[13/13] cpufreq: make sure frequency transitions are serialized

Message ID CAKohpo=8oZKiq1ghuipitbfMp-bPxpWPQbGx5SLj9+_nGegCfA@mail.gmail.com
State New
Headers show

Commit Message

Viresh Kumar June 24, 2013, 1:08 p.m.
On 24 June 2013 17:13, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Wednesday, June 19, 2013 02:23:07 PM Viresh Kumar wrote:
>>       case CPUFREQ_POSTCHANGE:
>> +             WARN_ON(!transition_ongoing--);
>
> Shouldn't we try to avoid going into the negative range here?

What about this patch? Find it attached to apply.

                 * "old frequency".
@@ -283,6 +293,13 @@ void __cpufreq_notify_transition(struct
cpufreq_policy *policy,
                break;

        case CPUFREQ_POSTCHANGE:
+               if (!transition_ongoing) {
+                       WARN(1, "No frequency transition in progress\n");
+                       return;
+               }
+
+               transition_ongoing--;
+
                adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);
                pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new,
                        (unsigned long)freqs->cpu);
@@ -1458,6 +1475,8 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,

        if (cpufreq_disabled())
                return -ENODEV;
+       if (transition_ongoing)
+               return -EBUSY;

        /* Make sure that target_freq is within supported range */
        if (target_freq > policy->max)

Comments

Rafael J. Wysocki June 24, 2013, 1:23 p.m. | #1
On Monday, June 24, 2013 06:38:17 PM Viresh Kumar wrote:
> On 24 June 2013 17:13, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > On Wednesday, June 19, 2013 02:23:07 PM Viresh Kumar wrote:
> >>       case CPUFREQ_POSTCHANGE:
> >> +             WARN_ON(!transition_ongoing--);
> >
> > Shouldn't we try to avoid going into the negative range here?
> 
> What about this patch? Find it attached to apply.
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 2d53f47..6624694 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -107,6 +107,9 @@ static void handle_update(struct work_struct *work);
>  static BLOCKING_NOTIFIER_HEAD(cpufreq_policy_notifier_list);
>  static struct srcu_notifier_head cpufreq_transition_notifier_list;
> 
> +/* Tracks status of transition */
> +static int transition_ongoing;
> +
>  static bool init_cpufreq_transition_notifier_list_called;
>  static int __init init_cpufreq_transition_notifier_list(void)
>  {
> @@ -264,6 +267,13 @@ void __cpufreq_notify_transition(struct
> cpufreq_policy *policy,
>         switch (state) {
> 
>         case CPUFREQ_PRECHANGE:
> +               if (transition_ongoing) {
> +                       WARN(1, "In middle of another frequency transition\n");
> +                       return;
> +               }

You can do

	if (WARN(transition_ongoing, "<text>"))
		return;

and below analogously.

> +
> +               transition_ongoing++;
> +
>                 /* detect if the driver reported a value as "old frequency"
>                  * which is not equal to what the cpufreq core thinks is
>                  * "old frequency".
> @@ -283,6 +293,13 @@ void __cpufreq_notify_transition(struct
> cpufreq_policy *policy,
>                 break;
> 
>         case CPUFREQ_POSTCHANGE:
> +               if (!transition_ongoing) {
> +                       WARN(1, "No frequency transition in progress\n");
> +                       return;
> +               }
> +
> +               transition_ongoing--;
> +
>                 adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);
>                 pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new,
>                         (unsigned long)freqs->cpu);
> @@ -1458,6 +1475,8 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
> 
>         if (cpufreq_disabled())
>                 return -ENODEV;
> +       if (transition_ongoing)
> +               return -EBUSY;
> 
>         /* Make sure that target_freq is within supported range */
>         if (target_freq > policy->max)

Thanks,
Rafael

Patch

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 2d53f47..6624694 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -107,6 +107,9 @@  static void handle_update(struct work_struct *work);
 static BLOCKING_NOTIFIER_HEAD(cpufreq_policy_notifier_list);
 static struct srcu_notifier_head cpufreq_transition_notifier_list;

+/* Tracks status of transition */
+static int transition_ongoing;
+
 static bool init_cpufreq_transition_notifier_list_called;
 static int __init init_cpufreq_transition_notifier_list(void)
 {
@@ -264,6 +267,13 @@  void __cpufreq_notify_transition(struct
cpufreq_policy *policy,
        switch (state) {

        case CPUFREQ_PRECHANGE:
+               if (transition_ongoing) {
+                       WARN(1, "In middle of another frequency transition\n");
+                       return;
+               }
+
+               transition_ongoing++;
+
                /* detect if the driver reported a value as "old frequency"
                 * which is not equal to what the cpufreq core thinks is