On 08/11/2012 16:45, "Tim Deegan" <t...@xen.org> wrote: >>> I wonder whether the overflow handling should just be removed, or made >>> conditional on a command-line parameter, or on the 32-bit platform counter >>> being at least somewhat likely to overflow before a softirq occurs -- it >>> seems lots of systems are using 14MHz HPET, and that gives us a couple of >>> minutes for the plt_overflow softirq to do its work before overflow occurs. >>> I think we would notice that outage in other ways. :) >> >> Iirc we added this for a good reason - to cover the, however >> unlikely, event of Xen running for very long without preemption. >> Presumably most of the cases got fixed meanwhile, and indeed >> a wraparound time on the order of minutes should make this >> superfluous, but as the case here shows that code did spot a >> severe anomaly (whatever that may turn out to be). > > ISTR when this code went in we were dealing with a timer that had a > period of about 4 seconds (ACPI PMTIMER?). It might well be OTT for the > HPET, but if there's something weird going on I'd like to track it down > while we have some sort of a handle on it.
It must have been the PMTIMER. It's the only counter narrower than 32 bits (legacy PIT we simulate as a 32-bit counter behind the scenes). -- Keir -- To UNSUBSCRIBE, email to debian-kernel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/ccc19409.51be9%k...@xen.org
