SYNOPSIS

In sys/watchdog.h

DESCRIPTION

The facility is used for controlling hardware and software watchdogs.

The device /dev/fido responds to a single ioctl(2) call, WDIOCPATPAT It takes a single argument which represents a timeout value specified as a power of two nanoseconds, or-ed with a flag selecting active or passive control of the watchdog.

WD_ACTIVE indicates that the will be kept from timing out from userland, for instance by the watchdogd(8) daemon. WD_PASSIVE indicates that the will be kept from timing out from the kernel.

The ioctl(2) call will return success if just one of the available watchdog(9) implementations supports setting the timeout to the specified timeout. This means that at least one watchdog is armed. If the call fails, for instance if none of watchdog(9) implementations support the timeout length, all watchdogs are disabled and must be explicitly re-enabled.

To disable the watchdogs pass WD_TO_NEVER If disarming the watchdog(s) failed an error is returned. The watchdog might still be armed!

RETURN VALUES

The ioctl returns zero on success and non-zero on failure.

Bq Er EOPNOTSUPP

No watchdog present in the kernel or none of the watchdogs supports the requested timeout value (timeout value other than 0).

Bq Er EOPNOTSUPP

Watchdog could not be disabled (timeout value of 0).

Bq Er EINVAL

Invalid flag combination passed.

EXAMPLES

#include <paths.h>
#include <sys/watchdog.h>
#define WDPATH  "/dev/" _PATH_WATCHDOG
int wdfd = -1;
static void
wd_init(void)
{
        wdfd = open(WDPATH, O_RDWR);
        if (wdfd == -1)
                err(1, WDPATH);
}
static void
wd_reset(u_int timeout)
{
        if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1)
                err(1, "WDIOCPATPAT");
}
/* in main() */
wd_init();
wd_reset(WD_ACTIVE|WD_TO_8SEC);
/* potential freeze point */
wd_reset(WD_TO_NEVER);

Enables a watchdog to recover from a potentially freezing piece of code.

"options SW_WATCHDOG"

in your kernel config adds a software watchdog in the kernel, dropping to KDB or panic-ing when firing.

HISTORY

The code first appeared in Fx 5.1 .

AUTHORS

An -nosplit The facility was written by An Poul-Henning Kamp Aq [email protected] . The software watchdog code and this manual page were written by An Sean Kelly Aq [email protected] . Some contributions were made by An Jeff Roberson Aq [email protected] .