[PATCH 4.16 54/72] cpufreq: schedutil: Avoid using invalid next_freq

From: Greg Kroah-Hartman
Date: Mon May 14 2018 - 03:00:09 EST

4.16-stable review patch. If anyone has any objections, please let me know.


From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

commit 97739501f207efe33145b918817f305b822987f8 upstream.

If the next_freq field of struct sugov_policy is set to UINT_MAX,
it shouldn't be used for updating the CPU frequency (this is a
special "invalid" value), but after commit b7eaf1aab9f8 (cpufreq:
schedutil: Avoid reducing frequency of busy CPUs prematurely) it
may be passed as the new frequency to sugov_update_commit() in

Fix that by adding an extra check for the special UINT_MAX value
of next_freq to sugov_update_single().

Fixes: b7eaf1aab9f8 (cpufreq: schedutil: Avoid reducing frequency of busy CPUs prematurely)
Reported-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Cc: 4.12+ <stable@xxxxxxxxxxxxxxx> # 4.12+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

kernel/sched/cpufreq_schedutil.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -290,7 +290,8 @@ static void sugov_update_single(struct u
* Do not reduce the frequency if the CPU has not been idle
* recently, as the reduction is likely to be premature then.
- if (busy && next_f < sg_policy->next_freq) {
+ if (busy && next_f < sg_policy->next_freq &&
+ sg_policy->next_freq != UINT_MAX) {
next_f = sg_policy->next_freq;

/* Reset cached freq as next_freq has changed */