Object invocation may be carried out by one thread in a service which may include multiple executing threads. In a mechanism for implementing a cancellation operation in a cooperative system, a thread identifies an operation to be cancelled. A cancel function has an argument comprising the thread identifier in which the operation is to be cancelled. The cancel function is called by a client process thread to cancel a pending object invocation initiated by the client process. An immediate or hard cancel causes the targeted client and cancel thread to return immediately. A discretionary or soft cancel does not affect the targeted client thread. In either case the server process is notified via a maintenance notification. The target thread of the cancel cannot be reused for other work until the cancel request or notification has returned.