Re: [PATCH 1/2] cpufreq: qcom-hw: Use initialized cpumask for thermal pressure update

Viresh Kumar
2022-01-19T06:40:39Z

On 19-01-22, 12:05, Viresh Kumar wrote:
> policy->cpus keeps on changing with CPU hotplug and this can leave
> your platform in an inconsistent state. For example, in case where you
> offline a CPU from policy, other CPUs get their thermal pressure
> updated, online the CPU back and all CPUs of a policy don't have the
> same settings anymore.
>
> There are few things we can do here now:
>
> - Check for empty related_cpus and return early. Since related_cpus is
> updated only once, this shall work just fine and must not be racy.
>
> While at it, I think we can also do something like this in
> topology_update_thermal_pressure() instead:
>
> cpu = cpumask_first(cpus);
> if (unlikely(cpu >= NR_CPUS))
> return;
>
> - And while writing this email, I dropped all other ideas in favor of
> change to topology_update_thermal_pressure() :)

And then I saw your second patch, which looks good as otherwise we
will not be able to catch the bug in our system where we are sending
the empty cpumask :)

So the other idea is:

- Revert, or bring back a new version of this and register the
interrupt from there. But that is also not a very clean solution.

commit 4bf8e582119e ("cpufreq: Remove ready() callback")

-

--
viresh