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Date: Tue, 25 Aug 2020 12:31:31 +0100 From: Ionela Voinescu <ionela.voinescu@....com> To: Viresh Kumar <viresh.kumar@...aro.org> Cc: rjw@...ysocki.net, dietmar.eggemann@....com, catalin.marinas@....com, sudeep.holla@....com, will@...nel.org, valentin.schneider@....com, linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v3 1/5] arch_topology: validate input frequencies to arch_set_freq_scale() On Tuesday 25 Aug 2020 at 11:26:18 (+0530), Viresh Kumar wrote: > On 24-08-20, 22:02, Ionela Voinescu wrote: > > The current frequency passed to arch_set_freq_scale() could end up > > being 0, signaling an error in setting a new frequency. Also, if the > > maximum frequency in 0, this will result in a division by 0 error. > > > > Therefore, validate these input values before using them for the > > setting of the frequency scale factor. > > > > Signed-off-by: Ionela Voinescu <ionela.voinescu@....com> > > Cc: Sudeep Holla <sudeep.holla@....com> > > Cc: Rafael J. Wysocki <rjw@...ysocki.net> > > --- > > drivers/base/arch_topology.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > > index 75f72d684294..1aca82fcceb8 100644 > > --- a/drivers/base/arch_topology.c > > +++ b/drivers/base/arch_topology.c > > @@ -33,6 +33,9 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq, > > unsigned long scale; > > int i; > > > > + if (!cur_freq || !max_freq) > > We should probably use unlikely() here. > > Rafael: Shouldn't this have a WARN_ON_ONCE() as well ? > I'll add the unlikely() as it's definitely useful. I'm somewhat on the fence about WARN_ON_ONCE() here. Wouldn't it work better in cpufreq_driver_fast_switch()? It would cover scenarios where the default arch_set_freq_scale() is used and flag potential hardware issues with setting frequency that are currently just ignored both here and in sugov_fast_switch(). Thanks, Ionela.
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