2020-01-18 08:38:21 +00:00
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/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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2018-10-10 09:53:07 +00:00
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#pragma once
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2020-02-09 14:50:13 +00:00
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#include <AK/Assertions.h>
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2020-06-12 13:38:24 +00:00
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#include <AK/Atomic.h>
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2020-06-12 13:44:17 +00:00
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#include <AK/Checked.h>
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2020-06-12 13:46:47 +00:00
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#include <AK/Noncopyable.h>
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2020-05-20 12:13:39 +00:00
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#include <AK/Platform.h>
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2020-02-09 14:50:13 +00:00
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#include <AK/StdLibExtras.h>
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2018-10-10 09:53:07 +00:00
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namespace AK {
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2018-12-19 21:28:09 +00:00
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template<class T>
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2020-12-06 02:47:20 +00:00
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constexpr auto call_will_be_destroyed_if_present(const T* object) -> decltype(const_cast<T*>(object)->will_be_destroyed(), TrueType {})
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2018-12-19 21:28:09 +00:00
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{
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2020-04-17 10:41:45 +00:00
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const_cast<T*>(object)->will_be_destroyed();
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2019-05-28 09:53:16 +00:00
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return {};
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2018-12-19 21:28:09 +00:00
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}
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constexpr auto call_will_be_destroyed_if_present(...) -> FalseType
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{
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2019-05-28 09:53:16 +00:00
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return {};
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2018-12-19 21:28:09 +00:00
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}
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2019-01-01 01:38:09 +00:00
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template<class T>
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2020-12-06 02:47:20 +00:00
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constexpr auto call_one_ref_left_if_present(const T* object) -> decltype(const_cast<T*>(object)->one_ref_left(), TrueType {})
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2019-01-01 01:38:09 +00:00
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{
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2020-04-17 10:41:45 +00:00
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const_cast<T*>(object)->one_ref_left();
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2019-05-28 09:53:16 +00:00
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return {};
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2019-01-01 01:38:09 +00:00
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}
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2019-06-21 13:29:31 +00:00
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constexpr auto call_one_ref_left_if_present(...) -> FalseType
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2019-01-01 01:38:09 +00:00
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{
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2019-05-28 09:53:16 +00:00
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return {};
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2019-01-01 01:38:09 +00:00
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}
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2019-06-21 13:29:31 +00:00
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class RefCountedBase {
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2020-08-26 19:52:24 +00:00
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AK_MAKE_NONCOPYABLE(RefCountedBase);
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AK_MAKE_NONMOVABLE(RefCountedBase);
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2018-10-10 09:53:07 +00:00
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public:
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2020-11-11 22:21:01 +00:00
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using RefCountType = unsigned int;
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2020-11-03 14:51:56 +00:00
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using AllowOwnPtr = FalseType;
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2020-06-12 13:33:38 +00:00
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2020-05-20 11:59:31 +00:00
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ALWAYS_INLINE void ref() const
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2018-10-10 09:53:07 +00:00
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{
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AK: Make RefPtr, NonnullRefPtr, WeakPtr thread safe
This makes most operations thread safe, especially so that they
can safely be used in the Kernel. This includes obtaining a strong
reference from a weak reference, which now requires an explicit
call to WeakPtr::strong_ref(). Another major change is that
Weakable::make_weak_ref() may require the explicit target type.
Previously we used reinterpret_cast in WeakPtr, assuming that it
can be properly converted. But WeakPtr does not necessarily have
the knowledge to be able to do this. Instead, we now ask the class
itself to deliver a WeakPtr to the type that we want.
Also, WeakLink is no longer specific to a target type. The reason
for this is that we want to be able to safely convert e.g. WeakPtr<T>
to WeakPtr<U>, and before this we just reinterpret_cast the internal
WeakLink<T> to WeakLink<U>, which is a bold assumption that it would
actually produce the correct code. Instead, WeakLink now operates
on just a raw pointer and we only make those constructors/operators
available if we can verify that it can be safely cast.
In order to guarantee thread safety, we now use the least significant
bit in the pointer for locking purposes. This also means that only
properly aligned pointers can be used.
2020-09-29 22:26:13 +00:00
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auto old_ref_count = m_ref_count.fetch_add(1, AK::MemoryOrder::memory_order_relaxed);
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2020-06-12 13:38:24 +00:00
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ASSERT(old_ref_count > 0);
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2020-06-12 13:44:17 +00:00
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ASSERT(!Checked<RefCountType>::addition_would_overflow(old_ref_count, 1));
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2018-10-10 09:53:07 +00:00
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}
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2021-01-03 23:41:49 +00:00
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[[nodiscard]] ALWAYS_INLINE bool try_ref() const
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2020-12-29 20:14:21 +00:00
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{
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RefCountType expected = m_ref_count.load(AK::MemoryOrder::memory_order_relaxed);
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for (;;) {
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if (expected == 0)
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return false;
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ASSERT(!Checked<RefCountType>::addition_would_overflow(expected, 1));
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if (m_ref_count.compare_exchange_strong(expected, expected + 1, AK::MemoryOrder::memory_order_acquire))
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return true;
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}
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}
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2020-06-12 13:33:38 +00:00
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ALWAYS_INLINE RefCountType ref_count() const
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2018-10-10 09:53:07 +00:00
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{
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AK: Make RefPtr, NonnullRefPtr, WeakPtr thread safe
This makes most operations thread safe, especially so that they
can safely be used in the Kernel. This includes obtaining a strong
reference from a weak reference, which now requires an explicit
call to WeakPtr::strong_ref(). Another major change is that
Weakable::make_weak_ref() may require the explicit target type.
Previously we used reinterpret_cast in WeakPtr, assuming that it
can be properly converted. But WeakPtr does not necessarily have
the knowledge to be able to do this. Instead, we now ask the class
itself to deliver a WeakPtr to the type that we want.
Also, WeakLink is no longer specific to a target type. The reason
for this is that we want to be able to safely convert e.g. WeakPtr<T>
to WeakPtr<U>, and before this we just reinterpret_cast the internal
WeakLink<T> to WeakLink<U>, which is a bold assumption that it would
actually produce the correct code. Instead, WeakLink now operates
on just a raw pointer and we only make those constructors/operators
available if we can verify that it can be safely cast.
In order to guarantee thread safety, we now use the least significant
bit in the pointer for locking purposes. This also means that only
properly aligned pointers can be used.
2020-09-29 22:26:13 +00:00
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return m_ref_count.load(AK::MemoryOrder::memory_order_relaxed);
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2018-10-10 09:53:07 +00:00
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}
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protected:
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2021-01-10 23:29:28 +00:00
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RefCountedBase() = default;
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2020-05-20 11:59:31 +00:00
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ALWAYS_INLINE ~RefCountedBase()
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2018-10-10 09:53:07 +00:00
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{
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AK: Make RefPtr, NonnullRefPtr, WeakPtr thread safe
This makes most operations thread safe, especially so that they
can safely be used in the Kernel. This includes obtaining a strong
reference from a weak reference, which now requires an explicit
call to WeakPtr::strong_ref(). Another major change is that
Weakable::make_weak_ref() may require the explicit target type.
Previously we used reinterpret_cast in WeakPtr, assuming that it
can be properly converted. But WeakPtr does not necessarily have
the knowledge to be able to do this. Instead, we now ask the class
itself to deliver a WeakPtr to the type that we want.
Also, WeakLink is no longer specific to a target type. The reason
for this is that we want to be able to safely convert e.g. WeakPtr<T>
to WeakPtr<U>, and before this we just reinterpret_cast the internal
WeakLink<T> to WeakLink<U>, which is a bold assumption that it would
actually produce the correct code. Instead, WeakLink now operates
on just a raw pointer and we only make those constructors/operators
available if we can verify that it can be safely cast.
In order to guarantee thread safety, we now use the least significant
bit in the pointer for locking purposes. This also means that only
properly aligned pointers can be used.
2020-09-29 22:26:13 +00:00
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ASSERT(m_ref_count.load(AK::MemoryOrder::memory_order_relaxed) == 0);
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2018-10-10 09:53:07 +00:00
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}
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2020-06-12 13:38:24 +00:00
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ALWAYS_INLINE RefCountType deref_base() const
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2019-03-16 12:48:56 +00:00
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{
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AK: Make RefPtr, NonnullRefPtr, WeakPtr thread safe
This makes most operations thread safe, especially so that they
can safely be used in the Kernel. This includes obtaining a strong
reference from a weak reference, which now requires an explicit
call to WeakPtr::strong_ref(). Another major change is that
Weakable::make_weak_ref() may require the explicit target type.
Previously we used reinterpret_cast in WeakPtr, assuming that it
can be properly converted. But WeakPtr does not necessarily have
the knowledge to be able to do this. Instead, we now ask the class
itself to deliver a WeakPtr to the type that we want.
Also, WeakLink is no longer specific to a target type. The reason
for this is that we want to be able to safely convert e.g. WeakPtr<T>
to WeakPtr<U>, and before this we just reinterpret_cast the internal
WeakLink<T> to WeakLink<U>, which is a bold assumption that it would
actually produce the correct code. Instead, WeakLink now operates
on just a raw pointer and we only make those constructors/operators
available if we can verify that it can be safely cast.
In order to guarantee thread safety, we now use the least significant
bit in the pointer for locking purposes. This also means that only
properly aligned pointers can be used.
2020-09-29 22:26:13 +00:00
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auto old_ref_count = m_ref_count.fetch_sub(1, AK::MemoryOrder::memory_order_acq_rel);
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2020-06-12 13:38:24 +00:00
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ASSERT(old_ref_count > 0);
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return old_ref_count - 1;
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2019-03-16 12:48:56 +00:00
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}
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2020-06-12 13:38:24 +00:00
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mutable Atomic<RefCountType> m_ref_count { 1 };
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2018-10-10 09:53:07 +00:00
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};
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2019-03-16 11:47:19 +00:00
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template<typename T>
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2019-06-21 13:29:31 +00:00
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class RefCounted : public RefCountedBase {
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2019-03-16 11:47:19 +00:00
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public:
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2020-12-29 20:14:21 +00:00
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bool unref() const
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2019-03-16 11:47:19 +00:00
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{
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2020-06-12 13:38:24 +00:00
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auto new_ref_count = deref_base();
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if (new_ref_count == 0) {
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2020-04-17 10:41:45 +00:00
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call_will_be_destroyed_if_present(static_cast<const T*>(this));
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delete static_cast<const T*>(this);
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2020-12-29 20:14:21 +00:00
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return true;
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2020-06-12 13:38:24 +00:00
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} else if (new_ref_count == 1) {
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2020-04-17 10:41:45 +00:00
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call_one_ref_left_if_present(static_cast<const T*>(this));
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2019-03-16 11:47:19 +00:00
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}
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2020-12-29 20:14:21 +00:00
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return false;
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2019-03-16 11:47:19 +00:00
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}
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};
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2018-10-10 09:53:07 +00:00
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}
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2019-06-21 13:29:31 +00:00
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using AK::RefCounted;
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