On 24 June 2013 17:13, Rafael J. Wysocki <rjw@xxxxxxx> 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;
+ }
+
+ 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)
Attachment:
0001-cpufreq-make-sure-frequency-transitions-are-serializ.patch
Description: Binary data
