From patchwork Thu Jun 17 21:27:43 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: 12329575 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=-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=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 E4FD4C49361 for ; Thu, 17 Jun 2021 21:28:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CFA04613E2 for ; Thu, 17 Jun 2021 21:28:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233113AbhFQVaW (ORCPT ); Thu, 17 Jun 2021 17:30:22 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:26602 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233125AbhFQVaO (ORCPT ); Thu, 17 Jun 2021 17:30:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623965285; 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=dAdah8VGuQn72TJlVoq7ahYZ+lMNJR+3mmSVKWZMutE=; b=jT3oPPxpdUesieYuMOXbqqnft7SsufHlevpPhfFazFqeDEMQcv66Reg+ULQ0rC1jcxAtxv lx1HTwlp+h9l0XmVrRyPlsEPEG7EvPnDQMWK1HSKbTjvOmDt5wbdVIUSb2aJ3Xl22DbxRj u3qnsfdA3g5WOcv5+p784A/yGHljj2Q= 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-538-NmCxkeuEOeiehp8BAoV9nw-1; Thu, 17 Jun 2021 17:28:04 -0400 X-MC-Unique: NmCxkeuEOeiehp8BAoV9nw-1 Received: by mail-ed1-f69.google.com with SMTP id y18-20020a0564022712b029038ffac1995eso2399529edd.12 for ; Thu, 17 Jun 2021 14:28:04 -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=dAdah8VGuQn72TJlVoq7ahYZ+lMNJR+3mmSVKWZMutE=; b=eoyduCaQcQipGkO6vq+fh3tiPxRetiXLASJ6tGCSJPLXJ7GExDdtxgITolpmi/pyOy N+dECvB5RUInn9qwp/EjgCA8pWDz3JHRR6OTv68pQz1tKEqz3+5bcPDQBchZBtZDI3M8 2dYisVN5wQx1g7tdWlrWJMIgjiRlqXRnWz79wJKKXmCFpyQ8IcIKulcvdB2rl4jZcWWs XkULzXIV3W1bAEbFAgWksV8dTM+1XeLOGMrkiLyYSRHpFgfVZ8J5mZMWAgpOF1wpUOt0 L90X7a8U4OfW08gEwValIdb9IlYyOlrLZi6d6x8t3r24Fr+tFtp3kc23sbBo6I8OCe/R qAKQ== X-Gm-Message-State: AOAM530rrUeuDDa9501HD8oqQ43hpEDrWMMIB+5GiRy2gNeHWgXo9mV6 BDgkSn90dkBHryA98p0QFYEPOrnYPHQF1ozcdyCkgD8hoMFlFYvdi4C0n6+2JodRcX9982yELj7 hVSckFXI8DWdo X-Received: by 2002:a50:ff0a:: with SMTP id a10mr436470edu.273.1623965282741; Thu, 17 Jun 2021 14:28:02 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzAR7MBrW4DjSCrWUTnO3yJRhsZzoQfEPwCrPjITjLEgp/KVyK6TzDvfdi+b7OXK36PkMlVfA== X-Received: by 2002:a50:ff0a:: with SMTP id a10mr436435edu.273.1623965282380; Thu, 17 Jun 2021 14:28:02 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id mm25sm100204ejb.125.2021.06.17.14.27.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Jun 2021 14:27:59 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id BD795180734; Thu, 17 Jun 2021 23:27:54 +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?= , Simon Horman , oss-drivers@netronome.com Subject: [PATCH bpf-next v3 11/16] nfp: remove rcu_read_lock() around XDP program invocation Date: Thu, 17 Jun 2021 23:27:43 +0200 Message-Id: <20210617212748.32456-12-toke@redhat.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210617212748.32456-1-toke@redhat.com> References: <20210617212748.32456-1-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 nfp 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. While this is not actually an issue for the nfp driver because it doesn't support XDP_REDIRECT (and thus doesn't call xdp_do_flush()), the rcu_read_lock() is still unneeded. And 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: Simon Horman Cc: oss-drivers@netronome.com Reviewed-by: Simon Horman Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c index eeb30680b4dc..a3d59abed6ae 100644 --- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c @@ -1819,7 +1819,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) struct xdp_buff xdp; int idx; - rcu_read_lock(); xdp_prog = READ_ONCE(dp->xdp_prog); true_bufsz = xdp_prog ? PAGE_SIZE : dp->fl_bufsz; xdp_init_buff(&xdp, PAGE_SIZE - NFP_NET_RX_BUF_HEADROOM, @@ -1919,6 +1918,10 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) pkt_off - NFP_NET_RX_BUF_HEADROOM, pkt_len, true); + /* This code is invoked within a single NAPI poll cycle + * and thus under local_bh_disable(), which provides the + * needed RCU protection. + */ act = bpf_prog_run_xdp(xdp_prog, &xdp); pkt_len = xdp.data_end - xdp.data; @@ -2036,7 +2039,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) if (!nfp_net_xdp_complete(tx_ring)) pkts_polled = budget; } - rcu_read_unlock(); return pkts_polled; }