From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5881C49361 for ; Tue, 15 Jun 2021 14:55:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A21626141D for ; Tue, 15 Jun 2021 14:55:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231652AbhFOO53 (ORCPT ); Tue, 15 Jun 2021 10:57:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:51806 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231481AbhFOO5Q (ORCPT ); Tue, 15 Jun 2021 10:57:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623768911; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=L2w+HImdAUwFSlY1hYWtFiNbCUvYk0lFrUyqVDU6cjY=; b=USSwCmitKWSUzEoS5gxxhVrzooq4NHeVp4lAVKzTEpKKM6k8+b5WueA6AnhvuE9nVLew91 TeubrFaBelfnptwCRypBxa6dwhhcCn+HRhCuIANLvnMJdWvvH1QGTsJq0MdxagcRl3YmGL zGyvxXmytPg75eoZFkiWdU35az1yuBo= Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-217-Z-rMrZtmMFaMa9MbEH-XSQ-1; Tue, 15 Jun 2021 10:55:10 -0400 X-MC-Unique: Z-rMrZtmMFaMa9MbEH-XSQ-1 Received: by mail-ej1-f72.google.com with SMTP id z6-20020a17090665c6b02903700252d1ccso4630815ejn.10 for ; Tue, 15 Jun 2021 07:55:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=L2w+HImdAUwFSlY1hYWtFiNbCUvYk0lFrUyqVDU6cjY=; b=THa3m0u6mpWIkEMXE1PQcAnf1vsMMB0RFulirUiK6x+NRBoDo9SIPP3McVDTS82X+O KT5kxmbAzZaK7wFiK3UVEJYFEabvfqh39+njn2MFSigH6H9eaKNL/adysocGpSqwfaJF DKdllzMFGyLw6dnaqYbMFOFiPgl4Ql3gDdDVQl84MfGO6alww4ETTe3fzSH45uhMgKuL 2Dmaa8s+WR0HuW3cWCvKPh/80E7UQ95fz++hk0U8cWiG8VzKoxf8EeyVndF/oIb5sTy+ TMaRq9U/AdJXsJsbETQ3HotMLwFIG3CntIGaJbkhCaQgQ0wK00dEA4VhuHVtcf0LMfdV gNag== X-Gm-Message-State: AOAM532uETZc2pW2okdMnLhnQ/nD9k9c0+rgDc1HucJaka+NXn5B3quu TIy4+4G9TuX1Zm65leYEETtH4vqyfRUYjFsITgFuuBqT9W4n/C+GR7G3h4KH29YErtLcuntI6Rm dkiqjHnTpB/IxAtzn X-Received: by 2002:a17:906:994d:: with SMTP id zm13mr20665186ejb.427.1623768908858; Tue, 15 Jun 2021 07:55:08 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzrD5ykD8QuStI7yTpQynBYBmFa7phE5jHXSY1xZ0QyxDdvR2QIW94oCmW587hJOv+QJQ4J5Q== X-Received: by 2002:a17:906:994d:: with SMTP id zm13mr20665154ejb.427.1623768908470; Tue, 15 Jun 2021 07:55:08 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id t5sm10267312eje.29.2021.06.15.07.55.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Jun 2021 07:55:06 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id DB6F6180730; Tue, 15 Jun 2021 16:54:58 +0200 (CEST) From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= To: bpf@vger.kernel.org, netdev@vger.kernel.org Cc: Martin KaFai Lau , Hangbin Liu , Jesper Dangaard Brouer , Magnus Karlsson , "Paul E . McKenney" , Jakub Kicinski , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , Madalin Bucur , Ioana Ciornei , Ioana Radulescu Subject: [PATCH bpf-next v2 07/16] freescale: remove rcu_read_lock() around XDP program invocation Date: Tue, 15 Jun 2021 16:54:46 +0200 Message-Id: <20210615145455.564037-8-toke@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210615145455.564037-1-toke@redhat.com> References: <20210615145455.564037-1-toke@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The dpaa and dpaa2 drivers have rcu_read_lock()/rcu_read_unlock() pairs around XDP program invocations. However, the actual lifetime of the objects referred by the XDP program invocation is longer, all the way through to the call to xdp_do_flush(), making the scope of the rcu_read_lock() too small. This turns out to be harmless because it all happens in a single NAPI poll cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock() misleading. Rather than extend the scope of the rcu_read_lock(), just get rid of it entirely. With the addition of RCU annotations to the XDP_REDIRECT map types that take bh execution into account, lockdep even understands this to be safe, so there's really no reason to keep it around. Cc: Madalin Bucur Cc: Ioana Ciornei Cc: Ioana Radulescu Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 11 ++++------- drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 6 +++--- 2 files changed, 7 insertions(+), 10 deletions(-) diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c index 177c020bf34a..98fdcbde687a 100644 --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c @@ -2558,13 +2558,9 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr, u32 xdp_act; int err; - rcu_read_lock(); - xdp_prog = READ_ONCE(priv->xdp_prog); - if (!xdp_prog) { - rcu_read_unlock(); + if (!xdp_prog) return XDP_PASS; - } xdp_init_buff(&xdp, DPAA_BP_RAW_SIZE - DPAA_TX_PRIV_DATA_SIZE, &dpaa_fq->xdp_rxq); @@ -2585,6 +2581,9 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr, } #endif + /* This code is invoked within a single NAPI poll cycle and thus under + * local_bh_disable(), which provides the needed RCU protection. + */ xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp); /* Update the length and the offset of the FD */ @@ -2638,8 +2637,6 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr, break; } - rcu_read_unlock(); - return xdp_act; } diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c index 8433aa730c42..964d85c9e37d 100644 --- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c +++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c @@ -352,8 +352,6 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv, u32 xdp_act = XDP_PASS; int err, offset; - rcu_read_lock(); - xdp_prog = READ_ONCE(ch->xdp.prog); if (!xdp_prog) goto out; @@ -363,6 +361,9 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv, xdp_prepare_buff(&xdp, vaddr + offset, XDP_PACKET_HEADROOM, dpaa2_fd_get_len(fd), false); + /* This code is invoked within a single NAPI poll cycle and thus under + * local_bh_disable(), which provides the needed RCU protection. + */ xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp); /* xdp.data pointer may have changed */ @@ -414,7 +415,6 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv, ch->xdp.res |= xdp_act; out: - rcu_read_unlock(); return xdp_act; } -- 2.31.1