[PATCH 6/6] rcu: Add comment to rcu_do_batch() identifying rcuoc code path

From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
To: linux-kernel@vger.kernel.org,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Neeraj Upadhyay <quic_neeraju@quicinc.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Joel Fernandes <joel@joelfernandes.org>
Cc: rcu@vger.kernel.org
Subject: [PATCH 6/6] rcu: Add comment to rcu_do_batch() identifying rcuoc code path
Date: Wed, 15 Mar 2023 19:38:51 +0000	[thread overview]
Message-ID: <20230315193851.8598-6-joel@joelfernandes.org> (raw)
In-Reply-To: <20230315193851.8598-1-joel@joelfernandes.org>

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit adds a comment to help explain why the "else" clause of the
in_serving_softirq() "if" statement does not need to enforce a time limit.
The reason is that this "else" clause handles rcuoc kthreads that do not
block handlers for other softirq vectors.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 kernel/rcu/tree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8e880c09ab59..06cc6a6ad819 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2131,6 +2131,8 @@ static void rcu_do_batch(struct rcu_data *rdp)
 				break;
 			}
 		} else {
+			// In rcuoc context, so no worries about depriving
+			// other softirq vectors of CPU cycles.
 			local_bh_enable();
 			lockdep_assert_irqs_enabled();
 			cond_resched_tasks_rcu_qs();
-- 
2.40.0.rc1.284.g88254d51c5-goog

