Re: Changing CPU frequency in atomic (schedule / scheduler_tick)

On Tue, Aug 18, 2015 at 9:16 AM, Guru Prasad <[email protected]> wrote:
> We're working on a research system where we're trying to achieve
> optimal frequency selection on a per-process basis. To do so, I added
> additional fields to struct task_struct to store the (computed)
> optimal frequency and set it. The code that computes the optimal
> frequency is calculated on every scheduler_tick().
>
> I'm having trouble calling cpufreq_set_rate() from both a)
> scheduler_tick() and b) schedule().

Its not just about mutex-lock. The two scheduler functions mentioned above
are called from atomic context, but they can't call anything which can
potentially
sleep.

cpufreq_set_rate() or any clk_rate_set() can potentially sleep, and so must
not be called from there. Best do it from a workqueue.

--
viresh