From patchwork Tue Jun 15 14:54:43 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: 460898 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 38222C49361 for ; Tue, 15 Jun 2021 14:55:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08C9D61584 for ; Tue, 15 Jun 2021 14:55:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231346AbhFOO5L (ORCPT ); Tue, 15 Jun 2021 10:57:11 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:22129 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231274AbhFOO5J (ORCPT ); Tue, 15 Jun 2021 10:57:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623768904; 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=bmidfz0+CJmOWuJ1Ds56KwPBuWWIUyMrF1VbqTWEQjA=; b=LQ8sfZHrWMzCACzx9XHzBzUoD19ELMK2n2/Q9PmVSJWfvFySgUJlY55dXmN++MEjXjuirx i8VRmRn+E8PuWnJZd0AGdUjHiItbah2rt7uAdg8kF121CGAWakOpTpgLq2PH/PeXzThK10 sL7RC5oyRKJo1tcY6InRAiuttdnLZ5I= 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-167-zrCV6V5yPMidgSl97lFm9Q-1; Tue, 15 Jun 2021 10:55:01 -0400 X-MC-Unique: zrCV6V5yPMidgSl97lFm9Q-1 Received: by mail-ed1-f69.google.com with SMTP id df3-20020a05640230a3b029039179c0f290so20694042edb.13 for ; Tue, 15 Jun 2021 07:55:01 -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=bmidfz0+CJmOWuJ1Ds56KwPBuWWIUyMrF1VbqTWEQjA=; b=Ug2FZCKDWI7y48pzp72Llw1oV6G43hCT1GPBWM1BEAZci5OpO7yB5iBcgop8LSX8zG fms7c/MIAnXI5upuvENc23olhSqMT6OnWAOkNxpmTbFQ4clZx7izoAQgjVSZBIfOrTKM InNnqOoIGzzzVSrCcY1rNO5eKhtCi9sl9MFjCSbunRQevP/2iQe/v4QaIr3DIcDzhrkq t8V/ICzOJ9WTIup7XDVrsBCkacgnBH15H/rp4s6d3eLVsud0IIQKGiSkVTfYcVoF2Z95 kWO1wZXFc8oAYl2IKpq5nsiVKmFZhLmCDCEnXJjSmo7YoW6As+CXqhhCZYbzAIQbUkzz haVg== X-Gm-Message-State: AOAM5316+N0svGwQl3t206qNCzQQEIrscVM6r10pdNUzUPFGBx05jU+b dh+SyH7ufk2fJcHSGW6SQTNJU01wFq6KN7BJdDip+KrLot4MMIJeNzHsxwhgEFTbO9umk5bMD5w Ef2/aMhoNp85YVr3c X-Received: by 2002:a05:6402:702:: with SMTP id w2mr23790300edx.189.1623768900337; Tue, 15 Jun 2021 07:55:00 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzNRBKZlwf2ReOVkRIekxwBZ2n5A2DWRM9fshz8kMlqUDSUxWOoQYe/r7X+b9O8Xp4q8OQ9cQ== X-Received: by 2002:a05:6402:702:: with SMTP id w2mr23790285edx.189.1623768900198; Tue, 15 Jun 2021 07:55:00 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id kf3sm9320945ejc.8.2021.06.15.07.54.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Jun 2021 07:54:59 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id C4240180727; 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?= , Guy Tzalik , Saeed Bishara Subject: [PATCH bpf-next v2 04/16] ena: remove rcu_read_lock() around XDP program invocation Date: Tue, 15 Jun 2021 16:54:43 +0200 Message-Id: <20210615145455.564037-5-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 ena 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: Guy Tzalik Cc: Saeed Bishara Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/amazon/ena/ena_netdev.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c index 881f88754bf6..cd5f03691b4c 100644 --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c @@ -385,7 +385,9 @@ static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp) u64 *xdp_stat; int qid; - 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. + */ xdp_prog = READ_ONCE(rx_ring->xdp_bpf_prog); if (!xdp_prog) @@ -443,8 +445,6 @@ static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp) ena_increase_stat(xdp_stat, 1, &rx_ring->syncp); out: - rcu_read_unlock(); - return verdict; }