Software sanity monitor

• US 6,665,758 B1
• Filed: 10/04/1999
• Issued: 12/16/2003
• Est. Priority Date: 10/04/1999
• Status: Expired due to Term

• Current Assignee: NCR Voyix Corporation
• Original Assignee: NCR Corporation (NCR Voyix Corporation)
• Inventors: Heske, Theodore III, Belknap, William M., Frazier, Ralph E., Blanford, Denis M.
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): Chung-Trans, X.
• Application Number:
  US09/411,497
• Time in Patent Office: 1,534 Days
• Field of Search: 710/210, 710/260, 710/262, 710/266, 713/502, 714/2, 714/47, 714/48, 714/55, 714/38, 714/44, 717/124, 717/126, 717/127, 709/102, 709/107
• US Class Current: 710/200
• CPC Class Codes: G06F 11/0757 by exceeding a time limit, i.e. time-out, e.g. watchdogs
• CPC Class Codes: G06F 9/4881 Scheduling strategies for dispatcher, e.g. round robin, multi-level priority queues

Abstract

Disclosed is a Software Sanity Monitor for automatically detecting and remedying software lock-up conditions without user intervention. Users often refer to these conditions as “hangs” or “forever loops”. Although the Software Sanity Monitor uses the operating software'"'"'s information, it is designed to execute independent of the operating system software; thereby, eliminating reliance on a “sane” operating system. If a “hang” condition is detected, the Software Sanity Monitor will automatically restart the system after logging the failure and, optionally, notify the user or host system.

Claims

1. A computer-implemented method of preventing a computer system lock-up, comprising:

starting a first timer;

monitoring a second timer and determining when the second timer periodic time interval elapses;

sampling operating software scheduling information of the computer system to verify lower priority programs have continued to run;

if the lower priority programs have continued to run, restarting the first timer such that the first timer does not interrupt the computer system;

restarting the second timer;

if the lower priority programs have not continued to run, allowing the first timer to expire and interrupt the computer system; and

taking control of the computer system by a monitoring program.

2. The method of claim 1, wherein the first timer is separate from a clock of the computer system, and the first timer provides an unmaskable interrupt.

3. The method of claim 1, comprising starting the first timer upon computer system initialization.

4. The method of claim 1, wherein the second timer is not separate from a clock of the computer system, and the second timer provides a maskable interrupt.

5. The method of claim 1, comprising subsequent to said taking step, sampling the scheduling information, and if it is determined the lower priority programs have not run or the computer system has reached an idle loop, performing a system recovery.

6. The method of claim 1, comprising determining the computer system is in an idle loop and interrupts are disabled.

7. The method of claim 6, determining the computer system is properly functioning by determining lower priority programs continue to execute or the idle loop is reached within a predetermined maximum time period.

8. The method of claim 7, wherein the predetermined maximum time period is defined as the sum of the second timer and the first timer.

9. The method of claim 1, comprising a low run-time priority mark.

10. The method of claim 9, comprising resetting the low run-time priority mark when the idle loop is reached.

11. The method of claim 1, wherein said taking step is performed by a Software Sanity Monitor.

12. The method of claim 1, wherein the monitoring program executes independently of the operating system of the computer system.

13. The method of claim 12, comprising logging any instances where the monitoring program has taken control due to the operating system becoming insane.

14. The method of claim 1, comprising updating a global field whenever the operating system switches to a lower run-time priority program from a higher run-time priority program.

15. The method of claim 14, comprising checking a task switch schedule count for the next lowest run-time priority.

16. The method of claim 15, comprising incrementing the task switch schedule count after a higher priority task exits allowing or scheduling a lower run-time priority task to run.

17. The method of claim 1, wherein the first timer has evaluation logic which is interrupt service routine code.

18. An article including a computer readable medium having stored thereon a plurality of sequences of instructions, said plurality of sequences of instructions including sequences of instructions which, when executed by a processor, cause said processor to perform the steps of:

starting a first timer;

monitoring a second timer and determining when the second timer periodic time interval elapses;

sampling operating software scheduling information of the computer system to verify lower priority programs have continued to run;

if the lower priority programs have continued to run, restarting the first timer such that the first timer does not interrupt the computer system;

restarting the second timer;

if the lower priority programs have not continued to run, allowing the first timer to expire and interrupt the computer system; and

taking control of the computer system by a monitoring program.

19. A computer system, comprising:

a processor; and

a memory coupled to said processor, the memory having stored therein sequences of instructions, which, when executed by said processor, causes said processor to perform the steps of;

starting a first timer;

monitoring a second timer and determining when the second timer periodic time interval elapses;

sampling operating software scheduling information of the computer system to verify lower priority programs have continued to run;

if the lower priority programs have continued to run, restarting the first timer such that the first timer does not interrupt the computer system;

restarting the second timer;

if the lower priority programs have not continued to run, allowing the first timer to expire and interrupt the computer system; and

taking control of the computer system by a monitoring program.