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https://github.com/RGBCube/serenity
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545ce5b595
The platform independent Processor.h file includes the shared processor code and includes the specific platform header file. All references to the Arch/x86/Processor.h file have been replaced with a reference to Arch/Processor.h.
87 lines
2.3 KiB
C++
87 lines
2.3 KiB
C++
/*
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* Copyright (c) 2021, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Atomic.h>
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#include <Kernel/Arch/Processor.h>
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namespace Kernel {
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template<typename AtomicRefCountType>
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class AtomicEdgeAction {
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public:
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template<typename FirstRefAction>
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bool ref(FirstRefAction first_ref_action)
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{
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AtomicRefCountType expected = 0;
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AtomicRefCountType desired = (1 << 1) | 1;
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// Least significant bit indicates we're busy protecting/unprotecting
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for (;;) {
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if (m_atomic_ref_count.compare_exchange_strong(expected, desired, AK::memory_order_relaxed))
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break;
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Processor::wait_check();
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expected &= ~1;
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desired = expected + (1 << 1);
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VERIFY(desired > expected);
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if (expected == 0)
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desired |= 1;
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}
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atomic_thread_fence(AK::memory_order_acquire);
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if (expected == 0) {
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first_ref_action();
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// drop the busy flag
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m_atomic_ref_count.store(desired & ~1, AK::memory_order_release);
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return true;
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}
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return false;
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}
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template<typename LastRefAction>
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bool unref(LastRefAction last_ref_action)
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{
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AtomicRefCountType expected = 1 << 1;
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AtomicRefCountType desired = (1 << 1) | 1;
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// Least significant bit indicates we're busy protecting/unprotecting
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for (;;) {
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if (m_atomic_ref_count.compare_exchange_strong(expected, desired, AK::memory_order_relaxed))
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break;
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Processor::wait_check();
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expected &= ~1;
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VERIFY(expected != 0); // Someone should always have at least one reference
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if (expected == 1 << 1) {
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desired = (1 << 1) | 1;
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} else {
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desired = expected - (1 << 1);
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VERIFY(desired < expected);
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}
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}
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AK::atomic_thread_fence(AK::memory_order_release);
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if (expected == 1 << 1) {
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last_ref_action();
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// drop the busy flag and release reference
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m_atomic_ref_count.store(0, AK::memory_order_release);
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return true;
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}
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return false;
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}
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private:
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Atomic<AtomicRefCountType> m_atomic_ref_count { 0 };
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};
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}
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