[TAP5-1520] ConcurrentModificationException while modify unclaimed private collection from different Threads

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 5.2.5
• Component/s: tapestry-core
• Assignee: Unassigned
• Reporter: Maxim Ulanovskiy
• Created: 05/May/11 09:55
• Updated: 05/May/11 12:33
• Resolved: 05/May/11 12:33

Description

TestCase: create two parallel requests to the page bellow
first request to read action - /TestConcurrency.read
second request to write action - /TestConcurrency.write

TestConcurrency.tml:
...
<t:actionlink t:id="read">read</t:actionlink>
<t:actionlink t:id="write">write</t:actionlink>
...

public class TestConcurrency {

private List<String> testDie = new ArrayList<String>();

public void onActivate()

{ for(int i=0; i<1000; i++) testDie.add("init"); }

void onActionFromRead()

{ for(String s : testDie) System.out.println(s); }

void onActionFromWrite()

{ for(int i=0; i<100000; i++) testDie.add("testDie"+i); }

}

From what I've found out with debugger is that direct access to List<String> testDie is replaced with UnclaimedFieldWorker.UnclaimedFieldConduit but when PerthreadManagerImpl is called it fails to find thread local value in internal map and returnes default value - the same object for both threads:
public class PerthreadManagerImpl {

<T> PerThreadValue<T> createValue(final Object key)
{
return new PerThreadValue<T>()
{
public T get()

{ return get(null); }

public T get(T defaultValue)
{
Map map = getPerthreadMap();
// NO SUCH KEY IN map
if (map.containsKey(key))

{ Object storedValue = map.get(key); if (storedValue == NULL_VALUE) return null; return (T) storedValue; }

return defaultValue;
}