Patch "cpufreq: schedutil: Use idle_calls counter of the remote CPU" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    cpufreq: schedutil: Use idle_calls counter of the remote CPU

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     cpufreq-schedutil-use-idle_calls-counter-of-the-remote-cpu.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 466a2b42d67644447a1765276259a3ea5531ddff Mon Sep 17 00:00:00 2001
From: Joel Fernandes <joelaf@google.com>
Date: Thu, 21 Dec 2017 02:22:45 +0100
Subject: cpufreq: schedutil: Use idle_calls counter of the remote CPU

From: Joel Fernandes <joelaf@google.com>

commit 466a2b42d67644447a1765276259a3ea5531ddff upstream.

Since the recent remote cpufreq callback work, its possible that a cpufreq
update is triggered from a remote CPU. For single policies however, the current
code uses the local CPU when trying to determine if the remote sg_cpu entered
idle or is busy. This is incorrect. To remedy this, compare with the nohz tick
idle_calls counter of the remote CPU.

Fixes: 674e75411fc2 (sched: cpufreq: Allow remote cpufreq callbacks)
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 include/linux/tick.h             |    1 +
 kernel/sched/cpufreq_schedutil.c |    2 +-
 kernel/time/tick-sched.c         |   13 +++++++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -119,6 +119,7 @@ extern void tick_nohz_idle_exit(void);
 extern void tick_nohz_irq_exit(void);
 extern ktime_t tick_nohz_get_sleep_length(void);
 extern unsigned long tick_nohz_get_idle_calls(void);
+extern unsigned long tick_nohz_get_idle_calls_cpu(int cpu);
 extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
 extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
 #else /* !CONFIG_NO_HZ_COMMON */
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -244,7 +244,7 @@ static void sugov_iowait_boost(struct su
 #ifdef CONFIG_NO_HZ_COMMON
 static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu)
 {
-	unsigned long idle_calls = tick_nohz_get_idle_calls();
+	unsigned long idle_calls = tick_nohz_get_idle_calls_cpu(sg_cpu->cpu);
 	bool ret = idle_calls == sg_cpu->saved_idle_calls;
 
 	sg_cpu->saved_idle_calls = idle_calls;
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1010,6 +1010,19 @@ ktime_t tick_nohz_get_sleep_length(void)
 }
 
 /**
+ * tick_nohz_get_idle_calls_cpu - return the current idle calls counter value
+ * for a particular CPU.
+ *
+ * Called from the schedutil frequency scaling governor in scheduler context.
+ */
+unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
+{
+	struct tick_sched *ts = tick_get_tick_sched(cpu);
+
+	return ts->idle_calls;
+}
+
+/**
  * tick_nohz_get_idle_calls - return the current idle calls counter value
  *
  * Called from the schedutil frequency scaling governor in scheduler context.


Patches currently in stable-queue which might be from joelaf@google.com are

queue-4.14/cpufreq-schedutil-use-idle_calls-counter-of-the-remote-cpu.patch