Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM

Peter Zijlstra
2010-12-09T18:00:53Z

On Thu, 2010-12-09 at 09:43 -0800, Venkatesh Pallipadi wrote:
>
> The same problem will be there with below code, with irq_delta >
> delta, clock_task can go backwards which is not good.
> + delta -= irq_delta;
> + rq->clock_task += delta;
>
> The reason for this is rq->clock and irqtime updates kind of happen
> independently and specifically, if a rq->clock update happens while we
> are in a softirq, we may have this case of going backwards on the next
> update.

But how can irq_delta > delta?, we measure it using the same clock.