cpufreq: schedutil: Avoid using invalid next_freq

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
sugov_update_single().

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@linaro.org>
Cc: 4.12+ <stable@vger.kernel.org> # 4.12+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index d6717a3..81eb789 100644 (file)
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -282,7 +282,8 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
                 * 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 */