Latch mechanism for concurrent computing environments

• US 7,013,463 B2
• Filed: 06/27/2001
• Issued: 03/14/2006
• Est. Priority Date: 10/06/2000
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Huras, Matthew A., Winer, Michael J., Lyle, Robert W., Sachedina, Aamer
• Primary Examiner(s): An, Meng-Al T.
• Assistant Examiner(s): Tang, Kenneth
• Application Number:
  US09/894,215
• Publication Number:
  US 20020042809A1
• Time in Patent Office: 1,721 Days
• Field of Search: 718100-108
• US Class Current: 718/100
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

A system, method and computer readable medium containing programming structions for an improved latch mechanism for use in a programming environment running concurrent tasks is disclosed. According to one aspect of the present invention, a latch is provided to a first task which is requesting access to a resource. After such access, the first task holds the latch, which is also released from the first task. The first task holding the latch marks the latch stealable, and if the latch is not marked stolen by another task, the first task can mark the latch unstealable. In another embodiment of the present invention, if the first task is provided a latch marked stealable, the resource associated with the stealable latch will be placed in a consistent state before the first task accesses the resource.

Claims

1. A computer-implemented method for providing access to a resource in a programming environment supporting concurrent tasks, comprising:

(a) providing a latch to a first task, wherein the first task requests the latch to obtain access to the resource;

(b) accessing the resource with the first task;

(c) marking the latch stealable and held by a holding task, rather than releasing the latch, wherein marking the latch stealable permits a second task to acquire the latch in response to the latch being marked stealable;

(d) marking the latch unstealable if the first task again requests the latch to obtain access to the resource prior to the latch being requested by a second task seeking access to the resource; and

(e) marking a set of flags for a latch;

i. stealable, wherein the resource is not placed in a consistent state because the latch is marked stealable;

ii. stolen, wherein the resource is placed in a consistent state and then accessed by the second task;

or

iii. unstealable, wherein the first task again requests the latch to obtain access to the resource and the latch has not been requested by a second task seeking access to the resource, as requested by the latch.

2. The method of claim 1, wherein providing a latch to a first task further comprises:

(a1) providing to the first task a latch marked stealable and held by a holding task; and

(a2) placing the resource in a consistent state prior to the first task accessing the resource.

3. A computer readable medium containing program instructions for providing access to a resource in a programming environment supporting concurrent tasks, the program instructions for:

(a) providing a latch to a first task, wherein the first task requests the latch to obtain access to the resource;

(b) accessing the resource with the first task;

(c) marking the latch stealable and held by a holding task, rather than releasing the latch, wherein marking the latch stealable permits a second task to acquire the latch in response to the latch being marked stealable;

(d) marking the latch unstealable if the first task again requests the latch to obtain access to the resource prior to the latch being requested by a second task seeking access to the resource; and

(e) marking a set of flags for a latch;

iv. stealable, wherein the resource is not placed in a consistent state because the latch is marked stealable;

v. stolen, wherein the resource is placed in a consistent state and then accessed by the second task;

or

vi. unstealable, wherein the first task again requests the latch to obtain access to the resource and the latch has not been requested by a second task seeking access to the resource, as requested by the latch.

4. The computer readable medium of claim 3, wherein providing a latch to a first task further comprises:

(a1) providing to the first task a latch marked stealable and held by a holding task; and

(a2) placing the resource in a consistent state prior to the first task accessing the resource.

5. A latch mechanism for a computer programming environment supporting concurrent tasks, comprising:

means for providing a latch for a resource to a first task, whereby the first task holds the latch;

means for the first task to mark the latch stealable and held by a holding task, rather than releasing the latch, wherein marking the latch stealable permits a second task to acquire the latch in response to the latch being marked stealable;

means for the first task to mark the latch unstealable if the first task again requests the latch to obtain access to the resource prior to the latch being requrested by a second task seeking access to the latch; and

means for using a set of flags for marking a latch stealable, wherein the resource is not placed in a consistent state because the latch is marked stealable, stolen, wherein the resource is placed in a consistent state and then accessed by the second task, or unstealable, wherein the first task is again provided with the latch and the latch has not been provided to a second task seeking access to the resource.

6. The latch mechanism of claim 5, wherein the means for providing a latch to the first task further comprising:

means for the first task to be provided, on request, with a latch marked stealable and held by a holding task, and means for placing any resources associated with the latch in a consistent state prior to the first task accessing the resources.