Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   "Joel Fernandes (Google)" <joel@joelfernandes.org>
To:     linux-kernel@vger.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Jonathan Corbet <corbet@lwn.net>,
        Josh Triplett <josh@joshtriplett.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        linux-doc@vger.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        neeraju@codeaurora.org, "Paul E. McKenney" <paulmck@kernel.org>,
        peterz@infradead.org, Randy Dunlap <rdunlap@infradead.org>,
        rcu@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
        tglx@linutronix.de, vineethrp@gmail.com
Subject: [PATCH v4 2/5] rcu/tree: Clarify comments about FQS loop reporting quiescent states
Date:   Fri,  7 Aug 2020 13:07:19 -0400
Message-Id: <20200807170722.2897328-3-joel@joelfernandes.org>
In-Reply-To: <20200807170722.2897328-1-joel@joelfernandes.org>
References: <20200807170722.2897328-1-joel@joelfernandes.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

At least since v4.19, the FQS loop no longer reports quiescent states
for offline CPUs unless it is an emergency.

This commit therefore fixes the comment in rcu_gp_init() to match the
current code.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 kernel/rcu/tree.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a49fa3b60faa..2fb66cdbfa25 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1701,9 +1701,11 @@ static bool rcu_gp_init(void)
 
 	/*
 	 * Apply per-leaf buffered online and offline operations to the
-	 * rcu_node tree.  Note that this new grace period need not wait
-	 * for subsequent online CPUs, and that quiescent-state forcing
-	 * will handle subsequent offline CPUs.
+	 * rcu_node tree. Note that this new grace period need not wait for
+	 * subsequent online CPUs, and that RCU hooks in the CPU offlining
+	 * path, when combined with checks in this function, will handle CPUs
+	 * that are currently going offline or that go offline later. Refer to
+	 * RCU's Requirements documentation about hotplug requirements as well.
 	 */
 	rcu_state.gp_state = RCU_GP_ONOFF;
 	rcu_for_each_leaf_node(rnp) {
-- 
2.28.0.236.gb10cc79966-goog