Interface system and method for asynchronously updating a share resource with locking facility

• US 6,449,614 B1
• Filed: 03/25/1999
• Issued: 09/10/2002
• Est. Priority Date: 03/25/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Marcotte, Scott T.
• Primary Examiner(s): Alam, Hosain T.
• Assistant Examiner(s): HWANG, JOON H
• Application Number:
  US09/275,792
• Time in Patent Office: 1,265 Days
• Field of Search: 707/1-10, 707/100, 707/101, 707/102, 707/200, 707/201, 711/141-143, 709/229, 709/100-108
• US Class Current: 1/1
• CPC Class Codes: G06F 2209/523 Mode
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• 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

Tasks make updates requested by calling tasks to a shared resource serially in a first come first served manner, atomically, but not necessarily synchronously, such that a current task holding an exclusive lock on the shared resource makes the updates on behalf of one or more calling tasks queued on the lock. Updates waiting in a queue on the lock to the shared resource may be made while the lock is held, and others deferred for post processing after the lock is released. Some update requests may also, at the calling application'"'"'s option, be executed synchronously. Provision is made for nested asynchronous locking. Data structures (wait_elements) describing update requests may queued in a wait queue for update requests awaiting execution by a current task, other than the calling task, currently holding an exclusive lock on the shared resource. Other queues are provided for queuing data structures removed from the wait queue but not yet processed; data structures for requests to unlock or downgrade a lock; data structures for requests which have been processed and need to be returned to free storage; and data structures for requests that need to be awakened or that describe post processing routines that are to be run while the lock is not held.

Claims

1. A method for allowing applications including an asynchronous locking facility to update a resource via locking without task suspension or task switching, comprising the steps of:

queuing a request to update a resource requested by a first task onto a lock for said resource; and

operating a second task holding said lock on said resource to execute said request before releasing said lock.

2. The method of claim 1, further comprising the steps of:

providing a plurality of two or more update routines for updating said resource, including a first update routine and a second update routine;

said second task executing said first update routine before releasing said lock; and

selectively executing said second update routine after said second task has released said lock;

thereby reducing lock contention.

3. The method of claim 2, further comprising the step of:

passing a return code from said second task to said asynchronous locking facility.

4. The method of claim 3, said return code being a work_nopostwork return code for bypassing execution of said second update routine.

5. The method of claim 3, said return code being a work_dontunlock return code for complex nesting of asynchronous locks.

6. The method of claim 2, further comprising the step of:

specifying a plurality of task types for executing said update routines;

thereby selectively enabling multi-program language environments and multi-execution environment environments, and partitioning of tasks into logical classes.

7. The method of claim 6, further comprising the step of:

selectively passing a task_type parameter to tasks executing said update routines, said task_type parameter specifying the type of task on which said tasks are running.

8. The method of claim 2, further comprising the step of:

passing one or more user parameters from said application to said update routines.

9. The method of claim 2, further comprising the steps of:

selectively executing a lock_Resource macro or an unlock_Resource macro; and

responsive to obtaining or releasing a lock in exclusive mode without contention, returning a work_inline return code instructing the caller to run post processing code in line.

10. The method of claim 1, further comprising the step of:

passing a sync_flag parameter from said asynchronous locking facility to tasks executing said requests, said parameter specifying whether said tasks are running on a calling thread or asynchronously on another thread.

11. The method of claim 1, further comprising the step of:

responsive to an application supplied maximum, restricting the number of requests for asynchronous updates queued on said lock.

12. The method of claim 1, further comprising the step of:

queuing a plurality of update requests on said lock from a plurality of tasks for sequential execution in queued order by said second task.

13. A method for allowing applications including an asynchronous locking facility to update a resource via locking selectively synchronously, or asynchronously without task suspension or task switching, comprising the steps of:

selectively queuing a request to update a resource requested by a first task onto a lock for said resource; and

selectively operating a second task holding said lock on said resource to execute said request before releasing said lock.

14. A program storage device readable by a machine, tangibly embodying a program of instructions executable by a machine to perform method steps for allowing applications including an asynchronous locking facility to update a resource via locking without task suspension or task switching, said method steps comprising:

queuing a request to update a resource requested by a first task onto a lock for said resource; and

operating a second task holding said lock on said resource to execute said request before releasing said lock.

15. An article of manufacture comprising:

a computer useable medium having computer readable program code means embodied therein for allowing applications including an asynchronous locking facility to update a resource via locking without task suspension or task switching, the computer readableprogram means in said article of manufacture comprising;

computer readable program code means for causing a computer to effect queuing a request to update a resource requested by a first task onto a lock for said resource; and

computer readable program code means for causing a computer to effect operating a second task holding said lock on said resource to execute said request before releasing said lock.

16. A interface system for enabling asynchronous updating of a shared resource, comprising:

a plurality data structures for defining resource update requests; and

a wait queue for queuing data structures describing update requests awaiting execution by a current task, other than the calling task, currently holding an exclusive lock on said shared resource.

17. The interface system of claim 16, further comprising:

a taken queue for queuing data structures removed from said wait queue but not yet processed;

an unlock queue for queuing data structures for requests to unlock or downgrade a lock;

a return queue for queuing data structures for requests which have been processed and need to be returned to free storage; and

a post queue for queuing data structures for requests that need to be awakened or that describe post processing routines that are to be run while said lock is not held.

18. The interface system of claim 16, said lock comprising:

a state parameter field for storing state bits defining the said of said lock;

a wait queue field for anchoring said wait queue; and

a maximum queued field for specifying the maximum number of queued update requests allowed before asynchronous update calls will be made to wait.

19. The interface system of claim 16, the state parameter of said lock comprising:

first indicia (E) specifying whether said lock is held exclusive;

second indicia (W) specifying whether said wait queue is empty;

third indicia (L) specifying whether said lock is held in a higher priority state;

fourth indicia (P) specifying whether said maximum number of queued update requests allowed has been exceed; and

fifth indicia (R) specifying the number of said update requests on said lock.

20. The interface system of claim 16, said data structure comprising:

a next field for storing a forward pointer to a next data structure in a queue;

a previous field for storing a backward pointer to a previous data structure in a queue;

an wait field for specifying whether said data structure represents a task being made to wait;

an action field for specifying the action requested, said action being one of obtain lock, release lock, downgrade lock, upgrade lock, and work unit;

a type field for specifying the type of lock to obtain or release;

a work function field for accessing in an array of functions the function to run while holding a lock to update a resource;

a work process field for storing a first function argument for said resource update routine;

a work argument field for storing a second function argument for said resource update routine;

a work return code field for storing a return value of said resource update routine;

a function pointer field for accessing a function array;

a post work field for identifying in said function array a post processing function; and

a post argument field for storing a post processing argument.