linux-kernel - [PATCH 17/22] sched/core: fix opencoded cpumask_any

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Date:   Tue, 10 May 2022 08:47:45 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        David Laight <David.Laight@...LAB.COM>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joe Perches <joe@...ches.com>,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Nicholas Piggin <npiggin@...il.com>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Peter Zijlstra <peterz@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Matti Vaittinen <Matti.Vaittinen@...rohmeurope.com>,
        linux-kernel@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>, Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Mel Gorman <mgorman@...e.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Valentin Schneider <vschneid@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 17/22] sched/core: fix opencoded cpumask_any_but()

sched_core_cpu_starting() and sched_core_cpu_deactivate() implement
opencoded cpumask_any_but(). Fix it.

CC: Ben Segall <bsegall@...gle.com>
CC: Daniel Bristot de Oliveira <bristot@...hat.com>
CC: Dietmar Eggemann <dietmar.eggemann@....com>
CC: Ingo Molnar <mingo@...hat.com>
CC: Juri Lelli <juri.lelli@...hat.com>
CC: Mel Gorman <mgorman@...e.de>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: Valentin Schneider <vschneid@...hat.com>
CC: Vincent Guittot <vincent.guittot@...aro.org>
CC: linux-kernel@...r.kernel.org
Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 kernel/sched/core.c | 33 +++++++++++++--------------------
 1 file changed, 13 insertions(+), 20 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f5ebc392493d..9700001948d0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6125,7 +6125,7 @@ static void queue_core_balance(struct rq *rq)
 static void sched_core_cpu_starting(unsigned int cpu)
 {
 	const struct cpumask *smt_mask = cpu_smt_mask(cpu);
-	struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
+	struct rq *rq = cpu_rq(cpu), *core_rq;
 	unsigned long flags;
 	int t;
 
@@ -6138,19 +6138,16 @@ static void sched_core_cpu_starting(unsigned int cpu)
 		goto unlock;
 
 	/* find the leader */
-	for_each_cpu(t, smt_mask) {
-		if (t == cpu)
-			continue;
-		rq = cpu_rq(t);
-		if (rq->core == rq) {
-			core_rq = rq;
-			break;
-		}
-	}
+	t = cpumask_any_but(smt_mask, cpu);
+	if (t >= nr_cpu_ids)
+		goto unlock;
 
-	if (WARN_ON_ONCE(!core_rq)) /* whoopsie */
+	rq = cpu_rq(t);
+	if (WARN_ON_ONCE(rq->core != rq)) /* whoopsie */
 		goto unlock;
 
+	core_rq = rq;
+
 	/* install and validate core_rq */
 	for_each_cpu(t, smt_mask) {
 		rq = cpu_rq(t);
@@ -6168,7 +6165,7 @@ static void sched_core_cpu_starting(unsigned int cpu)
 static void sched_core_cpu_deactivate(unsigned int cpu)
 {
 	const struct cpumask *smt_mask = cpu_smt_mask(cpu);
-	struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
+	struct rq *rq = cpu_rq(cpu), *core_rq;
 	unsigned long flags;
 	int t;
 
@@ -6185,16 +6182,12 @@ static void sched_core_cpu_deactivate(unsigned int cpu)
 		goto unlock;
 
 	/* find a new leader */
-	for_each_cpu(t, smt_mask) {
-		if (t == cpu)
-			continue;
-		core_rq = cpu_rq(t);
-		break;
-	}
-
-	if (WARN_ON_ONCE(!core_rq)) /* impossible */
+	t = cpumask_any_but(smt_mask, cpu);
+	if (t >= nr_cpu_ids)
 		goto unlock;
 
+	core_rq = cpu_rq(t);
+
 	/* copy the shared state to the new leader */
 	core_rq->core_task_seq             = rq->core_task_seq;
 	core_rq->core_pick_seq             = rq->core_pick_seq;
-- 
2.32.0