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 <[email protected]> Cc: [email protected] Cc: tito <[email protected]> Signed-off-by: Rasmus Villemoes <[email protected]> --- v3: typo fix v2: change default to n, reword help text and commit log accordingly. miscutils/watchdog.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/miscutils/watchdog.c b/miscutils/watchdog.c index 0ed10bcf1..959e4995d 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 +//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)) @@ -73,6 +88,7 @@ static void watchdog_open(const char* device) /* 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 +98,7 @@ static void watchdog_open(const char* device) shutdown_watchdog(); xmove_fd(xopen(device, O_WRONLY), 3); +#endif } int watchdog_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; -- 2.29.2 _______________________________________________ busybox mailing list [email protected] http://lists.busybox.net/mailman/listinfo/busybox
