An improved approach to pcell caching is disclosed that enables safe and efficient multi-user access to pcell caches. Locking structures are used in conjunction with counters to provide multi-user support for pcell caches. When a modification occurs to cached pcell data, an update is made to the appropriate counter(s). The value(s) of the counters are checked to determine whether the item of data operated upon by an entity is still valid or if another concurrent entity has made changes to the data.