linux-kernel - [PATCH 15/16] refscale: Add srcu_read_lock

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Message-ID: <20241112145159.23032-16-frederic@kernel.org>
Date: Tue, 12 Nov 2024 15:51:58 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: "Paul E. McKenney" <paulmck@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Neeraj Upadhyay <neeraj.upadhyay@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	rcu <rcu@...r.kernel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	bpf@...r.kernel.org,
	Neeraj Upadhyay <Neeraj.Upadhyay@....com>,
	Frederic Weisbecker <frederic@...nel.org>
Subject: [PATCH 15/16] refscale: Add srcu_read_lock_lite() support using "srcu-lite"

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

This commit creates a new srcu-lite option for the refscale.scale_type
module parameter that selects srcu_read_lock_lite() and
srcu_read_unlock_lite().

[ paulmck: Apply Dan Carpenter feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: <bpf@...r.kernel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
 kernel/rcu/refscale.c | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 0db9db73f57f..338e7c5ac44a 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -212,6 +212,36 @@ static const struct ref_scale_ops srcu_ops = {
 	.name		= "srcu"
 };
 
+static void srcu_lite_ref_scale_read_section(const int nloops)
+{
+	int i;
+	int idx;
+
+	for (i = nloops; i >= 0; i--) {
+		idx = srcu_read_lock_lite(srcu_ctlp);
+		srcu_read_unlock_lite(srcu_ctlp, idx);
+	}
+}
+
+static void srcu_lite_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
+{
+	int i;
+	int idx;
+
+	for (i = nloops; i >= 0; i--) {
+		idx = srcu_read_lock_lite(srcu_ctlp);
+		un_delay(udl, ndl);
+		srcu_read_unlock_lite(srcu_ctlp, idx);
+	}
+}
+
+static const struct ref_scale_ops srcu_lite_ops = {
+	.init		= rcu_sync_scale_init,
+	.readsection	= srcu_lite_ref_scale_read_section,
+	.delaysection	= srcu_lite_ref_scale_delay_section,
+	.name		= "srcu-lite"
+};
+
 #ifdef CONFIG_TASKS_RCU
 
 // Definitions for RCU Tasks ref scale testing: Empty read markers.
@@ -1082,9 +1112,10 @@ ref_scale_init(void)
 	long i;
 	int firsterr = 0;
 	static const struct ref_scale_ops *scale_ops[] = {
-		&rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops,
-		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops, &jiffies_ops,
-		&typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,
+		&rcu_ops, &srcu_ops, &srcu_lite_ops, RCU_TRACE_OPS RCU_TASKS_OPS
+		&refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops,
+		&clock_ops, &jiffies_ops, &typesafe_ref_ops, &typesafe_lock_ops,
+		&typesafe_seqlock_ops,
 	};
 
 	if (!torture_init_begin(scale_type, verbose))
-- 
2.46.0