linux-kernel - [PATCH] sched: Use non-atomic cpumask_{set,clear}

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Date:   Tue, 12 Feb 2019 14:57:01 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH] sched: Use non-atomic cpumask_{set,clear}_cpu()

The cpumasks updated here are not subject to concurrency and using
atomic bitops for them is pointless and expensive. Use the non-atomic
variants instead.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 kernel/sched/fair.c      | 6 +++---
 kernel/sched/isolation.c | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8abd1c271499..8213ff6e365d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6097,7 +6097,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
 		bool idle = true;
 
 		for_each_cpu(cpu, cpu_smt_mask(core)) {
-			cpumask_clear_cpu(cpu, cpus);
+			__cpumask_clear_cpu(cpu, cpus);
 			if (!available_idle_cpu(cpu))
 				idle = false;
 		}
@@ -9105,7 +9105,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
 
 			/* Prevent to re-select dst_cpu via env's CPUs */
-			cpumask_clear_cpu(env.dst_cpu, env.cpus);
+			__cpumask_clear_cpu(env.dst_cpu, env.cpus);
 
 			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
 			env.dst_cpu	 = env.new_dst_cpu;
@@ -9132,7 +9132,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 
 		/* All tasks on this runqueue were pinned by CPU affinity */
 		if (unlikely(env.flags & LBF_ALL_PINNED)) {
-			cpumask_clear_cpu(cpu_of(busiest), cpus);
+			__cpumask_clear_cpu(cpu_of(busiest), cpus);
 			/*
 			 * Attempting to continue load balancing at the current
 			 * sched_domain level only makes sense if there are
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 81faddba9e20..b02d148e7672 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -80,7 +80,7 @@ static int __init housekeeping_setup(char *str, enum hk_flags flags)
 		cpumask_andnot(housekeeping_mask,
 			       cpu_possible_mask, non_housekeeping_mask);
 		if (cpumask_empty(housekeeping_mask))
-			cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
+			__cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
 	} else {
 		cpumask_var_t tmp;
 
-- 
2.20.1.321.g9e740568ce00