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Program-Check Interrupt Suspension Mechanism

IP.com Disclosure Number: IPCOM000104857D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 104K

Publishing Venue

IBM

Related People

Greenstein, PG: AUTHOR [+2]

Abstract

A mechanism is disclosed for suspending program-check interrupts (PCIs), testing the condition of the suspended PCI, cleaning up the condition of the suspended PCI, and unsuspending PCIs.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 48% of the total text.

Program-Check Interrupt Suspension Mechanism

      A mechanism is disclosed for suspending program-check
interrupts (PCIs), testing the condition of the suspended PCI,
cleaning up the condition of the suspended PCI, and unsuspending
PCIs.

      The mechanism consists of:

      PCI Control Mask (PCM):  A mask consisting of two parts of
equal length:

      PCI Suspension Mask (PSM):  The bit mask where each bit
corresponds to the program-check interruption subclass.  The mask is
used to control the generation of the PCIs of the specified
subclass(es).  When the bit in the PSM corresponding to a specific
PCI subclass is set, the interruptions of that subclass are
suspended.  Note that a PCI suspended by means of this mechanism
never occurs but the condition can be detected (the exception is
still generated by the hardware).  Zeroing the mask will not cause
the interrupt to be generated post-factum.

      PCI Occurrence Mask (POM):  The bit mask where each bit
corresponds to the program-check interruption subclass.  The mask is
used to signal an occurence of an exception of a specified subclass.
When an exception occurs, the corresponding bit is set in this mask.

      LOAD PCM (LPCM) Instruction:  The LPCM instruction is used to
update the contents of the PCM by copying a bit mask from storage
into PCM.  It may result in some PCI subclasses being suspended.

      STORE PCM (SPCM) Instruction:  The SPCM instruction is used to
copy the contents of the PCM into a specified storage location.  It
may be used to interrogate the occurrence of suspended PCI
subclasses.

      A subset of all architected exceptions is supported by this
mechanism.  The subset of the PCI subclass mask that is eligible for
suspension depends on the authorization mode of the program.
Problem-state programs are only allowed to suspend
data-contents-related exceptions (e.g., overflow), while
supervisor-state programs are allowed to suspend all subclasses
supported by this facility, including operation, various addressing
exceptions, etc..  Setting an invalid mask on LPCM causes a
program-check.  The mask specified with a LPCM instruction is
effective starting with the next sequential instruction after the
LPCM successfully completes.

      The following table shows an example of a sequence of
operations on the PCM:

Function         Instruction    PSM     POM     Data transfer
------------     -----------    ---     ---     -------------
Suspend             LPCM        0100    0000    PCM<--storage
Event(1)                        0100    0100    Inspect storage
PCM                             0100    0100    PCM-->storage
Clear               LPCM        0100    0000    PCM<--storage
Unsuspend           LPCM        0000    0000    PCM<--storage

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