linux-kernel - [PATCH 4.13 26/33] Revert "x86: CPU: Fix up "cpu MHz" in /proc/cpuinfo"

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Date:   Mon, 13 Nov 2017 13:56:47 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, WANG Chao <chao.wang@...oud.cn>,
        Ingo Molnar <mingo@...nel.org>,
        Rafael J Wysocki <rafael.j.wysocki@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.13 26/33] Revert "x86: CPU: Fix up "cpu MHz" in /proc/cpuinfo"

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@...ux-foundation.org>

commit ea0ee33988778fb73e4f45e7c73fb735787e2f32 upstream.

This reverts commit 941f5f0f6ef5338814145cf2b813cf1f98873e2f.

Sadly, it turns out that we really can't just do the cross-CPU IPI to
all CPU's to get their proper frequencies, because it's much too
expensive on systems with lots of cores.

So we'll have to revert this for now, and revisit it using a smarter
model (probably doing one system-wide IPI at open time, and doing all
the frequency calculations in parallel).

Reported-by: WANG Chao <chao.wang@...oud.cn>
Reported-by: Ingo Molnar <mingo@...nel.org>
Cc: Rafael J Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/cpu/Makefile     |    2 +-
 arch/x86/kernel/cpu/aperfmperf.c |   11 ++++-------
 arch/x86/kernel/cpu/proc.c       |    4 +---
 3 files changed, 6 insertions(+), 11 deletions(-)

--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -21,7 +21,7 @@ obj-y			+= common.o
 obj-y			+= rdrand.o
 obj-y			+= match.o
 obj-y			+= bugs.o
-obj-y			+= aperfmperf.o
+obj-$(CONFIG_CPU_FREQ)	+= aperfmperf.o
 
 obj-$(CONFIG_PROC_FS)	+= proc.o
 obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o
--- a/arch/x86/kernel/cpu/aperfmperf.c
+++ b/arch/x86/kernel/cpu/aperfmperf.c
@@ -42,6 +42,10 @@ static void aperfmperf_snapshot_khz(void
 	s64 time_delta = ktime_ms_delta(now, s->time);
 	unsigned long flags;
 
+	/* Don't bother re-computing within the cache threshold time. */
+	if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
+		return;
+
 	local_irq_save(flags);
 	rdmsrl(MSR_IA32_APERF, aperf);
 	rdmsrl(MSR_IA32_MPERF, mperf);
@@ -70,7 +74,6 @@ static void aperfmperf_snapshot_khz(void
 
 unsigned int arch_freq_get_on_cpu(int cpu)
 {
-	s64 time_delta;
 	unsigned int khz;
 
 	if (!cpu_khz)
@@ -79,12 +82,6 @@ unsigned int arch_freq_get_on_cpu(int cp
 	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)
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -77,11 +77,9 @@ static int show_cpuinfo(struct seq_file
 		seq_printf(m, "microcode\t: 0x%x\n", c->microcode);
 
 	if (cpu_has(c, X86_FEATURE_TSC)) {
-		unsigned int freq = arch_freq_get_on_cpu(cpu);
+		unsigned int freq = cpufreq_quick_get(cpu);
 
 		if (!freq)
-			freq = cpufreq_quick_get(cpu);
-		if (!freq)
 			freq = cpu_khz;
 		seq_printf(m, "cpu MHz\t\t: %u.%03u\n",
 			   freq / 1000, (freq % 1000));