[PATCH 49/70] cpufreq: interactive: avoid underflow on active time calculation

[BÃlint Czobor]

From: Minsung Kim <ms925.kim@xxxxxxxxxxx>

Check for idle time delta less than elapsed time delta, avoid
underflow computing active time.

Change-Id: I3e4c6ef1ad794eec49ed379c0c50fa727fd6ad28
Signed-off-by: Minsung Kim <ms925.kim@xxxxxxxxxxx>
Signed-off-by: BÃlint Czobor <czoborbalint@xxxxxxxxx>
---
 drivers/cpufreq/cpufreq_interactive.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c
index b4d12b2..7303f50 100644
--- a/drivers/cpufreq/cpufreq_interactive.c
+++ b/drivers/cpufreq/cpufreq_interactive.c
@@ -325,7 +325,12 @@ static u64 update_load(int cpu)
 	now_idle = get_cpu_idle_time(cpu, &now);
 	delta_idle = (unsigned int)(now_idle - pcpu->time_in_idle);
 	delta_time = (unsigned int)(now - pcpu->time_in_idle_timestamp);
-	active_time = delta_time - delta_idle;
+
+	if (delta_time <= delta_idle)
+		active_time = 0;
+	else
+		active_time = delta_time - delta_idle;
+
 	pcpu->cputime_speedadj += active_time * pcpu->policy->cur;
 
 	pcpu->time_in_idle = now_idle;
-- 
1.7.9.5

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