linux-kernel - [tip: core/rcu] srcu: Remove superfluous sdp->srcu_lock

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Message-ID: <162506087428.395.11085466467426386302.tip-bot2@tip-bot2>
Date:   Wed, 30 Jun 2021 13:47:54 -0000
From:   "tip-bot2 for Frederic Weisbecker" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Josh Triplett <josh@...htriplett.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Uladzislau Rezki <urezki@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: core/rcu] srcu: Remove superfluous sdp->srcu_lock_count zero filling

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     94df76a1971d9c61eb2c67ae10cc294b68cbd03b
Gitweb:        https://git.kernel.org/tip/94df76a1971d9c61eb2c67ae10cc294b68cbd03b
Author:        Frederic Weisbecker <frederic@...nel.org>
AuthorDate:    Fri, 02 Apr 2021 01:47:03 +02:00
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Mon, 10 May 2021 16:03:34 -07:00

srcu: Remove superfluous sdp->srcu_lock_count zero filling

Because alloc_percpu() zeroes out the allocated memory, there is no need
to zero-fill newly allocated per-CPU memory.  This commit therefore removes
the loop zeroing the ->srcu_lock_count and ->srcu_unlock_count arrays
from init_srcu_struct_nodes().  This is the only use of that function's
is_static parameter, which this commit also removes.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Lai Jiangshan <jiangshanlai@...il.com>
Cc: Neeraj Upadhyay <neeraju@...eaurora.org>
Cc: Josh Triplett <josh@...htriplett.org>
Cc: Joel Fernandes <joel@...lfernandes.org>
Cc: Uladzislau Rezki <urezki@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/srcutree.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index e26547b..3414aff 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -80,7 +80,7 @@ do {									\
  * srcu_read_unlock() running against them.  So if the is_static parameter
  * is set, don't initialize ->srcu_lock_count[] and ->srcu_unlock_count[].
  */
-static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
+static void init_srcu_struct_nodes(struct srcu_struct *ssp)
 {
 	int cpu;
 	int i;
@@ -148,14 +148,6 @@ static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
 		timer_setup(&sdp->delay_work, srcu_delay_timer, 0);
 		sdp->ssp = ssp;
 		sdp->grpmask = 1 << (cpu - sdp->mynode->grplo);
-		if (is_static)
-			continue;
-
-		/* Dynamically allocated, better be no srcu_read_locks()! */
-		for (i = 0; i < ARRAY_SIZE(sdp->srcu_lock_count); i++) {
-			sdp->srcu_lock_count[i] = 0;
-			sdp->srcu_unlock_count[i] = 0;
-		}
 	}
 }
 
@@ -179,7 +171,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
 		ssp->sda = alloc_percpu(struct srcu_data);
 	if (!ssp->sda)
 		return -ENOMEM;
-	init_srcu_struct_nodes(ssp, is_static);
+	init_srcu_struct_nodes(ssp);
 	ssp->srcu_gp_seq_needed_exp = 0;
 	ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
 	smp_store_release(&ssp->srcu_gp_seq_needed, 0); /* Init done. */