This is a note to let you know that I've just added the patch titled

cpufreq: schedutil: Reset cached_raw_freq when not in sync with next_freq

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: cpufreq-schedutil-reset-cached_raw_freq-when-not-in-sync-with-next_freq.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 07458f6a5171d97511dfbdf6ce549ed2ca0280c7 Mon Sep 17 00:00:00 2001

From: Viresh Kumar viresh.kumar@linaro.org Date: Wed, 8 Nov 2017 20:23:55 +0530 Subject: cpufreq: schedutil: Reset cached_raw_freq when not in sync with next_freq

From: Viresh Kumar viresh.kumar@linaro.org

commit 07458f6a5171d97511dfbdf6ce549ed2ca0280c7 upstream.

'cached_raw_freq' is used to get the next frequency quickly but should always be in sync with sg_policy->next_freq. There is a case where it is not and in such cases it should be reset to avoid switching to incorrect frequencies.

Consider this case for example:

- policy->cur is 1.2 GHz (Max) - New request comes for 780 MHz and we store that in cached_raw_freq. - Based on 780 MHz, we calculate the effective frequency as 800 MHz. - We then see the CPU wasn't idle recently and choose to keep the next freq as 1.2 GHz. - Now we have cached_raw_freq is 780 MHz and sg_policy->next_freq is 1.2 GHz. - Now if the utilization doesn't change in then next request, then the next target frequency will still be 780 MHz and it will match with cached_raw_freq. But we will choose 1.2 GHz instead of 800 MHz here.

Fixes: b7eaf1aab9f8 (cpufreq: schedutil: Avoid reducing frequency of busy CPUs prematurely) Signed-off-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

--- kernel/sched/cpufreq_schedutil.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -282,8 +282,12 @@ 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) { next_f = sg_policy->next_freq; + + /* Reset cached freq as next_freq has changed */ + sg_policy->cached_raw_freq = 0; + } } sugov_update_commit(sg_policy, time, next_f); }

Patches currently in stable-queue which might be from viresh.kumar@linaro.org are

queue-4.14/cpufreq-schedutil-reset-cached_raw_freq-when-not-in-sync-with-next_freq.patch