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/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Atomic.h>
#include <AK/Types.h>
#include <Kernel/Arch/x86/CPU.h>
#include <Kernel/Forward.h>
namespace Kernel {
template<typename BaseType = u32>
class SpinLock {
AK_MAKE_NONCOPYABLE(SpinLock);
AK_MAKE_NONMOVABLE(SpinLock);
public:
SpinLock() = default;
ALWAYS_INLINE u32 lock()
{
u32 prev_flags;
Processor::current().enter_critical(prev_flags);
while (m_lock.exchange(1, AK::memory_order_acquire) != 0) {
Processor::wait_check();
}
return prev_flags;
}
ALWAYS_INLINE void unlock(u32 prev_flags)
{
VERIFY(is_locked());
m_lock.store(0, AK::memory_order_release);
Processor::current().leave_critical(prev_flags);
}
[[nodiscard]] ALWAYS_INLINE bool is_locked() const
{
return m_lock.load(AK::memory_order_relaxed) != 0;
}
ALWAYS_INLINE void initialize()
{
m_lock.store(0, AK::memory_order_relaxed);
}
private:
Atomic<BaseType> m_lock { 0 };
};
class RecursiveSpinLock {
AK_MAKE_NONCOPYABLE(RecursiveSpinLock);
AK_MAKE_NONMOVABLE(RecursiveSpinLock);
public:
RecursiveSpinLock() = default;
ALWAYS_INLINE u32 lock()
{
auto& proc = Processor::current();
FlatPtr cpu = FlatPtr(&proc);
u32 prev_flags;
proc.enter_critical(prev_flags);
FlatPtr expected = 0;
while (!m_lock.compare_exchange_strong(expected, cpu, AK::memory_order_acq_rel)) {
if (expected == cpu)
break;
Processor::wait_check();
expected = 0;
}
m_recursions++;
return prev_flags;
}
ALWAYS_INLINE void unlock(u32 prev_flags)
{
VERIFY(m_recursions > 0);
VERIFY(m_lock.load(AK::memory_order_relaxed) == FlatPtr(&Processor::current()));
if (--m_recursions == 0)
m_lock.store(0, AK::memory_order_release);
Processor::current().leave_critical(prev_flags);
}
[[nodiscard]] ALWAYS_INLINE bool is_locked() const
{
return m_lock.load(AK::memory_order_relaxed) != 0;
}
[[nodiscard]] ALWAYS_INLINE bool own_lock() const
{
return m_lock.load(AK::memory_order_relaxed) == FlatPtr(&Processor::current());
}
ALWAYS_INLINE void initialize()
{
m_lock.store(0, AK::memory_order_relaxed);
}
private:
Atomic<FlatPtr> m_lock { 0 };
u32 m_recursions { 0 };
};
template<typename LockType>
class [[nodiscard]] ScopedSpinLock {
AK_MAKE_NONCOPYABLE(ScopedSpinLock);
public:
ScopedSpinLock() = delete;
ScopedSpinLock& operator=(ScopedSpinLock&&) = delete;
ScopedSpinLock(LockType& lock)
: m_lock(&lock)
{
VERIFY(m_lock);
m_prev_flags = m_lock->lock();
m_have_lock = true;
}
ScopedSpinLock(ScopedSpinLock&& from)
: m_lock(from.m_lock)
, m_prev_flags(from.m_prev_flags)
, m_have_lock(from.m_have_lock)
{
from.m_lock = nullptr;
from.m_prev_flags = 0;
from.m_have_lock = false;
}
~ScopedSpinLock()
{
if (m_lock && m_have_lock) {
m_lock->unlock(m_prev_flags);
}
}
ALWAYS_INLINE void lock()
{
VERIFY(m_lock);
VERIFY(!m_have_lock);
m_prev_flags = m_lock->lock();
m_have_lock = true;
}
ALWAYS_INLINE void unlock()
{
VERIFY(m_lock);
VERIFY(m_have_lock);
m_lock->unlock(m_prev_flags);
m_prev_flags = 0;
m_have_lock = false;
}
[[nodiscard]] ALWAYS_INLINE bool have_lock() const
{
return m_have_lock;
}
private:
LockType* m_lock { nullptr };
u32 m_prev_flags { 0 };
bool m_have_lock { false };
};
}
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