Patent ID: 6892257

Claim:
A method of processing data, said method comprising the steps of: (i) retrieving a semaphore value corresponding to a processing resource from a semaphore value store; (ii) storing semaphore identifying data indicative of which semaphore value has been retrieved; (iii) determining from said semaphore value whether or not said processing resource is available for exclusive access by a requesting exclusive access requestor; and (iv) writing a new semaphore value to said semaphore value store, said new semaphore value being indicative of exclusive access being granted to said exclusive access requestor, returning a result value indicative of whether or not said new semaphore value was written in said semaphore value store, and checking said semaphore identifying data to determine whether or not said semaphore identifying data has been cleared between said step of retrieving and said step of writing; and (v) in response to execution of an exclusive access clear instruction by an exclusive access requestor, clearing stored semaphore identifying data for said exclusive access requestor; wherein if said semaphore identifying data has been cleared, then writing of said new semaphore value is not attempted.