linux-kernel - [PATCH 4.14 46/62] cpufreq: schedutil: Avoid using invalid next

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Date:   Mon, 14 May 2018 08:49:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH 4.14 46/62] cpufreq: schedutil: Avoid using invalid next_freq

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

------------------

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

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

---
 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
@@ -282,7 +282,8 @@ 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 */