Re: [PATCH v2] schedutil: Allow cpufreq requests to be made even when kthread kicked

[Viresh Kumar]

On 22-05-18, 11:51, Patrick Bellasi wrote:
> It could happen, but using:
> 
>    raw_spin_lock_irqsave(&sg_policy->update_lock, flags);
>    freq = READ_ONCE(sg_policy->next_freq)
>    WRITE_ONCE(sg_policy->work_in_progress, false);
>    raw_spin_unlock_irqrestore(&sg_policy->update_lock, flags);
> 
>                        if (!READ_ONCE(sg_policy->work_in_progress)) {
>                            WRITE_ONCE(sg_policy->work_in_progress, true);
>                            irq_work_queue(&sg_policy->irq_work);
>                        }

I think its better to get locking in place for non-fast switching case in
single-policy systems right now.

> should fix it by enforcing the ordering as well as documenting the
> concurrent access.
> 
> However, in the "sched update" side, where do we have the sequence:
> 
>    sg_policy->next_freq = 0;
>    sg_policy->next_freq = real-next-freq;

Ah, that was just an example of what a compiler may do (though it shouldn't do).

-- 
viresh