mirror of
https://github.com/LadybirdBrowser/ladybird.git
synced 2024-11-22 15:40:19 +00:00
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++
/*
|
|
* Copyright (c) 2021, the SerenityOS developers.
|
|
*
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <AK/Atomic.h>
|
|
#include <Kernel/Arch/Processor.h>
|
|
|
|
namespace Kernel {
|
|
|
|
template<typename AtomicRefCountType>
|
|
class AtomicEdgeAction {
|
|
public:
|
|
template<typename FirstRefAction>
|
|
bool ref(FirstRefAction first_ref_action)
|
|
{
|
|
AtomicRefCountType expected = 0;
|
|
AtomicRefCountType desired = (1 << 1) | 1;
|
|
// Least significant bit indicates we're busy protecting/unprotecting
|
|
for (;;) {
|
|
if (m_atomic_ref_count.compare_exchange_strong(expected, desired, AK::memory_order_relaxed))
|
|
break;
|
|
|
|
Processor::wait_check();
|
|
|
|
expected &= ~1;
|
|
desired = expected + (1 << 1);
|
|
VERIFY(desired > expected);
|
|
if (expected == 0)
|
|
desired |= 1;
|
|
}
|
|
|
|
atomic_thread_fence(AK::memory_order_acquire);
|
|
|
|
if (expected == 0) {
|
|
first_ref_action();
|
|
|
|
// drop the busy flag
|
|
m_atomic_ref_count.store(desired & ~1, AK::memory_order_release);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
template<typename LastRefAction>
|
|
bool unref(LastRefAction last_ref_action)
|
|
{
|
|
AtomicRefCountType expected = 1 << 1;
|
|
AtomicRefCountType desired = (1 << 1) | 1;
|
|
// Least significant bit indicates we're busy protecting/unprotecting
|
|
for (;;) {
|
|
if (m_atomic_ref_count.compare_exchange_strong(expected, desired, AK::memory_order_relaxed))
|
|
break;
|
|
|
|
Processor::wait_check();
|
|
|
|
expected &= ~1;
|
|
VERIFY(expected != 0); // Someone should always have at least one reference
|
|
|
|
if (expected == 1 << 1) {
|
|
desired = (1 << 1) | 1;
|
|
} else {
|
|
desired = expected - (1 << 1);
|
|
VERIFY(desired < expected);
|
|
}
|
|
}
|
|
|
|
AK::atomic_thread_fence(AK::memory_order_release);
|
|
|
|
if (expected == 1 << 1) {
|
|
last_ref_action();
|
|
|
|
// drop the busy flag and release reference
|
|
m_atomic_ref_count.store(0, AK::memory_order_release);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
private:
|
|
Atomic<AtomicRefCountType> m_atomic_ref_count { 0 };
|
|
};
|
|
|
|
}
|