Add iterator checking to ListHashSet
Created attachment 398934 [details]
Comment on attachment 398934 [details]
Is WeakPtr thread safe?
(In reply to Anders Carlsson from comment #2)
> Is WeakPtr thread safe?
It uses ThreadSafeRefCounted, so I think yes.
Committed r261440: <https://trac.webkit.org/changeset/261440>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 398934 [details].
(In reply to Darin Adler from comment #3)
> (In reply to Anders Carlsson from comment #2)
> > Is WeakPtr thread safe?
> It uses ThreadSafeRefCounted, so I think yes.
WeakPtr<T>::get returns weird results in multi-threaded environment. This is slightly different from `std::weak_ptr<T>::lock()`.
So, in general, it is not encouraged that we use WeakPtr<T> in multi-threading use because it does not work as expected.
However, in this use case, it is OK.
1. T inherits CanMakeWeakPtr<T> and ThreadSafeRefCounted<T>.
2. In thread A, we create Ref<T>.
3. In thread A, we create WeakPtr<T> from Ref<T>
4. We pass WeakPtr<T> to another thread B.
5. B thread is attempting to call WeakPtr<T>::get().
6. At the same time, in thread A, we start destroying Ref<T>.
7. Before (6) calls WeakPtrImpl::clear(), (5) gets a non nullptr T*.
8. Just after (5) gets non nullptr T*, (7) destroys Ref<T> completely.
WeakPtr<T>::get can return a non-nullptr even if the obtained T* is half-destroyed right now.
So, it is possible that we could miss some cases that T* is already destroyed while WeakPtr<T>::get returns non-nullptr.
But since this is for assertion, false-negative is OK.
Reverted r261440 for reason:
Caused 6 TestWTF.WTF failures
Committed r261486: <https://trac.webkit.org/changeset/261486>
Created attachment 399092 [details]
This new patch fixes the TestWTF.WTF failures. Would appreciate review since more has changed now.
Created attachment 399100 [details]
Committed r261818: <https://trac.webkit.org/changeset/261818>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 399100 [details].