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 2830BC49EA2 for ; Thu, 17 Jun 2021 21:37:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11C1961241 for ; Thu, 17 Jun 2021 21:37:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230361AbhFQVjj (ORCPT ); Thu, 17 Jun 2021 17:39:39 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:36336 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229683AbhFQVjf (ORCPT ); Thu, 17 Jun 2021 17:39:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623965846; 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=V+K4Rzii9x9DcPIEElTMZYJsTVD8g+UmhuIcex1BLcU=; b=iy0RQ42oSxyAWuNLaDe3zANnlZ1ty8ssmtHdf/4yPwKpfDqIeZpgtrri2V8A+GL93FKRN7 yCYhK3a3914EGO1eT/4X3M0ipNyrKnifNd0kBd7r2u2d6wYOP3HzMX/ahxRay7uOROEU/3 VSTCaf+HRTIY1FoxY6ZDrmKao22g714= 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-272-hAZh_o_pMamlFaoXON7GvA-1; Thu, 17 Jun 2021 17:37:25 -0400 X-MC-Unique: hAZh_o_pMamlFaoXON7GvA-1 Received: by mail-ed1-f70.google.com with SMTP id cb4-20020a0564020b64b02903947455afa5so599154edb.9 for ; Thu, 17 Jun 2021 14:37:25 -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=V+K4Rzii9x9DcPIEElTMZYJsTVD8g+UmhuIcex1BLcU=; b=b9ak4D0e62oEaTmxIzEJJilxsxsUSlXQWC0QttTpwk/W1IWTT9mpuPkxYSbs89QaK5 a0qTG5pChfwwY1qrBgqEa6wwet2iHA88CVrdBmtvldd/TKWpH0peyihKISeMH+aPbwzN vGPT+alXfXOjwHyw8DSvzwfMwNForcVzqoSn3qVetInKY97VSbwn3ex77Ss2CdEy7g/Z Rzuocfhah0q/SjS8fnZq2TRKFpDMDYZTVSNcrEYbrNbqnIZoBdMOZIYkbxWRF8Yx1/dv Oi0mDc1DLfVNVitCpwyN/vRmMP/Dj9wi2lbSLNJ7/2aqBVMgn8d/maroG583HdhFEcFi 2inA== X-Gm-Message-State: AOAM533QJ5DvQNOLR++ZE916na8KQmYs0M3w3qViRFIDGWm9oZFDEfOT cHj7SYdsFp3c2M/tcsWMy25sZBFN4RAx8AEJrfj8fsHKXCZSbacIf4Y52K/T+v8U0NuQz3H8DSD 07OsxnJ42/U26KQ5T X-Received: by 2002:a17:907:7b9d:: with SMTP id ne29mr7692193ejc.167.1623965844476; Thu, 17 Jun 2021 14:37:24 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyT3fEGEihEGarB3fpS2Al0EXij4hKluNygNZjVN8leQ1wAJxPYopgkOlxKigP3A1jBe4lPvA== X-Received: by 2002:a17:907:7b9d:: with SMTP id ne29mr7692177ejc.167.1623965844289; Thu, 17 Jun 2021 14:37:24 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id q9sm5018510edw.51.2021.06.17.14.37.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Jun 2021 14:37:22 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 9A79C18072F; Thu, 17 Jun 2021 23:27:54 +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?= , Sunil Goutham , linux-arm-kernel@lists.infradead.org Subject: [PATCH bpf-next v3 06/16] thunderx: remove rcu_read_lock() around XDP program invocation Date: Thu, 17 Jun 2021 23:27:38 +0200 Message-Id: <20210617212748.32456-7-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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The thunderx 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. Cc: Sunil Goutham Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/cavium/thunder/nicvf_main.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_main.c b/drivers/net/ethernet/cavium/thunder/nicvf_main.c index c33b4e837515..1d752815c69a 100644 --- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c +++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c @@ -555,9 +555,10 @@ static inline bool nicvf_xdp_rx(struct nicvf *nic, struct bpf_prog *prog, xdp_prepare_buff(&xdp, hard_start, data - hard_start, len, false); orig_data = xdp.data; - rcu_read_lock(); + /* This code is invoked within a single NAPI poll cycle and thus under + * local_bh_disable(), which provides the needed RCU protection. + */ action = bpf_prog_run_xdp(prog, &xdp); - rcu_read_unlock(); len = xdp.data_end - xdp.data; /* Check if XDP program has changed headers */ -- 2.32.0