linux-kernel - [PATCH net 2/3] mptcp: remove unneeded lock when listing scheds

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Message-Id: <20241021-net-mptcp-sched-lock-v1-2-637759cf061c@kernel.org>
Date: Mon, 21 Oct 2024 12:25:27 +0200
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>, 
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 Gregory Detal <gregory.detal@...il.com>, Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, stable@...r.kernel.org
Subject: [PATCH net 2/3] mptcp: remove unneeded lock when listing scheds

mptcp_get_available_schedulers() needs to iterate over the schedulers'
list only to read the names: it doesn't modify anything there.

In this case, it is enough to hold the RCU read lock, no need to combine
this with the associated spin lock.

Fixes: 73c900aa3660 ("mptcp: add net.mptcp.available_schedulers")
Cc: stable@...r.kernel.org
Suggested-by: Paolo Abeni <pabeni@...hat.com>
Reviewed-by: Geliang Tang <geliang@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 net/mptcp/sched.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index 78ed508ebc1b8dd9f0e020cca1bdd86f24f0afeb..df7dbcfa3b71370cc4d7e4e4f16cc1e41a50dddf 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -60,7 +60,6 @@ void mptcp_get_available_schedulers(char *buf, size_t maxlen)
 	size_t offs = 0;

 	rcu_read_lock();
-	spin_lock(&mptcp_sched_list_lock);
 	list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
 		offs += snprintf(buf + offs, maxlen - offs,
 				 "%s%s",
@@ -69,7 +68,6 @@ void mptcp_get_available_schedulers(char *buf, size_t maxlen)
 		if (WARN_ON_ONCE(offs >= maxlen))
 			break;
 	}
-	spin_unlock(&mptcp_sched_list_lock);
 	rcu_read_unlock();
 }

-- 
2.45.2