cpuidle: Menu governor fix wrong usage of measured_us

There is a bug in menu governor where we have
		if (data->elapsed_us < data->elapsed_us + measured_us)

with measured_us already having elapsed_us added in tickless case here
	unsigned int measured_us =
		cpuidle_get_last_residency(dev) + data->elapsed_us;

Also, it should be last_residency, not measured_us, that need to be used to
do comparing and distinguish between expected & non-expected events.

Refactor menu_reflect() to fix these two problems.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Wei Gang <gang.wei@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

1 files changed, 19 insertions, 12 deletions

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index b8f3e21530b..8d7cf3f3145 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -74,9 +74,9 @@ static void menu_reflect(struct cpuidle_device *dev)
 {
         struct menu_device *data = &__get_cpu_var(menu_devices);
         int last_idx = data->last_state_idx;
-        unsigned int measured_us =
-                cpuidle_get_last_residency(dev) + data->elapsed_us;
+        unsigned int last_idle_us = cpuidle_get_last_residency(dev);
         struct cpuidle_state *target = &dev->states[last_idx];
+        unsigned int measured_us;
 
         /*
          * Ugh, this idle state doesn't support residency measurements, so we
@@ -84,20 +84,27 @@ static void menu_reflect(struct cpuidle_device *dev)
          * for one full standard timer tick.  However, be aware that this
          * could potentially result in a suboptimal state transition.
          */
-        if (!(target->flags & CPUIDLE_FLAG_TIME_VALID))
-                measured_us = USEC_PER_SEC / HZ;
+        if (unlikely(!(target->flags & CPUIDLE_FLAG_TIME_VALID)))
+                last_idle_us = USEC_PER_SEC / HZ;
 
-        /* Predict time remaining until next break event */
-        if (measured_us + BREAK_FUZZ < data->expected_us - target->exit_latency) {
-                data->predicted_us = max(measured_us, data->last_measured_us);
+        /*
+         * measured_us and elapsed_us are the cumulative idle time, since the
+         * last time we were woken out of idle by an interrupt.
+         */
+        if (data->elapsed_us <= data->elapsed_us + last_idle_us)
+                measured_us = data->elapsed_us + last_idle_us;
+        else
+                measured_us = -1;
+
+        /* Predict time until next break event */
+        data->predicted_us = max(measured_us, data->last_measured_us);
+
+        if (last_idle_us + BREAK_FUZZ <
+            data->expected_us - target->exit_latency) {
                 data->last_measured_us = measured_us;
                 data->elapsed_us = 0;
         } else {
-                if (data->elapsed_us < data->elapsed_us + measured_us)
-                        data->elapsed_us = measured_us;
-                else
-                        data->elapsed_us = -1;
-                data->predicted_us = max(measured_us, data->last_measured_us);
+                data->elapsed_us = measured_us;
         }
 }