Re: [PATCH 1/4] base/drivers/arch_topology: Remove useless check

From: Daniel Lezcano
Date: Tue Oct 30 2018 - 09:35:28 EST

On 30/10/2018 09:33, Viresh Kumar wrote:
> On 30-10-18, 08:55, Daniel Lezcano wrote:
>> The workqueue is called from init_cpu_capacity_callback(). This one is
>> called in the notifier callback. IOW the notification callback
>> unregisters itself. But if it is not registered, it won't unregister,
>> hence it won't call the workqueue and init_cpu_capacity_notifier() is
>> not called.
> Sorry, couldn't understand most of your reply :)

Logical, I didn't understand your initial comment :)

> Though let me try to explain the problem I was trying to show you..
> cpufreq-notifier-callback
> -> init_cpu_capacity_callback()
> -> free raw capacity
> -> queue_work() to unregister the notifier
> -> return
> ->init_cpu_capacity_callback() called again before work was processed.
> -> If we don't check raw_capacity, we may end up using
> NULL pointer, as the notifier isn't unregistered yet.

Oh, nice catch.

I'm wondering if having a statically per_cpu variable, even if it is not
free at the end, isn't worth regarding the twisted code we end up with
an allocation.

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