Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Thu, 14 Mar 2019 10:33:04 +0100 | Subject | Re: [PATCH 5/7] x86/tsc: Update cpufreq transition notifier to handle multiple CPUs |
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On Thu, Mar 14, 2019 at 7:43 AM Viresh Kumar <viresh.kumar@linaro.org> wrote: > > The cpufreq core currently calls the cpufreq transition notifier > callback once for each affected CPU. This is going to change soon and > the cpufreq core will call the callback only once for each cpufreq > policy. The callback must look at the newly added field in struct > cpufreq_freqs, "cpus", which contains policy->related_cpus (both > online/offline CPUs) and perform per-cpu actions for them if any. > > This patch updates time_cpufreq_notifier() to use the new "cpus" field, > update per-cpu data for all the related CPUs and call set_cyc2ns_scale() > for all online related_cpus. > > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> > --- > arch/x86/kernel/tsc.c | 31 ++++++++++++++++++++----------- > 1 file changed, 20 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c > index 3fae23834069..587a6aa72f38 100644 > --- a/arch/x86/kernel/tsc.c > +++ b/arch/x86/kernel/tsc.c > @@ -956,28 +956,37 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, > void *data) > { > struct cpufreq_freqs *freq = data; > - unsigned long *lpj; > - > - lpj = &boot_cpu_data.loops_per_jiffy; > -#ifdef CONFIG_SMP > - if (!(freq->flags & CPUFREQ_CONST_LOOPS)) > - lpj = &cpu_data(freq->cpu).loops_per_jiffy; > -#endif > + bool boot_cpu = !IS_ENABLED(CONFIG_SMP) || freq->flags & CPUFREQ_CONST_LOOPS; > + unsigned long lpj; > + int cpu; > > if (!ref_freq) { > ref_freq = freq->old; > - loops_per_jiffy_ref = *lpj; > tsc_khz_ref = tsc_khz; > + > + if (boot_cpu) > + loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy; > + else > + loops_per_jiffy_ref = cpu_data(cpumask_first(freq->cpus)).loops_per_jiffy; > } > + > if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || > (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) { > - *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); > - > + lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); > tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new); > + > if (!(freq->flags & CPUFREQ_CONST_LOOPS)) > mark_tsc_unstable("cpufreq changes"); > > - set_cyc2ns_scale(tsc_khz, freq->cpu, rdtsc()); > + if (boot_cpu) { > + boot_cpu_data.loops_per_jiffy = lpj; > + } else { > + for_each_cpu(cpu, freq->cpus)
This needs to iterate over policy->cpus or you change the behavior.
Not that it will matter a lot (x86 in one CPU per policy anyway in the vast majority of cases), but it is a change nevertheless. Moreover, I'm not even sure if doing that for offline CPUs makes sense.
> + cpu_data(cpu).loops_per_jiffy = lpj; > + } > + > + for_each_cpu_and(cpu, freq->cpus, cpu_online_mask) > + set_cyc2ns_scale(tsc_khz, cpu, rdtsc()); > } > > return 0; > --
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