[PATCH 2/3] rcu: simplify the prototype of rcu_boost_kthread_setaffinity()

[Pingfan Liu <kernelfans@gmail.com>]

Previously, the outgoing parameter is needed by rcutree_affinity_setting() since
when rcutree_offline_cpu() is called, ->qsmaskinitnext contains the outgoing cpu.

Now, it is not necessary and the prototype of
rcu_boost_kthread_setaffinity() can be simplified.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: rcu@vger.kernel.org
---
 kernel/rcu/tree.c        |  6 +++---
 kernel/rcu/tree_plugin.h | 12 +++++-------
 2 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b90f6487fd45..f0535bd210b6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -145,7 +145,7 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
 			      unsigned long gps, unsigned long flags);
 static void rcu_init_new_rnp(struct rcu_node *rnp_leaf);
 static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf);
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp);
 static void invoke_rcu_core(void);
 static void rcu_report_exp_rdp(struct rcu_data *rdp);
 static void sync_sched_exp_online_cleanup(int cpu);
@@ -2170,7 +2170,7 @@ int rcutree_dead_cpu(unsigned int cpu)
 
 	WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1);
 	/* Adjust any no-longer-needed kthreads. */
-	rcu_boost_kthread_setaffinity(rnp, -1);
+	rcu_boost_kthread_setaffinity(rnp);
 	// Stop-machine done, so allow nohz_full to disable tick.
 	tick_dep_clear(TICK_DEP_BIT_RCU);
 	return 0;
@@ -3996,7 +3996,7 @@ int rcutree_online_cpu(unsigned int cpu)
 	if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
 		return 0; /* Too early in boot for scheduler work. */
 	sync_sched_exp_online_cleanup(cpu);
-	rcu_boost_kthread_setaffinity(rdp->mynode, -1);
+	rcu_boost_kthread_setaffinity(rdp->mynode);
 
 	// Stop-machine done, so allow nohz_full to disable tick.
 	tick_dep_clear(TICK_DEP_BIT_RCU);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 438ecae6bd7e..0bf6de185af5 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1217,11 +1217,10 @@ static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
  * served by the rcu_node in question.  The CPU hotplug lock is still
  * held, so the value of rnp->qsmaskinit will be stable.
  *
- * We don't include outgoingcpu in the affinity set, use -1 if there is
- * no outgoing CPU.  If there are no CPUs left in the affinity set,
- * this function allows the kthread to execute on any CPU.
+ * If there are no CPUs left in the affinity set, this function allows the
+ * kthread to execute on any CPU.
  */
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp)
 {
 	struct task_struct *t = rnp->boost_kthread_task;
 	unsigned long mask = rcu_rnp_online_cpus(rnp);
@@ -1234,8 +1233,7 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
 		return;
 	mutex_lock(&rnp->boost_kthread_mutex);
 	for_each_leaf_node_possible_cpu(rnp, cpu)
-		if ((mask & leaf_node_cpu_bit(rnp, cpu)) &&
-		    cpu != outgoingcpu)
+		if ((mask & leaf_node_cpu_bit(rnp, cpu)))
 			cpumask_set_cpu(cpu, cm);
 	cpumask_and(cm, cm, housekeeping_cpumask(HK_TYPE_RCU));
 	if (cpumask_empty(cm))
@@ -1261,7 +1259,7 @@ static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
 {
 }
 
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp)
 {
 }
 
-- 
2.31.1