linux-kernel - [PATCH rcu 2/5] rcu/nocb: Move rcu_nocb_is_setup to rcu

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Date:   Mon, 18 Apr 2022 15:56:39 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        rostedt@...dmis.org, Frederic Weisbecker <frederic@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Uladzislau Rezki <uladzislau.rezki@...y.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boqun Feng <boqun.feng@...il.com>
Subject: [PATCH rcu 2/5] rcu/nocb: Move rcu_nocb_is_setup to rcu_state

From: Frederic Weisbecker <frederic@...nel.org>

This commit moves the RCU nocb initialization witness within rcu_state
to consolidate RCU's global state.

Reported-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Neeraj Upadhyay <quic_neeraju@...cinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@...y.com>
Cc: Joel Fernandes <joel@...lfernandes.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tree.h      |  1 +
 kernel/rcu/tree_nocb.h | 13 +++++--------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 926673ebe355..f6a3d54585c9 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -364,6 +364,7 @@ struct rcu_state {
 	arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
 						/* Synchronize offline with */
 						/*  GP pre-initialization. */
+	int nocb_is_setup;			/* nocb is setup from boot */
 };
 
 /* Values for rcu_state structure's gp_flags field. */
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 02e1d05a11fc..3c00240833d6 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -60,9 +60,6 @@ static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
  * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
  * If the list is invalid, a warning is emitted and all CPUs are offloaded.
  */
-
-static bool rcu_nocb_is_setup;
-
 static int __init rcu_nocb_setup(char *str)
 {
 	alloc_bootmem_cpumask_var(&rcu_nocb_mask);
@@ -72,7 +69,7 @@ static int __init rcu_nocb_setup(char *str)
 			cpumask_setall(rcu_nocb_mask);
 		}
 	}
-	rcu_nocb_is_setup = true;
+	rcu_state.nocb_is_setup = true;
 	return 1;
 }
 __setup("rcu_nocbs", rcu_nocb_setup);
@@ -1172,10 +1169,10 @@ void __init rcu_init_nohz(void)
 				return;
 			}
 		}
-		rcu_nocb_is_setup = true;
+		rcu_state.nocb_is_setup = true;
 	}
 
-	if (!rcu_nocb_is_setup)
+	if (!rcu_state.nocb_is_setup)
 		return;
 
 #if defined(CONFIG_NO_HZ_FULL)
@@ -1233,7 +1230,7 @@ static void rcu_spawn_cpu_nocb_kthread(int cpu)
 	struct task_struct *t;
 	struct sched_param sp;
 
-	if (!rcu_scheduler_fully_active || !rcu_nocb_is_setup)
+	if (!rcu_scheduler_fully_active || !rcu_state.nocb_is_setup)
 		return;
 
 	/* If there already is an rcuo kthread, then nothing to do. */
@@ -1279,7 +1276,7 @@ static void __init rcu_spawn_nocb_kthreads(void)
 {
 	int cpu;
 
-	if (rcu_nocb_is_setup) {
+	if (rcu_state.nocb_is_setup) {
 		for_each_online_cpu(cpu)
 			rcu_spawn_cpu_nocb_kthread(cpu);
 	}
-- 
2.31.1.189.g2e36527f23