System and method for providing cooperative interrupts in a preemptive task scheduling environment

• US 5,911,065 A
• Filed: 08/05/1997
• Issued: 06/08/1999
• Est. Priority Date: 05/05/1995
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Robbin, Jeffrey L., Jacklin, Kelly B., Iarocci, John J., Williams, Russell T.
• Primary Examiner(s): Banankham, Majid A.
• Application Number:
  US08/906,068
• Time in Patent Office: 672 Days
• Field of Search: 395/670, 395/672, 395/677, 395/673, 395/200.33
• US Class Current: 718/107
• CPC Class Codes: G06F 9/45537 Provision of facilities of other operating environments, e.g. WINE I/O emulation G06F13/105
• CPC Class Codes: G06F 9/4812 by interrupt, e.g. masked

Abstract

A system and method for executing applications written in a cooperative scheduling environment in a preemptive task scheduling environment, ensuring that the time sequence for the delivery of interrupts is not altered in the preemptive task scheduling environment, efficiently disabling all cooperative interrupts in response to a request from an application, efficiently scheduling all cooperative interrupts, and efficiently executing emulated instructions while preserving the integrity of the emulated instructions. The system and method utilize a process server to enforce the cooperative scheduling, a cooperative interrupt server and a holds queue to enforce the interrupt requirements, and special context data to ensure the compatibility of applications designed using an old instruction set architecture.

Claims

1. In a computer-based system having a processor, a controller, a memory module, and a preemptive operating system that does not support cooperative scheduling, a method for executing within the preemptive operating system, a first application designed to operate on a cooperative scheduling operating system, comprising the steps of:

receiving a cooperative interrupt associated with the first application;

storing an address of a completion routine, associated with the first application, in a queue allocated in the memory module, said completion routine including an interrupt handling procedure for servicing said cooperative interrupt;

determining if said completion routine is permitted to execute; and

executing said completion routine under control of a cooperative interrupt server responsive to said queue, if said completion routine is permitted to execute.

2. The method of claim 1, further comprising the step of:

suspending execution of a second application that is designed to operate on the cooperative scheduling operating system, if said completion routine is permitted to execute.

3. The method of claim 1, further comprising the step of:

disabling said completion routine by setting one or more disable bits in the memory module using an atomic operation that does not access the controller.

4. The method of claim 3, wherein said step of determining if said completion routine is permitted to execute includes the steps of:

determining if an emulator is executing an emulated instruction; and

determining if said emulator is executing an instruction at a boundary of said emulated instruction, if said emulator is executing said emulated instruction.

5. The method of claim 4, wherein the step of determining if said completion routine is permitted to execute includes the step of:

setting one or more special context bits in said emulator.

6. The method of claim 5, wherein the step of setting one or more special context bits includes the steps of:

storing a value in a special context mask if said emulator is executing an emulated instruction;

performing a logical OR operation between said special context mask and said special context bits; and

storing the result of the logical OR operation in said special context bits.

7. The method of claim 1, further comprising the step of:

interrupting the execution of said first application to execute a second application designed to operate on an operating system supporting preemptive task scheduling.

8. The method of claim 1, further comprising the steps of:

receiving a second cooperative interrupt associated with a second application;

storing the address of a second completion routine, associated with a third application designed to operate in the cooperative scheduling environment, in the queue allocated in the memory module, said second completion routine including a procedure for servicing said second cooperative interrupt;

determining if said second completion routine is permitted to execute, if said first completion routine is not executing;

setting a cooperative interrupt pending indicator if said first completion routine is executing; and

executing said second completion routine using said cooperative interrupt server responsive to the queue if said second routine is permitted to execute, said cooperative interrupt server ensuring that all cooperative interrupts are responded to in a same response sequence of the cooperative scheduling operating system supporting the cooperative interrupts.

9. The method of claim 8, further comprising the step of:

suspending execution of said second application if said second completion routine is permitted to execute.

10. The method of claim 1, further comprising the step of:

suspending all cooperative applications except for a current cooperative application to ensure that the only cooperative application that can execute is said current cooperative application.

11. A computer-based preemptive operating system, having a processor, for executing a first application and a second application designed to operate on a cooperative scheduling operating system using cooperative interrupts, the system comprising:

a first queue, for storing information related to the operation of the first application;

a process server, disposed to communicate with said first queue, for ensuring that only one of the first application and the second application has access to the processor in accordance with a cooperative scheduling environment;

a completion routine, associated with the first application, for servicing a first cooperative interrupt associated with the first application;

a second queue, for storing the address of said completion routine;

a cooperative interrupt server, disposed to communicate with said second queue, for receiving the address of each completion routine in response to the corresponding cooperative interrupt associated with the completion routine being received, for servicing each cooperative interrupt, and for ensuring that each cooperative interrupt is serviced in a same sequence that the cooperative interrupts are serviced in the cooperative scheduling operating system; and

a controller, coupled to said first queue, said process server, and said cooperative interrupt server, for controlling access to said first queue and said second queue, and for providing a preemptive scheduling environment.

12. The system of claim 11, further comprising:

a disable mechanism, disposed to receive signals from one of the first application, the second application, and the completion routine, for preventing the servicing of cooperative interrupts by said cooperative interrupt server, without accessing said controller.

13. The system of claim 12, wherein said disable mechanism further comprises:

an emulated instruction indicator, disposed to receive signals from said controller, for storing information indicating that an emulated instruction is executing, said disable mechanism preventing the servicing of the cooperative interrupts by said cooperative interrupt server when said emulated instruction indicator is set.

14. The system of claim 13, further comprising:

a memory location, located within the first application, for notifying the second application that a cooperative interrupt is pending;

wherein said controller modifies said memory location when a cooperative interrupt is pending and said emulated instruction indicator is set.

15. In a computer-based system having a processor, a controller, a memory module, and a preemptive operating system that does not support cooperative scheduling, a method for executing in the preemptive operating system, a plurality of applications designed to operate on a cooperative scheduling operating system, comprising the steps of:

asynchronously receiving a plurality of cooperative interrupts, each cooperative interrupt associated with one of the plurality of applications, each cooperative interrupt further associated with a completion routine for servicing the cooperative interrupt;

determining whether at least one completion routine is permitted to execute; and

synchronously executing each of the plurality of cooperative interrupts under control of a task scheduler according to an order in which the cooperative interrupts were asynchronously received.