On Fri, Feb 2, 2018 at 1:53 PM, Prateek Sood <prsood@xxxxxxxxxxxxxx> wrote:
> 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 for the inputs, I will send a formal patch.
Bo Yan has posted something really similar already, however:
https://patchwork.kernel.org/patch/10181101/
so I would prefer to apply a new version of that one with the latest
comment taken into account:
https://patchwork.kernel.org/patch/10183075/
for the credit to go to the first submitter.
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