lkml.org 
[lkml]   [2022]   [Oct]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] thermal: intel_powerclamp: Use first online CPU as control_cpu
On 2022-10-13 at 15:27:30 +0200, Rafael J. Wysocki wrote:
> On Thu, Oct 13, 2022 at 3:10 PM Chen Yu <yu.c.chen@intel.com> wrote:
> >
> > On 2022-10-13 at 14:50:28 +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > >
> > > 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.
> > >
> > > Link: https://lore.kernel.org/linux-pm/20221011113646.GA12080@duo.ucw.cz/
> > > Fixes: 68b99e94a4a2 ("thermal: intel_powerclamp: Use get_cpu() instead of smp_processor_id() to avoid crash")
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > > ---
> > > drivers/thermal/intel/intel_powerclamp.c | 6 +-----
> > > 1 file changed, 1 insertion(+), 5 deletions(-)
> > >
> > > Index: linux-pm/drivers/thermal/intel/intel_powerclamp.c
> > > ===================================================================
> > > --- linux-pm.orig/drivers/thermal/intel/intel_powerclamp.c
> > > +++ linux-pm/drivers/thermal/intel/intel_powerclamp.c
> > > @@ -516,11 +516,7 @@ static int start_power_clamp(void)
> > > cpus_read_lock();
> > >
> > > /* prefer BSP */
> > Above comment line is not true any more, might delete it as well?
>
> Well, why not? If CPU0 is the BSP, it is still preferred as before.
>
I see. Got it.

thanks,
Chenyu
> > Reviewed-by: Chen Yu <yu.c.chen@intel.com>
>
> Thanks!
>
> > > - 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);
> > >
> > >
> > >

\
 
 \ /
  Last update: 2022-10-13 15:55    [W:0.040 / U:0.624 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site