Re: schedule_timeout sleeps too long after dividing CPU frequency

Viresh Kumar <[email protected]> Thu, 14 May 2015 07:43:28 +0530

Newsgroups	org.kernel.vger.cpufreq,org.infradead.lists.linux-arm-kernel,org.kernel.vger.linux-pm
Message-ID	<CAOh2x==aCLxCWX9K57hOFVEP1eLo_OYZPe0YvbFvpkXcoSp_hQ@mail.gmail.com>

On Wed, May 13, 2015 at 10:21 PM, Mason <[email protected]> wrote:
> $ git diff v3.14.41 HEAD >tango.patch && xz tango.patch
>
> I don't understand the IRQ-related part yet
> ( arch/arm/mach-tangox/irq.c and drivers/irqchip/irq-gic.c )
>
> If anyone spots the problem, that would make my day.
>
> I tested with a loadable module whose init function is
>
> static int __init ts_init(void)
> {
>         long res;
>         printk("ABOUT TO SLEEP\n");
>         set_current_state(TASK_INTERRUPTIBLE);
>         res = schedule_timeout(HZ);
>         printk("WAKE UP res=%ld\n", res);
>         return 0;
> }
>
> Loading the module, with cpufreq divided by 9, prints:
> [ 1738.962982] ABOUT TO SLEEP
> [ 1747.956191] WAKE UP res=0

I hope you are also matching this time with a physical watch,
to make sure 38->47 is really 9 seconds :)