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SubjectRe: [RFC PATCH 04/19] cpufreq: bring data structures close to their locks
Hi,

On 12/01/16 14:57, Viresh Kumar wrote:
> On 11-01-16, 23:07, Peter Zijlstra wrote:
> > On Mon, Jan 11, 2016 at 05:35:45PM +0000, Juri Lelli wrote:
> > > +/**
> > > + * Iterate over governors
> > > + *
> > > + * cpufreq_governor_list is protected by cpufreq_governor_mutex.
> > > + */
> > > +static LIST_HEAD(cpufreq_governor_list);
> > > +static DEFINE_MUTEX(cpufreq_governor_mutex);
> > > +#define for_each_governor(__governor) \
> > > + list_for_each_entry(__governor, &cpufreq_governor_list, governor_list)
> >
> > So you could stuff the lockdep_assert_held() you later add intididually
> > into the for_each_governor macro, impossible to forget that way.
>
> How exactly? I couldn't see how it can be done in a neat and clean
> way.
>

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)

/**
@@ -508,7 +509,6 @@ static struct cpufreq_governor *find_governor(const char *str_governor)
{
struct cpufreq_governor *t;

- lockdep_assert_held(&cpufreq_governor_mutex);
for_each_governor(t)
if (!strncasecmp(str_governor, t->name, CPUFREQ_NAME_LEN))
return t;
Since for_each_governor() is not used in if conditions that should be
fine?

Thanks,

- Juri

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