1. A method of tracking real time use of I/O control blocks on a processing unit basis in a multiprocessing computing system including a plurality of processing units, wherein said I/O control blocks are used to serialize processing unit operations in said computing system, the method comprising: assigning a task control block to each of the processing units; each of the processing units, locking a plurality of I/O control blocks for exclusive use by the processing unit in order to serialize processing unit operations, including the steps of using specified routines to lock the I/O control blocks for exclusive use by the processing units, and identifying in each of the locked I/O control blocks the routine used to lock the control block; for each of the processing units, maintaining in the task control block assigned to the processing unit, a list of all of the plurality of I/O control blocks locked by the processing unit; and in the event of a defined failure of one of the processing units, using the list, in the task control block assigned to said one of the processing units, of the I/O control blocks locked by said one of the processing units, to identify and to determine, the locations of all of the plurality of control blocks locked by said one of the processing units; and using information in the task control block assigned to said one of the processing units to release all of said identified control blocks, in said list in the task control block assigned to said one of the processing units, from the lock by said one of the processing units to facilitate recovery of the computing system from said defined failure.