Re: [PATCH] sched/cputime: correct account of irqtime

[Pingfan Liu]

On Wed, Oct 14, 2020 at 9:02 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Mon, Oct 12, 2020 at 09:50:44PM +0800, Pingfan Liu wrote:
> > __do_softirq() may be interrupted by hardware interrupts. In this case,
> > irqtime_account_irq() will account the time slice as CPUTIME_SOFTIRQ by
> > mistake.
> >
> > By passing irqtime_account_irq() an extra param about either hardirq or
> > softirq, irqtime_account_irq() can handle the above case.
>
> I'm not sure I see the scenario in which it goes wrong.
>
> irqtime_account_irq() is designed such that we're called with the old
> preempt_count on enter and the new preempt_count on exit. This way we'll
> accumuate the delta to the previous context.
>
Oops! You are right, the time delta between a softirq and a
interrupting hardirq should be accounted into the softrq.

Thanks for your clear explanation.

Regards,
Pingfan