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SubjectRe: [PATCH] cpufreq: schedutil: Update cached "current frequency" when limits change
On 07/11/2017 10:24 PM, Viresh Kumar wrote:
> On 11-07-17, 19:24, Saravana Kannan wrote:
>> Currently, the governor calculates the next frequency, set the current CPU
>> frequency (policy->cur). It also assumes the current CPU frequency doesn't
>> change if the next frequency isn't calculated again and hence caches the
>> "current frequency".
>>
>> However, this isn't true when CPU min/max frequency limits are changed. So,
>> there's room for the CPU frequency to get stuck at the wrong level if the
>> calculated next frequency doesn't change across multiple limits updates.
>>
>> Fix this by updating the cached "current frequency" when limits changes the
>> current CPU frequency.
>>
>> Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
>> ---
>> kernel/sched/cpufreq_schedutil.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
>> index 076a2e3..fe0b2fb 100644
>> --- a/kernel/sched/cpufreq_schedutil.c
>> +++ b/kernel/sched/cpufreq_schedutil.c
>> @@ -226,6 +226,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
>>
>> busy = sugov_cpu_is_busy(sg_cpu);
>>
>> + raw_spin_lock(&sg_policy->update_lock);
>> if (flags & SCHED_CPUFREQ_RT_DL) {
>> next_f = policy->cpuinfo.max_freq;
>> } else {
>> @@ -240,6 +241,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
>> next_f = sg_policy->next_freq;
>> }
>> sugov_update_commit(sg_policy, time, next_f);
>> + raw_spin_unlock(&sg_policy->update_lock);
>
> We wouldn't allow locking here until the time we can :)
>
>> }
>>
>> static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
>> @@ -637,10 +639,14 @@ static void sugov_stop(struct cpufreq_policy *policy)
>> static void sugov_limits(struct cpufreq_policy *policy)
>> {
>> struct sugov_policy *sg_policy = policy->governor_data;
>> + unsigned long flags;
>>
>> if (!policy->fast_switch_enabled) {
>> mutex_lock(&sg_policy->work_lock);
>> cpufreq_policy_apply_limits(policy);
>> + raw_spin_lock_irqsave(&sg_policy->update_lock, flags);
>> + sg_policy->next_freq = policy->cur;
>> + raw_spin_unlock_irqrestore(&sg_policy->update_lock, flags);
>> mutex_unlock(&sg_policy->work_lock);
>> }
>
> Did you miss the following part which is after the closing } here ?
>
> sg_policy->need_freq_update = true;
>
> As this should already take care of the problem you are worried about. Or did I
> misunderstood your problem completely ?
>
Yup, I did. Thanks! Ignore patch please.

--
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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