On Thu, Apr 23, 2015 at 10:01:04PM +0200, Thomas Gleixner wrote: > On Thu, 23 Apr 2015, Alexander Shishkin wrote: > > > The problem with using cycle counter for NMI watchdog is that its > > frequency changes with the corresponding core's frequency. This means > > that, in particular, if the core frequency scales up, watchdog NMI will > > arrive more frequently than what user requested through watchdog_thresh > > and also increasing the probability of setting off the hardlockup detector, > > because the corresponding hrtimer will keep firing at the same intervals > > regardless of the core frequency. And, if the core can turbo to up to 2.5x > > its base frequency (and therefore TSC) [1], we'll have the hrtimer and NMI > > So you are saying that this M-5Y10 has a non-constant TSC again? You > really can't be serious about that. The TSC is constant, but the maximum frequency can be >=2.5TSC, so the watchdog which uses cycles can have that much error. -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html