On Thu, Aug 19, 2010 at 08:42:56PM -0700, Andrew Morton wrote: > On Thu, 19 Aug 2010 22:57:49 -0400 Don Zickus <dzickus@xxxxxxxxxx> wrote: > > > On Wed, Aug 18, 2010 at 01:01:56PM -0700, Andrew Morton wrote: > > @@ -430,6 +437,9 @@ static int watchdog_enable(int cpu) > > wake_up_process(p); > > } > > > > + /* if any cpu succeeds, watchdog is considered enabled for the system */ > > + watchdog_enabled = 1; > > + > > return 0; > > } > > > > @@ -452,9 +462,6 @@ static void watchdog_disable(int cpu) > > per_cpu(softlockup_watchdog, cpu) = NULL; > > kthread_stop(p); > > } > > - > > - /* if any cpu succeeds, watchdog is considered enabled for the system */ > > - watchdog_enabled = 1; > > } > > > > static void watchdog_enable_all_cpus(void) > > hm, the code seems a bit screwy. Maybe it was always thus. No, watchdog_enabled was something newly created for the lockup dectector. > > watchdog_enabled gets set in the per-cpu function but it gets cleared > in the all-cpus function. Asymmetric. Yes it is by design. I was using watchdog_enabled as a global state variable. As soon as one cpu was enabled, I would set the bit. But only if all the cpus disabled the watchdog would I clear the bit. > > Also afacit the action of cpu-hotunplug+cpu-hotplug will reenable the > watchdog on a CPU which was supposed to have it disabled. Perhaps you > could recheck that and make sure it all makes sense - perhaps we need a > separate state variable which is purely "current setting of > /proc/sys/kernel/nmi_watchdog" and doesn't get altered internally. I wasn't tracking it on a per cpu basis. I didn't see a need to. The watchdog should globally be on/off across the system. If a system comes up and one of the cpus could not bring the watchdog online for some reason, then that is a problem. If a cpu-hotunplug+cpu-hotplug fixes it, all the better. :-) Also, if I wanted to track it per cpu, there is a bunch of status bits in per-cpu variables that could let the code know whether a particular cpu watchdog is on/off for either hardlockup or softlockup. Cheers, Don -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
