linux-kernel - Re: [PATCH 1/8] cpufreq: Revert commit a66b2e to fix cpufreq regression during suspend/resume

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Date:	Fri, 12 Jul 2013 12:48:10 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	rjw@...k.pl, toralf.foerster@....de, robert.jarzmik@...el.com,
	durgadoss.r@...el.com, tianyu.lan@...el.com,
	lantianyu1986@...il.com, dirk.brandewie@...il.com,
	stern@...land.harvard.edu, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] cpufreq: Revert commit a66b2e to fix cpufreq
 regression during suspend/resume

On 12 July 2013 03:45, Srivatsa S. Bhat
<srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> commit a66b2e (cpufreq: Preserve sysfs files across suspend/resume) has
> unfortunately caused several things in the cpufreq subsystem to break subtly
> after a suspend/resume cycle.
>
> The intention of that patch was to retain the file permissions of the
> cpufreq related sysfs files across suspend/resume. To achieve that, the commit
> completely removed the calls to cpufreq_add_dev() and __cpufreq_remove_dev()
> during suspend/resume transitions. But the problem is that those functions
> do 2 kinds of things:
>   1. Low-level initialization/tear-down that are critical to the correct
>      functioning of cpufreq-core.
>   2. Kobject and sysfs related initialization/teardown.
>
> Ideally we should have reorganized the code to cleanly separate these two
> responsibilities, and skipped only the sysfs related parts during
> suspend/resume. Since we skipped the entire callbacks instead (which also
> included some CPU and cpufreq-specific critical components), cpufreq
> subsystem started behaving erratically after suspend/resume.
>
> So revert the commit to fix the regression. We'll revisit and address the
> original goal of that commit separately, since it involves quite a bit of
> careful code reorganization and appears to be non-trivial.
>
> (While reverting the commit, note that another commit f51e1eb "cpufreq:
> Fix cpufreq regression after suspend/resume" already reverted part of the
> original set of changes. So revert only the remaining ones).
>
> Cc: stable@...r.kernel.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
>
>  drivers/cpufreq/cpufreq.c       |    4 +++-
>  drivers/cpufreq/cpufreq_stats.c |    6 ++----
>  2 files changed, 5 insertions(+), 5 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
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