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SubjectRe: [PATCH v4 2/4] PM / devfreq: Fix kernel warning with cpufreq passive register fail
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On 22. 6. 15. 08:09, Christian 'Ansuel' Marangi wrote:
> When the cpufreq passive register path from the passive governor fails,
> the cpufreq_passive_unregister is called and a kernel WARNING is always
> reported.
> This is caused by the fact that the devfreq driver already call the
> governor unregister with the GOV_STOP, for this reason the second
> cpufreq_passive_unregister always return error and a WARN is printed
> from the WARN_ON function.
> Remove the unregister call from the error handling of the cpufreq register
> notifier as it's fundamentally wrong and already handled by the devfreq
> core code.
>
> Fixes: a03dacb0316f ("PM / devfreq: Add cpu based scaling support to passive governor")
> Signed-off-by: Christian 'Ansuel' Marangi <ansuelsmth@gmail.com>
> ---
> drivers/devfreq/governor_passive.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> index 95de336f20d5..dcc9dd518197 100644
> --- a/drivers/devfreq/governor_passive.c
> +++ b/drivers/devfreq/governor_passive.c
> @@ -331,7 +331,6 @@ static int cpufreq_passive_register_notifier(struct devfreq *devfreq)
> err_put_policy:
> cpufreq_cpu_put(policy);
> err:
> - WARN_ON(cpufreq_passive_unregister_notifier(devfreq));
>
> return ret;
> }

I think that it is necessary to free the resource when error happen.
Also, after merging the your patch1, I think that cpufreq_passive_unregister_notifier(devfreq)
will not return error. Instead, just 0 for success.

Instead, 'err_free_cpu_data' and 'err_put_policy' goto statement are wrong exception
handling. If fix the exception handling code in cpufreq_passive_register_notifier
as following and with your patch1, I'll handle the resource for free/un-registration
when error happen during cpufreq_passive_register_notifier.


diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
index a35b39ac656c..0246e0731fc0 100644
--- a/drivers/devfreq/governor_passive.c
+++ b/drivers/devfreq/governor_passive.c
@@ -289,22 +289,23 @@ static int cpufreq_passive_register_notifier(struct devfreq *devfreq)
parent_cpu_data = kzalloc(sizeof(*parent_cpu_data),
GFP_KERNEL);
if (!parent_cpu_data) {
+ cpufreq_cpu_put(policy);
ret = -ENOMEM;
- goto err_put_policy;
+ goto err;
}

cpu_dev = get_cpu_device(cpu);
if (!cpu_dev) {
dev_err(dev, "failed to get cpu device\n");
ret = -ENODEV;
- goto err_free_cpu_data;
+ goto err;
}

opp_table = dev_pm_opp_get_opp_table(cpu_dev);
if (IS_ERR(opp_table)) {
dev_err(dev, "failed to get opp_table of cpu%d\n", cpu);
ret = PTR_ERR(opp_table);
- goto err_free_cpu_data;
+ goto err;
}

parent_cpu_data->dev = cpu_dev;
@@ -326,10 +327,6 @@ static int cpufreq_passive_register_notifier(struct devfreq *devfreq)

return ret;

-err_free_cpu_data:
- kfree(parent_cpu_data);
-err_put_policy:
- cpufreq_cpu_put(policy);
err:
WARN_ON(cpufreq_passive_unregister_notifier(devfreq));



--
Best Regards,
Samsung Electronics
Chanwoo Choi

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