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Inside Macintosh: Networking With Open Transport / Part 2 - Open Transport Reference

Chapter 23 - Programming With Open Transport Reference / Functions

Entering and Leaving Hardware Interrupt Time /

OTScheduleInterruptTask

Schedules a task for execution at hardware interrupt time.

C INTERFACE

Boolean OTScheduleInterruptTask(long dtCookie)

C++ INTERFACE

None. C++ applications use the C interface to this function.

PARAMETERS

dtCookie

A reference that identifies the task to be scheduled. This reference is returned by the OTCreateDeferredTask function, which you use to create the task.

function result

The result is true if the deferred task is scheduled. If it returns false and the dtCookie parameter has a valid value (other than 0), then the task is already scheduled to run. If dtCookie is invalid (a value of 0), the function returns false and does nothing.

DISCUSSION

The OTScheduleInterruptTask function schedules the task associated with the dtCookie parameter for execution at deferred task time.This function calls the OTEnterInterrupt and the OTLeaveInterrupt functions, so you do not need to make separate calls to those functions when calling the OTScheduleInterruptTask function.

The OTScheduleInterruptTask function behaves exactly like the function OTScheduleDeferredTask. You should call it instead of calling the OTScheduleDeferredTask function if you are calling from hardware interrupt time.

When Open Transport calls your callback function, it passes it the arg parameter you specified when you created the task. (For 68000 code, Open Transport also restores the A5 global world to what it was when you originally called OTCreateDeferredTask.)

You can call this function any time. If you have not yet destroyed a task, you can use this function to reschedule it multiple times.

If you make multiple calls to the OTScheduleInterruptTask function before the task is executed, additional tasks are not scheduled; only one instance of each unique task will be scheduled at a time.

If you want to call Open Transport from an interrupt, you can use this function (and the OTCreateDeferredTask function) instead of the standard Deferred Task Manager function DTInstall to create a deferred task that permits you to call Open Transport functions. This allows Open Transport to adapt to changes in the underlying operating system without affecting your code.

WARNING

Open Transport does not keep track of outstanding deferred task requests. It is the caller's responsibility to ensure that all outstanding deferred task requests have either executed or have been cancelled. If this is not done, and the calling process terminates before the deferred task executes, the processor will crash when it attempts to execute the task.

SPECIAL CONSIDERATIONS

You can call this Open Transport function at hardware interrupt time without calling the OTEnterInterrupt function first and the OTLeaveInterrupt function afterward.

SEE ALSO

The OTCreateDeferredTask function.

The OTDestroyDeferredTask function.