linux-kernel - [PATCH rcu 03/14] rcu: Eliminate rcu_implicit_dynticks

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Message-Id: <20210915233343.3906738-3-paulmck@kernel.org>
Date:   Wed, 15 Sep 2021 16:33:32 -0700
From:   "Paul E. McKenney" <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>
Subject: [PATCH rcu 03/14] rcu: Eliminate rcu_implicit_dynticks_qs() local variable rnhqp

The rcu_implicit_dynticks_qs() function's local variable rnhqp references
the ->rcu_need_heavy_qs field in the rcu_data structure referenced by
the function parameter rdp, with a rather odd method for computing
the pointer to this field.  This commit therefore simplifies things
and saves a few lines of code by replacing each instance of rnhqp with
&rdp->need_heavy_qs.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tree.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c89f5e6c4154..18d2f35d1450 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1219,7 +1219,6 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp)
 static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 {
 	unsigned long jtsq;
-	bool *rnhqp;
 	bool *ruqp;
 	struct rcu_node *rnp = rdp->mynode;
 
@@ -1286,12 +1285,11 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 	 */
 	jtsq = READ_ONCE(jiffies_to_sched_qs);
 	ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
-	rnhqp = per_cpu_ptr(&rcu_data.rcu_need_heavy_qs, rdp->cpu);
-	if (!READ_ONCE(*rnhqp) &&
+	if (!READ_ONCE(rdp->rcu_need_heavy_qs) &&
 	    (time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
 	     time_after(jiffies, rcu_state.jiffies_resched) ||
 	     rcu_state.cbovld)) {
-		WRITE_ONCE(*rnhqp, true);
+		WRITE_ONCE(rdp->rcu_need_heavy_qs, true);
 		/* Store rcu_need_heavy_qs before rcu_urgent_qs. */
 		smp_store_release(ruqp, true);
 	} else if (time_after(jiffies, rcu_state.gp_start + jtsq)) {
-- 
2.31.1.189.g2e36527f23