On 23 October 2013 14:43, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> I got another solution which is much simpler, and I really can't believe
> (psychologically) that it will solve all the problems we were talking about..
> Please see if there is any loophole in there..
Ping!!
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index ec391d7..e4ed89a 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -340,6 +340,13 @@ static void __cpufreq_notify_transition(struct
> cpufreq_policy *policy,
> }
> }
>
> +void cpufreq_notify_transition_each_cpu(struct cpufreq_policy *policy,
> + struct cpufreq_freqs *freqs, unsigned int state)
> +{
> + for_each_cpu(freqs->cpu, policy->cpus)
> + __cpufreq_notify_transition(policy, freqs, state);
> +}
> +
> /**
> * cpufreq_notify_transition - call notifier chain and adjust_jiffies
> * on frequency transition.
> @@ -351,8 +358,34 @@ static void __cpufreq_notify_transition(struct
> cpufreq_policy *policy,
> void cpufreq_notify_transition(struct cpufreq_policy *policy,
> struct cpufreq_freqs *freqs, unsigned int state)
> {
> - for_each_cpu(freqs->cpu, policy->cpus)
> - __cpufreq_notify_transition(policy, freqs, state);
> + if ((state != CPUFREQ_PRECHANGE) && (state != CPUFREQ_POSTCHANGE))
> + return cpufreq_notify_transition_each_cpu(policy, freqs, state);
> +
> + /* Serialize pre-post notifications */
> + mutex_lock(&policy->transition_lock);
> + if (unlikely(WARN_ON(!policy->transition_ongoing &&
> + (state == CPUFREQ_POSTCHANGE)))) {
> + mutex_unlock(&policy->transition_lock);
> + return;
> + }
> +
> + if (state == CPUFREQ_PRECHANGE) {
> + while (policy->transition_ongoing) {
> + mutex_unlock(&policy->transition_lock);
> + cpu_relax();
> + mutex_lock(&policy->transition_lock);
> + }
> +
> + policy->transition_ongoing = true;
> + mutex_unlock(&policy->transition_lock);
> + }
> +
> + cpufreq_notify_transition_each_cpu(policy, freqs, state);
> +
> + if (state == CPUFREQ_POSTCHANGE) {
> + policy->transition_ongoing = false;
> + mutex_unlock(&policy->transition_lock);
> + }
> }
> EXPORT_SYMBOL_GPL(cpufreq_notify_transition);
>
> @@ -950,6 +983,8 @@ static struct cpufreq_policy *cpufreq_policy_alloc(void)
> goto err_free_cpumask;
>
> INIT_LIST_HEAD(&policy->policy_list);
> + mutex_init(&policy->transition_lock);
> +
> return policy;
>
> err_free_cpumask:
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 0aba2a6c..bb76909 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -85,6 +85,8 @@ struct cpufreq_policy {
> struct list_head policy_list;
> struct kobject kobj;
> struct completion kobj_unregister;
> + bool transition_ongoing; /* Tracks
> transition status */
> + struct mutex transition_lock;
> };
--
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