From patchwork Tue Jun 15 14:54:48 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: 460894 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 560CCC48BDF for ; Tue, 15 Jun 2021 14:55:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41B8F61584 for ; Tue, 15 Jun 2021 14:55:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231627AbhFOO51 (ORCPT ); Tue, 15 Jun 2021 10:57:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42767 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231486AbhFOO5Q (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=rY2VfBWw6NJ0/51nfkfzpQbN8Kg/IiRrFOK+qEg2pA4=; b=fJGgf0fmYBJ/yu0/oXh4QqvwosS682jmUbvzFLAYILs+04z/ZSo+vIWOx3rQRiOnxmQiHj CVePXs21ZwsBkDr+QwU1sRz+RlvDxV8gv0kGFi65fwRtybe/n/qr34v4Mwz7yX8WadHDHb GtryHSWYT6U9TJ8tzaEaDSsBnZqB6lQ= Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-526-49Q8_mNDMYCUBCAY2mZF5A-1; Tue, 15 Jun 2021 10:55:09 -0400 X-MC-Unique: 49Q8_mNDMYCUBCAY2mZF5A-1 Received: by mail-ed1-f69.google.com with SMTP id s25-20020aa7c5590000b0290392e051b029so17410110edr.11 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=rY2VfBWw6NJ0/51nfkfzpQbN8Kg/IiRrFOK+qEg2pA4=; b=nw+cegES9CuYA4wIjVZpreTY0+6IavH6unmtR10qHJfOpHwdNsrtZLHIgBBmYR6+gF rzoFLAJ3cyAE1ntACGYIf720SqBAnFqvjIgA0hQ8fMHm+zO15RNPthFIe6EDRW8YPLzr EZCQE8/7Is5kMNe31KjxKx3nRexWMISR2Wi4XDoNs1AVA2QWi5g1vruMlaN1iqXUzYgB 4LuTSjVkEVRUJlugSUpX07y1FtCRhTUwNyWG04ZmCqzfxN3KL6+c2Ee7Cqn5Mm7uj5+v l8ot0fPh1NLN/1CD+tqHBKXVPChz8hDlu/GfCkO/s54BGWpN0od7hBt3dAxnQI1nGAUY FKaQ== X-Gm-Message-State: AOAM530FhDK5On1m8WAOwz3Jusng9fUlnsySHO0HqQt9YfKDidQFMmtc rjq+8UhhIF4V12Q0x4nTIL1NDi2y0A1+R55895HQi/J4cc8pqHUpwE0itJCyHLRb9gJd7PNCY04 GxsW37cSV0MDCOSwD X-Received: by 2002:a17:906:dfd1:: with SMTP id jt17mr21253047ejc.486.1623768908510; Tue, 15 Jun 2021 07:55:08 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxUc77COnG0WIdO1tAjDrhLpnKaKhnq5sFxyuzHGltCcw1hnUBlYA0poEo+mX++Ywz8VM61xg== X-Received: by 2002:a17:906:dfd1:: with SMTP id jt17mr21253020ejc.486.1623768908212; 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 cf26sm10281358ejb.38.2021.06.15.07.55.04 (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 E6CA1180732; Tue, 15 Jun 2021 16:54:58 +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-?= =?utf-8?q?J=C3=B8rgensen?= , Thomas Petazzoni , Marcin Wojtas , Russell King Subject: [PATCH bpf-next v2 09/16] marvell: remove rcu_read_lock() around XDP program invocation Date: Tue, 15 Jun 2021 16:54:48 +0200 Message-Id: <20210615145455.564037-10-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 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The mvneta and mvpp2 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: Thomas Petazzoni Cc: Marcin Wojtas Cc: Russell King Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/marvell/mvneta.c | 6 ++++-- drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 8 ++++---- 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c index 7d5cd9bc6c99..c2e9cbebc8d1 100644 --- a/drivers/net/ethernet/marvell/mvneta.c +++ b/drivers/net/ethernet/marvell/mvneta.c @@ -2370,7 +2370,6 @@ static int mvneta_rx_swbm(struct napi_struct *napi, /* Get number of received packets */ rx_todo = mvneta_rxq_busy_desc_num_get(pp, rxq); - rcu_read_lock(); xdp_prog = READ_ONCE(pp->xdp_prog); /* Fairness NAPI loop */ @@ -2421,6 +2420,10 @@ static int mvneta_rx_swbm(struct napi_struct *napi, goto next; } + /* This code is invoked within a single NAPI poll cycle and thus + * under local_bh_disable(), which provides the needed RCU + * protection. + */ if (xdp_prog && mvneta_run_xdp(pp, rxq, xdp_prog, &xdp_buf, frame_sz, &ps)) goto next; @@ -2448,7 +2451,6 @@ static int mvneta_rx_swbm(struct napi_struct *napi, xdp_buf.data_hard_start = NULL; sinfo.nr_frags = 0; } - rcu_read_unlock(); if (xdp_buf.data_hard_start) mvneta_xdp_put_buff(pp, rxq, &xdp_buf, &sinfo, -1); diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c index b2259bf1d299..658db1720826 100644 --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c @@ -3852,8 +3852,6 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi, int rx_done = 0; u32 xdp_ret = 0; - rcu_read_lock(); - xdp_prog = READ_ONCE(port->xdp_prog); /* Get number of received packets and clamp the to-do */ @@ -3925,6 +3923,10 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi, MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM, rx_bytes, false); + /* This code is invoked within a single NAPI poll cycle + * and thus under local_bh_disable(), which provides the + * needed RCU protection. + */ ret = mvpp2_run_xdp(port, xdp_prog, &xdp, pp, &ps); if (ret) { @@ -3988,8 +3990,6 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi, mvpp2_bm_pool_put(port, pool, dma_addr, phys_addr); } - rcu_read_unlock(); - if (xdp_ret & MVPP2_XDP_REDIR) xdp_do_flush_map();