From patchwork Wed Jun 23 11:07:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= X-Patchwork-Id: 12339637 X-Patchwork-Delegate: bpf@iogearbox.net 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=-19.1 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=ham 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 7E6B6C48BE5 for ; Wed, 23 Jun 2021 11:14:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 68A366102A for ; Wed, 23 Jun 2021 11:14:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230124AbhFWLQR (ORCPT ); Wed, 23 Jun 2021 07:16:17 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:47193 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230302AbhFWLQE (ORCPT ); Wed, 23 Jun 2021 07:16:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624446827; 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=c8O4Yimc+TSjNewaWd3nzsqZvk1ap2sDHxPur5LQuO8=; b=aQ7zXUPViRfdZBC+NloimgYK1k7AMUjLdsGxcWKHMOIzBfSAsigHaYt+qDhDo00m74Q4Rv 8EblEsMhIKRfJLjFg3pUQ3E5mrEMCztLJGAQeHnvRf2SmfAX11NpvCeYDoYzoRlTc0n1mo RJa2Pvip5wL5l5EfWyVVqNdksSrTK2Y= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-38-j6LQDQG6NHysmPaWEi-RbQ-1; Wed, 23 Jun 2021 07:13:45 -0400 X-MC-Unique: j6LQDQG6NHysmPaWEi-RbQ-1 Received: by mail-ed1-f70.google.com with SMTP id t11-20020a056402524bb029038ffacf1cafso1118559edd.5 for ; Wed, 23 Jun 2021 04:13:45 -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=c8O4Yimc+TSjNewaWd3nzsqZvk1ap2sDHxPur5LQuO8=; b=RLhSiAjMNjUjbJbIhWfTD4oWLfCDqqWsygo11oTs/iXE63S+T/DKDfNgYRXoNlKYXS Sqqhk73T9y3/S/AeTyOLUea6CQAVigXO+Dy3AlZcK5VFU90uzqILWOSwrpcWmCrdpK05 Z84EIjRlgBhdtVg2GbjzdASIoiAISB3me2KHYOCdZ0a7X5mrhV8fkgiLoXGpZr1U00Of qQaxhIM+rfcYwWZVd6k/PCxxDH1WMvWIMHKcyKvWH2YaZVE6uKJuQtKcy2fhfh1s8UQI MmZoG3241fv1Djb2DZjvGxgnkl/VAJWHmRaOFkybk/zn37gC6P4m/69hbgoe4ypVpzOk by+w== X-Gm-Message-State: AOAM533r1qRrHbmRyINTcpkIu1Bk038vlTu0oj/1r2yEuPyyAfWyexSQ QZRtE1gNX3tEtMRVh9wZevE9+fYXf0uCrUuJt6Qc3rnBIRyDzlJf3+8xC7gNer6esL/PFT+F3ux TKSGPUBthFRzU X-Received: by 2002:a50:fb14:: with SMTP id d20mr3291893edq.187.1624446824538; Wed, 23 Jun 2021 04:13:44 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzsSY5GdO8QnMV3L9SPl1VreJbS+DP/2ecehYnp9BW+UbIigCzyGSGeiKpi3x7jyvffXawbww== X-Received: by 2002:a50:fb14:: with SMTP id d20mr3291871edq.187.1624446824347; Wed, 23 Jun 2021 04:13:44 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id q20sm7334738ejb.71.2021.06.23.04.13.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Jun 2021 04:13:43 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 5654518073D; Wed, 23 Jun 2021 13:07:28 +0200 (CEST) From: =?utf-8?q?Toke_H=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_H=C3=B8iland-J=C3=B8rgensen?= , Tariq Toukan Subject: [PATCH bpf-next v4 13/19] mlx4: remove rcu_read_lock() around XDP program invocation Date: Wed, 23 Jun 2021 13:07:21 +0200 Message-Id: <20210623110727.221922-14-toke@redhat.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210623110727.221922-1-toke@redhat.com> References: <20210623110727.221922-1-toke@redhat.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The mlx4 driver has 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. Also switch the RCU dereferences in the driver loop itself to the _bh variants. Cc: Tariq Toukan Reviewed-by: Tariq Toukan Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/mellanox/mlx4/en_rx.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c index e35e4d7ef4d1..3f08c14d0441 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c @@ -679,9 +679,7 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud ring = priv->rx_ring[cq_ring]; - /* Protect accesses to: ring->xdp_prog, priv->mac_hash list */ - rcu_read_lock(); - xdp_prog = rcu_dereference(ring->xdp_prog); + xdp_prog = rcu_dereference_bh(ring->xdp_prog); xdp_init_buff(&xdp, priv->frag_info[0].frag_stride, &ring->xdp_rxq); doorbell_pending = false; @@ -744,7 +742,7 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud /* Drop the packet, since HW loopback-ed it */ mac_hash = ethh->h_source[MLX4_EN_MAC_HASH_IDX]; bucket = &priv->mac_hash[mac_hash]; - hlist_for_each_entry_rcu(entry, bucket, hlist) { + hlist_for_each_entry_rcu_bh(entry, bucket, hlist) { if (ether_addr_equal_64bits(entry->mac, ethh->h_source)) goto next; @@ -899,8 +897,6 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud break; } - rcu_read_unlock(); - if (likely(polled)) { if (doorbell_pending) { priv->tx_cq[TX_XDP][cq_ring]->xdp_busy = true;