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Message-ID: <20231027095842.GA30868@redhat.com>
Date: Fri, 27 Oct 2023 11:58:42 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: David Howells <dhowells@...hat.com>,
Marc Dionne <marc.dionne@...istor.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Chuck Lever <chuck.lever@...cle.com>, linux-afs@...ts.infradead.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] rxrpc_find_service_conn_rcu: use read_seqbegin() rather than
read_seqbegin_or_lock()
read_seqbegin_or_lock() makes no sense unless you make "seq" odd
after the lockless access failed. See thread_group_cputime() as
an example, note that it does nextseq = 1 for the 2nd round.
So this code can use read_seqbegin() without changing the current
behaviour.
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
net/rxrpc/conn_service.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/net/rxrpc/conn_service.c b/net/rxrpc/conn_service.c
index 89ac05a711a4..bfafe58681d9 100644
--- a/net/rxrpc/conn_service.c
+++ b/net/rxrpc/conn_service.c
@@ -25,7 +25,7 @@ struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
struct rxrpc_conn_proto k;
struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
struct rb_node *p;
- unsigned int seq = 0;
+ unsigned int seq;
k.epoch = sp->hdr.epoch;
k.cid = sp->hdr.cid & RXRPC_CIDMASK;
@@ -35,7 +35,7 @@ struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
* under just the RCU read lock, so we have to check for
* changes.
*/
- read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
+ seq = read_seqbegin(&peer->service_conn_lock);
p = rcu_dereference_raw(peer->service_conns.rb_node);
while (p) {
@@ -49,9 +49,8 @@ struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
break;
conn = NULL;
}
- } while (need_seqretry(&peer->service_conn_lock, seq));
+ } while (read_seqretry(&peer->service_conn_lock, seq));
- done_seqretry(&peer->service_conn_lock, seq);
_leave(" = %d", conn ? conn->debug_id : -1);
return conn;
}
--
2.25.1.362.g51ebf55
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