[PATCH 03/10] rcu: Make locking explicit in do_nocb_deferred_wakeup_common()

Frederic Weisbecker
2020-05-13T16:47:29Z

It can either be called inline (locally or CPU hotplug locked) when
rdp->nocb_defer_wakeup is pending or from the nocb timer. In both cases
the rdp is offlined and we want to take the nocb lock.

Clarify the locking rules and expectations.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
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>
---
kernel/rcu/tree_plugin.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 1d22b16c03e0..1dd3fdd675a1 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2142,9 +2142,9 @@ static void do_nocb_deferred_wakeup_common(struct rcu_data *rdp)
unsigned long flags;
int ndw;

- rcu_nocb_lock_irqsave(rdp, flags);
+ raw_spin_lock_irqsave(&rdp->nocb_lock, flags);
if (!rcu_nocb_need_deferred_wakeup(rdp)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
+ raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
return;
}
ndw = READ_ONCE(rdp->nocb_defer_wakeup);
--
2.25.0