ADC Home > Reference Library > Technical Notes > Legacy Documents > Carbon >

Legacy Documentclose button

Important: This document is part of the Legacy section of the ADC Reference Library. This information should not be used for new development.

Current information on this Reference Library topic can be found here:

Inside Macintosh: Processes Errata

CONTENTS

This Technical Note discusses known errors and omissions in Inside Macintosh: Processes.

[Oct 01 1994]






Topics

  • Correction to Figure 1-1 October 1994
  • Clarification of Installing Persistent VBL Tasks October 1994
  • Clarification of GetVBLQHdr October 1994
  • Clarification of Interrupt Priorities During VBL Tasks October 1994
  • Correction to Listing 8-1 October 1994
  • Correction to Glossary Entry October 1994

Back to top

Chapter 1 - Introduction to Processes and Tasks

Correction to Figure 1-1

Page 1-4, The Cooperative Multitasking Environment

Figure 1-1 shows the wrong application icon in the menu bar. The SurfWriter icon should be in the menu bar labeling the application menu, not the Finder icon.

Back to top

Chapter 4 - Vertical Retrace Manager

Clarification of Installing Persistent VBL Tasks

Page 4-20, Installing a Persistent VBL Task

The description of installing a persistent VBL task is partly incorrect. The documentation states that "if you want to install a persistent system-based VBL task, you need to load its VBL task record into the system partition." This is incorrect, and it is not what is demonstrated in Listing 4-15. Listing 4-15 shows how to put the VBL task code (or enough of it to fool the Vertical Retrace Manager) into the system partition.

However, Listing 4-15 needs a call to FlushInstructionCache added immediately before the call to VInstall. In addition, it is preferable to code the error-handling part of Listing 4-15 like this:

SysHeapPtr := NewPtrSys(kJMPSize);
IF SysHeapPtr = NIL THEN
    BEGIN
        InstallPersistentVBL := MemError;
        Exit(InstallPersistentVBL );
    END;

Clarification of GetVBLQHdr

Page 4-28

GetVBLQHdr returns a pointer to the head of the VBL queue. One of the bits of the qFlags field of the VBL queue header indicates whether a VBL task is currently executing. The correct bit is bit 6 of the first byte of the qFlags field, or bit 14 of the entire two-byte field. Versions of A/UX prior to 3.1 incorrectly used bit 6 of the entire two-byte field.

Back to top

Chapter 6 - Deferred Task Manager

Clarification of Interrupt Priorities During VBL Tasks

Pages 6-3, 6-5, About the Deferred Task Manager

The documentation states "If the current application is then interrupted by a vertical retrace interrupt, the interrupt priority is set to 1 during the servicing of the interrupt and restored to 0 upon completion." This is not strictly correct. T he Vertical Retrace Manager actually restores the interrupt mask to 0 before running VBL tasks. As a result, VBL tasks can be interrupted by future level-1 interrupts, although a VBL task cannot interrupt another VBL task.

On page 6-5, the documentation states "Suppose that your application installs and activates a Time Manager task, which is triggered by level-2 interrupts." Actually, Time Manager interrupts are level-1 interrupts.

Also on page 6-5, there is occasional mention of the status register being restored to 0. In fact, only three bits of the status register (the processor priority level) are restored to 0. All other bits are unchanged.

Back to top

Chapter 8 - Shutdown Manager

Correction to Listing 8-1

Page 8-8, Sending a Shutdown or Restart Event

Listing 8-1 on page 8-8 contains several errors. The constant kFinderSig should be defined to be 'MACS'. In addition, that constant cannot be passed directly to the AECreateDesc function. Instead, you must declare a variable of type OSType and assign kFinderSig to it, as follows:

CONST
    kFinderSig = 'MACS';
VAR
    ...
    signature: OSType
BEGIN
    signature := kFinderSig;
    myErr := AECreateDesc(typeApplSignature, @signature, ...);
    ...

Back to top

Glossary

Correction to Glossary Entry

Page GL-2

The entry interrupt handle should be interrupt handler.

Back to top

References

Inside Macintosh: Processes

Back to top

Downloadables

Acrobat gif

Acrobat version of this Note (40K)

Download


Back to top


Did this document help you?
Yes: Tell us what works for you.
It’s good, but: Report typos, inaccuracies, and so forth.
It wasn’t helpful: Tell us what would have helped.