linux-kernel - [PATCH v3 12/14] net: amt: Remove redundant rcu_read_lock/unlock() in spin

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250916044735.2316171-13-dolinux.peng@gmail.com>
Date: Tue, 16 Sep 2025 12:47:33 +0800
From: pengdonglin <dolinux.peng@...il.com>
To: tj@...nel.org,
	tony.luck@...el.com,
	jani.nikula@...ux.intel.com,
	ap420073@...il.com,
	jv@...sburgh.net,
	freude@...ux.ibm.com,
	bcrl@...ck.org,
	trondmy@...nel.org,
	longman@...hat.com,
	kees@...nel.org
Cc: bigeasy@...utronix.de,
	hdanton@...a.com,
	paulmck@...nel.org,
	linux-kernel@...r.kernel.org,
	linux-rt-devel@...ts.linux.dev,
	linux-nfs@...r.kernel.org,
	linux-aio@...ck.org,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	netdev@...r.kernel.org,
	intel-gfx@...ts.freedesktop.org,
	linux-wireless@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	linux-s390@...r.kernel.org,
	cgroups@...r.kernel.org,
	pengdonglin <dolinux.peng@...il.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	pengdonglin <pengdonglin@...omi.com>
Subject: [PATCH v3 12/14] net: amt: Remove redundant rcu_read_lock/unlock() in spin_lock

From: pengdonglin <pengdonglin@...omi.com>

Since commit a8bb74acd8efe ("rcu: Consolidate RCU-sched update-side function definitions")
there is no difference between rcu_read_lock(), rcu_read_lock_bh() and
rcu_read_lock_sched() in terms of RCU read section and the relevant grace
period. That means that spin_lock(), which implies rcu_read_lock_sched(),
also implies rcu_read_lock().

There is no need no explicitly start a RCU read section if one has already
been started implicitly by spin_lock().

Simplify the code and remove the inner rcu_read_lock() invocation.

Cc: Taehee Yoo <ap420073@...il.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: pengdonglin <pengdonglin@...omi.com>
Signed-off-by: pengdonglin <dolinux.peng@...il.com>
---
 drivers/net/amt.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/drivers/net/amt.c b/drivers/net/amt.c
index ed86537b2f61..aaed9fbc7526 100644
--- a/drivers/net/amt.c
+++ b/drivers/net/amt.c
@@ -295,7 +295,6 @@ static void amt_source_work(struct work_struct *work)
 
 	tunnel = gnode->tunnel_list;
 	spin_lock_bh(&tunnel->lock);
-	rcu_read_lock();
 	if (gnode->filter_mode == MCAST_INCLUDE) {
 		amt_destroy_source(snode);
 		if (!gnode->nr_sources)
@@ -306,7 +305,6 @@ static void amt_source_work(struct work_struct *work)
 		 */
 		snode->status = AMT_SOURCE_STATUS_D_FWD;
 	}
-	rcu_read_unlock();
 	spin_unlock_bh(&tunnel->lock);
 }
 
@@ -426,7 +424,6 @@ static void amt_group_work(struct work_struct *work)
 		goto out;
 	}
 
-	rcu_read_lock();
 	for (i = 0; i < buckets; i++) {
 		hlist_for_each_entry_safe(snode, t,
 					  &gnode->sources[i], node) {
@@ -443,7 +440,6 @@ static void amt_group_work(struct work_struct *work)
 		amt_del_group(amt, gnode);
 	else
 		gnode->filter_mode = MCAST_INCLUDE;
-	rcu_read_unlock();
 	spin_unlock_bh(&tunnel->lock);
 out:
 	dev_put(amt->dev);
@@ -1327,11 +1323,9 @@ static void amt_clear_groups(struct amt_tunnel_list *tunnel)
 	int i;
 
 	spin_lock_bh(&tunnel->lock);
-	rcu_read_lock();
 	for (i = 0; i < amt->hash_buckets; i++)
 		hlist_for_each_entry_safe(gnode, t, &tunnel->groups[i], node)
 			amt_del_group(amt, gnode);
-	rcu_read_unlock();
 	spin_unlock_bh(&tunnel->lock);
 }
 
@@ -1343,11 +1337,9 @@ static void amt_tunnel_expire(struct work_struct *work)
 	struct amt_dev *amt = tunnel->amt;
 
 	spin_lock_bh(&amt->lock);
-	rcu_read_lock();
 	list_del_rcu(&tunnel->list);
 	amt->nr_tunnels--;
 	amt_clear_groups(tunnel);
-	rcu_read_unlock();
 	spin_unlock_bh(&amt->lock);
 	kfree_rcu(tunnel, rcu);
 }
-- 
2.34.1