[PATCH] sched/fair: Remove sd->nohz_idle

[Vincent Guittot]

sd->nohz_idle is used to call once inc|dec of &sd->shared->nr_busy_cpus
when entering or leaving idle state but the call to
set_cpu_sd_state_idle|busy is already protected by rq->nohz_tick_stopped
being already set or clear.

Remove the useless sd->nohz_idle field which equals !rq->nohz_tick_stopped.

Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 include/linux/sched/topology.h |  1 -
 kernel/sched/fair.c            | 16 ++++------------
 2 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index a1e1032426dc..59e498006072 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -82,7 +82,6 @@ struct sched_domain {
 	unsigned int cache_nice_tries;	/* Leave cache hot tasks for # tries */
 	unsigned int imb_numa_nr;	/* Nr running tasks that allows a NUMA imbalance */
 
-	int nohz_idle;			/* NOHZ IDLE status */
 	int flags;			/* See SD_* */
 	int level;
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d57c02e82f3a..888875e91073 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12818,12 +12818,8 @@ static void set_cpu_sd_state_busy(int cpu)
 	rcu_read_lock();
 	sd = rcu_dereference_all(per_cpu(sd_llc, cpu));
 
-	if (!sd || !sd->nohz_idle)
-		goto unlock;
-	sd->nohz_idle = 0;
-
-	atomic_inc(&sd->shared->nr_busy_cpus);
-unlock:
+	if (likely(sd))
+		atomic_inc(&sd->shared->nr_busy_cpus);
 	rcu_read_unlock();
 }
 
@@ -12847,12 +12843,8 @@ static void set_cpu_sd_state_idle(int cpu)
 	rcu_read_lock();
 	sd = rcu_dereference_all(per_cpu(sd_llc, cpu));
 
-	if (!sd || sd->nohz_idle)
-		goto unlock;
-	sd->nohz_idle = 1;
-
-	atomic_dec(&sd->shared->nr_busy_cpus);
-unlock:
+	if (likely(sd))
+		atomic_dec(&sd->shared->nr_busy_cpus);
 	rcu_read_unlock();
 }
 
-- 
2.43.0