johnculviner / adventureswithlocks Goto Github PK

Hey,
I copied my comment from the blog here as well because I wanna warn the users of that code that two last lockers (NamedReaderWriterLocker and NamedLocker) are not thread safe and may lead to incorrect behavior if you use RemoveLock methods. That's because lock (_lockDict.GetOrAdd(name, s => new object())) will be translated to something similar to:

1: try{
2: var obj = _lockDict.GetOrAdd(name, s => new object());
3: Monitor.Enter(obj);
.....
}
finally{
Monitor.Exit(obj);
}

And there is no critical section between lines 2 and 3, it could happen that between those method calls some other thread could easily call RemoveLock and remove lock object. And all next calls with the same lock name will use different lock object.

And similar issue applies to the last one (NamedReaderWriterLocker ).