Control unit threshold timeout controls for software missing interrupt handlers in operating systems
First Claim
1. Support controls within an I/O control unit (CU) for operating with a plurality of host system adapter interfaces located in the CU for connecting the CU to host systems that send I/O requests to the CU and use timeout detection for determining when a requested I/O device attached to the CU has failed to perform a requested I/O operation, the CU comprising:
- a plurality of device lock bits respectively associated with I/O devices connected to the CU to control a connection of any of the I/O devices to any of the adapter interfaces for an I/O operation,a busy bit, a threshold timer associated with each of the adapter interfaces, and a stored threshold timeout value for operating with the timer for determining occurrence of a threshold timeout,bit testing controls for each of the adapter interfaces for attempting to set to a lock state an available one of the lock bits associated with an I/O device required by a current I/O request received by the adapter interface which may contend for the lock state with a current I/O request received by any other of the adapter interfaces simultaneously attempting to obtain use of the associated I/O device,busy bit controls associated with the adapter interface for setting the associated busy bit to a busy state when a waiting I/O request is received by the adapter interface while the associated lock bit is set to the locked state for a current I/O request using the associated I/O device,timer starting controls for resetting and starting the timer associated with the adapter interface when the associated lock bit is set to a lock state,long busy controls in the CU associated with each adapter interface for generating a long busy signal to the adapter interface if the associated timer exceeds the threshold timeout while a locked state exists for the lock bit, and the long busy controls transferring the long busy signal from the adapter interface for transmission external to the CU, andoperation completion controls associated with each lock bit for generating a no-longer long-busy signal when the device lock is set to an unlocked state after the threshold timeout is exceeded, and the operation completion controls transferring the no-longer long busy signal to the adapter interface for transmission external to the CU.
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Accused Products
Abstract
I/O control unit (CU) features for supporting multiple host operating systems (OSs) which use missing interrupt handler (MIH) timeout functions for detecting potential failures of requested I/O device operations. These CU features support multiple host OSs by preventing them from falsely indicating I/O device failures, when in fact the device has not failed but is merely processing one or more other requests for other host Oss.
116 Citations
17 Claims
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1. Support controls within an I/O control unit (CU) for operating with a plurality of host system adapter interfaces located in the CU for connecting the CU to host systems that send I/O requests to the CU and use timeout detection for determining when a requested I/O device attached to the CU has failed to perform a requested I/O operation, the CU comprising:
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a plurality of device lock bits respectively associated with I/O devices connected to the CU to control a connection of any of the I/O devices to any of the adapter interfaces for an I/O operation, a busy bit, a threshold timer associated with each of the adapter interfaces, and a stored threshold timeout value for operating with the timer for determining occurrence of a threshold timeout, bit testing controls for each of the adapter interfaces for attempting to set to a lock state an available one of the lock bits associated with an I/O device required by a current I/O request received by the adapter interface which may contend for the lock state with a current I/O request received by any other of the adapter interfaces simultaneously attempting to obtain use of the associated I/O device, busy bit controls associated with the adapter interface for setting the associated busy bit to a busy state when a waiting I/O request is received by the adapter interface while the associated lock bit is set to the locked state for a current I/O request using the associated I/O device, timer starting controls for resetting and starting the timer associated with the adapter interface when the associated lock bit is set to a lock state, long busy controls in the CU associated with each adapter interface for generating a long busy signal to the adapter interface if the associated timer exceeds the threshold timeout while a locked state exists for the lock bit, and the long busy controls transferring the long busy signal from the adapter interface for transmission external to the CU, and operation completion controls associated with each lock bit for generating a no-longer long-busy signal when the device lock is set to an unlocked state after the threshold timeout is exceeded, and the operation completion controls transferring the no-longer long busy signal to the adapter interface for transmission external to the CU. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method within an I/O control unit (CU) for supporting I/O device failure detection by any of a plurality of host systems which may be connected to I/O interface adapters in the CU that receives I/O requests from the host systems, the CU method communicating information from the CU to the host systems to support missing interrupt timeout detection in the host systems in a manner that prevents any host system from falsely indicating operational failure by a requested I/O device attached to the CU, the CU performing the steps of:
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associating a plurality of lock bits with respective I/O devices connected to the CU to control a connection of any of the I/O devices to any of the adapter interfaces for an I/O operation, structuring with each interface adapter a busy bit, a threshold timer, and a stored threshold timeout value for operating the timer to determine an occurrence of a threshold timeout, conditionally testing by any interface adapter the state of the lock bit associated with an I/O device required by a current I/O request received by the interface adapter while simultaneous I/O requests are being made for plural interface adapters trying to obtain use of the same I/O device, setting the associated busy bit to a busy state when a waiting I/O request is received by the interface adapter while the lock bit is set to the locked state for a current I/O request using the associated I/O device, resetting and starting the timer for the interface adapter when a tested lock bit is set to a lock state, generating a long busy signal for the interface adapter if the timer exceeds the threshold timeout while a locked state exists for the lock bit, and transferring the long busy signal from the interface adapter to a host system requesting the I/O device to communicate that the I/O device remains busy with a current I/O request obtaining the lock state, and outputting a no-longer long-busy signal from the interface adapter to indicate the I/O device has completed a requested I/O operation when the device lock is set to an unlocked state after the threshold timeout is exceeded. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. Support controls within an I/O control unit (CU) for operating with one or more host operating systems (OSs) that send I/O requests to the CU for an operation by a requested I/O device attached to the CU, the CU comprising:
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an operation code signal for indicating an I/O command being currently performed by the I/O device for an I/O program associated with an I/O request from an OS, a command detector for testing the operation code signal to determine whether the command is a long command, an interrupt signal generator for generating a long-busy interrupt signal if the command detector determines the command is a long command, sending the long-busy interrupt signal to a processor for communicating the long busy interrupt signal to the OS which issued the I/O request to enable the OS to extend a primary missing interrupt handler (MIH) timeout period to a secondary MIH timeout period before the end of the primary MIH timeout period for preventing the primary MIH timeout period from ending with a timeout which would falsely indicate a potential I/O device operation failure.
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Specification