linux-kernel - Re: [PATCH] cpufreq: skip cpufreq resume if it's not suspended

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Date:   Mon, 05 Feb 2018 09:50:28 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Bo Yan <byan@...dia.com>, Saravana Kannan <skannan@...eaurora.org>,
        sgurrappadi@...dia.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: skip cpufreq resume if it's not suspended

On Monday, February 5, 2018 5:01:18 AM CET Viresh Kumar wrote:
> On 02-02-18, 13:28, Bo Yan wrote:
> > On 02/02/2018 11:34 AM, Saravana Kannan wrote:
> > >I rather have this fixed in the dpm_suspend/resume() code. This is just
> > >masking the first issue that's being caused by unbalanced error handling.
> > >If that means adding flags in dpm_suspend/resume() then that's what we
> > >should do right now and clean it up later if it can be improved. Making
> > >cpufreq more messy doesn't seem like the right answer.
> 
> +1
> 
> > dpm_suspend and dpm_resume by themselves are not balanced in this particular
> > case. As it's currently structured, dpm_resume can't be omitted even if
> > dpm_suspend is skipped due to earlier failure.  I think checking
> > cpufreq_suspended flag is a reasonable compromise. If we can find a way to
> > make dpm_suspend/dpm_resume also balanced, that will be best.
> 
> I think cpufreq is just one of the users which broke. Others didn't break
> because:
> 
> - They don't have a complicated resume part.
> - Or we just don't know that they broke.

No and no.

> Resuming something that never suspended is just broken by design. Yeah, its much
> simpler in this particular case to fix cpufreq core but the
> suspend/resume/hibernation part is really core kernel and should be fixed to
> avoid such band-aids.

By design (which I admit may be confusing) it should be fine to call
dpm_resume_end() after a failing dpm_suspend_start(), whatever the reason
for the failure is.  cpufreq_suspend/resume() don't take that into account,
everybody else does.

Thanks,
Rafael