Re: Early hang with 2.6.21-rc4-rt1

Roland Dreier
2007-03-25T17:02:05Z

> I finally got curious enough to want to debug why starting kvm with
> tun/tap networking produces a bunch of
>
> rtc: lost some interrupts at 1024Hz.
>
> messages. So I'm assuming it's a ~millisecond irqs-off section
> somewhere.

And after everything, it's a heisenbug -- I repeatably get that lost
interrupts message on stock 2.6.21-rc4 but never on -rt1 with
CONFIG_LATENCY_TRACE.

Any suggestion of where to look? My /proc/latency_trace stays
stubbornly empty -- are there any sysctls I need to change from their
default to get latency tracing? I'm a complete noob when it comes to
the -rt patch, so I'm not sure what the right way to use the tracing
infrastructure to track down this lost rtc interrupts issue is.

Thanks,
Roland