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SubjectRe: [PATCH] cpufreq: skip cpufreq resume if it's not suspended
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On Tuesday, January 23, 2018 10:57:55 PM CET Bo Yan wrote:
> cpufreq_resume can be called even without preceding cpufreq_suspend.
> This can happen in following scenario:
>
> suspend_devices_and_enter
> --> dpm_suspend_start
> --> dpm_prepare
> --> device_prepare : this function errors out
> --> dpm_suspend: this is skipped due to dpm_prepare failure
> this means cpufreq_suspend is skipped over
> --> goto Recover_platform, due to previous error
> --> goto Resume_devices
> --> dpm_resume_end
> --> dpm_resume
> --> cpufreq_resume
>
> In case schedutil is used as frequency governor, cpufreq_resume will
> eventually call sugov_start, which does following:
>
> memset(sg_cpu, 0, sizeof(*sg_cpu));
> ....
>
> This effectively erases function pointer for frequency update, causing
> crash later on. The function pointer would have been set correctly if
> subsequent cpufreq_add_update_util_hook runs successfully, but that
> function returns earlier because cpufreq_suspend was not called:
>
> if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
> return;
>
> Ideally, suspend should succeed, then things will be fine. But even
> in case of suspend failure, system should not crash.
>
> The fix is to check cpufreq_suspended first, if it's false, that means
> cpufreq_suspend was not called in the first place, so do not resume
> cpufreq.
>
> Signed-off-by: Bo Yan <byan@nvidia.com>
> ---
> drivers/cpufreq/cpufreq.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 41d148af7748..95b1c4afe14e 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1680,6 +1680,10 @@ void cpufreq_resume(void)
> if (!cpufreq_driver)
> return;
>
> + if (unlikely(!cpufreq_suspended)) {
> + pr_warn("%s: resume after failing suspend\n", __func__);
> + return;
> + }
> cpufreq_suspended = false;
>
> if (!has_target() && !cpufreq_driver->resume)

I've just edited this patch somewhat (mostly by dropping the pr_warn())
and queued it up.

Thanks,
Rafael

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