"cpufreq: fix serialization issues with freq change notifiers" breaks cpufreq too
Rafael J. Wysocki
rjw at sisk.pl
Mon Sep 9 19:12:49 EDT 2013
On Monday, September 09, 2013 11:42:41 PM Guennadi Liakhovetski wrote:
> Hi Rafael
>
> On Mon, 9 Sep 2013, Rafael J. Wysocki wrote:
>
> > Hi,
> >
> > On Monday, September 09, 2013 05:11:10 PM Guennadi Liakhovetski wrote:
> > > Sorry guys, I'm trying my best to stop this patch from propagating to
> > > stable and to get it fixed asap, so, the CC list might be a bit excessive.
> > > Also trying to fix the originally spare cc list, which makes it impossible
> > > for me to reply to the original thread, instead have to start a new one.
> >
> > I'm not sure what you're talking about. What exactly was wrong with the
> > original CC list in particular?
>
> I think you advised once to cc cpufreq related mails to linux-pm too at
> least.
Yes, I did.
> I haven't found this patch in my pm archive, have I missed it there?
Quite frankly, I don't remember if it was there. ISTR having it it patchwork,
which would mean that it was there, but well.
> > > Commit
> > >
> > > commit dceff5ce18801dddc220d6238628619c93bc3cb6
> > > Author: Viresh Kumar <viresh.kumar at linaro.org>
> > > Date: Sun Sep 1 22:19:37 2013 +0530
> > >
> > > cpufreq: fix serialization issues with freq change notifiers
> > >
> > > breaks .transition_ongoing counting.
> >
> > Do you know how exactly it breaks that? If so, care to share that knowledge?
>
> No, I don't. I only know that in __cpufreq_driver_target() the check for
>
> if (policy->transition_ongoing) {
> write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> return -EBUSY;
> }
>
> is failing with this patch and cpufreq-cpu0.
OK, we need to figure out that, then.
> > > This leads to cpufreq-cpu0 not working any more. In particular switching the
> > > governor from performance to powersave directly after boot doesn't result in
> > > a frequency switch any more. Reverting this patch fixes the problem again.
> >
> > However, this is a regression fix, so I'd prefer to fix the problem on top of
> > it instead of reverting this commit entirely.
>
> If I understood correctly, this patch fixed some warnings, that, however,
> didn't disrupt functionality, is this right? Whereas the patch really
> seems to break working set ups.
It fixed warnings that indicated problems and those problems should rather be
avoided.
Thanks,
Rafael
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