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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2018-05-23 11:47:45 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2018-05-24 10:21:18 +0200
commita61dec7447456858dfc88fe056017a91ab903ed0 (patch)
treecc296fea94a97c09349f4dbf057a61dd2b004f92 /kernel/sched
parent152db033d77589df9ff1b93c1b311d4cd2e93bd0 (diff)
cpufreq: schedutil: Avoid missing updates for one-CPU policies
Commit 152db033d775 (schedutil: Allow cpufreq requests to be made even when kthread kicked) made changes to prevent utilization updates from being discarded during processing a previous request, but it left a small window in which that still can happen in the one-CPU policy case. Namely, updates coming in after setting work_in_progress in sugov_update_commit() and clearing it in sugov_work() will still be dropped due to the work_in_progress check in sugov_update_single(). To close that window, rearrange the code so as to acquire the update lock around the deferred update branch in sugov_update_single() and drop the work_in_progress check from it. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Juri Lelli <juri.lelli@redhat.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/cpufreq_schedutil.c70
1 files changed, 47 insertions, 23 deletions
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 178946e36393..fd76497efeb1 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -100,25 +100,41 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
return delta_ns >= sg_policy->freq_update_delay_ns;
}
-static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
- unsigned int next_freq)
+static bool sugov_update_next_freq(struct sugov_policy *sg_policy, u64 time,
+ unsigned int next_freq)
{
- struct cpufreq_policy *policy = sg_policy->policy;
-
if (sg_policy->next_freq == next_freq)
- return;
+ return false;
sg_policy->next_freq = next_freq;
sg_policy->last_freq_update_time = time;
- if (policy->fast_switch_enabled) {
- next_freq = cpufreq_driver_fast_switch(policy, next_freq);
- if (!next_freq)
- return;
+ return true;
+}
+
+static void sugov_fast_switch(struct sugov_policy *sg_policy, u64 time,
+ unsigned int next_freq)
+{
+ struct cpufreq_policy *policy = sg_policy->policy;
+
+ if (!sugov_update_next_freq(sg_policy, time, next_freq))
+ return;
+
+ next_freq = cpufreq_driver_fast_switch(policy, next_freq);
+ if (!next_freq)
+ return;
- policy->cur = next_freq;
- trace_cpu_frequency(next_freq, smp_processor_id());
- } else if (!sg_policy->work_in_progress) {
+ policy->cur = next_freq;
+ trace_cpu_frequency(next_freq, smp_processor_id());
+}
+
+static void sugov_deferred_update(struct sugov_policy *sg_policy, u64 time,
+ unsigned int next_freq)
+{
+ if (!sugov_update_next_freq(sg_policy, time, next_freq))
+ return;
+
+ if (!sg_policy->work_in_progress) {
sg_policy->work_in_progress = true;
irq_work_queue(&sg_policy->irq_work);
}
@@ -363,13 +379,6 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
ignore_dl_rate_limit(sg_cpu, sg_policy);
- /*
- * For slow-switch systems, single policy requests can't run at the
- * moment if update is in progress, unless we acquire update_lock.
- */
- if (sg_policy->work_in_progress)
- return;
-
if (!sugov_should_update_freq(sg_policy, time))
return;
@@ -391,7 +400,18 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
sg_policy->cached_raw_freq = 0;
}
- sugov_update_commit(sg_policy, time, next_f);
+ /*
+ * This code runs under rq->lock for the target CPU, so it won't run
+ * concurrently on two different CPUs for the same target and it is not
+ * necessary to acquire the lock in the fast switch case.
+ */
+ if (sg_policy->policy->fast_switch_enabled) {
+ sugov_fast_switch(sg_policy, time, next_f);
+ } else {
+ raw_spin_lock(&sg_policy->update_lock);
+ sugov_deferred_update(sg_policy, time, next_f);
+ raw_spin_unlock(&sg_policy->update_lock);
+ }
}
static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
@@ -435,7 +455,11 @@ sugov_update_shared(struct update_util_data *hook, u64 time, unsigned int flags)
if (sugov_should_update_freq(sg_policy, time)) {
next_f = sugov_next_freq_shared(sg_cpu, time);
- sugov_update_commit(sg_policy, time, next_f);
+
+ if (sg_policy->policy->fast_switch_enabled)
+ sugov_fast_switch(sg_policy, time, next_f);
+ else
+ sugov_deferred_update(sg_policy, time, next_f);
}
raw_spin_unlock(&sg_policy->update_lock);
@@ -450,11 +474,11 @@ static void sugov_work(struct kthread_work *work)
/*
* Hold sg_policy->update_lock shortly to handle the case where:
* incase sg_policy->next_freq is read here, and then updated by
- * sugov_update_shared just before work_in_progress is set to false
+ * sugov_deferred_update() just before work_in_progress is set to false
* here, we may miss queueing the new update.
*
* Note: If a work was queued after the update_lock is released,
- * sugov_work will just be called again by kthread_work code; and the
+ * sugov_work() will just be called again by kthread_work code; and the
* request will be proceed before the sugov thread sleeps.
*/
raw_spin_lock_irqsave(&sg_policy->update_lock, flags);