From patchwork Thu Jun 17 21:27:48 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: 12329569 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 8BC3DC48BE5 for ; Thu, 17 Jun 2021 21:28:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6ED26613E2 for ; Thu, 17 Jun 2021 21:28:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233159AbhFQVaQ (ORCPT ); Thu, 17 Jun 2021 17:30:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:26210 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233083AbhFQVaM (ORCPT ); Thu, 17 Jun 2021 17:30:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623965284; 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=URoBjUEpro9U64xROBMZeKvvFlHbDEw9khuYvYfphMY=; b=OCfiPrSpkjdBK1L4Ao3s928FwmsIZVCdW9AO5EhBIKy6GmqNMUSm8PeyjqWZEI2hAUAzOZ MR2gtbONZjk9txF7CYtNuZ3MwK3WALyMtnsiGGo/N8peUTiXcurGK98FifEnxoEGYQEhbB YdecEcgyJZnlV92uxvTk1ZNV9xPSvr4= Received: from mail-ej1-f69.google.com (mail-ej1-f69.google.com [209.85.218.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-454-VezdYB3-PPutLWdtEI7bow-1; Thu, 17 Jun 2021 17:28:02 -0400 X-MC-Unique: VezdYB3-PPutLWdtEI7bow-1 Received: by mail-ej1-f69.google.com with SMTP id z6-20020a17090665c6b02903700252d1ccso3011491ejn.10 for ; Thu, 17 Jun 2021 14:28:02 -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=URoBjUEpro9U64xROBMZeKvvFlHbDEw9khuYvYfphMY=; b=I0grLI8Uds0Pfg+l2QG+3cwfv7/gSRqywS4tvxHG8Y7cTgocn+XEITwP5fJobMJqLQ /oC0UnE2JCsSvF2P6O2qUcaL2B8Yb/e9ZOEmE4MvWEid4HwDX3InwT+YRnRF4ogudQ3y QpiBe8LQd9mFdgy1077JwgJA5seVOBH/7r8xDjhjoUI2CjjzgypipuhSUHanI/vOeIgC rD6tuSSjEf6FFAsKkBVIoWrgVEQxBfU5N7gbyqPWmegdUdebDcGjn5V72ohJkZdoZKwL GsbBC3caJq8rNwjYTLrXsD+030N/PwDipapdU87RAWvSEW8YX/Qbxootiueb3xGVkC+C wMkg== X-Gm-Message-State: AOAM533dlyCMqPdridicSZKGlBaPaZnzg34rYYKG4Yn8BfTAbx5DJZOd B/8sM34bD8g6xr40wZJCfQLuOeDPn5l35g71iXB/Dt9aWwQmCcrAwBihVVQyEMpYliO67Z6Fth5 OZPH/0mGMMfUM X-Received: by 2002:a17:906:1c4e:: with SMTP id l14mr7493114ejg.172.1623965281348; Thu, 17 Jun 2021 14:28:01 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxBED07LUChvl53lkxSTodZZSwtVeK7ggiDn0AD9irgpsF1jIRBNNK0HPoUFkO1vHM4IXH08A== X-Received: by 2002:a17:906:1c4e:: with SMTP id l14mr7493097ejg.172.1623965281090; Thu, 17 Jun 2021 14:28:01 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id og6sm94201ejc.108.2021.06.17.14.27.58 (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 E3BD4180739; 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?= , Grygorii Strashko , linux-omap@vger.kernel.org Subject: [PATCH bpf-next v3 16/16] net: ti: remove rcu_read_lock() around XDP program invocation Date: Thu, 17 Jun 2021 23:27:48 +0200 Message-Id: <20210617212748.32456-17-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 cpsw 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: Grygorii Strashko Cc: linux-omap@vger.kernel.org Tested-by: Grygorii Strashko Reviewed-by: Grygorii Strashko Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/ti/cpsw_priv.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/drivers/net/ethernet/ti/cpsw_priv.c b/drivers/net/ethernet/ti/cpsw_priv.c index 5862f0a4a975..25fa7304a542 100644 --- a/drivers/net/ethernet/ti/cpsw_priv.c +++ b/drivers/net/ethernet/ti/cpsw_priv.c @@ -1328,14 +1328,13 @@ int cpsw_run_xdp(struct cpsw_priv *priv, int ch, struct xdp_buff *xdp, struct bpf_prog *prog; u32 act; - rcu_read_lock(); - prog = READ_ONCE(priv->xdp_prog); - if (!prog) { - ret = CPSW_XDP_PASS; - goto out; - } + if (!prog) + return CPSW_XDP_PASS; + /* 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(prog, xdp); /* XDP prog might have changed packet data and boundaries */ *len = xdp->data_end - xdp->data; @@ -1378,10 +1377,8 @@ int cpsw_run_xdp(struct cpsw_priv *priv, int ch, struct xdp_buff *xdp, ndev->stats.rx_bytes += *len; ndev->stats.rx_packets++; out: - rcu_read_unlock(); return ret; drop: - rcu_read_unlock(); page_pool_recycle_direct(cpsw->page_pool[ch], page); return ret; }