| Date | Tue, 25 Oct 2022 10:20:40 +0200 | From | Pavel Machek <> | Subject | Re: [PATCH 4.9 158/159] thermal: intel_powerclamp: Use first online CPU as control_cpu |
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Hi!
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > commit 4bb7f6c2781e46fc5bd00475a66df2ea30ef330d upstream. > > Commit 68b99e94a4a2 ("thermal: intel_powerclamp: Use get_cpu() instead > of smp_processor_id() to avoid crash") fixed an issue related to using > smp_processor_id() in preemptible context by replacing it with a pair > of get_cpu()/put_cpu(), but what is needed there really is any online > CPU and not necessarily the one currently running the code. Arguably, > getting the one that's running the code in there is confusing. > > For this reason, simply give the control CPU role to the first online > one which automatically will be CPU0 if it is online, so one check > can be dropped from the code for an added benefit.
While this is nice cleanup (and I complained about original code being interesting) original code still looks okay and we don't really need this in stable.
Thanks and best regards, Pavel
> +++ b/drivers/thermal/intel_powerclamp.c > @@ -518,11 +518,7 @@ static int start_power_clamp(void) > get_online_cpus(); > > /* prefer BSP */ > - control_cpu = 0; > - if (!cpu_online(control_cpu)) { > - control_cpu = get_cpu(); > - put_cpu(); > - } > + control_cpu = cpumask_first(cpu_online_mask); > > clamping = true; > schedule_delayed_work(&poll_pkg_cstate_work, 0); >
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