Stack usage in computer-related operating systems

• US 20040045003A1
• Filed: 09/11/2002
• Published: 03/04/2004
• Est. Priority Date: 08/28/2002
• Status: Active Grant

• Current Assignee: LiveDevices Ltd. (Robert Bosch GmbH)
• Original Assignee: LiveDevices Ltd. (Robert Bosch GmbH)
• Inventors: Lake, David
• Granted Patent: US 7,225,443 B2
• Time in Patent Office: Days
• US Class Current: 718/103
• CPC Class Codes: G06F 9/4484 Executing subprograms
• CPC Class Codes: G06F 9/4881 Scheduling strategies for dispatcher, e.g. round robin, multi-level priority queues

Abstract

Methods, devices, configuration tools and operating systems are disclosed for reducing memory and processor usage in a computer operating system utilising a processor, a memory and a single stack, the operating system comprising a plurality of tasks divided into predetermined priority categories, including preemptive tasks and at least one task that voluntarily yields control of the processor to tasks of lower priority than itself in predetermined circumstances, wherein each task has associated therewith a stack pointer, and wherein the at least one task, when started, has its stack pointer set to a precalculated worst-case value guaranteed to leave sufficient space in the stack beneath the stack pointer for any preemptive tasks of lower priority, and wherein the at least one task has allocated to it an area of memory into which its stack contents is saved, a size of the area of memory being determined by a declared precalculated worst-case stack usage of the at least one task at any point at which the at least one task may yield control of the processor. Embodiments of the present invention enable a plurality of tasks to run on a single stack, thus saving memory and processor usage.

Claims

1. A method of reducing memory and processor usage in a computer operating system utilising a processor, a memory and a single stack, the operating system comprising a plurality of tasks divided into predetermined priority categories, including preemptive tasks and at least one task that voluntarily yields control of the processor to tasks of lower priority than itself in predetermined circumstances, wherein each task has associated therewith a stack pointer, and wherein the at least one task, when started, has its stack pointer set to a precalculated worst-case value guaranteed to leave sufficient space in the stack beneath the stack pointer for any preemptive tasks of lower priority, and wherein the at least one task has allocated to it an area of memory into which its stack contents is saved, a size of the area of memory being determined by a declared precalculated worst-case stack usage of the at least one task at any point at which the at least one task may yield control of the processor.

2. A method according to claim 1, wherein any operating system functions that may cause a task voluntarily to yield control of the processor are implemented such that, on detecting a need to yield control, they cause the curt stack pointer and stack space between the task'"'"'s known base stack pointer and the current stack pointer value to be saved into the area of memory

3. A method according to claim 2, wherein the said operating system functions, on return control of the processor to the task, cause the stack to be restored from the area of memory and the stack pointer to be set to its previous value before control of the processor was yielded.

4. A configuration tool for reducing memory and processor usage in a computer operating system utilising a processor, a memory and a single stack, the operating system comprising a plurality of tasks divided into predetermined priority categories, including preemptive tasks and at least one task that voluntarily yields control of the processor to tasks of lower priority than itself in predetermined circumstances, wherein each task has associated therewith a stack pointer, and wherein the tool is adapted to calculate a worst-case stack pointer value for the at least one task guaranteed to leave sufficient space in the stack beneath the stack pointer for any preemptive tasks of lower priority than the at least one task, and wherein the tool is adapted to allocate to the at least one task an area of memory into which the stack contents of the at least one task is saved, a size of the area of memory being determined by a declared worst-case stack usage, calculated by the tool, of the at least one task at any point at which the at least one task may yield control of the processor.

5. A tool as claimed in claim 4, adapted such that any operating system functions that may cause a task voluntarily to yield control of the processor are implemented such that, on detecting a need to yield control, they cause the current stack pointer and stack space between the task'"'"'s known base stack pointer and the current stack pointer value to be saved into the area of memory.

6. A tool as claimed in claim 5, adapted such that the said operating system functions, on returning control of the processor to the task, cause the stack to be restored from the area of memory and the stack pointer to be set to its previous value before control of the processor was yielded.

7. A software product comprising a configuration tool as claimed in claim 4.

8. A software product as claimed in claim 7, stored on a data carrier such as a floppy disk, optical disk, flash memory device or any other type of data carrier.

9. A computing device programmed with a configuration tool for reducing memory and processor usage in a computer operating system utilising a processor, a memory and a single stack, the operating system comprising a plurality of tasks divided into predetermined priority categories, including preemptive tasks and at least one task that voluntarily yields control of the processor to tasks of lower priority than itself in predetermined circumstances, wherein each task has associated therewith a stack pointer, and wherein the tool is adapted to calculate a worst-case stack pointer value for the at least one task guaranteed to leave sufficient space in the stack beneath the stack pointer for any preemptive tasks of lower priority than the at least one task, and wherein the tool is adapted to allocate to the at least one task an area of memory into which the stack contents of the at least one task is saved, a size of the area of memory being determined by a declared worst-case stack usage, calculated by the tool, of the at least one task at any point at which the at least one task may yield control of the processor.

10. A device as claimed in claim 9, adapted such that any operating system functions that may cause a task voluntarily to yield control of the processor are implemented such that, on detecting a need to yield control, they cause the current stack pointer and stack space between the task'"'"'s known base stack pointer and the current stack pointer value to be saved into the area of memory.

11. A device as claimed in claim 10, adapted such that the said operating system functions, on returning control of the processor to the task, cause the stack to be restored from the area of memory and the stack pointer to be set to its previous value before control of the processor was yielded.

12. A computer operating system utilising a processor, a memory and a single stack, the operating system comprising a plurality of tasks divided into predetermined priority categories, including preemptive tasks and at least one task that voluntarily yields control of the processor to tasks of lower priority than itself in predetermined circumstances, wherein each task has associated therewith a stack pointer, and wherein the at least one task, when started, has its stack pointer set to a precalculated worst-case value guaranteed to leave sufficient space in the stack beneath the stack pointer for any preemptive tasks of lower priority, and wherein the at least one task has allocated to it an area of memory into which its stack contents is saved, a size of the area of memory being determined by a declared precalculated worst-case stack usage of the at least one task at any point at which the at least one task may yield control of the processor.

13. An operating system as claimed in claim 12, adapted such that any operating system functions that may cause a task voluntarily to yield control of the processor are implemented such that, on detecting a need to yield control, they cause the current stack pointer and stack space between the task'"'"'s known base stack pointer and the current stack pointer value to be saved into the area of memory.

14. An operating system as claimed in claim 13, adapted such that the said operating system functions, on returning control of the processor to the task, cause the stack to be restored from the area of memory and the stack pointer to be set to its previous value before control of the processor was yielded.

15. A computing device programmed with an operating system utilising a processor, a memory and a single stack, the operating system comprising a plurality of tasks divided into predetermined priority categories, including preemptive tasks and at least one task that voluntarily yields control of the processor to tasks of lower priority than itself in predetermined circumstances, wherein each task has associated therewith a stack pointer, and wherein the at least one task, when running, has its stack pointer set to a precalculated worst-case value guaranteed to leave sufficient space in the stack beneath the stack pointer for any preemptive tasks of lower priority, and wherein the at least one task has allocated to it an area of memory into which its stack contents is saved, a size of the area of memory being determined by a declared precalculated worst-case stack usage of the at least one task at any point at which the at least one task may yield control of the processor.

16. A device as claimed in claim 15, adapted such that any operating system functions that may cause a task voluntarily to yield control of the processor are implemented such that, on detecting a need to yield control, they cause the current stack pointer and stack space between the task'"'"'s known base stack pointer and the current stack pointer value to be saved into the area of memory.

17. A device as claimed in claim 16, adapted such that the said operating system functions, on returning control of the processor to the task, cause the stack to be restored from the area of memory and the stack pointer to be set to its previous value before control of the processor was yielded.

18. A method of reducing memory and processor usage, substantially as hereinbefore described with reference to FIGS. 3 to 5 of the accompanying drawings.

19. A configuration tool for reducing memory and processor usage, substantially as hereinbefore described with reference to FIGS. 3 to 5 of the accompanying drawings.

20. A computing device programmed with a configuration tool for reducing memory and processor usage, substantially as hereinbefore described with reference to FIGS. 3 to 5 of the accompanying drawings.

21. A computer operating system, substantially as hereinbefore described with reference to FIGS. 3 to 5 of the accompanying drawings.

22. A computing device programmed with an operating system, substantially as hereinbefore described with reference to FIGS. 3 to 5 of the accompanying drawings.