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=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 BF529C49EA6 for ; Thu, 17 Jun 2021 21:28:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9D8F60D07 for ; Thu, 17 Jun 2021 21:28:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233056AbhFQVaK (ORCPT ); Thu, 17 Jun 2021 17:30:10 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:39869 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232079AbhFQVaK (ORCPT ); Thu, 17 Jun 2021 17:30:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623965281; 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=gpw0jr2etcJQOtwBBETmSUpHlhu94Ou8Nardir8qwr8=; b=CMai4sOtFpXBo6gptTIoEADYAbeiSYp3t1qHoeeBXkmdt+U+mQxqupsM8MgAkqixY/+dMq dvuyCEXOz0LqhXagVWh/CqcVF/aoDXHuDtZKqsfRastsPD07nuBmW/+HWE0FXh6Z8QRwW9 QQfcnvP1/LXr6GZjk/lm+oFEMdMfoCc= Received: from mail-ej1-f71.google.com (mail-ej1-f71.google.com [209.85.218.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-272-LmTqsbu1M6adUUxb4VLfQA-1; Thu, 17 Jun 2021 17:28:00 -0400 X-MC-Unique: LmTqsbu1M6adUUxb4VLfQA-1 Received: by mail-ej1-f71.google.com with SMTP id br12-20020a170906d14cb02904311c0f32adso3026706ejb.9 for ; Thu, 17 Jun 2021 14:28:00 -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=gpw0jr2etcJQOtwBBETmSUpHlhu94Ou8Nardir8qwr8=; b=sv/9MyNywdNk4dnd6v4Dj1JEebKCD9rz3Cj49KauNNgWOqTJsxfbfKA3EWjyUX3n3z jF7c8vMxMsRZF/gRlGIjRmDkMYFAyh3GSEy/kC7WKXmlMA74OWA9/tf7pz5dzbaLh5O9 98Y2jOlJ46vZDWo0JGI5NcH1zY+k+1rlnhprUpgZlXwMfQZiRtbvhqReAqTIPzUyTxdn 2qfRQpQIQxsglS3HZBq56V/zGjOFlAJLfJIhVkt+LxDRyRk2yaYm8T2jyO3ReLbIiwMD MWJD9HbKIEoKcHyKZUuYdp2MoPuoA2dGokB3flsaJ4h2JzktZc4zvYIm80poVEWgUwLD zg8w== X-Gm-Message-State: AOAM530iKfRgPmyX5ylbdl0Ed/iFsaPsOzuGh7sqLZEb6D85JWTtVZhi 4RrfbDEdP5ENOH0/L1p2v2Hs4/vZk1ep8QDjeq/VHARoER6/xgFgbKkVzJen4GH/+x7rrVZoA/b 42pn9ksh3DM+4 X-Received: by 2002:a17:906:22c7:: with SMTP id q7mr7355896eja.547.1623965279114; Thu, 17 Jun 2021 14:27:59 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwJ0vfR8rrkBi2MA3Q9968M4U2OVMwrReOPcnhagocHm36uIqqyWEHWUNmgXDLaWB74kPUh2Q== X-Received: by 2002:a17:906:22c7:: with SMTP id q7mr7355863eja.547.1623965278752; Thu, 17 Jun 2021 14:27:58 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id g16sm93259ejh.92.2021.06.17.14.27.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Jun 2021 14:27:55 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 8C8D1180728; 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?= , Guy Tzalik , Saeed Bishara Subject: [PATCH bpf-next v3 04/16] ena: remove rcu_read_lock() around XDP program invocation Date: Thu, 17 Jun 2021 23:27:36 +0200 Message-Id: <20210617212748.32456-5-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: bpf@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; } -- 2.32.0