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.
