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Method-and-apparatus-for-controlling-a-re-entrant-synchronization-lock-tenure-in-a-multiprocessor-system

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Method and apparatus for controlling a re-entrant synchronization lock tenure in a multiprocessor system

Details

Inventors: Barton, Richard R.;
Assignee: NCR Corporation (Dayton, OH)
Primary Examiner: Heckler; Thomas M.
Assistant Examiner:
Attorney, Agent or Firm: Martin; Paul W., Penrod; Jack R.

A method and apparatus for extending a tenure of a process that owns a system process that has shared data or resources and also is requesting the owned system process. The ability to extend the tenure of the owning process allows the nesting of requests to the system process. By properly ordering how the requests are nested, deadlocks may be avoided. Additionally, by extending the tenure of a current process, some unnecessary changes in processor instructions and data may be avoided and processing efficiency increased.

DETAILED DESCRIPTION Accordingly the present invention provides a method for use in a multiple processor computer system that changes a tenure of a current owner of a reentrant synchronization lock in order to allow the current owner to re-enter the locked process and exchange information therewith.
In one aspect, the present invention of a method for changing a tenure of the current owner of a re-entrant synchronization lock to allow the current owner to re-enter the locked process includes the steps of accessing a first set of data that identifies the process that is the current owner of the synchronization lock, determining if the process that is the current owner of the synchronization lock is the same process as the one that is requesting ownership of the synchronization lock.
If it is the same process, the tenure level of the synchronization lock is increased by one and the method is exited.
If the requesting process is not the current owner, then the method acquires exclusive access to a second set of data that represents a state of the synchronization lock.
The method reads the second set of data and determines if the synchronization lock of the requested process is owned by any process.
If the synchronization lock is not owned, the method assigns the current lock requester as the current owner of the synchronization lock, assigns a current tenure level of the current owner to one, releases the exclusive access to the set of data and exits the method.
In another aspect, the present invention of a method for use in a multiple processor computer system for changing a tenure of a current owner of a reentrant synchronization lock includes the steps of if the requesting process is not the current owner, then the method acquires exclusive access to a set of data that represents a current state of the synchronization lock.
The method reads the set of data and determines if the synchronization lock of the requested process is owned by another process.
If the synchronization lock is owned, the method releases said exclusive access to the set of data and performs a separate predetermined contention process so the unfulfilled requesting process may contend for the requested process upon a release of the synchronization lock

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