NOHZ: Properly feed cpufreq ondemand governor

A call from irq_exit() may occasionally pause the timing
info for cpufreq ondemand governor. This results in the
cpufreq ondemand governor to fail to calculate the 
system load properly. Thus, relocate the checks for this
particular case to keep the governor always functional.

Signed-off-by: Eero Nurkkala <ext-eero.nurkkala@nokia.com>
Reported-by: Tero Kristo <tero.kristo@nokia.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 9 insertions, 3 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d3f1ef4d5cb..a3562ce5498 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -222,6 +222,15 @@ void tick_nohz_stop_sched_tick(int inidle)
 
         cpu = smp_processor_id();
         ts = &per_cpu(tick_cpu_sched, cpu);
+
+        /*
+         * Call to tick_nohz_start_idle stops the last_update_time from being
+         * updated. Thus, it must not be called in the event we are called from
+         * irq_exit() with the prior state different than idle.
+         */
+        if (!inidle && !ts->inidle)
+                goto end;
+
         now = tick_nohz_start_idle(ts);
 
         /*
@@ -239,9 +248,6 @@ void tick_nohz_stop_sched_tick(int inidle)
         if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
                 goto end;
 
-        if (!inidle && !ts->inidle)
-                goto end;
-
         ts->inidle = 1;
 
         if (need_resched())