Whenever we are changing frequency of a cpu, we are calling PRECHANGE and POSTCHANGE notifiers. They must be serialized. i.e. PRECHANGE or POSTCHANGE shouldn't be called twice contiguously.
This can happen due to bugs in users of __cpufreq_driver_target() or actual cpufreq drivers who are sending these notifiers.
This patch adds some protection against this. Now, we keep track of the last transaction and see if something went wrong.
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- drivers/cpufreq/cpufreq.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 2d53f47..92cb8b3 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 +267,8 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy, switch (state) {
case CPUFREQ_PRECHANGE: + WARN_ON(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 +288,8 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy, break;
case CPUFREQ_POSTCHANGE: + WARN_ON(!transition_ongoing--); + adjust_jiffies(CPUFREQ_POSTCHANGE, freqs); pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new, (unsigned long)freqs->cpu); @@ -1458,6 +1465,8 @@ 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)