On 02/02/2018 05:18 PM, Rafael J. Wysocki wrote:
> On Friday, February 2, 2018 12:41:58 PM CET Prateek Sood wrote:
>> Hi Viresh,
>>
>> One scenario is there where a kernel panic is observed in
>> cpufreq during suspend/resume.
>>
>> pm_suspend()
>> suspend_devices_and_enter()
>> dpm_suspend_start()
>> dpm_prepare()
>>
>> Failure in dpm_prepare() happend with following dmesg:
>>
>> [ 3746.316062] PM: Device xyz not prepared for power transition: code -16
>> [ 3746.316071] PM: Some devices failed to suspend, or early wake event detected
>>
>>
>> pm_suspend()
>> suspend_devices_and_enter()
>> dpm_suspend_start()
>> dpm_prepare() //failed
>> dpm_resume_end()
>> dpm_resume()
>> cpufreq_resume()
>> cpufreq_start_governor()
>> sugov_start()
>> cpufreq_add_update_util_hook()
>>
>> After failure in dpm_prepare(), dpm_resume() called
>> cpufreq_resume(). Corresponding cpufreq_suspend() was not
>> called due to failure of dpm_prepare().
>>
>> This resulted in WARN_ON(per_cpu(cpufreq_update_util_data, cpu))
>> in cpufreq_add_update_util_hook() and cpufreq_add_update_util_hook->func
>> being inconsistent state. It caused crash in scheduler.
>>
>> Following are some of the ways to mitigate this issue. Could
>> you please provide feedback on below two approaches or suugest
>> a better way to fix this problem.
>>
>> -----------------------8<------------------------------
>>
>> Co-developed-by: Gaurav Kohli <gkohli@xxxxxxxxxxxxxx>
>> Signed-off-by: Gaurav Kohli <gkohli@xxxxxxxxxxxxxx>
>> Signed-off-by: Prateek Sood <prsood@xxxxxxxxxxxxxx>
>>
>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>> index 02a497e..732e5a2 100644
>> --- a/drivers/base/power/main.c
>> +++ b/drivers/base/power/main.c
>> @@ -1038,6 +1038,7 @@ void dpm_resume(pm_message_t state)
>> {
>> struct device *dev;
>> ktime_t starttime = ktime_get();
>> + bool valid_resume = false;
>>
>> trace_suspend_resume(TPS("dpm_resume"), state.event, true);
>> might_sleep();
>> @@ -1055,6 +1056,7 @@ void dpm_resume(pm_message_t state)
>> }
>>
>> while (!list_empty(&dpm_suspended_list)) {
>> + valid_resume = true;
>> dev = to_device(dpm_suspended_list.next);
>> get_device(dev);
>> if (!is_async(dev)) {
>> @@ -1080,7 +1082,8 @@ void dpm_resume(pm_message_t state)
>> async_synchronize_full();
>> dpm_show_time(starttime, state, 0, NULL);
>>
>> - cpufreq_resume();
>> + if (valid_resume)
>> + cpufreq_resume();
>> trace_suspend_resume(TPS("dpm_resume"), state.event, false);
>> }
>>
>> --------------------8<--------------------------------------
>>
>> Signed-off-by: Prateek Sood <prsood@xxxxxxxxxxxxxx>
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 421f318..439eab8 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1648,7 +1648,7 @@ void cpufreq_suspend(void)
>> {
>> struct cpufreq_policy *policy;
>>
>> - if (!cpufreq_driver)
>> + if (!cpufreq_driver || cpufreq_suspended)
>> return;
>>
>> if (!has_target() && !cpufreq_driver->suspend)
>> @@ -1683,7 +1683,7 @@ void cpufreq_resume(void)
>> struct cpufreq_policy *policy;
>> int ret;
>>
>> - if (!cpufreq_driver)
>> + if (!cpufreq_driver || !cpufreq_suspended)
>> return;
>>
>> cpufreq_suspended = false;
>
> Since we have cpufreq_suspended already, the second one is better.
>
> Thanks,
> Rafael
>
Thanks Rafael for the inputs, I will send a formal patch.
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