[2.6.20.17 review 57/58] CPUFREQ: ondemand: add a check to avoid negative load calculation

Willy Tarreau
2007-08-22T09:09:52Z

[-- Attachment #1: 0057-CPUFREQ-ondemand-add-a-check-to-avoid-negative-loa.patch --]
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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>
---
drivers/cpufreq/cpufreq_ondemand.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 3bfaeb5..1d11d13 100644
--- 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) {
--
1.5.2.5

--