From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC94F11C88 for ; Mon, 12 Jun 2023 10:41:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73790C433EF; Mon, 12 Jun 2023 10:41:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1686566461; bh=WNT4vcYyXMab3jtwc0MSonqEVv5QbK/cjKDw7Ij02Dw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=C0dTGaqiXocIqttnMPzsYwR0jQEMS+A3zCkyx5ro4daDhjwkVkFZRbgxmr90onMgz qlqEUo5F+XfuS6m2fjSH1SqDiTWwzurwVx2gvuYQOOOQl2acZoNB1G4UgJMSpXIeSO E7iwYxqr7OMd1LfRqXBd0Ou7DEdwDL1/1loLg+EA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , Simon Horman , Kuniyuki Iwashima , "David S. Miller" , Sasha Levin Subject: [PATCH 6.1 041/132] rfs: annotate lockless accesses to sk->sk_rxhash Date: Mon, 12 Jun 2023 12:26:15 +0200 Message-ID: <20230612101712.117327668@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230612101710.279705932@linuxfoundation.org> References: <20230612101710.279705932@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Eric Dumazet [ Upstream commit 1e5c647c3f6d4f8497dedcd226204e1880e0ffb3 ] Add READ_ONCE()/WRITE_ONCE() on accesses to sk->sk_rxhash. This also prevents a (smart ?) compiler to remove the condition in: if (sk->sk_rxhash != newval) sk->sk_rxhash = newval; We need the condition to avoid dirtying a shared cache line. Fixes: fec5e652e58f ("rfs: Receive Flow Steering") Signed-off-by: Eric Dumazet Reviewed-by: Simon Horman Reviewed-by: Kuniyuki Iwashima Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- include/net/sock.h | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index f11b98bd0244c..2f35b82a123f8 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1148,8 +1148,12 @@ static inline void sock_rps_record_flow(const struct sock *sk) * OR an additional socket flag * [1] : sk_state and sk_prot are in the same cache line. */ - if (sk->sk_state == TCP_ESTABLISHED) - sock_rps_record_flow_hash(sk->sk_rxhash); + if (sk->sk_state == TCP_ESTABLISHED) { + /* This READ_ONCE() is paired with the WRITE_ONCE() + * from sock_rps_save_rxhash() and sock_rps_reset_rxhash(). + */ + sock_rps_record_flow_hash(READ_ONCE(sk->sk_rxhash)); + } } #endif } @@ -1158,15 +1162,19 @@ static inline void sock_rps_save_rxhash(struct sock *sk, const struct sk_buff *skb) { #ifdef CONFIG_RPS - if (unlikely(sk->sk_rxhash != skb->hash)) - sk->sk_rxhash = skb->hash; + /* The following WRITE_ONCE() is paired with the READ_ONCE() + * here, and another one in sock_rps_record_flow(). + */ + if (unlikely(READ_ONCE(sk->sk_rxhash) != skb->hash)) + WRITE_ONCE(sk->sk_rxhash, skb->hash); #endif } static inline void sock_rps_reset_rxhash(struct sock *sk) { #ifdef CONFIG_RPS - sk->sk_rxhash = 0; + /* Paired with READ_ONCE() in sock_rps_record_flow() */ + WRITE_ONCE(sk->sk_rxhash, 0); #endif } -- 2.39.2