[tip:core/rcu] sched: Replace synchronize_sched() with synchronize_rcu()

["tip-bot for Paul E. McKenney" <tipbot@xxxxxxxxx>]

Commit-ID:  b290ebcf7bc4638b38c413f192963f4b74e45b7b
Gitweb:     https://git.kernel.org/tip/b290ebcf7bc4638b38c413f192963f4b74e45b7b
Author:     Paul E. McKenney <paulmck@xxxxxxxxxxxxx>
AuthorDate: Tue, 6 Nov 2018 19:13:54 -0800
Committer:  Paul E. McKenney <paulmck@xxxxxxxxxxxxx>
CommitDate: Fri, 25 Jan 2019 15:28:22 -0800

sched: Replace synchronize_sched() with synchronize_rcu()

Now that synchronize_rcu() waits for preempt-disable regions of
code as well as RCU read-side critical sections, synchronize_sched()
can be replaced by synchronize_rcu(), in fact, synchronize_sched()
is now completely equivalent to synchronize_rcu().  This commit
therefore replaces synchronize_sched() with synchronize_rcu() so that
synchronize_sched() can eventually be removed entirely.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
 kernel/sched/cpufreq.c           | 4 ++--
 kernel/sched/cpufreq_schedutil.c | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/cpufreq.c b/kernel/sched/cpufreq.c
index 22bd8980f32f..835671f0f917 100644
--- a/kernel/sched/cpufreq.c
+++ b/kernel/sched/cpufreq.c
@@ -48,8 +48,8 @@ EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
  *
  * Clear the update_util_data pointer for the given CPU.
  *
- * Callers must use RCU-sched callbacks to free any memory that might be
- * accessed via the old update_util_data pointer or invoke synchronize_sched()
+ * Callers must use RCU callbacks to free any memory that might be
+ * accessed via the old update_util_data pointer or invoke synchronize_rcu()
  * right after this function to avoid use-after-free.
  */
 void cpufreq_remove_update_util_hook(int cpu)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 033ec7c45f13..2efe629425be 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -859,7 +859,7 @@ static void sugov_stop(struct cpufreq_policy *policy)
 	for_each_cpu(cpu, policy->cpus)
 		cpufreq_remove_update_util_hook(cpu);
 
-	synchronize_sched();
+	synchronize_rcu();
 
 	if (!policy->fast_switch_enabled) {
 		irq_work_sync(&sg_policy->irq_work);