[PATCH] rcu-tasks: Update comments in call_rcu_tasks_generic()

[Zqiang]

Currently, the comments: "We can't create the thread unless interrupts
are enabled." from 'commit 4929c913bda5 ("rcu: Make call_rcu_tasks()
tolerate first call with irqs disabled")', now the kthread creation
has been move to core_initcall() time from 'commit c63eb17ff06d
("rcu: Create call_rcu_tasks() kthread at boot time")', and use the
irq_work does deferred wakeup. this commit therefore update comments
in call_rcu_tasks_generic().

Signed-off-by: Zqiang <qiang.zhang@xxxxxxxxx>
---
 kernel/rcu/tasks.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index a2ca79d1dd6a..089a0d5a5cc9 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -395,7 +395,11 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func,
 		raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
 	}
 	rcu_read_unlock();
-	/* We can't create the thread unless interrupts are enabled. */
+	// We can't create the kthread with interrupts disabled,
+	// or a spinlock might be held, the kthread creation has
+	// been move to core_initcall() time.
+	// at the same time, use the irq_work does deferred wakeup
+	// to avoid potential lockdep splat.
 	if (needwake && READ_ONCE(rtp->kthread_ptr))
 		irq_work_queue(&rtpcp->rtp_irq_work);
 }
-- 
2.17.1