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AK: Remove thread safety gunk from userspace WeakPtr

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The implicit thread safety stuff is only needed by the kernel version
of WeakPtr, as userspace already makes no guarantees about this.
This commit is contained in:
Andreas Kling 2022-01-31 12:40:30 +01:00
parent 30fcb07fe8
commit 51e5cc4e13
2 changed files with 7 additions and 33 deletions
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36
AK/WeakPtr.h
View file

@ -153,40 +153,10 @@ template<typename T>
template<typename U>
inline WeakPtr<U> Weakable<T>::make_weak_ptr() const
{
if constexpr (IsBaseOf<RefCountedBase, T>) {
// Checking m_being_destroyed isn't sufficient when dealing with
// a RefCounted type.The reference count will drop to 0 before the
// destructor is invoked and revoke_weak_ptrs is called. So, try
// to add a ref (which should fail if the ref count is at 0) so
// that we prevent the destructor and revoke_weak_ptrs from being
// triggered until we're done.
if (!static_cast<const T*>(this)->try_ref())
return {};
} else {
// For non-RefCounted types this means a weak reference can be
// obtained until the ~Weakable destructor is invoked!
if (m_being_destroyed.load(AK::MemoryOrder::memory_order_acquire))
return {};
}
if (!m_link) {
// There is a small chance that we create a new WeakLink and throw
// it away because another thread beat us to it. But the window is
// pretty small and the overhead isn't terrible.
m_link.assign_if_null(adopt_ref(*new WeakLink(const_cast<T&>(static_cast<const T&>(*this)))));
}
if (!m_link)
m_link = adopt_ref(*new WeakLink(const_cast<T&>(static_cast<T const&>(*this))));
WeakPtr<U> weak_ptr(m_link);
if constexpr (IsBaseOf<RefCountedBase, T>) {
// Now drop the reference we temporarily added
if (static_cast<const T*>(this)->unref()) {
// We just dropped the last reference, which should have called
// revoke_weak_ptrs, which should have invalidated our weak_ptr
VERIFY(!weak_ptr.strong_ref());
return {};
}
}
return weak_ptr;
return WeakPtr<U>(m_link);
}
template<typename T>

4
AK/Weakable.h
View file

@ -113,7 +113,9 @@ protected:
~Weakable()
{
#ifdef KERNEL
m_being_destroyed.store(true, AK::MemoryOrder::memory_order_release);
#endif
revoke_weak_ptrs();
}
@ -125,7 +127,9 @@ protected:
private:
mutable RefPtr<WeakLink> m_link;
#ifdef KERNEL
Atomic<bool> m_being_destroyed { false };
#endif
};
}