[concurrency-interest] 8145539: (coll) AbstractMap.keySet and .values should not be volatile

Volker.Borchert at atis-systems.com Volker.Borchert at atis-systems.com
Wed Apr 20 09:50:37 EDT 2016


> The block in navigableKeySet() is semantically the same as suggested in
> the Javadoc: it reads the non-volatile $navigableKeySet exactly once.

Sorry, I can't see the difference between

	KeySet<K> nks = navigableKeySet;
	return (nks != null) ? nks : (navigableKeySet = new KeySet<>(this));

and

	NavigableMap<K, V> km = descendingMap;
	return (km != null) ? km : (descendingMap = new DescendingSubMap<>(this, ...));

and

	EntrySet es = entrySet;
	return (es != null) ? es : (entrySet = new EntrySet());

and

	Collection<V> vs = values;
	return (vs != null) ? vs : (values = new Values());

but only the last one was changed. Am I just routine-blinded?

> The patch changed keySet() and values() that were doing two racy reads.

TreeMap.keySet() delegates to navigableKeySet() so the patch to AbstractMap
won't affect it.

Regards

	vb

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