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This step would ideally not have been necessary (increases amount of refactoring and templates necessary, which in turn increases build times), but it gives us a couple of nice properties: - SpinlockProtected inside Singleton (a very common combination) can now obtain any lock rank just via the template parameter. It was not previously possible to do this with SingletonInstanceCreator magic. - SpinlockProtected's lock rank is now mandatory; this is the majority of cases and allows us to see where we're still missing proper ranks. - The type already informs us what lock rank a lock has, which aids code readability and (possibly, if gdb cooperates) lock mismatch debugging. - The rank of a lock can no longer be dynamic, which is not something we wanted in the first place (or made use of). Locks randomly changing their rank sounds like a disaster waiting to happen. - In some places, we might be able to statically check that locks are taken in the right order (with the right lock rank checking implementation) as rank information is fully statically known. This refactoring even more exposes the fact that Mutex has no lock rank capabilites, which is not fixed here.
185 lines
4.7 KiB
C++
185 lines
4.7 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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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 <AK/Types.h>
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#include <Kernel/Arch/Processor.h>
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#include <Kernel/Locking/LockRank.h>
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namespace Kernel {
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template<LockRank Rank>
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class Spinlock {
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AK_MAKE_NONCOPYABLE(Spinlock);
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AK_MAKE_NONMOVABLE(Spinlock);
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public:
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Spinlock() = default;
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InterruptsState lock()
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{
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InterruptsState previous_interrupts_state = processor_interrupts_state();
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Processor::enter_critical();
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Processor::disable_interrupts();
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while (m_lock.exchange(1, AK::memory_order_acquire) != 0)
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Processor::wait_check();
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track_lock_acquire(m_rank);
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return previous_interrupts_state;
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}
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void unlock(InterruptsState previous_interrupts_state)
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{
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VERIFY(is_locked());
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track_lock_release(m_rank);
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m_lock.store(0, AK::memory_order_release);
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Processor::leave_critical();
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restore_processor_interrupts_state(previous_interrupts_state);
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}
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[[nodiscard]] ALWAYS_INLINE bool is_locked() const
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{
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return m_lock.load(AK::memory_order_relaxed) != 0;
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}
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ALWAYS_INLINE void initialize()
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{
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m_lock.store(0, AK::memory_order_relaxed);
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}
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private:
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Atomic<u8> m_lock { 0 };
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static constexpr LockRank const m_rank { Rank };
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};
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template<LockRank Rank>
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class RecursiveSpinlock {
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AK_MAKE_NONCOPYABLE(RecursiveSpinlock);
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AK_MAKE_NONMOVABLE(RecursiveSpinlock);
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public:
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RecursiveSpinlock() = default;
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InterruptsState lock()
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{
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InterruptsState previous_interrupts_state = processor_interrupts_state();
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Processor::disable_interrupts();
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Processor::enter_critical();
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auto& proc = Processor::current();
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FlatPtr cpu = FlatPtr(&proc);
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FlatPtr expected = 0;
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while (!m_lock.compare_exchange_strong(expected, cpu, AK::memory_order_acq_rel)) {
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if (expected == cpu)
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break;
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Processor::wait_check();
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expected = 0;
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}
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if (m_recursions == 0)
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track_lock_acquire(m_rank);
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m_recursions++;
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return previous_interrupts_state;
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}
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void unlock(InterruptsState previous_interrupts_state)
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{
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VERIFY_INTERRUPTS_DISABLED();
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VERIFY(m_recursions > 0);
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VERIFY(m_lock.load(AK::memory_order_relaxed) == FlatPtr(&Processor::current()));
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if (--m_recursions == 0) {
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track_lock_release(m_rank);
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m_lock.store(0, AK::memory_order_release);
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}
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Processor::leave_critical();
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restore_processor_interrupts_state(previous_interrupts_state);
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}
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[[nodiscard]] ALWAYS_INLINE bool is_locked() const
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{
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return m_lock.load(AK::memory_order_relaxed) != 0;
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}
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[[nodiscard]] ALWAYS_INLINE bool is_locked_by_current_processor() const
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{
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return m_lock.load(AK::memory_order_relaxed) == FlatPtr(&Processor::current());
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}
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ALWAYS_INLINE void initialize()
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{
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m_lock.store(0, AK::memory_order_relaxed);
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}
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private:
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Atomic<FlatPtr> m_lock { 0 };
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u32 m_recursions { 0 };
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static constexpr LockRank const m_rank { Rank };
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};
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template<typename LockType>
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class [[nodiscard]] SpinlockLocker {
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AK_MAKE_NONCOPYABLE(SpinlockLocker);
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public:
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SpinlockLocker() = delete;
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SpinlockLocker& operator=(SpinlockLocker&&) = delete;
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SpinlockLocker(LockType& lock)
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: m_lock(&lock)
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{
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VERIFY(m_lock);
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m_previous_interrupts_state = m_lock->lock();
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m_have_lock = true;
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}
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SpinlockLocker(SpinlockLocker&& from)
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: m_lock(from.m_lock)
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, m_previous_interrupts_state(from.m_previous_interrupts_state)
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, m_have_lock(from.m_have_lock)
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{
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from.m_lock = nullptr;
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from.m_previous_interrupts_state = InterruptsState::Disabled;
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from.m_have_lock = false;
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}
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~SpinlockLocker()
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{
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if (m_lock && m_have_lock) {
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m_lock->unlock(m_previous_interrupts_state);
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}
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}
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ALWAYS_INLINE void lock()
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{
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VERIFY(m_lock);
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VERIFY(!m_have_lock);
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m_previous_interrupts_state = m_lock->lock();
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m_have_lock = true;
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}
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ALWAYS_INLINE void unlock()
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{
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VERIFY(m_lock);
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VERIFY(m_have_lock);
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m_lock->unlock(m_previous_interrupts_state);
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m_previous_interrupts_state = InterruptsState::Disabled;
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m_have_lock = false;
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}
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[[nodiscard]] ALWAYS_INLINE bool have_lock() const
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{
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return m_have_lock;
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}
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private:
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LockType* m_lock { nullptr };
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InterruptsState m_previous_interrupts_state { InterruptsState::Disabled };
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bool m_have_lock { false };
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};
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}
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