PROVIDING A WRAPPER AROUND NATIVE SYNCHRONIZATION OBJECTS

• US 20070234368A1
• Filed: 03/31/2006
• Published: 10/04/2007
• Est. Priority Date: 03/31/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Shankar P, Shiva
• Granted Patent: US 8,028,296 B2
• Time in Patent Office: Days
• US Class Current: 719/310
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

A facility for managing a synchronization mechanism that supports initialization, acquisition, release, and deletion operations is described. When a thread seeks to perform the acquisition operation, the facility permits performance of the acquisition operation only if the initialization operation has been performed more recently than the deletion operation. When a thread seeks to perform the deletion operation, the facility waits until any threads that are seeking to perform the acquisition operation or have performed the acquisition operation more recently than the release operation have performed the release operation before deleting the synchronization mechanism.

Claims

1. A computer-readable medium whose contents implement in a computing system functions for accessing a synchronization mechanism, the functions comprising:

a safe initialization function called by a thread to initialize the synchronization mechanism;

a safe acquisition function called by a thread to acquire the synchronization mechanism, in some cases after waiting for release of the synchronization mechanism by a thread that previously acquired the synchronization mechanism;

a safe release function called by a thread to release the synchronization mechanism after acquiring the synchronization mechanism; and

a safe deletion function called by the thread to delete the synchronization mechanism,

the safe acquisition function permitting calling threads to acquire or wait to acquire the synchronization mechanism only if the safe initialization function has been called more recently than the safe deletion function,

the safe deletion function deferring deletion of the synchronization mechanism until any threads that previously acquired the synchronization mechanism release it and until any threads waiting for the synchronization resume execution.

2. The computer-readable medium of claim 1 wherein the safe initialization mechanism sets a flag—

which the safe deletion function clears—

that is tested by the safe acquisition function in order to determine whether to permit calling threads to acquire or wait to acquire the synchronization mechanism.

3. The computer-readable medium of claim 1 wherein the safe deletion function:

requires a calling thread to acquire the synchronization mechanism;

after the calling thread has acquired the synchronization mechanism;

marks the synchronization mechanism for deletion; and

releases the synchronization mechanism on behalf of the calling thread.

4. The computer-readable medium of claim 3 wherein the safe acquisition function, for each calling thread that is permitted to acquire the synchronization mechanism after the synchronization mechanism is marked for deletion, requires the calling thread to immediately release the synchronization mechanism.

5. The computer-readable medium of claim 4 wherein the safe release function deletes the synchronization mechanism when (1) the synchronization mechanism is marked for deletion and (2) the calling thread is the last thread that has acquired or is waiting for the synchronization mechanism.

6. The computer-readable medium of claim 1 wherein the functions are provided as a wrapper around native functions implemented for accessing the synchronization mechanism.

7. A method in a computing system for managing a synchronization mechanism that supports initialization, acquisition, release, and deletion operations, comprising:

when a thread seeks to perform the acquisition operation, permitting performance of the acquisition operation only if the initialization operation has been performed more recently than the deletion operation; and

when a thread seeks to perform the deletion operation, waiting until any threads that are seeking to perform the acquisition operation or have performed the acquisition operation more recently than the release operation have performed the release operation before deleting the synchronization mechanism.

8. The method of claim 7, further comprising, when a thread seeks to perform the deletion operation, forcing any threads that are seeking to perform the release operation immediately after they are permitted to perform the acquisition operation.

9. The method of claim 7 wherein an operating system is executing on the computing system, and wherein the initialization, acquisition, release, and deletion operations of the synchronization mechanism are provided by a synchronization mechanism API of the operating system, and wherein the method is performed by a wrapper around the synchronization mechanism API of the operating system.

10. The method of claim 9 wherein the wrapper maintains one or more indications of (1) the number of threads that are seeking to perform the acquisition operation or have performed the acquisition operation more recently than the release operation, and (2) whether a thread is seeking to perform the deletion operation using atomic variable access operations.

11. The method of claim 10 wherein the wrapper maintains the indications using InterlockedXXX operations provided by the Microsoft Windows operating system.

12. The method of claim 9 wherein the wrapper is implemented as a safe synchronization mechanism object class.

13. The method of claim 9 wherein the wrapper is implemented in the operating system.

14. A multithreaded computing system, comprising:

an operating system;

a resource usable by one or more threads;

a native synchronization mechanism implemented by the operating system for synchronizing access to the resource; and

a synchronization mechanism wrapper through which threads access the native synchronization mechanism.

15. The computing system of claim 14 wherein the native synchronization mechanism is a critical section.

16. The computing system of claim 14 wherein the native synchronization mechanism is a mutex.

17. The computing system of claim 14 wherein the native synchronization mechanism is a semaphore.

18. The computing system of claim 14 wherein the native synchronization mechanism provides an initialization operation by which a thread can initialize the native synchronization mechanism for use, an acquisition operation by which a thread can acquire the native synchronization mechanism, and a deletion operation by which a thread can disable the native synchronization mechanism from use, and wherein the synchronization mechanism wrapper prevents any thread from performing the acquisition operation unless the initialization operation has been performed more recently than the deletion operation.

19. The computing system of claim 14, wherein the native synchronization mechanism provides an acquisition operation by which a thread can acquire the native synchronization mechanism and which may cause a thread to block that performs the acquisition operation while the native synchronization mechanism is owned by another thread, and a deletion operation by which a thread can disable the native synchronization mechanism from use, and wherein the synchronization mechanism wrapper prevents any thread from performing the deletion operation while any thread performing the acquisition operation is blocked.