1 /* vi: set sw=4 ts=4: */
3 * Mini watchdog implementation for busybox
5 * Copyright (C) 2003 Paul Mundt <lethal@linux-sh.org>
6 * Copyright (C) 2006 Bernhard Reutner-Fischer <busybox@busybox.net>
7 * Copyright (C) 2008 Darius Augulis <augulis.darius@gmail.com>
9 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
11 //config:config WATCHDOG
12 //config: bool "watchdog"
14 //config: select PLATFORM_LINUX
16 //config: The watchdog utility is used with hardware or software watchdog
17 //config: device drivers. It opens the specified watchdog device special file
18 //config: and periodically writes a magic character to the device. If the
19 //config: watchdog applet ever fails to write the magic character within a
20 //config: certain amount of time, the watchdog device assumes the system has
21 //config: hung, and will cause the hardware to reboot.
23 //applet:IF_WATCHDOG(APPLET(watchdog, BB_DIR_SBIN, BB_SUID_DROP))
25 //kbuild:lib-$(CONFIG_WATCHDOG) += watchdog.o
27 //usage:#define watchdog_trivial_usage
28 //usage: "[-t N[ms]] [-T N[ms]] [-F] DEV"
29 //usage:#define watchdog_full_usage "\n\n"
30 //usage: "Periodically write to watchdog device DEV\n"
31 //usage: "\n -T N Reboot after N seconds if not reset (default 60)"
32 //usage: "\n -t N Reset every N seconds (default 30)"
33 //usage: "\n -F Run in foreground"
35 //usage: "\nUse 500ms to specify period in milliseconds"
38 #include "linux/types.h" /* for __u32 */
39 #include "linux/watchdog.h"
41 #define OPT_FOREGROUND (1 << 0)
42 #define OPT_STIMER (1 << 1)
43 #define OPT_HTIMER (1 << 2)
45 static void shutdown_watchdog(void)
47 static const char V = 'V';
48 write(3, &V, 1); /* Magic, see watchdog-api.txt in kernel */
52 static void shutdown_on_signal(int sig UNUSED_PARAM)
54 remove_pidfile(CONFIG_PID_FILE_PATH "/watchdog.pid");
59 static void watchdog_open(const char* device)
61 /* Use known fd # - avoid needing global 'int fd' */
62 xmove_fd(xopen(device, O_WRONLY), 3);
64 /* If the watchdog driver can do something other than cause a reboot
65 * on a timeout, then it's possible this program may be starting from
66 * a state when the watchdog hadn't been previously stopped with
67 * the magic write followed by a close. In this case the driver may
68 * not start properly, so always do the proper stop first just in case.
72 xmove_fd(xopen(device, O_WRONLY), 3);
75 int watchdog_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
76 int watchdog_main(int argc, char **argv)
78 static const struct suffix_mult suffixes[] = {
85 unsigned stimer_duration; /* how often to restart */
86 unsigned htimer_duration = 60000; /* reboots after N ms if not restarted */
90 opt_complementary = "=1"; /* must have exactly 1 argument */
91 opts = getopt32(argv, "Ft:T:", &st_arg, &ht_arg);
93 /* We need to daemonize *before* opening the watchdog as many drivers
94 * will only allow one process at a time to do so. Since daemonizing
95 * is not perfect (child may run before parent finishes exiting), we
96 * can't rely on parent exiting before us (let alone *cleanly* releasing
97 * the watchdog fd -- something else that may not even be allowed).
99 if (!(opts & OPT_FOREGROUND))
100 bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
102 if (opts & OPT_HTIMER)
103 htimer_duration = xatou_sfx(ht_arg, suffixes);
104 stimer_duration = htimer_duration / 2;
105 if (opts & OPT_STIMER)
106 stimer_duration = xatou_sfx(st_arg, suffixes);
108 bb_signals(BB_FATAL_SIGS, shutdown_on_signal);
110 watchdog_open(argv[argc - 1]);
112 /* WDIOC_SETTIMEOUT takes seconds, not milliseconds */
113 htimer_duration = htimer_duration / 1000;
114 #ifndef WDIOC_SETTIMEOUT
115 # error WDIOC_SETTIMEOUT is not defined, cannot compile watchdog applet
117 # if defined WDIOC_SETOPTIONS && defined WDIOS_ENABLECARD
119 static const int enable = WDIOS_ENABLECARD;
120 ioctl_or_warn(3, WDIOC_SETOPTIONS, (void*) &enable);
123 ioctl_or_warn(3, WDIOC_SETTIMEOUT, &htimer_duration);
127 ioctl_or_warn(3, WDIOC_GETTIMEOUT, &htimer_duration);
128 printf("watchdog: SW timer is %dms, HW timer is %ds\n",
129 stimer_duration, htimer_duration * 1000);
132 write_pidfile(CONFIG_PID_FILE_PATH "/watchdog.pid");
136 * Make sure we clear the counter before sleeping,
137 * as the counter value is undefined at this point -- PFM
139 write(3, "", 1); /* write zero byte */
140 usleep(stimer_duration * 1000L);
142 return EXIT_SUCCESS; /* - not reached, but gcc 4.2.1 is too dumb! */