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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        "Paul E. McKenney" <paulmck@linux.ibm.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.2 227/313] rcu/tree: Fix SCHED_FIFO params
Date:   Thu,  3 Oct 2019 17:53:25 +0200
Message-Id: <20191003154555.383362319@linuxfoundation.org>
In-Reply-To: <20191003154533.590915454@linuxfoundation.org>
References: <20191003154533.590915454@linuxfoundation.org>
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From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit 130d9c331bc59a8733b47c58ef197a2b1fa3ed43 ]

A rather embarrasing mistake had us call sched_setscheduler() before
initializing the parameters passed to it.

Fixes: 1a763fd7c633 ("rcu/tree: Call setschedule() gp ktread to SCHED_FIFO outside of atomic region")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/rcu/tree.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 32ea75acba144..affa7aae758f3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3123,13 +3123,13 @@ static int __init rcu_spawn_gp_kthread(void)
 	t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name);
 	if (WARN_ONCE(IS_ERR(t), "%s: Could not start grace-period kthread, OOM is now expected behavior\n", __func__))
 		return 0;
-	if (kthread_prio)
+	if (kthread_prio) {
+		sp.sched_priority = kthread_prio;
 		sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
+	}
 	rnp = rcu_get_root();
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	rcu_state.gp_kthread = t;
-	if (kthread_prio)
-		sp.sched_priority = kthread_prio;
 	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	wake_up_process(t);
 	rcu_spawn_nocb_kthreads();
-- 
2.20.1