Watchdog timer using a high precision event timer

• US 7,689,875 B2
• Filed: 04/25/2002
• Issued: 03/30/2010
• Est. Priority Date: 04/25/2002
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Nelson, Eric Frank, Cahill, Jeremy Paul
• Primary Examiner(s): Puente; Emerson C
• Application Number:
  US10/133,555
• Publication Number:
  US 20030204792A1
• Time in Patent Office: 2,896 Days
• Field of Search: 714/23, 714/25, 714/51, 714/55, 714/56
• US Class Current: 714/55
• CPC Class Codes: G06F 11/0757 by exceeding a time limit, i.e. time-out, e.g. watchdogs

Abstract

A system and method for detecting and handling errors in a computer system are disclosed. The invention is configurable to permit selecting of timelength or time out values, assigned interrupts to be generated and error recover procedures so that failures of system events can be promptly detected and recovered from. The watchdog timer is started with a timelength or time out value and generates an interrupt (i.e., is triggered) if the period of time set as the timelength passes without receiving a reset. The watchdog timer interface interacts and controls the hardware based timer to obtain this watchdog timer functionality. The hardware based timer is generally a high precision timer that exists in hardware architecture for a computer system and is usable by system software. The watchdog timer interface controls and sets various parameters and/or registers of the hardware based timer in order to provide the desired functionality of a watchdog timer. Thus, another software component can call and interact with the watchdog timer interface for a system event and view the watchdog timer interface as a watchdog timer (i.e., the operation of the hardware based timer is transparent).

Claims

1. A watchdog timer system comprising:

a hardware timer that one of increments and decrements a counter value toward a compare value every tick period and that generates an interrupt when the compare value equals the counter value; and

a watchdog timer programming interface that configures the hardware timer to function as a watchdog timer by;

specifying the compare value to the hardware timer, the watchdog timer programming interface determining the compare value at least in part by computing a ratio of a timelength parameter associated with a system event received from a software application and the tick period;

setting the counter value of the hardware timer to an initial value;

setting the interrupt to a desired interrupt;

enabling the hardware timer to update the counter value every tick period; and

resetting the hardware timer upon successful processing of the system event.

2. The system of claim 1, further comprising an exception handler that is executed in response to the interrupt being generated and that performs error recovery procedures.

3. The system of claim 2, the exception handler being a component of an operating system.

4. The system of claim 1, wherein the watchdog timer programming interface resets the hardware timer by resetting the counter value to zero.

5. The system of claim 1, the watchdog timer programming interface enables the hardware timer on receiving a start parameter.

6. The system of claim 1, the hardware timer being a 64 bit timer.

7. The system of claim 1, the hardware timer being a 32 bit timer.

8. The system of claim 1, the hardware timer being an up-counter.

9. The system of claim 1, the hardware timer being a down-counter.

10. The system of claim 1, the watchdog timer programming interface being at least partially implemented in kernel mode.

11. The system of claim 1, wherein the software application calls the watchdog timer programming interface with the timelength parameter for a system event.

12. The system of claim 11, the system event being backing up a computer system.

13. The system of claim 11, the system event being communicating with a network server.

14. The system of claim 11, the software application being a component of an operating system.

15. The system of claim 11, the software application being a hardware abstraction layer.

16. The system of claim 11, the software application operative to call the watchdog timer programming interface with a reset parameter to avoid generation of the interrupt.

17. A method of operating a computing device comprising a hardware timer, the method comprising:

operating the computing device such that the hardware timer is controlled through a software interface programmed to;

set a compare value of the hardware timer to a computed value, the computed value being based on a ratio of a desired time out of a system event to a tick period; and

set a counter value of the hardware timer to an initial value.

18. The method of claim 17, wherein the software interface is further programmed to periodically reset the hardware timer prior to an interrupt being generated.

19. The method of claim 18, wherein the software interface is further programmed to reset the hardware timer by disabling the hardware timer, setting the counter value to the initial value and enabling the hardware timer.

20. The method of claim 17, wherein the software interface is further programmed to disable the generalized hardware timer on successful processing of the system event.

21. The method of claim 17, wherein the software interface is further programmed to set an interrupt to be a desired interrupt.

22. The method of claim 17, further comprising executing an exception handler triggered by an interrupt generated by the hardware timer.

23. A method of detecting and handling errors utilizing a watchdog timer, the method comprising:

determining a timelength parameter;

staring a watchdog timer system for a system event according to the timelength parameter, the watchdog timer system having a standard hardware timer configured by a watchdog timer interface, the configuration relates to setting a compare value of the standard hardware timer to a computed value, the computed value being based at least in part on a ratio of the timelength parameter and a tick period of the standard hardware timer;

resetting the watchdog timer system during successful processing of the system event;

halting the watchdog timer system on successful processing to the system event; and

generating an interrupt on the timer expiring.

24. The method of claim 23, further comprising handling failure of the system event on the interrupt being generated.

25. A computer-readable storage medium storing computer executable instructions of components operable to perform a method of operating a hardware timer as a watchdog timer, comprising:

a component for setting a compare value of the hardware timer to a computed value, the computed value being based at least in part on a ratio of a timelength parameter defined by a desired time out of a system event and a tick period of the hardware timer;

a component for setting a counter value of the hardware timer to an initial value; and

a watchdog timer interface component for configuring the hardware timer to operate as a watchdog timer, a timing mode of the hardware timer configured by the watchdog timer interface.