On 01/14/14 at 04:41pm, Dave Young wrote: > On 01/14/14 at 09:26am, Wim Van Sebroeck wrote: > > Hi Dave, > > > > > In kdump kernel watchdog could interrupt vmcore capturing because we > > > have no way to disable/stop it while crashing happens. > > > > > > Add a module parameter stop_before_register so watchdog can be stopped > > > before register in driver loading path. Thus we can try to load the > > > watchdog driver as early as possible in kdump kernel to ensure vmcore > > > capturing. > > > > > > Don Zickus mentioned that there's the case that bios start the watchdog > > > and it is expected that the kernel keep the watchdog alive. To address > > > this case I added the module parameter which is false by default so > > > it will stop the watchdog only when user provice kernel cmdline > > > "watchdog.stop_before_register=1". > > > > > > Signed-off-by: Dave Young <[email protected]> > > > --- > > > drivers/watchdog/watchdog_core.c | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > --- linux.orig/drivers/watchdog/watchdog_core.c > > > +++ linux/drivers/watchdog/watchdog_core.c > > > @@ -42,6 +42,7 @@ > > > > > > static DEFINE_IDA(watchdog_ida); > > > static struct class *watchdog_class; > > > +static bool stop_before_register; > > > > > > static void watchdog_check_min_max_timeout(struct watchdog_device *wdd) > > > { > > > @@ -119,6 +120,9 @@ int watchdog_register_device(struct watc > > > if (wdd->ops->start == NULL || wdd->ops->stop == NULL) > > > return -EINVAL; > > > > > > + if (stop_before_register) > > > + wdd->ops->stop(wdd); > > > + > > > watchdog_check_min_max_timeout(wdd); > > > > > > /* > > > @@ -220,6 +224,8 @@ static void __exit watchdog_exit(void) > > > subsys_initcall(watchdog_init); > > > module_exit(watchdog_exit); > > > > > > +module_param(stop_before_register, bool, 0644); > > > + > > > MODULE_AUTHOR("Alan Cox <[email protected]>"); > > > MODULE_AUTHOR("Wim Van Sebroeck <[email protected]>"); > > > MODULE_DESCRIPTION("WatchDog Timer Driver Core"); > > > > Hmm, need to look closer to this, but my first thought is: > > what about devices that cannot be stopped once started... > > They should be able to override this module_parameter... > > Hi, Wim > > Thanks for quick feedback! > > I'm not sure the meaning of "cannot be stopped", if it means that > the policy that it should not be stopped, I think since the watchdog_core > is always built-in so the param can only be provided via boot cmdline it would > be fine?
Hmm, the wdt driver can be removed then insmod again. I think you are talking about the nowayout, for this case probably should add below: if (stop_before_register && !nowayout) stop it. But is there a general way for checkout nowayout, could you give some hints? > > For device which really *cannot* stop, the stop() will fail silently? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
