watchdog: make open-write-close-open functionality a config knob
The behaviour introduced by commit 31c765081dc4 ("watchdog: stop
watchdog first on startup") causes warnings in the kernel log when the
nowayout feature is enabled:
[ 16.212184] watchdog: watchdog0: nowayout prevents watchdog being stopped!
[ 16.212196] watchdog: watchdog0: watchdog did not stop!
The latter may also appear by itself in case the watchdog is of the
type that cannot be stopped once started (e.g. the common
always-running gpio_wdt kind).
These warnings can be somewhat ominous and distracting, so allow
configuring whether to use this open-write-close-open sequence rather
than just open. Also saves a bit of .text when disabled:
function old new delta
shutdown_on_signal 31 58 +27
watchdog_main 339 306 -33
shutdown_watchdog 34 - -34
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 1/1 up/down: 27/-67) Total: -40 bytes
Make it default n:
- It's a workaround for one specific type of watchdog (and
that seems to be a defect in the kernel driver)
- Even when not enabled in busybox config, it can easily be
implemented outside busybox
- Code size
- Commit 31c765081dc4 should be considered a regression for all the
boards that now end up with KERN_CRIT warnings in dmesg.
- The author of that commit said "This use case is evidently rare, so
if it is indeed causing problems for other people I'd OK then I
understand whatever needs to be done." in the v1 thread.
Cc: Matt Spinler <mspinler@linux.vnet.ibm.com>
Cc: deweloper@wp.pl
Cc: tito <farmatito@tiscali.it>
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/miscutils/watchdog.c b/miscutils/watchdog.c
index 0ed10bc..44649ca 100644
--- a/miscutils/watchdog.c
+++ b/miscutils/watchdog.c
@@ -18,6 +18,21 @@
//config: watchdog applet ever fails to write the magic character within a
//config: certain amount of time, the watchdog device assumes the system has
//config: hung, and will cause the hardware to reboot.
+//config:
+//config:config FEATURE_WATCHDOG_OPEN_TWICE
+//config: bool "Open watchdog device twice, closing it gracefully in between"
+//config: depends on WATCHDOG
+//config: default n # this behavior was essentially a hack for a broken driver
+//config: help
+//config: When enabled, the watchdog device is opened and then immediately
+//config: magic-closed, before being opened a second time. This may be necessary
+//config: for some watchdog devices, but can cause spurious warnings in the
+//config: kernel log if the nowayout feature is enabled. Also, if this workaround
+//config: is really needed for you machine to work properly, consider whether
+//config: it should be fixed in the kernel driver instead. Even when disabled,
+//config: the behaviour is easily emulated with a "printf 'V' > /dev/watchdog"
+//config: immediately before starting the busybox watchdog daemon. Say n unless
+//config: you know that you absolutely need this.
//applet:IF_WATCHDOG(APPLET(watchdog, BB_DIR_SBIN, BB_SUID_DROP))
@@ -50,10 +65,6 @@
# define WDIOS_ENABLECARD 2
#endif
-#define OPT_FOREGROUND (1 << 0)
-#define OPT_STIMER (1 << 1)
-#define OPT_HTIMER (1 << 2)
-
static void shutdown_watchdog(void)
{
static const char V = 'V';
@@ -73,6 +84,7 @@
/* Use known fd # - avoid needing global 'int fd' */
xmove_fd(xopen(device, O_WRONLY), 3);
+#if ENABLE_FEATURE_WATCHDOG_OPEN_TWICE
/* If the watchdog driver can do something other than cause a reboot
* on a timeout, then it's possible this program may be starting from
* a state when the watchdog hadn't been previously stopped with
@@ -82,6 +94,7 @@
shutdown_watchdog();
xmove_fd(xopen(device, O_WRONLY), 3);
+#endif
}
int watchdog_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
@@ -100,6 +113,9 @@
char *st_arg;
char *ht_arg;
+#define OPT_FOREGROUND (1 << 0)
+#define OPT_STIMER (1 << 1)
+#define OPT_HTIMER (1 << 2)
opts = getopt32(argv, "^" "Ft:T:" "\0" "=1"/*must have exactly 1 arg*/,
&st_arg, &ht_arg
);
@@ -132,7 +148,7 @@
#if 0
ioctl_or_warn(3, WDIOC_GETTIMEOUT, &htimer_duration);
printf("watchdog: SW timer is %dms, HW timer is %ds\n",
- stimer_duration, htimer_duration * 1000);
+ stimer_duration, htimer_duration);
#endif
write_pidfile_std_path_and_ext("watchdog");