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51 lines
1.5 KiB
C++
51 lines
1.5 KiB
C++
// Copyright (c) 2013 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_SPIN_LOCK_H
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#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_SPIN_LOCK_H
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#include <atomic>
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#include <memory>
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#include <mutex>
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#include "base/base_export.h"
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#include "base/compiler_specific.h"
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// Spinlock is a simple spinlock class based on the standard CPU primitive of
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// atomic increment and decrement of an int at a given memory address. These are
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// intended only for very short duration locks and assume a system with multiple
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// cores. For any potentially longer wait you should use a real lock, such as
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// |base::Lock|.
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namespace base {
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namespace subtle {
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class BASE_EXPORT SpinLock {
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public:
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constexpr SpinLock() = default;
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~SpinLock() = default;
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using Guard = std::lock_guard<SpinLock>;
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ALWAYS_INLINE void lock() {
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static_assert(sizeof(lock_) == sizeof(int),
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"int and lock_ are different sizes");
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if (LIKELY(!lock_.exchange(true, std::memory_order_acquire)))
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return;
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LockSlow();
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}
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ALWAYS_INLINE void unlock() { lock_.store(false, std::memory_order_release); }
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private:
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// This is called if the initial attempt to acquire the lock fails. It's
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// slower, but has a much better scheduling and power consumption behavior.
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void LockSlow();
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std::atomic_int lock_{0};
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};
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} // namespace subtle
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} // namespace base
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#endif // BASE_ALLOCATOR_PARTITION_ALLOCATOR_SPIN_LOCK_H
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