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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.
67 means that at least one watchdog is armed.
68 If the call fails, for instance if
71 implementations support the timeout length, all watchdogs are disabled and must
72 be explicitly re-enabled.
74 To disable the watchdogs pass
76 If disarming the watchdog(s) failed an error is returned.
80 The ioctl returns zero on success and non-zero on failure.
83 No watchdog present in the kernel or
84 none of the watchdogs supports the requested timeout value
85 (timeout value other than 0).
87 Watchdog could not be disabled (timeout value of 0).
89 Invalid flag combination passed.
92 .Bd -literal -offset indent
94 #include <sys/watchdog.h>
96 #define WDPATH "/dev/" _PATH_WATCHDOG
102 wdfd = open(WDPATH, O_RDWR);
107 wd_reset(u_int timeout)
109 if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1)
110 err(1, "WDIOCPATPAT");
115 wd_reset(WD_ACTIVE|WD_TO_8SEC);
116 /* potential freeze point */
117 wd_reset(WD_TO_NEVER);
120 Enables a watchdog to recover from a potentially freezing piece of code.
122 .Dl "options SW_WATCHDOG"
124 in your kernel config adds a software watchdog in the kernel, dropping to KDB
125 or panic-ing when firing.
132 code first appeared in
138 facility was written by
139 .An Poul-Henning Kamp Aq phk@FreeBSD.org .
140 The software watchdog code and this manual page were written by
141 .An Sean Kelly Aq smkelly@FreeBSD.org .
142 Some contributions were made by
143 .An Jeff Roberson Aq jeff@FreeBSD.org .
147 option has not yet been implemented.