Re: [PATCH v3 1/5] arch_topology: validate input frequencies to arch_set_freq_scale()
On 25-08-20, 12:31, Ionela Voinescu wrote: > 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 > > > Cc: Sudeep Holla > > > Cc: Rafael J. Wysocki > > > --- > > > 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(). I think validation and the WARN (if required) must all happen at the same place. Considering that there can be many callers of a routine, like this one, it is better to put all that in the end function only. Maybe we can add the same in the dummy arch_set_freq_scale() if required. -- viresh
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 > > Cc: Sudeep Holla > > Cc: Rafael J. Wysocki > > --- > > 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.
Re: [PATCH v3 1/5] arch_topology: validate input frequencies to arch_set_freq_scale()
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 > Cc: Sudeep Holla > Cc: Rafael J. Wysocki > --- > 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 ? > + return; > + > /* >* If the use of counters for FIE is enabled, just return as we don't >* want to update the scale factor with information from CPUFREQ. > -- > 2.17.1 -- viresh
