On Sunday, September 01, 2013 10:56:02 AM Viresh Kumar wrote:
> We can't take a big lock around __cpufreq_governor() as this causes recursive
> locking for some cases. But calls to this routine must be serialized for every
> policy.
Care to explain here why it must be serialized?
> Lets introduce another variable which would guarantee serialization here.
>
> Signed-off-by: Viresh Kumar <viresh.ku...@linaro.org>
> ---
> drivers/cpufreq/cpufreq.c | 7 ++++++-
> include/linux/cpufreq.h | 1 +
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index f320a20..4d5723db 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1692,13 +1692,15 @@ static int __cpufreq_governor(struct cpufreq_policy
> *policy,
> policy->cpu, event);
>
> mutex_lock(&cpufreq_governor_lock);
> - if ((policy->governor_enabled && (event == CPUFREQ_GOV_START)) ||
> + if (policy->governor_busy ||
> + (policy->governor_enabled && (event == CPUFREQ_GOV_START)) ||
Again, broken white space, but I can fix it up.
> (!policy->governor_enabled && ((event == CPUFREQ_GOV_LIMITS) ||
> (event == CPUFREQ_GOV_STOP)))) {
> mutex_unlock(&cpufreq_governor_lock);
> return -EBUSY;
> }
>
> + policy->governor_busy = true;
> if (event == CPUFREQ_GOV_STOP)
> policy->governor_enabled = false;
> else if (event == CPUFREQ_GOV_START)
> @@ -1727,6 +1729,9 @@ static int __cpufreq_governor(struct cpufreq_policy
> *policy,
> ((event == CPUFREQ_GOV_POLICY_EXIT) && !ret))
> module_put(policy->governor->owner);
>
> + mutex_lock(&cpufreq_governor_lock);
> + policy->governor_busy = false;
> + mutex_unlock(&cpufreq_governor_lock);
> return ret;
> }
>
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index d568f39..cca885d 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -76,6 +76,7 @@ struct cpufreq_policy {
> struct cpufreq_governor *governor; /* see below */
> void *governor_data;
> bool governor_enabled; /* governor start/stop flag */
> + bool governor_busy;
>
> struct work_struct update; /* if update_policy() needs to be
> * called, but you're in IRQ context */
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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