Linux Kernel Watchdog Explained

The Linux kernel watchdog is used to monitor if a system is running. It is supposed to automatically reboot hanged systems due to unrecoverable software errors. The watchdog module is specific to the hardware or chip being used. Personal computer users don't need watchdog as they can reset the system manually.

1. How do you test a watchdog?
2. How do I trigger hardware watchdog?
3. How can you tell which task caused the watchdog to reset?
4. How do I use Dev watchdog?
5. What is the purpose of a watchdog?
6. How can I tell if watchdog is running on Linux?
7. How do I stop watchdog?
8. How do I enable watchdog?
9. What causes watchdog reset?
10. What is a watchdog?
11. What is watchdog in embedded system?
12. How is watchdog timeout determined?

How do you test a watchdog?

Use an existing non critical output like an led as a test signal. Program the board with a test sequence that will toggle the led and loop, And does not pet the watchdog. Test for the loop. Then program it to do a second loop, where it will not reach if the specified watchdog timer does not reboot.

How do I trigger hardware watchdog?

If you have a watchdog on your system and a driver that uses /dev/watchdog , all you have to do is kill the process that is feeding it; if there is no such process, then you can touch /dev/watchdog once to turn it on, and if you don't touch it again, it will reset.

How can you tell which task caused the watchdog to reset?

A per-task watchdog requires that the higher priority tasks yield for an adequate time so that all may kick the watchdog. To determine which task is at fault, you'll have to find the one that's starving the others. You'll need to measure task execution times between watchdog checks to locate the actual culprit.

How do I use Dev watchdog?

To kick or to feed the watchdog you can do it in two ways:

1. Write any character into '/dev/watchdog'. You can write any character into /dev/watchdog, but, my suggestion, don't write 'V' character (See the 'Starting-Stopping Watchdog' point above)
2. Use IOCTL to insert 'WDIOC_KEEPALIVE' value.

What is the purpose of a watchdog?

A watchdog timer is a simple countdown timer which is used to reset a microprocessor after a specific interval of time. In a properly operating system, software will periodically "pet" or restart the watchdog timer.

How can I tell if watchdog is running on Linux?

After the module is loaded, you can check /dev/watchdog on the Linux system. If this file is present, that means the watchdog kernel device driver or module was loaded. The system periodically keeps writing to /dev/watchdog. It is also called “kicking or feeding the watchdog”.

How do I stop watchdog?

How do I fix DPC watchdog violation?

1. Remove all external devices on your computer.
2. Change SATA AHCI controller.
3. Update the SSD firmware.
4. Check and fix disk errors with CHKDSK.
5. Remove newly installed software.
6. Scan and fix system files.
7. Run Event Viewer.

How do I enable watchdog?

Introduction. A watchdog on Linux is usually exported through a character device under /dev/watchdog. A simple API allows opening the device to enable the watchdog. Writing to it triggers the watchdog, and if the device is not cleanly closed, the watchdog will reboot the system.

What causes watchdog reset?

When the watchdog expires, the hardware will immediately reset the system. An interrupt can be enabled which will fire when the watchdog timer is getting close to expiration. In the interrupt handler, the software can decide to “feed” the watchdog to prevent the system from resetting.

What is a watchdog?

(Entry 1 of 2) 1 : a dog kept to guard property. 2 : one that guards against loss, waste, theft, or undesirable practices.

What is watchdog in embedded system?

A watchdog timer is a piece of hardware that can be used to automatically detect software anomalies and reset the processor if any occur. Generally speaking, a watchdog timer is based on a counter that counts down from some initial value to zero.

How is watchdog timeout determined?

If you know the maximum worst case execution time and the minimum execution time, you should set your watchdog as tightly as you can. If you don't know those values, but at least are confident you'll complete execution within your task period, then you should set the watchdog to twice the period.