20 instructions) when fairness is not an issue. 43 If zero-initialized, the mutex is considered unheld. 44 @ingroup synchronization */ 45 class spin_mutex { 46 public: 47 //! Constructors 48 spin_mutex() noexcept : m_flag(false) { 49 create_itt_sync(this, "tbb::spin_mutex", ""); 50 }; 51 52 //! Destructor 53 ~spin_mutex() = default; 54 55 //! No Copy 56 spin_mutex(const spin_mutex&) = delete; 57 spin_mutex& operator=(const spin_mutex&) = delete; 58 59 using scoped_lock = unique_scoped_lock<spin_mutex>; 60 61 //! Mutex traits 62 static constexpr bool is_rw_mutex = false; 63 static constexpr bool is_recursive_mutex = false; 64 static constexpr bool is_fair_mutex = false; 65 66 //! Acquire lock 67 /** Spin if the lock is taken */ 68 void lock() { 69 atomic_backoff backoff; 70 call_itt_notify(prepare, this); 71 while (m_flag.exchange(true)) backoff.pause(); 72 call_itt_notify(acquired, this); 73 } 74 75 //! Try acquiring lock (non-blocking) 76 /** Return true if lock acquired; false otherwise. */ 77 bool try_lock() { 78 bool result = !m_flag.exchange(true); 79 if (result) { 80 call_itt_notify(acquired, this); 81 } 82 return result; 83 } 84 85 //! Release lock 86 void unlock() { 87 call_itt_notify(releasing, this); 88 m_flag.store(false, std::memory_order_release); 89 } 90 91 protected: 92 std::atomic<bool> m_flag; 93 }; // class spin_mutex 94 95 #if TBB_USE_PROFILING_TOOLS 96 inline void set_name(spin_mutex& obj, const char* name) { 97 itt_set_sync_name(&obj, name); 98 } 99 #if (_WIN32||_WIN64) 100 inline void set_name(spin_mutex& obj, const wchar_t* name) { 101 itt_set_sync_name(&obj, name); 102 } 103 #endif //WIN 104 #else 105 inline void set_name(spin_mutex&, const char*) {} 106 #if (_WIN32||_WIN64) 107 inline void set_name(spin_mutex&, const wchar_t*) {} 108 #endif // WIN 109 #endif 110 } // namespace d1 111 } // namespace detail 112 113 inline namespace v1 { 114 using detail::d1::spin_mutex; 115 } // namespace v1 116 namespace profiling { 117 using detail::d1::set_name; 118 } 119 } // namespace tbb 120 121 #include "detail/_rtm_mutex.h" 122 123 namespace tbb { 124 inline namespace v1 { 125 #if __TBB_TSX_INTRINSICS_PRESENT 126 using speculative_spin_mutex = detail::d1::rtm_mutex; 127 #else 128 using speculative_spin_mutex = detail::d1::spin_mutex; 129 #endif 130 } 131 } 132 133 #endif /* __TBB_spin_mutex_H */ 134 135