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=-4.1 required=3.0 tests=DATE_IN_PAST_06_12, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 41AF1C2D0DB for ; Mon, 27 Jan 2020 17:11:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1FDBE22527 for ; Mon, 27 Jan 2020 17:11:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725907AbgA0RLf (ORCPT ); Mon, 27 Jan 2020 12:11:35 -0500 Received: from mga12.intel.com ([192.55.52.136]:37364 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725845AbgA0RLf (ORCPT ); Mon, 27 Jan 2020 12:11:35 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Jan 2020 09:11:35 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,370,1574150400"; d="scan'208";a="401386783" Received: from ranger.igk.intel.com ([10.102.21.164]) by orsmga005.jf.intel.com with ESMTP; 27 Jan 2020 09:11:32 -0800 Date: Mon, 27 Jan 2020 11:02:53 +0100 From: Maciej Fijalkowski To: John Fastabend Cc: bpf@vger.kernel.org, bjorn.topel@intel.com, songliubraving@fb.com, ast@kernel.org, daniel@iogearbox.net, toke@redhat.com, netdev@vger.kernel.org Subject: Re: [PATCH bpf-next v3 2/3] bpf: xdp, virtio_net use access ptr macro for xdp enable check Message-ID: <20200127100253.GA36124@ranger.igk.intel.com> References: <1580084042-11598-1-git-send-email-john.fastabend@gmail.com> <1580084042-11598-3-git-send-email-john.fastabend@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1580084042-11598-3-git-send-email-john.fastabend@gmail.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Sun, Jan 26, 2020 at 04:14:01PM -0800, John Fastabend wrote: > virtio_net currently relies on rcu critical section to access the xdp > program in its xdp_xmit handler. However, the pointer to the xdp program > is only used to do a NULL pointer comparison to determine if xdp is > enabled or not. > > Use rcu_access_pointer() instead of rcu_dereference() to reflect this. > Then later when we drop rcu_read critical section virtio_net will not > need in special handling. > > Acked-by: Jesper Dangaard Brouer > Signed-off-by: John Fastabend Acked-by: Maciej Fijalkowski