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cpufreq: schedutil: Don't skip freq update when limits change

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commit 600f5badb78c316146d062cfd7af4a2cfb655baa upstream.

To avoid reducing the frequency of a CPU prematurely, we skip reducing
the frequency if the CPU had been busy recently.

This should not be done when the limits of the policy are changed, for
example due to thermal throttling. We should always get the frequency
within the new limits as soon as possible.

Trying to fix this by using only one flag, i.e. need_freq_update, can
lead to a race condition where the flag gets cleared without forcing us
to change the frequency at least once. And so this patch introduces
another flag to avoid that race condition.

Fixes: ecd288429126 ("cpufreq: schedutil: Don't set next_freq to UINT_MAX")
Change-Id: Ifd3e127d5e7b33842a2f94a90e25541484df37fc
Cc: v4.18+ <stable@vger.kernel.org> # v4.18+
Reported-by: Doug Smythies <dsmythies@telus.net>
Tested-by: Doug Smythies <dsmythies@telus.net>
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>
Signed-off-by: Richard Raya <rdxzv.dev@gmail.com>
This commit is contained in:
Viresh Kumar 2019-08-07 12:36:01 +05:30 committed by Richard Raya
parent 897d9e3a9e
commit 16232faa0f
1 changed files with 9 additions and 3 deletions
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12
kernel/sched/cpufreq_schedutil.c
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@ -50,6 +50,7 @@ struct sugov_policy {
struct task_struct *thread;
bool work_in_progress;
bool limits_changed;
bool need_freq_update;
};
@ -106,7 +107,9 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
!cpufreq_can_do_remote_dvfs(sg_policy->policy))
return false;
if (unlikely(sg_policy->need_freq_update)) {
if (unlikely(sg_policy->limits_changed)) {
sg_policy->limits_changed = false;
sg_policy->need_freq_update = true;
return true;
}
/* No need to recalculate next freq for min_rate_limit_us
@ -354,7 +357,9 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
if (!sugov_should_update_freq(sg_policy, time))
return;
busy = use_pelt() && sugov_cpu_is_busy(sg_cpu);
/* Limits may have changed, don't skip frequency update */
busy = use_pelt() && !sg_policy->need_freq_update &&
sugov_cpu_is_busy(sg_cpu);
if (flags & SCHED_CPUFREQ_DL) {
/* clear cache when it's bypassed */
@ -833,6 +838,7 @@ static int sugov_start(struct cpufreq_policy *policy)
sg_policy->last_freq_update_time = 0;
sg_policy->next_freq = 0;
sg_policy->work_in_progress = false;
sg_policy->limits_changed = false;
sg_policy->need_freq_update = false;
sg_policy->cached_raw_freq = 0;
@ -888,7 +894,7 @@ static void sugov_limits(struct cpufreq_policy *policy)
raw_spin_unlock_irqrestore(&sg_policy->update_lock, flags);
}
sg_policy->need_freq_update = true;
sg_policy->limits_changed = true;
}
static struct cpufreq_governor schedutil_gov = {