On Tue, 2013-04-16 at 06:57 +0000, Pan, Zhenjie wrote: > Watchdog use performance monitor of cpu clock cycle to generate NMI to detect > hard lockup. > But when cpu's frequency changes, the event period will also change. > It's not as expected as the configration. > For example, set the NMI event handler period is 10 seconds when the cpu is > 2.0GHz. > If the cpu changes to 800MHz, the period will be 10*(2000/800)=25 seconds. > So it may make hard lockup detect not work if the watchdog timeout is not > long enough. > Now, set a notifier to listen to the cpu frequency change. > And dynamic re-config the NMI event to make the event period correct. >
Urgh,. does this really matter.. all we really want is for that NMI to hit eventually in the not too distant future. Does the frequency really matter _that_ much? Also, can't we simply pick an event that's invariant to the cpufreq nonsense? Something like CPU_CLK_UNHALTED.REF -- or better the fixed_ctr2 which nobody ever uses anyway. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
