linux-kernel - [PATCH tip/core/rcu 20/21] rcu/nocb: Code-style nits in callback-offloading toggling

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Date:   Tue,  5 Jan 2021 20:48:52 -0800
From:   paulmck@...nel.org
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: [PATCH tip/core/rcu 20/21] rcu/nocb: Code-style nits in callback-offloading toggling

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

This commit addresses a few code-style nits in callback-offloading
toggling, including one that predates this toggling.

Cc: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/rcu_segcblist.h | 19 ++++++-------------
 kernel/rcu/tree_plugin.h   | 10 +++++-----
 2 files changed, 11 insertions(+), 18 deletions(-)

diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index 3110602..9a19328 100644
--- a/kernel/rcu/rcu_segcblist.h
+++ b/kernel/rcu/rcu_segcblist.h
@@ -80,17 +80,12 @@ static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
 	return rcu_segcblist_test_flags(rsclp, SEGCBLIST_ENABLED);
 }
 
-/* Is the specified rcu_segcblist offloaded?  */
+/* Is the specified rcu_segcblist offloaded, or is SEGCBLIST_SOFTIRQ_ONLY set? */
 static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
 {
-	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU)) {
-		/*
-		 * Complete de-offloading happens only when SEGCBLIST_SOFTIRQ_ONLY
-		 * is set.
-		 */
-		if (!rcu_segcblist_test_flags(rsclp, SEGCBLIST_SOFTIRQ_ONLY))
-			return true;
-	}
+	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
+	    !rcu_segcblist_test_flags(rsclp, SEGCBLIST_SOFTIRQ_ONLY))
+		return true;
 
 	return false;
 }
@@ -99,10 +94,8 @@ static inline bool rcu_segcblist_completely_offloaded(struct rcu_segcblist *rscl
 {
 	int flags = SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP | SEGCBLIST_OFFLOADED;
 
-	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU)) {
-		if ((rsclp->flags & flags) == flags)
-			return true;
-	}
+	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) && (rsclp->flags & flags) == flags)
+		return true;
 
 	return false;
 }
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index bc63a6b..0ad278d 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2160,11 +2160,11 @@ static inline bool nocb_cb_wait_cond(struct rcu_data *rdp)
 static void nocb_cb_wait(struct rcu_data *rdp)
 {
 	struct rcu_segcblist *cblist = &rdp->cblist;
-	struct rcu_node *rnp = rdp->mynode;
-	bool needwake_state = false;
-	bool needwake_gp = false;
 	unsigned long cur_gp_seq;
 	unsigned long flags;
+	bool needwake_state = false;
+	bool needwake_gp = false;
+	struct rcu_node *rnp = rdp->mynode;
 
 	local_irq_save(flags);
 	rcu_momentary_dyntick_idle();
@@ -2217,8 +2217,8 @@ static void nocb_cb_wait(struct rcu_data *rdp)
 		swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
 						    nocb_cb_wait_cond(rdp));
 
-		/* ^^^ Ensure CB invocation follows _sleep test. */
-		if (smp_load_acquire(&rdp->nocb_cb_sleep)) {
+		// VVV Ensure CB invocation follows _sleep test.
+		if (smp_load_acquire(&rdp->nocb_cb_sleep)) { // ^^^
 			WARN_ON(signal_pending(current));
 			trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty"));
 		}
-- 
2.9.5