On Thursday 11 of October 2012 12:04:37 Daniel Lezcano wrote:
> On 10/07/2012 11:26 PM, Rafael J. Wysocki wrote:
> > On Tuesday 25 of September 2012 00:43:54 Daniel Lezcano wrote:
> >> With the tegra3 and the big.LITTLE [1] new architectures, several cpus
> >> with different characteristics (latencies and states) can co-exists on the
> >> system.
> >>
> >> The cpuidle framework has the limitation of handling only identical cpus.
> >>
> >> This patch removes this limitation by introducing the multiple driver
> >> support
> >> for cpuidle.
> >>
> >> This option is configurable at compile time and should be enabled for the
> >> architectures mentioned above. So there is no impact for the other
> >> platforms
> >> if the option is disabled. The option defaults to 'n'. Note the multiple
> >> drivers
> >> support is also compatible with the existing drivers, even if just one
> >> driver is
> >> needed, all the cpu will be tied to this driver using an extra small chunk
> >> of
> >> processor memory.
> >>
> >> The multiple driver support use a per-cpu driver pointer instead of a
> >> global
> >> variable and the accessor to this variable are done from a cpu context.
>
> Thanks Rafael for the review.
>
> I took into account all your remarks for the V2.
>
> [ cut ]
>
> >> +static int __cpuidle_register_all_cpu_driver(struct cpuidle_driver *drv)
> >> +{
> >> + int ret = 0;
> >> + int i, cpu;
> >> +
> >> + for_each_present_cpu(cpu) {
> >> + ret = __cpuidle_register_driver(drv, cpu);
> >> + if (!ret)
> >> + continue;
> >> + for (i = cpu - 1; i >= 0; i--)
> > I wonder if this is going to work in all cases. For example, is there any
> > guarantee that the CPU numbers start from 0 and that there are no gaps?
>
> AFAICS, the cpumask.h is not assuming the cpu numbers start from zero
> and they are contiguous.
>
> I will fix this reverse loop, thanks for spotting this.
>
> [ cut ]
>
> >> void cpuidle_unregister_driver(struct cpuidle_driver *drv)
> >> {
> >> spin_lock(&cpuidle_driver_lock);
> >> - __cpuidle_unregister_driver(drv);
> >> +#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
> >> + __cpuidle_unregister_all_cpu_driver(drv);
> >> +#else
> >> + __cpuidle_unregister_driver(drv, smp_processor_id());
> >> +#endif
> > I'm slightly cautious about using smp_processor_id() above.
> > get_cpu()/put_cpu() is the preferred way of doing this nowadays (although
> > this particular code is under the spinlock, so it should be OK).
> yes, get_cpu does preempt_disable() and smp_processor_id()
> As spin_lock does also preempt_disable() that should be ok.
> But I changed the code to use the preferred way.
Cool, thanks!
I've seen your new version and I'm going to look deeper into it in the next
few days, but I will be travelling from tomorrow through the end of the next
week, so I may be even slower to respond than usually. Sorry about that.
Thanks,
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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