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33 .Nd "hardware and software watchdog"
39 facility is used for controlling hardware and software watchdogs.
47 It takes a single argument which represents a timeout value specified as a
48 power of two nanoseconds, or-ed with a flag selecting active or passive control
54 will be kept from timing out from userland, for instance by the
60 will be kept from timing out from the kernel.
64 call will return success if just one of the available
66 implementations supports setting the timeout to the specified timeout.
68 means that at least one watchdog is armed.
69 If the call fails, for instance if
72 implementations support the timeout length, all watchdogs are disabled and must
73 be explicitly re-enabled.
75 To disable the watchdogs pass
77 If disarming the watchdog(s) failed an error is returned.
81 The ioctl returns zero on success and non-zero on failure.
84 No watchdog present in the kernel or
85 none of the watchdogs supports the requested timeout value
86 (timeout value other than 0).
88 Watchdog could not be disabled (timeout value of 0).
90 Invalid flag combination passed.
93 .Bd -literal -offset indent
95 #include <sys/watchdog.h>
97 #define WDPATH "/dev/" _PATH_WATCHDOG
103 wdfd = open(WDPATH, O_RDWR);
108 wd_reset(u_int timeout)
110 if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1)
111 err(1, "WDIOCPATPAT");
116 wd_reset(WD_ACTIVE|WD_TO_8SEC);
117 /* potential freeze point */
118 wd_reset(WD_TO_NEVER);
121 Enables a watchdog to recover from a potentially freezing piece of code.
123 .Dl "options SW_WATCHDOG"
125 in your kernel config adds a software watchdog in the kernel, dropping to KDB
126 or panic-ing when firing.
133 code first appeared in
139 facility was written by
140 .An Poul-Henning Kamp Aq phk@FreeBSD.org .
141 The software watchdog code and this manual page were written by
142 .An Sean Kelly Aq smkelly@FreeBSD.org .
143 Some contributions were made by
144 .An Jeff Roberson Aq jeff@FreeBSD.org .
148 option has not yet been implemented.