Ca, Inc.

Humberto Yeverino

Jonathan Lindo

Suman Cherukuri

Jeffrey Daudel

Arpad Jakab

Dickey B Singh

Marvin Justice

Aspects of an application program's execution which might be subject to non-determinism are performed in a deterministic manner while the application program's execution is being recorded in a virtual machine environment so that the application program's behavior, when played back in that virtual machine environment, will duplicate the behavior that the application program exhibited when originally executed and recorded. Techniques disclosed herein take advantage of the recognition that only minimal data needs to be recorded in relation to the execution of deterministic operations, which actually can be repeated 'verbatim' during replay, and that more highly detailed data should be recorded only in relation to non-deterministic operations, so that those non-deterministic operations can be deterministically simulated (rather than attempting to re-execute those operations under circumstances where the outcome of the re-execution might differ) based on the detailed data during replay.

Ensuring determinism during programmatic replay in a virtual machine

A replay core ensures that references to objects are removed at the same relative times and in the same relative order within a program's execution during both record time and replay time. A register method of a Finalizer class is modified to cause the register method to pass, to a specified programmatic mechanism, an object that was passed to the register method; modifying a finalize method of a class of the object to (a) cause the object to invoke a first method of the programmatic mechanism when the finalize method is invoked by a virtual machine and (b) prevent a remainder of the finalize method from completing under specified conditions, thereby causing a call to the finalize method to remain undispatched. The first method, when invoked, (a) adds, to the object, a reference that temporarily prevents the object from being deleted and (b) records an identifier of the object.

Techniques for ensuring deterministic thread context switching in a virtual machine application program include, in one embodiment, providing a single application-level mutex that threads of the executing application program are forced to acquire to execute application code of the virtual machine application program. During a first recorded execution of the virtual machine application program, a record is created and stored in a computer that indicates the order in which threads acquire the application-level mutex. In a subsequent replay execution of the virtual machine application program from the recording, threads of the virtual machine application program are managed to ensure that the application-level mutex is acquired by threads in the same order indicated in the record such that any race conditions that occurred during the recorded execution as a result of executing application code are reproduced during the subsequent replay execution thereby aiding application development personnel in identifying and isolating program errors and bugs related to race conditions.

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Menlo Park, CA, United States of America

Humberto Yeverino