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
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