Comment by tgv

Someone already replied, but in general when you conditionally acquire a resource, but continue on failing. E.g., if you manage to acquire it, defer the Close() call, otherwise try to get another resource.

Another example I found in my code is a conditional lock. The code runs through a list of objects it might have to update (note: it is only called in one thread). As an optimization, it doesn't acquire a lock on the list until it finds an object that has to be changed. That allows other threads to use/lock that list in the meantime instead of waiting until the list scan has finished.

I now realize I could have used an RWLock...