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From: Scott Wood <swood@redhat.com>
Date: Wed, 11 Sep 2019 17:57:28 +0100
Subject: [PATCH] rcu: Use rcuc threads on PREEMPT_RT as we did
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.3-rt1.tar.xz
While switching to the reworked RCU-thread code, it has been forgotten
to enable the thread processing on -RT.
Besides restoring behavior that used to be default on RT, this avoids
a deadlock on scheduler locks.
Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/rcu/tree.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -100,8 +100,10 @@ struct rcu_state rcu_state = {
static bool dump_tree;
module_param(dump_tree, bool, 0444);
/* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */
-static bool use_softirq = 1;
+static bool use_softirq = !IS_ENABLED(CONFIG_PREEMPT_RT);
+#ifndef CONFIG_PREEMPT_RT
module_param(use_softirq, bool, 0444);
+#endif
/* Control rcu_node-tree auto-balancing at boot time. */
static bool rcu_fanout_exact;
module_param(rcu_fanout_exact, bool, 0444);
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