Real time processor capable of concurrently running multiple independent JAVA machines

• US 6,374,286 B1
• Filed: 04/06/1998
• Issued: 04/16/2002
• Est. Priority Date: 04/06/1998
• Status: Expired due to Term

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Hardin, David S., Gee, John K., Mass, Allen P., Greve, David A., Wilding, Matthew M., Mykris, Nick M., Masters, Michael H.
• Primary Examiner(s): Courtenay, III, St. John
• Assistant Examiner(s): Nguyen, Van H.
• Application Number:
  US09/056,126
• Time in Patent Office: 1,471 Days
• Field of Search: 709/100-106, 709/107-108, 709/1, 710/260, 713/502
• US Class Current: 718/108
• CPC Class Codes: G06F 9/262 Arrangements for next microinstruction selection
• CPC Class Codes: G06F 9/30101 Special purpose registers
• CPC Class Codes: G06F 9/30141 Implementation provisions of register files, e.g. ports
• CPC Class Codes: G06F 9/30145 Instruction analysis, e.g. decoding, instruction word fields
• CPC Class Codes: G06F 9/30167 of immediate specifier, e.g. constants
• CPC Class Codes: G06F 9/45504 Abstract machines for programme code execution, e.g. Java virtual machine [JVM], interpreters, emulators
• CPC Class Codes: G06F 9/463 Program control block organisation
• CPC Class Codes: G06F 9/4825 Interrupt from clock, e.g. time of day
• CPC Class Codes: G06F 9/4843 by program, e.g. task dispatcher, supervisor, operating system

Abstract

Multiple Java Virtual Machines (JVMs) operate on a single direct execution JAVA processor with each JVM operating in a separate time slice called a partition. Each JVM has its own data and control structures and is assigned a fixed area of memory. Each partition is also allotted a fixed period of time in which to operate, and, at the end of the allotted time, a context switch is forced to another JVM operating in the next partition. The context switch does not transfer control directly from one JVM to another JVM. Instead, at the end of a partition time period control is switched from the currently operating JVM to a “master JVM” during a time period called an “interstice.” The master JVM handles system interrupts and housekeeping duties. At the end of the interstice time period, the master JVM starts a proxy thread associated with the next JVM to become operational. The proxy thread handles JVM-specific interrupts and checks the status of the associated JVM. If the JVM appears operational the proxy thread transfers control to the JVM thread. Time intervals such as partition times and interstice times are enforced by hardware timers and memory accesses are checked by address comparison circuitry to prevent a system failure due to a malfunction in either the master JVM or another JVM.

Claims

1. Apparatus for concurrently running a plurality of JAVA virtual machines (JVMs) on a single processor having a memory, the apparatus comprising:

an initiation mechanism which creates in the memory, data and control structures for each of the plurality of JVMs, the initiation mechanism designating one of the plurality of JVMs as a master JVM;

a first timer which periodically forces a context switch from a JVM which is operating to the master JVM whereupon the master JVM services system interrupts and performs housekeeping duties; and

a second timer operational after a predetermined interval of time which causes the master JVM to perform a context switch to the next JVM to become operational.

2. The apparatus according to claim 1 wherein the second timer activates a proxy thread after the predetermined interval of time, which proxy thread handles JVM-specific interrupts, checks the status of the next JVM and starts the next JVM.

3. The apparatus according to claim 1 wherein the data and control structures for each of the plurality of JVMs are referenced by a single table and wherein context switches are performed by changing references from a first table associated with one JVM to a second table associated with a second JVM.

4. The apparatus according to claim 1 wherein access to data and control structures is limited for each JVM to the data and control structures created for the each JVM by the initiation means and wherein the data and control structure access is checked by comparing an address used to access the data and control structure to predetermined limits.

5. The apparatus according to claim 4 wherein the master JVM has access to all data and control structures.

6. The apparatus according to claim 1 wherein the first timer is a hardware driven timer.

7. The apparatus according to claim 1 wherein the second timer is a hardware driven timer.

8. The apparatus according to claim 1 wherein the processor is a JAVA direct execution processor.

9. The apparatus according to claim 1 wherein the data and control structures include a control block which stores the status of a JVM during a context switch.

10. The apparatus according to claim 1 wherein the processor is controlled by microcode and wherein the same microcode is used to execute JVM.

11. A method for concurrently running a plurality of JAVA virtual machines (JVMs) on a single processor having a memory, the method comprising the steps of:

(a) creating in the memory, data and control structures for each of the plurality of JVMs;

(b) designating one of the plurality of JVMs as a master JVM;

(c) using a first timer to periodically force a context switch from a JVM which is operating to the master JVM whereupon the master JVM services system interrupts and performs housekeeping duties; and

(d) using a second timer to determine when a predetermined interval of time has elapsed and, at the expiration of the predetermined time period to cause the master JVM to perform a context switch to the next JVM to become operational.

12. The method according to claim 11 wherein step (d) comprises the steps of:

(d1) activating a proxy thread after the predetermined interval of time has elapsed;

(d2) using the proxy thread to handle JVM-specific interrupts, check the status of the next JVM and start the next JVM.

13. The method according to claim 11 wherein the data and control structures for each of the plurality of JVMs are referenced by a single table and wherein step (c) comprises the step of:

(c1) causing a context switch by changing references from a first table associated with one JVM to a second table associated with a second JVM.

14. The method according to claim 11 further comprising the step of:

(e) limiting access wherein access to data and control structures for each JVM to the data and control structures created for the each JVM by comparing an address used to access the data and control structure to predetermined limits.

15. The method according to claim 14 wherein step (e) comprises the step of:

(e1) allowing the master JVM to access all data and control structures.

16. The method according to claim 11 wherein the first timer is a hardware driven timer.

17. The method according to claim 11 wherein the second timer is a hardware driven timer.

18. The method according to claim 11 wherein the processor is a JAVA direct execution processor.

19. The method according to claim 11 wherein the data and control structures include a control block which stores the status of a JVM during a context switch.

20. The method according to claim 11 wherein the processor is controlled by microcode and wherein the same microcode is used to execute each of the plurality of JVMs.

21. A computer program product for concurrently running a plurality of JAVA virtual machines (JVMs) on a single processor having a memory, the computer program product comprising a computer usable medium having computer readable program code thereon, including:

program code which creates in the memory, data and control structures for each of the plurality of JVMs;

program code which designates one of the plurality of JVMs as a master JVM;

program code which responds to a first timer to periodically force a context switch from a JVM which is operating to the master JVM whereupon the master JVM services system interrupts and performs housekeeping duties; and

program code which responds to a second timer to determine when a predetermined interval of time has elapsed and, at the expiration of the predetermined time period to cause the master JVM to perform a context switch to the next JVM to become operational.

22. The computer program product according to claim 21 wherein the program code which responds to the second timer comprises program code which activates a proxy thread after the predetermined interval of time has elapsed;

and program code in the proxy thread which handles JVM-specific interrupts, checks the status of the next JVM and starts the next JVM.

23. The computer program product according to claim 21 wherein the data and control structures for each of the plurality of JVMs are referenced by a single table and wherein the program code which responds to the first timer causes a context switch by changing references from a first table associated with one JVM to a second table associated with a second JVM.

24. The computer program product according to claim 21 further comprising program code which limits access to data and control structures for each JVM to the data and control structures created for the each JVM by responding to a comparison of an address used to access the data and control structure to predetermined limits.

25. The computer program product according to claim 24 wherein the program code which limits access to data and control structures allows the master JVM to access all data and control structures.