Cancel instruction and command for determining the state of an I/O operation

• US 8,166,206 B2
• Filed: 02/14/2008
• Issued: 04/24/2012
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Yudenfriend, Harry M., Casper, Daniel F., Flanagan, John R., Kalos, Matthew J., Riedy, Dale F., Ricci, Louis W., Hathorn, Roger G., Sittmann, Gustav E., Njoku, Ugochukwu C., Huang, Catherine C., Carlson, Scott M.
• Primary Examiner(s): Lee, Chun-Kuan
• Assistant Examiner(s): Unelus, Ernest
• Application Number:
  US12/030,993
• Publication Number:
  US 20090210560A1
• Time in Patent Office: 1,531 Days
• Field of Search: 710/19, 710/3, 710/4, 710/5, 710/58, 711/1, 711/100, 711/101
• US Class Current: 710/5
• CPC Class Codes: G06F 13/122 where hardware performs an I/O function other than control of data transfer

Abstract

The state of an input/output (I/O) operation is determined in an I/O processing system. A command is received from an I/O operating system at a channel subsystem for initiating the I/O operation, a time period is for completion of the I/O operation, and the command for initiating the I/O operation is sent from the channel subsystem to the control unit. Responsive to the time period nearing elapsing without the I/O operation completing, a cancel instruction is received from the I/O operating system at the channel subsystem. Responsive to a determination by the I/O operating system to interrogate the control unit, an instruction to interrogate the control unit is received with the cancel instruction from the I/O operating system.

Claims

1. A non-transitory computer program product for determining a state of an input/output (I/O) operation in an I/O processing system, the I/O operation having an associated time limit, 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 a request from an operating system at a channel subsystem for initiating the I/O operation;

retrieving an I/O operation command from a location in memory specified by a command field in a transport control word (TCW), the TCW comprising the command field and an interrogate field;

sending the I/O operation command for initiating the I/O operation from the channel subsystem to the control unit;

responsive to a determination by the operating system that the time limit is nearing elapsing without the I/O operation completing, determining whether to send an interrogate command to the control unit, to request a response from the control unit indicating the state of the I/O operation being executed by an I/O device controlled by the control unit; and

responsive to determining whether to send the interrogate command, retrieving an interrogate command address by the channel subsystem from an interrogate field in the TCW, and responsive to the interrogate command address having a non-zero value, retrieving the interrogate command from a location in memory specified by the interrogate command address.

2. The computer program product of claim 1, further comprising setting the interrogate command address as a non-zero interrogate transport control word (TCW) address of an interrogate TCW in an interrogate TCW address field of the TCW to be used by a cancel subchannel instruction to request the sending of the interrogate command to the control unit.

3. The computer program product of claim 1, wherein determining whether to send the interrogate command to the control unit for determining the state of the I/O operation includes determining whether the I/O operation has started.

4. The computer program product of claim 3, wherein performing the method further comprises discarding an initiative to issue the interrogate command responsive to a determination that the I/O operation has not started.

5. The computer program product of claim 1, wherein determining whether to send an interrogate command to the control unit for determining the state of the I/O operation includes determining whether an interrogation operation is already in progress.

6. The computer program product of claim 5, wherein performing the method further comprises discarding an initiative to issue the interrogate command responsive to a determination that an interrogation operation is already in progress.

7. The computer program product of claim 1, wherein the method further comprises, responsive to a determination to send the interrogate command to the control unit, sending the interrogate command to the control unit and receiving a response from the control unit indicating a state of the I/O device in response to receipt of the interrogate command by the control unit, wherein the response from the control unit indicates whether the I/O device is reserved by another I/O processing system.

21. The computer program product of claim 1, wherein the interrogate command is included in an interrogate device command word (DCW), and the interrogate DCW is sent to the control unit via a transport command control block (TCCB).

8. An apparatus adapted for communicating with a control unit controlling an input/output (I/O) device for executing an I/O operation in an I/O processing system, the I/O operation having an associated time limit, the apparatus comprising:

a channel subsystem for communication with an operating system and the control unit, the channel subsystem configured to perform a method comprising;

receiving a request from the operating system for initiating the I/O operation;

retrieving an I/O operation command from a location in memory specified by a command field in a transport control word (TCW), the TCW comprising the command field and an interrogate field;

sending the I/O operation command for initiating the I/O operation to the control unit; and

responsive to a determination by the operating system that the time limit is nearing elapsing without the I/O operation completing, determining whether to send an interrogate command to the control unit, to request a response from the control unit indicating the state of the I/O operation being executed by an I/O device controlled by the control unit; and

responsive to determining whether to send the interrogate command, retrieving an interrogate command address by the channel subsystem from an interrogate field in the TCW, and responsive to the interrogate command address having a non-zero value, retrieving the interrogate command from a location in memory specified by the interrogate command address.

9. The apparatus of claim 8, wherein the method performed by the channel subsystem further comprises setting the interrogate command address as a non-zero interrogate transport control word (TCW) address of an interrogate TCW in an interrogate TCW address field of the TCW to be used by a cancel subchannel instruction to request the sending of the interrogate command to the control unit.

10. The apparatus of claim 8, wherein as part of determining whether to send the interrogate command to the control unit for determining the state of the I/O operation, the channel subsystem determines whether the I/O operation has started.

11. The apparatus of claim 10, wherein the channel subsystem discards an initiative to issue the interrogate command responsive to a determination that the I/O operation has not started.

12. The apparatus of claim 8, wherein as part of determining whether to send an interrogate command to the control unit for determining the state of the I/O operation, the channel subsystem determines whether an interrogation operation is already in progress.

13. The apparatus of claim 12, wherein the channel subsystem discards an initiative to issue the interrogate command responsive to a determination that an interrogation operation is already in progress.

14. The apparatus of claim 8, wherein the method performed by the apparatus further comprises, responsive to a determination to send the interrogate command to the control unit, sending the interrogate command to the control unit and receiving a response from the control unit indicating a state of the I/O device in response to receipt of the interrogate command by the control unit, wherein the response from the control unit indicates whether the I/O device is reserved by another I/O processing system.

22. The apparatus of claim 8, wherein the interrogate command is included in an interrogate device command word (DCW), and the interrogate DCW is sent to the control unit via a transport command control block (TCCB).

15. A method for determining a state of an input/output (I/O) operation in an I/O processing system, the I/O operation having an associated time limit, the method comprising:

receiving a request from an operating system at a channel subsystem for initiating the I/O operation;

retrieving an I/O operation command from a location in memory specified by a command field in a transport control word (TCW), the TCW comprising the command field and an interrogate field;

sending the I/O operation command for initiating the I/O operation from the channel subsystem to the control unit;

responsive to a determination by the operating system that the time limit is nearing elapsing without the I/O operation completing, determining whether to send an interrogate command to the control unit, to request a response from the control unit indicating the state of the I/O operation being executed by an I/O device controlled by the control unit; and

responsive to determining whether to send the interrogate command, retrieving an interrogate command address by the channel subsystem from an interrogate field in the TCW, and responsive to the interrogate command address having a non-zero value, retrieving the interrogate command from a location in memory specified by the interrogate command address.

16. The method of claim 15, further comprising setting the interrogate command address as a non-zero interrogate transport control word (TCW) address of an interrogate TCW in an interrogate TCW address field of the TCW to be used by a cancel subchannel instruction to request the sending of the interrogate command to the control unit.

17. The method of claim 15, wherein determining whether to send the interrogate command to the control unit for determining the state of the I/O operation includes determining whether the I/O operation has started.

18. The method of claim 17, further comprising discarding an initiative to issue the interrogate command responsive to a determination that the I/O operation has not started.

19. The method of claim 15, wherein determining whether to send an interrogate command to the control unit for determining the state of the I/O operation includes determining whether an interrogation operation is already in progress.

20. The method of claim 19, further comprising discarding an initiative to issue the interrogate command responsive to a determination that an interrogation operation is already in progress.

23. The method of claim 15, wherein the interrogate command is included in an interrogate device command word (DCW), and the interrogate DCW is sent to the control unit via a transport command control block (TCCB).