From f5bd71472372edd09e275283f6c5bc42b66514eb Mon Sep 17 00:00:00 2001
Message-Id: <f5bd71472372edd09e275283f6c5bc42b66514eb.1594742967.git.zanussi@kernel.org>
In-Reply-To: <832f7d97d6b989a5b4860dd2dbec58ad6ad5ab81.1594742966.git.zanussi@kernel.org>
References: <832f7d97d6b989a5b4860dd2dbec58ad6ad5ab81.1594742966.git.zanussi@kernel.org>
From: Scott Wood <swood@redhat.com>
Date: Sat, 27 Jul 2019 00:56:34 -0500
Subject: [PATCH 301/329] sched: migrate disable: Protect cpus_ptr with lock
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.132-rt59.tar.xz

[ Upstream commit 27ee52a891ed2c7e2e2c8332ccae0de7c2674b09 ]

Various places assume that cpus_ptr is protected by rq/pi locks,
so don't change it before grabbing those locks.

Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/sched/core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 03b3ff43d39f..c03ad7ae5f96 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7243,9 +7243,8 @@ migrate_disable_update_cpus_allowed(struct task_struct *p)
 	struct rq *rq;
 	struct rq_flags rf;
 
-	p->cpus_ptr = cpumask_of(smp_processor_id());
-
 	rq = task_rq_lock(p, &rf);
+	p->cpus_ptr = cpumask_of(smp_processor_id());
 	update_nr_migratory(p, -1);
 	p->nr_cpus_allowed = 1;
 	task_rq_unlock(rq, p, &rf);
@@ -7257,9 +7256,8 @@ migrate_enable_update_cpus_allowed(struct task_struct *p)
 	struct rq *rq;
 	struct rq_flags rf;
 
-	p->cpus_ptr = &p->cpus_mask;
-
 	rq = task_rq_lock(p, &rf);
+	p->cpus_ptr = &p->cpus_mask;
 	p->nr_cpus_allowed = cpumask_weight(&p->cpus_mask);
 	update_nr_migratory(p, 1);
 	task_rq_unlock(rq, p, &rf);
-- 
2.17.1

