Counter and flux bit locking for very fast shared serialization of

Abstract

Methods and apparatus are set forth for improving the performance of general purpose computing systems that utilize exclusive and shared seize mechanisms to assure the integrity of shared data objects, records, or other unit of synchronization. More particularly, methods and apparatus are set forth which allow concurrent reads of shared data objects in a coherent fashion, without always having to perform a seize. According to a preferred embodiment of the invention, read (shared) accesses can be performed in such a manner as to improve system performance by utilizing a method comprising the steps of: (a) determining, for a particular shared data object to be read, if the object is subject to an exclusive seize prior to any attempt, to read the object; (b) reading the object without causing a shared seize to be initiated if it was not subject to an exclusive seize as determined in step (a); (c) determining if the object is subject to an exclusive seize after reading it in accordance with step (b); and (d) determining if the object was subject to an exclusive seize while it was being read. If, as a result of performing the aforestated method, it can be concluded that the read took place without an exclusive seize immediately before, during and just after the read, then the data can be presumed valid. System performance is improved in such cases since the overhead associated with initiating a seize for the read is eliminated.