netdev - [PATCH net-next 2/6] ipv6: fib6_new

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Message-ID: <20221115091101.2234482-3-edumazet@google.com>
Date:   Tue, 15 Nov 2022 09:10:57 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>,
        David Ahern <dsahern@...nel.org>
Subject: [PATCH net-next 2/6] ipv6: fib6_new_sernum() optimization

Adopt atomic_try_cmpxchg() which is slightly more efficient.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: David Ahern <dsahern@...nel.org>
---
 net/ipv6/ip6_fib.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 413f66781e50de62d6b20042d84798e7da59165a..2438da5ff6da810d9f612fc66df4d28510f50f10 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -91,13 +91,12 @@ static void fib6_walker_unlink(struct net *net, struct fib6_walker *w)
 
 static int fib6_new_sernum(struct net *net)
 {
-	int new, old;
+	int new, old = atomic_read(&net->ipv6.fib6_sernum);
 
 	do {
-		old = atomic_read(&net->ipv6.fib6_sernum);
 		new = old < INT_MAX ? old + 1 : 1;
-	} while (atomic_cmpxchg(&net->ipv6.fib6_sernum,
-				old, new) != old);
+	} while (!atomic_try_cmpxchg(&net->ipv6.fib6_sernum, &old, new));
+
 	return new;
 }
 
-- 
2.38.1.431.g37b22c650d-goog