Coordinating reference counting between entities executing within separate address spaces

• US 7,581,232 B2
• Filed: 05/16/2005
• Issued: 08/25/2009
• Est. Priority Date: 05/16/2005
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Khalidi, Yousef A., Bernabeu-Auban, Jose M., Havens, Jeff L.
• Primary Examiner(s): Zhen; Li B
• Assistant Examiner(s): WU, QING YUAN
• Application Number:
  US11/130,308
• Publication Number:
  US 20060259489A1
• Time in Patent Office: 1,562 Days
• Field of Search: 709/203, 709223-229, 719/315, 719/316, 719/318, 719/328, 719/330, 718/104, 712/28, 707/206
• US Class Current: 719/330
• CPC Class Codes: G06F 2209/463 Naming
• CPC Class Codes: G06F 9/465 Distributed object oriented systems remote method invocation [RMI] G06F9/548
• CPC Class Codes: G06F 9/5016 the resource being the memory
• CPC Class Codes: G06F 9/5022 Mechanisms to release resources

Abstract

Reference counting is shared between an in-process service runtime and a machine-wide service. The service maintains a global reference count, a global export count, and an exports before revoke count. When the global reference count for a resource or object drops to zero, the machine-wide service deletes the table entry for the object or resource and sends an unref message including the value of the global export count to the sharing process. If the local export count is greater than the global export count of the unref, there are committed exports which have not yet been unreferenced. If both counts are the same, the committed exports have been accounted for and a revoke operation can be issued.

Claims

1. An inter-process communication system comprising:

a processor;

a trusted entity configured to intercept a message from a first process that has received a reference to an object, wherein the message is destined for a second process;

the trusted entity, in response to determining that the message is a message indicating that the first process is finished with the object reference, deleting an entry for the object in a table for the first process, decrementing a global reference count, the global reference count comprising a total of references to the object, and when the global reference count equals to zero, sending the message to the second process; and

the trusted entity, in response to receiving a revoke message from the second process, the second process comprising an exporting process that exported a reference to an object owned by the exporting process, the revoke message including a count of a number of times the object was exported, comparing the count included with the revoke message and a global export count of the object stored in a table for the second process, and sending the message to the second process.

2. The system of claim 1, wherein the table for the second process comprises the global export count, the global reference count and a count representing the quantity of exports of the object that must be received before a revoke operation can be initiated.

3. The system of claim 1, wherein the global reference count is incremented when the second process exports the reference to the object.

4. The system of claim 1, wherein the global reference count is incremented when the first process passes the reference to the object to another process.

5. The system of claim 1, wherein the message is sent when the count of the number of times the object was exported is equal to the global export count.

6. A method for coordinating reference counting comprising:

intercepting, by a trusted entity, a message from a first process that has received a reference to an object, wherein the message is destined for a second process;

in response to determining, by the trusted entity, that the message is a message indicating that the first process is finished with the object reference, deleting, by the trusted entity, an entry for the object in a table for the first process, decrementing a global reference count, the global reference count comprising a total of references to the object, and when the global reference count equals to zero, sending, by the trusted entity, the message to the second process; and

in response to receiving a revoke message from the second process, the second process comprising an exporting process that exported a reference to an object owned by the exporting process to the trusted entity, the revoke message including a count of a number of times the object was exported, comparing the count included with the revoke message and a global export count of the object stored in a table for the second process, and sending, by the trusted entity, the message to the second process.

7. The method of claim 6, further comprising, in response to determining that the global reference count is zero, sending the message indicating that there are no more object references to the object to the second process.

8. The method of claim 7, wherein the message sent to the second process includes the global export count comprising a count of a number of times the object was exported to at least one of a plurality of other processes.

9. A computer-readable storage medium storing thereon computer-executable instructions for coordinating reference counting between a machine-wide reference counting mechanism and a process within a inter-process communication system, the instructions when executed on a processor performing steps comprising:

intercepting a message from a first process that has received a reference to an object, wherein the message is destined for a second process;

in response to determining that the message is a message indicating that the first process is finished with the object reference, deleting an entry for the object in a table for the first process, decrementing a global reference count, the global reference count comprising a total of references to the object, and when the global reference count equals to zero, sending the message to the second process; and

in response to receiving a revoke message from the second process, the second process comprising an exporting process that exported a reference to an object owned by the exporting process, the revoke message including a count of a number of times the object was exported, comparing the count included with the revoke message and a global export count of the object stored in a table for the second process, and sending the message to the second process.

10. The computer-readable medium of claim 9, comprising further instructions for:

generating the table entry for the global reference count in the table for the second process.

11. The computer-readable medium of claim 10, wherein in response to determining that the first process passed the object reference to a third process, incrementing the global reference count for the object reference and failing to increment the global export count.

12. The computer-readable medium of claim 9, wherein the table for the second process comprises the global export count, the global reference count and a count representing the quantity of exports of the object that must be received before a revoke operation can be initiated.

13. The computer-readable medium of claim 9, wherein the global reference count is incremented when the first process passes the reference to the object to another process.

14. The computer-readable medium of claim 9, wherein the message is sent when the count of the number of times the object was exported is equal to the global export count.