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2 .\" Copyright (c) 2003, 2004 Sean M. Kelly <smkelly@FreeBSD.org>
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33 .Nd "hardware and software watchdog"
39 facility is used for controlling hardware and software watchdogs.
43 supports several optional
45 calls for configuration, and
46 responds to a single operational
50 It takes a single argument which represents a timeout value specified as a
51 power of two nanoseconds, or-ed with a flag selecting active or passive control
57 will be kept from timing out from userland, for instance by the
63 will be kept from timing out from the kernel.
68 call will return success if just one of the available
70 implementations supports setting the timeout to the specified timeout.
72 means that at least one watchdog is armed.
73 By default, this will be a hardware watchdog if one is present, but if
74 no hardware watchdog is able to process the request, a default software
76 If the call fails, for instance if
79 implementations support the timeout length, all watchdogs are disabled and must
80 be explicitly re-enabled.
82 To disable the watchdogs pass
84 If disarming the watchdog(s) failed an error is returned.
88 The optional configuration
90 commands are listed here, along with the type of the parameter used.
91 Examples of their use can be found in
93 .Bl -tag -width "WDIOC_SETSOFTTIMEOUTACT int "
94 .It Dv WDIOC_SETTIMEOUT Fa int
96 .It Dv WDIOC_GETTIMEOUT Fa int
98 .It Dv WDIOC_GETTIMELEFT Fa int
100 .It Dv WDIOC_GETPRETIMEOUT Fa int
102 .It Dv WDIOC_SETPRETIMEOUT Fa int
104 .It Dv WDIOC_SETPRETIMEOUTACT Fa int
105 Set the action when a pre-timeout occurs (see
108 .It Dv WDIOC_SETSOFT Fa int
109 Use an internal software watchdog instead of hardware.
110 There is also an external software watchdog, which is used by default
111 if no hardware watchdog was attached.
112 .It Dv WDIOC_SETSOFTTIMEOUTACT Fa int
113 Set the action whan a soft timeout occurs.
116 The actions that may be specified for the pre-timeout or the internal software
117 watchdog are listed here.
118 Multiple actions can be specified by ORing values together.
119 .Bl -tag -width WD_SOFT_PRINT
133 returns zero on success and non-zero on failure.
136 No watchdog present in the kernel or
137 none of the watchdogs supports the requested timeout value
138 (timeout value other than 0).
140 Watchdog could not be disabled (timeout value of 0).
142 Invalid flag combination passed.
147 operations return zero on success and non-zero on failure.
149 .Bd -literal -offset indent
151 #include <sys/watchdog.h>
153 #define WDPATH "/dev/" _PATH_WATCHDOG
159 wdfd = open(WDPATH, O_RDWR);
164 wd_reset(u_int timeout)
166 if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1)
167 err(1, "WDIOCPATPAT");
172 wd_reset(WD_ACTIVE|WD_TO_8SEC);
173 /* potential freeze point */
174 wd_reset(WD_TO_NEVER);
177 Enables a watchdog to recover from a potentially freezing piece of code.
179 .Dl "options SW_WATCHDOG"
181 in your kernel config forces a software watchdog in the kernel
182 to be configured even if a hardware watchdog is configured,
183 dropping to KDB or panicking when firing, depending
184 on the KDB and KDB_UNATTENDED kernel configuration options.
191 code first appeared in
197 facility was written by
198 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .
199 The software watchdog code and this manual page were written by
200 .An Sean Kelly Aq Mt smkelly@FreeBSD.org .
201 Some contributions were made by
202 .An Jeff Roberson Aq Mt jeff@FreeBSD.org .
206 option has not yet been implemented.