1. A computer program product for determining a state of an input/output (I/O) operation in an I/O processing system, comprising: a tangible storage medium readable by a processing circuit and storing instructions for executing by the processing circuit for performing a method comprising: receiving, at a channel subsystem, a request for performing the I/O operation from an I/O operating system; forwarding the request from the channel subsystem to a control unit controlling an I/O device for executing the I/O operation; after a predetermined amount of time passes without receiving indication from the control unit that the I/O operation is completed, receiving, at the channel subsystem, an interrogation request from the I/O operating system for determining the state of the I/O operation; responsive to receipt of the interrogation request at the channel subsystem, sending an interrogation command from the channel subsystem to the control unit to determine the state of the I/O operation; and receiving, at the channel subsystem, a response from the control unit indicating the state of the I/O operation, wherein the response includes information indicating a state of the I/O device executing the I/O operation, a state of the control unit controlling the I/O device executing the I/O operation, and the state of the I/O operation being executed.