Locking tool data objects in a framework environment

• US 6,026,401 A
• Filed: 10/14/1997
• Issued: 02/15/2000
• Est. Priority Date: 10/14/1997
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Loi, Lok Tin, Brealey, Christopher Lawrence, Lauzon, David Martin, Klicnik, Vladimir, Johnston, Jeffrey Grant, Seelemann, Dirk Alexander II
• Primary Examiner(s): HOMERE, JEAN RAYMOND
• Application Number:
  US08/950,116
• Time in Patent Office: 854 Days
• Field of Search: 707/8, 707/9, 707/103, 707/201, 711/150, 711/145, 395/200.4
• US Class Current: 1/1
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users

Abstract

When data, such as tool data, is commonly accessible, there is a danger that concurrent user processes will make overlapping modifications and leave the data in an incomplete or incomprehensible state. The invention provides a locking mechanism to guard against this. The lock objects are maintained in pool or repository. Two types of lock objects are provided; shareable locks that may be shared by many user processes and permit only read access to the locked data, and exclusive locks, useable by only one user process at a time, that permit the owning process to modify the locked data.

Claims

1. A mechanism for locking data objects for common tool access in an application development environment comprising:

a repository comprising lock objects, each lock object having data to designate its state as occupied or free of an owning process; and

means for referencing lock objects from the data objects;

wherein the lock objects comprise;

shareable locks each having an indicator to designate its state as owned by multiple processes; and

exclusive locks each having an indicator to designate its state as owned by a single process;

wherein the indicator for each shareable lock comprises a reserved process identifier; and

wherein the indicator for each exclusive lock comprises a process identifier for the owning since process.

2. A mechanism, according to claim 1, further comprising means for destructing lock objects, said means for destructing comprising, in the case of an exclusive lock;

means for determining if a data object referenced from the exclusive lock has been modified; and

means for delaying lock destruction until any modifications to the data object have been saved.

3. A mechanism, according to claim 1, wherein exclusive locks persist across saves unless explicitly destructed.

4. A mechanism, according to claim 1, wherein a lock object in a free state can be occupied by an owning process as either a shareable lock or an exclusive lock.