Commit 941f5f0f authored by Rafael J. Wysocki's avatar Rafael J. Wysocki Committed by Linus Torvalds
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x86: CPU: Fix up "cpu MHz" in /proc/cpuinfo

Commit 890da9cf (Revert "x86: do not use cpufreq_quick_get() for
/proc/cpuinfo "cpu MHz"") is not sufficient to restore the previous
behavior of "cpu MHz" in /proc/cpuinfo on x86 due to some changes
made after the commit it has reverted.

To address this, make the code in question use arch_freq_get_on_cpu()
which also is used by cpufreq for reporting the current frequency of
CPUs and since that function doesn't really depend on cpufreq in any
way, drop the CONFIG_CPU_FREQ dependency for the object file
containing it.

Also refactor arch_freq_get_on_cpu() somewhat to avoid IPIs and
return cached values right away if it is called very often over a
short time (to prevent user space from triggering IPI storms through

Fixes: 890da9cf (Revert "x86: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz"")
Cc:   # 4.13 - together with 890da9cf

Signed-off-by: default avatarRafael J. Wysocki <>
Signed-off-by: default avatarLinus Torvalds <>
parent 5cb0512c
......@@ -22,7 +22,7 @@ obj-y += common.o
obj-y += rdrand.o
obj-y += match.o
obj-y += bugs.o
obj-$(CONFIG_CPU_FREQ) += aperfmperf.o
obj-y += aperfmperf.o
obj-$(CONFIG_PROC_FS) += proc.o
obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o
......@@ -42,10 +42,6 @@ static void aperfmperf_snapshot_khz(void *dummy)
s64 time_delta = ktime_ms_delta(now, s->time);
unsigned long flags;
/* Don't bother re-computing within the cache threshold time. */
rdmsrl(MSR_IA32_APERF, aperf);
rdmsrl(MSR_IA32_MPERF, mperf);
......@@ -74,6 +70,7 @@ static void aperfmperf_snapshot_khz(void *dummy)
unsigned int arch_freq_get_on_cpu(int cpu)
s64 time_delta;
unsigned int khz;
if (!cpu_khz)
......@@ -82,6 +79,12 @@ unsigned int arch_freq_get_on_cpu(int cpu)
if (!static_cpu_has(X86_FEATURE_APERFMPERF))
return 0;
/* Don't bother re-computing within the cache threshold time. */
time_delta = ktime_ms_delta(ktime_get(), per_cpu(samples.time, cpu));
khz = per_cpu(samples.khz, cpu);
if (khz && time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
return khz;
smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1);
khz = per_cpu(samples.khz, cpu);
if (khz)
......@@ -78,8 +78,10 @@ static int show_cpuinfo(struct seq_file *m, void *v)
seq_printf(m, "microcode\t: 0x%x\n", c->microcode);
if (cpu_has(c, X86_FEATURE_TSC)) {
unsigned int freq = cpufreq_quick_get(cpu);
unsigned int freq = arch_freq_get_on_cpu(cpu);
if (!freq)
freq = cpufreq_quick_get(cpu);
if (!freq)
freq = cpu_khz;
seq_printf(m, "cpu MHz\t\t: %u.%03u\n",
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