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SubjectRe: [RFC PATCH 04/19] cpufreq: bring data structures close to their locks
On 12/01/16 12:58, Peter Zijlstra wrote:
> On Tue, Jan 12, 2016 at 11:21:25AM +0000, Juri Lelli wrote:
> > I tried to see if something like for_each_domain() can be done, but here
> > we use list_for_each_entry() macro. Peter, do you mean something like
> > the following?
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 78b1e2f..1a847a6 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -39,6 +39,7 @@
> > static LIST_HEAD(cpufreq_governor_list);
> > static DEFINE_MUTEX(cpufreq_governor_mutex);
> > #define for_each_governor(__governor) \
> > + lockdep_assert_held(&cpufreq_governor_mutex); \
> > list_for_each_entry(__governor, &cpufreq_governor_list, governor_list)
>
> That fails for things like:
>
> if (blah)
> for_each_governor(...) {
> }
>
> which looks like valid C -- even though our Coding Style says the if
> should have { } on.
>
> I was thinking of either open coding the for statement and adding it to
> the first statement like:
>
> #define for_each_governor(__g) \
> for (_g = list_first_entry(&cpufreq_governor_list, typeof(*_g), governor_list, lockdep_assert_held(), \
> ..... )
>
> Or use something like this:
>
> lkml.kernel.org/r/20150422154212.GE3007@worktop.Skamania.guest
>
> #define for_each_governor(_g) \
> list_for_each_entry(_g, &cpufreq_governor_list, governor_list)
> if (lockdep_assert_held(..), false)
> ;
> else
>
> Which should preserve C syntax rules.
>

Oh, nice this! I'll try it.

Thanks,

- Juri

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