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WATCHDOG(4)            FreeBSD Kernel Interfaces Manual            WATCHDOG(4)

NAME
     watchdog - hardware and software watchdog

SYNOPSIS
     #include <sys/watchdog.h>

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

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

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

     [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.

SEE ALSO
     watchdogd(8), watchdog(9)

HISTORY
     The watchdog code first appeared in FreeBSD 5.1.

AUTHORS
     The watchdog facility was written by Poul-Henning Kamp <phk@FreeBSD.org>.
     The software watchdog code and this manual page were written by Sean
     Kelly <smkelly@FreeBSD.org>.  Some contributions were made by Jeff
     Roberson <jeff@FreeBSD.org>.

BUGS
     The WD_PASSIVE option has not yet been implemented.

FreeBSD 11.0-PRERELEASE        December 21, 2009       FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | SEE ALSO | HISTORY | AUTHORS | BUGS

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