[PATCH] CPUFREQ: ondemand: add a check to avoid negative load calculation

Due to rounding and inexact jiffy accounting, idle_ticks can sometimes
be higher than total_ticks. Make sure those cases are handled as
zero load case.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 3bfaeb5776247e5f7bfe5ea94f10caa90b16a5d3..1d11d13fb2889e77ea1a1d30df921af243bffe3a 100644 (file)
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -334,7 +334,7 @@ static struct attribute_group dbs_attr_group = {
 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 {
        unsigned int idle_ticks, total_ticks;
-       unsigned int load;
+       unsigned int load = 0;
        cputime64_t cur_jiffies;
 
        struct cpufreq_policy *policy;
@@ -380,7 +380,8 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
                if (tmp_idle_ticks < idle_ticks)
                        idle_ticks = tmp_idle_ticks;
        }
-       load = (100 * (total_ticks - idle_ticks)) / total_ticks;
+       if (likely(total_ticks > idle_ticks))
+               load = (100 * (total_ticks - idle_ticks)) / total_ticks;
 
        /* Check for frequency increase */
        if (load > dbs_tuners_ins.up_threshold) {