NAME¶
watchdog —
hardware and software
watchdog
SYNOPSIS¶
#include <sys/watchdog.h>
DESCRIPTION¶
The
watchdog facility is used for controlling hardware and
software watchdogs.
/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 (timeout value other than
0).
- [
EOPNOTSUPP
]
- Watchdog could not be disabled (timeout value of 0).
- [
EINVALID
]
- Invalid flag combination passed.
- [
EINVALID
]
- None of the watchdogs supports the requested timeout
value.
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.
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.
BUGS¶
The
WD_PASSIVE
option has not yet been implemented.
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⟩.