Re: [PATCH v4 2/2] locking/pvqspinlock, hv: Enable PV qspinlock for Hyper-V

Yi Sun
2018-10-10T08:11:47Z

On 18-10-10 07:50:26, Ingo Molnar wrote:
>
> * Yi Sun <yi.y.sun@linux.intel.com> wrote:
>
> > On 18-10-09 12:54:27, Ingo Molnar wrote:
> > >
> > > * Yi Sun <yi.y.sun@linux.intel.com> wrote:
> > >
> > > > Follow PV spinlock mechanism to implement the callback functions
> > > > to allow the CPU idling and kicking operations on Hyper-V.
> > >
> > > > +#if defined(CONFIG_SMP)
> > > > + smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
> > > > +#endif
> > >
> > > What's wrong with using the common pattern of:
> > >
> > > #ifdef CONFIG_SMP
> > >
> > > ?
> >
> > There is no difference between "#ifdef" and "#if defined". I just copied
> > it from "hv_smp_prepare_boot_cpu()". Do you need me submit a fix patch
> > after this set is merged?
>
> It's equivalent code, my point was that '#ifdef CONFIG_XYZ' is the shorter, more canonical
> pattern we use in the kernel most of the time, it's shorter, easier to read. We only use
> defined() for longer preprocessor directive conditions, and it's a pattern for "there's
> something more complex here than a simple CONFIG_XYZ dependency".
>
> Anyway, Thomas fixed it up in the latest iteration.
>
> Thanks,
>
> Ingo

Thank you! I will notice it in the future.

BRs,
Yi Sun