135 lines
3.4 KiB
C++
135 lines
3.4 KiB
C++
/*
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Copyright (c) 2005-2021 Intel Corporation
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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#ifndef __TBB_spin_mutex_H
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#define __TBB_spin_mutex_H
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#include "detail/_namespace_injection.h"
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#include "detail/_mutex_common.h"
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#include "profiling.h"
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#include "detail/_assert.h"
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#include "detail/_utils.h"
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#include "detail/_scoped_lock.h"
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#include <atomic>
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namespace tbb {
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namespace detail {
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namespace d1 {
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#if __TBB_TSX_INTRINSICS_PRESENT
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class rtm_mutex;
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#endif
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/** A spin_mutex is a low-level synchronization primitive.
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While locked, it causes the waiting threads to spin in a loop until the lock is released.
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It should be used only for locking short critical sections
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(typically less than 20 instructions) when fairness is not an issue.
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If zero-initialized, the mutex is considered unheld.
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@ingroup synchronization */
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class spin_mutex {
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public:
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//! Constructors
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spin_mutex() noexcept : m_flag(false) {
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create_itt_sync(this, "tbb::spin_mutex", "");
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};
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//! Destructor
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~spin_mutex() = default;
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//! No Copy
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spin_mutex(const spin_mutex&) = delete;
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spin_mutex& operator=(const spin_mutex&) = delete;
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using scoped_lock = unique_scoped_lock<spin_mutex>;
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//! Mutex traits
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static constexpr bool is_rw_mutex = false;
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static constexpr bool is_recursive_mutex = false;
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static constexpr bool is_fair_mutex = false;
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//! Acquire lock
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/** Spin if the lock is taken */
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void lock() {
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atomic_backoff backoff;
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call_itt_notify(prepare, this);
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while (m_flag.exchange(true)) backoff.pause();
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call_itt_notify(acquired, this);
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}
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//! Try acquiring lock (non-blocking)
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/** Return true if lock acquired; false otherwise. */
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bool try_lock() {
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bool result = !m_flag.exchange(true);
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if (result) {
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call_itt_notify(acquired, this);
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}
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return result;
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}
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//! Release lock
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void unlock() {
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call_itt_notify(releasing, this);
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m_flag.store(false, std::memory_order_release);
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}
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protected:
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std::atomic<bool> m_flag;
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}; // class spin_mutex
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#if TBB_USE_PROFILING_TOOLS
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inline void set_name(spin_mutex& obj, const char* name) {
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itt_set_sync_name(&obj, name);
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}
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#if (_WIN32||_WIN64)
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inline void set_name(spin_mutex& obj, const wchar_t* name) {
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itt_set_sync_name(&obj, name);
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}
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#endif //WIN
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#else
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inline void set_name(spin_mutex&, const char*) {}
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#if (_WIN32||_WIN64)
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inline void set_name(spin_mutex&, const wchar_t*) {}
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#endif // WIN
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#endif
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} // namespace d1
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} // namespace detail
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inline namespace v1 {
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using detail::d1::spin_mutex;
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} // namespace v1
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namespace profiling {
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using detail::d1::set_name;
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}
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} // namespace tbb
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#include "detail/_rtm_mutex.h"
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namespace tbb {
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inline namespace v1 {
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#if __TBB_TSX_INTRINSICS_PRESENT
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using speculative_spin_mutex = detail::d1::rtm_mutex;
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#else
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using speculative_spin_mutex = detail::d1::spin_mutex;
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#endif
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}
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}
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#endif /* __TBB_spin_mutex_H */
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