Re: [Update PATCH 1/1] Cpufreq: Make governor data on nonboot cpus across system suspend/resume

Rafael J. Wysocki
2013-11-16T00:26:57Z

On Friday, November 15, 2013 04:15:34 PM Lan Tianyu wrote:
> Currently, governor of nonboot cpus will be put to EXIT when system suspend.
> Since all these cpus will be unplugged and the governor usage_count decreases
> to zero. The governor data and its sysfs interfaces will be freed or released.
> This makes user config of these governors loss during suspend and resume.

First off, do we have a pointer to a bug report related to that?

Second, what does need to be done to reproduce this problem?

> This doesn't happen on the governor covering boot cpu because it isn't
> unplugged during system suspend.
>
> To fix this issue, skipping governor exit during system suspend and check
> policy governor data to determine whether the governor is really needed
> to be initialized when do init. If not, return EALREADY to indicate the
> governor has been initialized and should do nothing. __cpufreq_governor()
> convert EALREADY to 0 as return value for INIT event since governor is
> still under INIT state and can do START operation.
>
> Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
> ---
> Fix some typos
>
> drivers/cpufreq/cpufreq.c | 5 ++++-
> drivers/cpufreq/cpufreq_governor.c | 13 ++++++++++++-
> 2 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 02d534d..38f2e4a 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1239,7 +1239,7 @@ static int __cpufreq_remove_dev_finish(struct device *dev,
>
> /* If cpu is last user of policy, free policy */
> if (cpus == 1) {
> - if (has_target()) {
> + if (has_target() && !frozen) {
> ret = __cpufreq_governor(policy,
> CPUFREQ_GOV_POLICY_EXIT);
> if (ret) {
> @@ -1822,6 +1822,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
> ((event == CPUFREQ_GOV_POLICY_EXIT) && !ret))
> module_put(policy->governor->owner);
>
> + if ((event == CPUFREQ_GOV_POLICY_INIT) && ret == -EALREADY)
> + ret = 0;
> +
> return ret;
> }
>
> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> index 0806c31..ddb93af 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -204,9 +204,20 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
>
> switch (event) {
> case CPUFREQ_GOV_POLICY_INIT:
> + /*
> + * In order to keep governor data across suspend/resume,
> + * Governor doesn't exit when suspend and will be
> + * reinitialized when resume. Here check policy governor
> + * data to determine whether the governor has been exited.
> + * If not, return EALREADY.
> + */
> if (have_governor_per_policy()) {
> - WARN_ON(dbs_data);
> + if (dbs_data)
> + return -EALREADY;
> } else if (dbs_data) {
> + if (policy->governor_data == dbs_data)
> + return -EALREADY;
> +
> dbs_data->usage_count++;
> policy->governor_data = dbs_data;
> return 0;
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.