Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     rcu@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, kernel-team@meta.com,
        rostedt@goodmis.org,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        "Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH v2 rcu 05/16] rcu: Refactor code a bit in rcu_nocb_do_flush_bypass()
Date:   Mon, 21 Nov 2022 17:04:10 -0800
Message-Id: <20221122010421.3799681-5-paulmck@kernel.org>
In-Reply-To: <20221122010408.GA3799268@paulmck-ThinkPad-P17-Gen-1>
References: <20221122010408.GA3799268@paulmck-ThinkPad-P17-Gen-1>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: "Joel Fernandes (Google)" <joel@joelfernandes.org>

This consolidates the code a bit and makes it cleaner. Functionally it
is the same.

Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tree_nocb.h | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index d6e4c076b0515..213daf81c057f 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -327,10 +327,11 @@ static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
  *
  * Note that this function always returns true if rhp is NULL.
  */
-static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp_in,
 				     unsigned long j, bool lazy)
 {
 	struct rcu_cblist rcl;
+	struct rcu_head *rhp = rhp_in;
 
 	WARN_ON_ONCE(!rcu_rdp_is_offloaded(rdp));
 	rcu_lockdep_assert_cblist_protected(rdp);
@@ -345,16 +346,16 @@ static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
 
 	/*
 	 * If the new CB requested was a lazy one, queue it onto the main
-	 * ->cblist so we can take advantage of a sooner grade period.
+	 * ->cblist so that we can take advantage of the grace-period that will
+	 * happen regardless. But queue it onto the bypass list first so that
+	 * the lazy CB is ordered with the existing CBs in the bypass list.
 	 */
 	if (lazy && rhp) {
-		rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, NULL);
-		rcu_cblist_enqueue(&rcl, rhp);
-		WRITE_ONCE(rdp->lazy_len, 0);
-	} else {
-		rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
-		WRITE_ONCE(rdp->lazy_len, 0);
+		rcu_cblist_enqueue(&rdp->nocb_bypass, rhp);
+		rhp = NULL;
 	}
+	rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
+	WRITE_ONCE(rdp->lazy_len, 0);
 
 	rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl);
 	WRITE_ONCE(rdp->nocb_bypass_first, j);
-- 
2.31.1.189.g2e36527f23