LINUX system watchdog __linux

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Watchdog timer (wdt,watch Dog timer) It is actually a counter that generally gives a watchdog a large number of programs that start running after the watchdog starts to count backwards. If the program is working properly, over time the CPU should issue instructions for the watchdog to reset and start counting again. If the watchdog is reduced to 0 it is considered that the program is not working properly, forcing the entire system to reset.

The system uses the main chip built-in hardware watchdog and the external hardware watchdog at the same time, the dual maintenance system stability.

The built-in hardware watchdog starts feeding the dog from the Uboot, and the external hardware watchdog starts feeding the dog from the system into the kernel. So that the whole operation of the system can always be detected whether the operation is normal, to avoid the system can not recover for a long time.

Stop the watchdog dog feeding when checking for abnormal or reboot the system, avoid the failure of the system after using reboot and so on to reboot the system.

Linux hardware watchdog

Demand

The watchdog's role is to prevent the program from dying, or to say that the program is running. Commonly used WDT chips such as MAX813, 5045, IMP 813, and so on, the hardware watchdog's clear watchdog time is very short usually within a few seconds.

Linux can use the watchdog inside the software watchdog chip, but it always feels unreliable. But the use of external hardware watchdog, clear watchdog time is too short, generally a few seconds, the Linux kernel boot time is too long, can not feed the dog within a few seconds, will cause the system repeatedly restarted. It is difficult to insert a dog-feeding statement evenly and intermittently in the kernel boot. This program provides a reliable way to increase the external watchdog.

Characteristics

In addition to power, program restart, chip reset, watchdog can always be effective.

System in Bootstrap,uboot,linux any place to crash, watchdog can reset the chip

The scheme is suitable to delay the watchdog action cycle.

After repeated testing, the actual use of the external watchdog scheme to fully achieve the design objectives.