On Thu, 2013-05-16 at 19:56 +0200, Peter Zijlstra wrote: > I suppose the fundamental question was: will receiving NMIs negate > NO_HZ_FULL's > functionality? That is, will the getting of NMIs make us drop out of > NO_HZ_FULL > and re-enable all sorts of things?
It shouldn't. The nmi_enter() notifies RCU that it can no longer ignore this CPU, where as nmi_enter() tells it that it can ignore it, as it has re-entered user space. > > Because clearly RCU needs to exit from EQS, which might (or might not) mean > leaving NO_HZ_FULL. Yep, but the two are pretty much agnostic from each other. We only need to leave NO_HZ_FULL if RCU (or anything for that matter) required having a tick again. But as Paul said, getting an NMI in idle wont restart the tick, so there's no need to restart it here either. Now if an NMI were to do a call_rcu() then it would require a tick. But NMIs doing call_rcu() has much bigger issues to worry about ;-) -- Steve > > I'm not entirely up-to-date on those details. -- 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/
