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().

Change-Id: I516963d8b0fda677e9d82290c0f3d4dc3cb6e477
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 dee7a12c6d1bb7b1d3623b7e24c35d6c894293d8..af0d2ef5b2ae5e1b9a003be087b47436b4277751 100644 (file)
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -368,7 +368,8 @@ 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 */