| Message ID | 1452533760-13787-5-git-send-email-juri.lelli@arm.com |
|---|---|
| State | New |
| Headers | show |
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. -- viresh
On 12/01/16 12:36, Juri Lelli wrote: > 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. > This second approach doesn't really play well with lockdep_assert_held definition, right? However, it seems I could make this work with #ifdef CONFIG_LOCKDEP #define for_each_governor(__gov) \ for (__gov = list_first_entry(&cpufreq_governor_list, \ typeof(*__gov), \ governor_list), \ WARN_ON(debug_locks && \ !lockdep_is_held(&cpufreq_governor_mutex)); \ &__gov->governor_list != (&cpufreq_governor_list); \ __gov = list_next_entry(__gov, governor_list)) #else /* !CONFIG_LOCKDEP */ #define for_each_governor(__gov) \ list_for_each_entry(__gov, &cpufreq_governor_list, governor_list) #endif /* CONFIG_LOCKDEP */ Thanks, - Juri
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 2e41356..00a00cd 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -31,7 +31,25 @@ #include <linux/tick.h> #include <trace/events/power.h> +/** + * 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) + +/** + * The "cpufreq driver" - the arch- or hardware-dependent low + * level driver of CPUFreq support, and its spinlock (cpufreq_driver_lock). + * This lock also protects cpufreq_cpu_data array and cpufreq_policy_list. + */ +static struct cpufreq_driver *cpufreq_driver; +static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data); static LIST_HEAD(cpufreq_policy_list); +static DEFINE_RWLOCK(cpufreq_driver_lock); static inline bool policy_is_inactive(struct cpufreq_policy *policy) { @@ -86,21 +104,6 @@ static struct cpufreq_policy *first_policy(bool active) #define for_each_inactive_policy(__policy) \ for_each_suitable_policy(__policy, false) -/* Iterate over governors */ -static LIST_HEAD(cpufreq_governor_list); -#define for_each_governor(__governor) \ - list_for_each_entry(__governor, &cpufreq_governor_list, governor_list) - -/** - * The "cpufreq driver" - the arch- or hardware-dependent low - * level driver of CPUFreq support, and its spinlock. This lock - * also protects the cpufreq_cpu_data array. - */ -static struct cpufreq_driver *cpufreq_driver; -static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data); -static DEFINE_RWLOCK(cpufreq_driver_lock); -static DEFINE_MUTEX(cpufreq_governor_mutex); - /* Flag to suspend/resume CPUFreq governors */ static bool cpufreq_suspended;
Currently it is not easy to figure out which lock/mutex protects which data structure. Clean things up by moving data structures and their locks/mutexs closer; also, change comments to document relations further. Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Juri Lelli <juri.lelli@arm.com> --- drivers/cpufreq/cpufreq.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-) -- 2.2.2