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Re: [Xen-devel] "Time went backwards" messages


On 5 Apr 2005, at 09:28, Keir Fraser wrote:

I have a high end IBM system with 4 HT CPUs, am running xen-unstable
with only Dom0 active, and I get lots of "Timer ISR/n: Time went
backwards" messages.  This is a short segment from dmesg:

The errors are coming from the per-vcpu timer interrupt that is only used in SMP guest builds. I can well imagine there are some 'latent correctness issues' around that code. :-) If you get messages starting 'Timer ISR: Time went backwards' then that would be more worrying.

Okay, I've fixed up the timer code for SMP quite a bit. In particular, secondary cpus were updating shared time information with no locks held. I expect that with the current unstable repository you will no longer see the time-went-backwards messages.

 -- Keir


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