linux-kernel - [PATCH v2 rcu 02/13] srcu: Introduce srcu_gp_is

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Message-Id: <20241011173931.2050422-2-paulmck@kernel.org>
Date: Fri, 11 Oct 2024 10:39:20 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: frederic@...nel.org,
	rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	kernel-team@...a.com,
	rostedt@...dmis.org,
	"Paul E. McKenney" <paulmck@...nel.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
Subject: [PATCH v2 rcu 02/13] srcu: Introduce srcu_gp_is_expedited() helper function

Even though the open-coded expressions usually fit on one line, this
commit replaces them with a call to a new srcu_gp_is_expedited()
helper function in order to improve readability.

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>
---
 kernel/rcu/srcutree.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 9ff4ded609ba5..e29c6cbffbcb0 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -418,6 +418,16 @@ static void check_init_srcu_struct(struct srcu_struct *ssp)
 	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
 }
 
+/*
+ * Is the current or any upcoming grace period to be expedited?
+ */
+static bool srcu_gp_is_expedited(struct srcu_struct *ssp)
+{
+	struct srcu_usage *sup = ssp->srcu_sup;
+
+	return ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_needed_exp));
+}
+
 /*
  * Returns approximate total of the readers' ->srcu_lock_count[] values
  * for the rank of per-CPU counters specified by idx.
@@ -622,7 +632,7 @@ static unsigned long srcu_get_delay(struct srcu_struct *ssp)
 	unsigned long jbase = SRCU_INTERVAL;
 	struct srcu_usage *sup = ssp->srcu_sup;
 
-	if (ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_needed_exp)))
+	if (srcu_gp_is_expedited(ssp))
 		jbase = 0;
 	if (rcu_seq_state(READ_ONCE(sup->srcu_gp_seq))) {
 		j = jiffies - 1;
@@ -867,7 +877,7 @@ static void srcu_gp_end(struct srcu_struct *ssp)
 	spin_lock_irq_rcu_node(sup);
 	idx = rcu_seq_state(sup->srcu_gp_seq);
 	WARN_ON_ONCE(idx != SRCU_STATE_SCAN2);
-	if (ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_needed_exp)))
+	if (srcu_gp_is_expedited(ssp))
 		cbdelay = 0;
 
 	WRITE_ONCE(sup->srcu_last_gp_end, ktime_get_mono_fast_ns());
-- 
2.40.1