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33 .Nd "hardware and software watchdog"
39 facility is used for controlling hardware and software watchdogs.
46 It takes a single argument which represents a timeout value specified as a
47 power of two nanoseconds, or-ed with a flag selecting active or passive control
53 will be kept from timing out from userland, for instance by the
59 will be kept from timing out from the kernel.
63 call will return success if just one of the available
65 implementations supports setting the timeout to the specified timeout. This
66 means that at least one watchdog is armed. If the call fails, for instance if
69 implementations support the timeout length, all watchdogs are disabled and must
70 be explicitly re-enabled.
72 To disable the watchdogs pass
74 If disarming the watchdog(s) failed an error is returned. The watchdog might
77 The ioctl returns zero on success and non-zero on failure.
80 No watchdog present in the kernel (timeout value other than 0).
82 Watchdog could not be disabled (timeout value of 0).
84 Invalid flag combination passed.
86 None of the watchdogs supports the requested timeout value.
89 .Bd -literal -offset indent
91 #include <sys/watchdog.h>
93 #define WDPATH "/dev/" _PATH_WATCHDOG
99 wdfd = open(WDPATH, O_RDWR);
104 wd_reset(u_int timeout)
106 if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1)
107 err(1, "WDIOCPATPAT");
112 wd_reset(WD_ACTIVE|WD_TO_8SEC);
113 /* potential freeze point */
114 wd_reset(WD_TO_NEVER);
117 Enables a watchdog to recover from a potentially freezing piece of code.
119 .Bd -literal -offset indent
123 in your kernel config adds a software watchdog in the kernel, dropping to KDB
124 or panic-ing when firing.
131 code first appeared in
136 option has not yet been implemented.
141 facility was written by
142 .An Poul-Henning Kamp Aq phk@FreeBSD.org .
143 The software watchdog code and this manual page were written by
144 .An Sean Kelly Aq smkelly@FreeBSD.org .
145 Some contributions were made by
146 .An Jeff Roberson Aq jeff@FreeBSD.org .